Development of Power Distribution
System including Smart Grid
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Development of Electricity
Infrastructures in Sub Saharan Africa
Rob Stephen
South Africa
presentation to AORC 24-26 February 2016
AORC conference 24-26 February New Delhi
About Eskom
Generation capacity – 31 March 2015
• Strategic 100% state-owned electricity
utility, strongly supported by the
government
• Supplies approximately 95% of South
Africa’s electricity
• Performed 159 853 household
electrification connections during the year
Hydro
Pumped Storage
1.4%
3.4%
4.4%
• As at 31 March 2015:
– 5.3 million customers (2014:
5.2 million)
– Net maximum generating
capacity of 42.0GW
– 17.4GW of new generation
capacity being built, of which
6.2GW already commissioned
– Approximately 368 331 km of
cables and power lines
– 41 787 employees in the group
(2014: 46 919)
5.7%
Nuclear
Gas
3
Coal
42.0GW
of nominal
capacity
85.1%
Africa challenges/ opportunities
• Vast potential of (bulk) electric energy available
• Power system needs expansion
(interconnections, long distance bulk transmission)
• Rural remote areas need solutions (island
systems, on grid, off grid, long distance
connections)
• Millions of people still without electricity.
• Low Cost Transmission Lines are vital
• Flexible solutions are important - HVAC convertible
to higher HVAC or even HVDC
Size of Africa
4
Southern African Network
6000km
to Egypt
&
Europe
3000km
to South
Africa
Inga
40GW
Gas
Hydro
Coal
Gas
Coal
Wind,
Solar
Nuclear
Long Distance
Both HVAC and HVDC
Transmission projects in Africa
5
Error!Error!
Low density, high cost,
low demand, no
address, pre paid
meters.
House cannot support
connection, house may
move, long distance to
repair faults
6
Examples of relevant
technological developments
• 500 kV polymer cables for DC
• OHL up to 1100 kV AC
• IT tools for system analysis, control and automation
• Models for system operation and training
• Robot guided maintenance
• Energy storage on the horizon (Batteries, thermoelectric)
• Microgrid technology for island systems
Long Distance Transmission by
HVDC:
• Standard +/- 500 kV
• China / India +/- 800 kV
• Single bi-poles for
+/- 1100 kV, 10 000 MW
discussed
• Multi level converters
up 2000 MW with OHL
Losses down to around 1% !!
AORC, Delhi, 24-26 Feb 2016
7
Off grid solutions
• Issues are payment, maintenance and energy
storage.
• Renewable requires energy storage
• Batteries last 3-5 years – disposal, replacement.
• Maintenance problematic with long distances.
• Monthly payment not acceptable for migrant
workers
• Require solutions for technology as well as social
issues.
Challenges for long distance
transmission
• Resilient to floods, winds, lightning and other
severe weather impacts
• Minimal faults due to pollution, birds and fire
• Lines need to be virtually maintenance free and
have a long life
8
Proposed Solution : Guyed
Structures
 Low Cost
 Performs Well
 Strong and
Flexible
Further Optimisation – Guyed Strain
Heavy Angle - Guyed Mast
528D
9
Line Compaction – Compact
No need for
Cross Rope Tower
Transpositions
Improved Surge
Impedance
Loading
Effective for long
distance bulk
power
Lower Losses
Line Compaction – Compact Cross
Rope Tower Electrical Tests
Important
Balance insulation strength with expected stresses (lightning
and switching overvoltages)
10
HVDC Guyed Solutions
+/- 350kV Namibia-Zambia (already built – 950km)
(300MW one pole operating, later 600MW Bipole)
+/-800kV Westcor and Inga-South-Africa
Cost Effective Tower Solutions
100%
4500km
4000km
67%
43%
From 2.5 faults per 100km for self support
to less than 1 fault per 100km for cross rope
11
Overall Line Cost Reduced
Up to
35%
Savings
Line Cost Comparison – Easy Terrain
Cost Savings
R450,000
R375,000
R300,000
R225,000
46%
Saving
52%
Saving
Misc Costs
Insulation
Hardware
Tower Erection
Tower Supply
Foundations
R150,000
R75,000
R0
0-15 degree structures20
15-30 degree structures
12
Cigre’s role
• Share the technology solutions to Africa
• Tutorials, symposia, conferences
• E-cigre
• Enable sharing of electrification experiences
around the world
• Social, political and economic issues
• Technology experiences
• Rural on and off grid solutions
Conclusion
• Vast potential for Generation in Africa
• Technology exists for long distance transmission
• Technology exists for rural electrification both grid
and off grid
• Need solutions in political, social and economic
areas to realise electrification
Acknowledgements
• R. Vajeth for low cost towers
• K. Froehlich for slides from Cape Town Symposium
• K. Leask for slides on Africa
13
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC
Technical Meeting
2016on
– International
Conference
Global Trendsshift
in the Development
Self Healing
Distribution
Networks
in India context
– on
a paradigm
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global Trends in the Development of Power T&D System including Smart Grid”
Mr. Vikram Gandotra, Siemens Ltd, India
Mr. Roland Schmidt, Siemens AG, Germany
Self Healing Distribution Networks in India context – a paradigm shift
Mr. Vikram Gandotra, Siemens Ltd, India
Mr. Roland Schmidt, Siemens AG, Germany
SUMMARY
With distribution automation solutions being highly cost-effective compared to solutions based on
primary technology, distribution automation can provide substantial technical and commercial
advantages to network operators. Such advanced self-healing automation concepts offered by
autonomously operating breakers can be realized using technologies and equipment that is readily
available today. Benefits are:
 Only a small amount of distribution network has to be automated
 Different concepts are available to solve dedicated requirements of the network operator
SUMMARY
 Flexible solution supporting centralized and distributed configurations
 Cost-effective
and future-proof
for automatic
and rapid fault
analysis, to solutions based on
With distribution
automation
solutions solution
being highly
cost-effective
compared
fault location
and restoration
of power supply
are still available
primary technology,
distribution
automation
can provide
substantial technical and commercial

SCADA
system
connectivity
to
self-healing
solution
is
usefulautomation
for monitoringconcepts
and controloffered
purposesby
advantages to network operators. Such advanced self-healing
 Improvement of distribution grid reliability indicators (e.g. SAIDI, SAIFI) by reduction of outages
autonomously
operating breakers can be realized using technologies and equipment that is readily
 Avoid penalties and secure power supply for critical loads like e.g. hospitals and data centers.
available today. Benefits are:
 Only a small
amount of distribution network has to be automated
The power distribution utilities in India like in other parts of the world are facing increased pressure to
uninterrupted
supply and
fast restoration
in requirements
supply in case ofofoutages.
To achieve
this the
 Differentprovide
concepts
are available
to solve
dedicated
the network
operator
utilities not only need to strengthen their grids but also implement newer solutions for more efficient
 Flexiblefault
solution
supporting
distributed
isolation
and servicecentralized
restoration onand
their
networks inconfigurations
order to reduce the outage time & the
number
of
affected
consumers
to
the
minimum.
 Cost-effective and future-proof solution for automatic and rapid fault analysis,
fault location and restoration of power supply are still available
 SCADA system connectivity to self-healing solution is useful for monitoring and control purposes
 Improvement of distribution grid reliability indicators (e.g. SAIDI, SAIFI) by reduction of outages
KEYWORDS
 Avoid penalties
and secure power supply for critical loads like e.g. hospitals and data centers.
Self Healing Solutions
Automated
Switching
The power Central
distribution
utilities
in India like in other parts of the world are facing increased pressure to
Distributed
Automated
Switching
provide uninterrupted supply and fast restoration in supply in case of outages. To achieve this the
Semi-Distributed Automated Switching
utilities not only need to strengthen their grids but also implement newer solutions for more efficient
fault isolation and service restoration on their networks in order to reduce the outage time & the
number of affected
consumers to the minimum.
schmidtroland@siemens.com,
vikram.gandotra@siemens.com
14
Fault and outage management - More efficient fault handling, more reliable networks
A major requirement on electricity supply systems is high supply reliability for the customer – which
is mainly determined by the distribution networks. Supply reliability is influenced by various technical
and organizational factors, and typically quantified using criteria such as SAIDI and SAIFI. In general,
customer expectations on supply reliability are steadily increasing – in some cases explicit power
quality criteria are even included in negotiated contracts between customers and utilities.
Self-healing solutions for supply restoration within seconds
A grid fault is a stressful situation for operator in the control center. During the fault period, they have
to perform a lot of tasks in order to restore power to the healthy section of the distribution grid as
quick as possible, among other activities, they will:
- collect and analyze grid status information
- identify faulty grid sections
- derive appropriate measures
- isolate the fault
- restore service
- inform service crews
- coordinate service crew operation
- restore normal grid reconfiguration after the fault has been repaired.
In case of disruptions affect a larger area - during bad weather, for example - the level of stress further
increases, because several outages may occur at the same time. Self-healing solutions for automated
switching, fault isolation and service restoration help avoid such stress and allow operating personnel
to concentrate on repair work and service crew coordination. Furthermore, these solutions are ideally
suited to handle outages that affect critical power consumers, such as industrial plant or Data Centre.
In these cases, supply interruptions must be fixed within less than a minute, and manual outage
handling in a control center usually fails to achieve such short restoration times. The implementation
of central, semi-distributed, and distributed applications allow further reliability improvements.
Central automated switching solution for fault isolation and service restoration
Figure 1: Central automated switching solution for fault isolation and service restoration
15
1
Fault indicator or Feeder Condition Monitor together with telecontrol system determines the type and
location of the fault in the affected substations and signals this to the control center. In a customized
configuration, the fault condition monitor, the telecontrol unit and the control center operate together.
The control center provides two main applications for fault localization and service restoration in a
distribution grid (Figure 1): The fault location (FLOC) of permanent faults evaluates real-time data
received from the feeder breakers, reclosers, and other units as well as leveraging impedance values
returned from feeder IEDs. Fault isolation and service restoration (FISR) determines a set of switching
operations to isolate specified sections of the grid and to restore service to de-energized areas of the
grid to ensure that substation transformer capacities and other constraints like line overloads or voltage
deviations are considered. The tailored configuration of fault isolation and service restoration
equipment enables the effortless management of a large number of widely distributed devices in the
grid. This helps prevent loss of revenue caused by power supply interruptions as well as penalties. The
fault isolation and restoration of supply is performed from the control center within a few minutes, and
no personnel on site are needed.
Distributed automated switching solution for isolation and service restoration
The type and location of faults, such as short circuits and ground faults are unequivocally detected by
the fault indicator and forwarded by automation unit. The in the ring installed automation units
exchange the fault information with each other. The decision in which sequence the necessary actions
are to be carried out is done hence to the generic self-healing algorithm implemented in the automation
units. The restoration process is performed in steps automatically. Between each step the self-healing
algorithm verifies the correct execution based on the information exchanged among the distributed
automation units.
Thanks to the IEC 61850 protocol used (Figure 2 and 3) and its defined engineering, all parameters
can be transferred nearly afford less to the data base of the control centre system using ICD/SCD files.
The universal use of the IEC 61850 protocol, from the process to the power control level, is
implemented in a seamless communication approach.
Figure 2: Distributed automated switching solution for isolation and service restoration in cable grid
16
2
Figure 3: Distributed automated switching for isolation and service restoration for overhead lines
A distributed solution offers several benefits:
 Cost-effective and future-proof solution for automatic and rapid fault analysis, fault location,
and restoration of power supply
 Flexible solution supporting central and distributed configurations
 Automated switching procedure to return to normal operation - No manual intervention
required
 SCADA system connectivity to self-healing solution for monitoring and control purposes
 Improvement of distribution grid reliability indicators (e.g. SAIDI, SAIFI) by reduction of
outages
Semi-distributed automated switching for isolation and service restoration
The regional controller is located on the level of primary substation. It is based on an intelligent
substation automation system ensures local self-healing automation and also provides additional
supervisory information. It is located in the primary substation as a link between the central SCADA
system and the intelligent field devices .Protection relays like SIPROTEC monitor and protect
distribution feeders in the primary substation. Disconnectors and switches at the ring main units can be
controlled and monitored via a customized distribution automation box including RTUs and FPIs
(Figure 4).
Standard ANSI protection functions in the Protection relay handle critical fault situations by tripping
circuit breakers at the in-feed point (Figure 5). The distribution automation box sends the status of the
distribution network to the regional controller to analyze and take further actions. The regional
controller is set up to:
Detect fault locations using fault indications from the field
Manage standardized switching sequences for fault isolation
Handle further action for reconfiguration and service restoration
Simplified engineering using generic algorithms to match any grid structure
17
3
Figure 4: Semi-distributed automated switching for isolation and service restoration for cable grids
Figure 5: Semi-distributed automated switching for isolation and service restoration for overhead
lines
A semi-distributed solution offers several benefits:
 Reduced fault localization costs
 Optimized deployment of personnel
 Significant workload reduction for switching personnel in the event of a fault thanks to selfhealing
 Open solution can flexibly adapt to existing mini substations
 Reliability thanks to automated and tested algorithms
 No manual intervention required for power restoration
 Extreme workload reduction in the event of several simultaneous faults, e.g. due to rough
weather conditions.
18
4
Intelligence Replaces Copper - Optimizing Distribution Networks for the Future (Example of a
Distribution Network Operator based in Germany)
The transition to a new energy mix is moving at full speed, and Niederstetten, in the German state of
Baden-Württemberg, is an example of how to successfully adapt to it. Distribution grid operator Netze
BW is implementing a grid automation solution for the catchment area around the city, which will
serve as a model for future projects. The aim is to allow the existing distribution grid to operate with
maximum autonomy by equipping it with as much distributed intelligence as possible and using as few
additional medium-voltage cables as necessary. The solution is based on proven energy automation
technology, which is to be used in a new configuration.
Overview of project objectives:
Implementation of distributed intelligence with a self-healing functionality
 Improvement to voltage stability, including voltage optimization

Development of standardized solutions to automate secondary substations

Reliable fault management to reduce the SAIDI value (System Average Interruption Duration
Index)
Figure 6: Configuration scheme of semi-distributed self-healing solution in Niederstetten at Netze
BW, Germany
Netze BW decided to rely on intelligent systems, in combination with proven automation technology.
The main emphasis is on network monitoring and fault management with intelligent measuring
technology and long-range control for active voltage stability. For this purpose, nine of the 84
secondary substations located at the most important nodal points are to be equipped with energy
automation technology, and five substations in the dead-end feeders equipped with voltage
measurement systems. The measured data can be monitored and transferred by remote transmission.
The core element of the modernization project is a distributed grid area controller in the Niederstetten
substation, based on a Siemens SICAM energy automation system. This is responsible for voltage
control and fault management and provides the communications connection. By acting as a link
between the central SCADA (Supervisory Control and Data Acquisition) system and the intelligent
19
5
field devices, it also enables the controller to restore affected grid sections in case of a fault without
human. The distributed grid intelligence makes operation of the distribution grid very energy- and
cost-efficient, since the installed automation solution means there is no need for a costly grid
expansion intervention. Improved fault detection and rapid troubleshooting result in a significant
reduction in SAIDI value and thus substantial cost savings.
Secondary Distribution network in Indian Utilities
The Secondary Distribution Network of the Indian power distribution utility sees the maximum
number of the outages in the electrical grid, which is not a surprise as this part of the network is
exposed to the vagaries of nature like vegetation, destructive cyclones and also several other unwanted
human interventions. The utility’s resources are stretched to manage these outages and restore the
power supply to its consumers and look for robust technical solutions in this area. The challenge lies in
restoring the power to the maximum possible number of consumers in the shortest possible time.
Various practices and technologies have been followed by the utilities to meet the target of satisfactory
fault isolation and service restoration.
At the same time there is a marked increase in use of electricity of larger sections of the Indian
population due to rise in purchasing power on one hand and the easier availability of electrical
appliances like fans, pumps, heaters, air conditioners and refrigerators on the other. Once a consumer
gets used to an appliance, it modifies the lifestyle and they are taken for granted. For example the
young generation today finds it difficult to believe that air conditioners in homes and most offices was
a rarity in New Delhi some years ago. IT & telecommunication loads need continuous uptime of
power supply and these applications have become part of our life. Similarly availability of stable
power supply in most Indian cities is also today taken as a ‘granted’. As a result newer generations are
less tolerant to any grid outages. Also the industrial process industry and Commercial consumers like
BPOs & Data Centers need high quality of uninterrupted power supply from the Grid. If the grid
supply is not reliable they will invest in own captive generation even if it is at a price higher than that
charged by the Utility. Outages over a long period of time are known to be a cause of riot-like
situations by the affected people.
The Indian Power Distribution Utilities are at different maturity levels. One world is that of networks
in large cities like Delhi, Mumbai, Kolkata, Ahmedabad and this is quite different from that in rest of
the country. In the first set of cities we have the secondary distribution networks which have been built
to ensure a reliable power supply with robust electrical elements (cables, transformers, RMUs,etc)
with field intelligence in the form of RTUs and communication infrastructure. The electrical networks
have been generally designed to provide redundancies through multiple feeders for a set of consumers.
These utilities are ready to take up the next level of improvement in their monitoring and control
capabilities through more intelligence being built into the Secondary Distribution networks. Some
pilots have been undertaken which have given satisfactory results. The increased visibility and the
20
6
possibility of control of the feeders is a force-multiplier for the utility engineers with which the end
consumer is assured of better availability. Most of these utilites have provided for a centralized
SCADA/ DMS which covers most of the primary network and in some cases a part of the secondary
network.
In the second set of utility networks there is again a difference in the networks of cities which in many
cases have close to satisfactory condition of electrical elements but usually without redundancy in
source of supply at the Secondary Distribution level and in semi-rural/rural areas where not only there
is no redundancy in supply networks but also the condition of the electrical elements needs drastic
improvement. The Government of India’s ambitious programs like RAPDRP and IPDS are designed
to improve the Distribution networks, but still a lot needs to be done given the scale of the India power
networks.
The grid networks are very old and designed for catering to loads planned several decades earlier. Due
to increase of population, business activities and urbanization the peak loads in our cities have
witnessed rapid growth. With the rapid increase in the loading of the network the network elements
are often subjected to stresses and hence this leads to frequent faults. This means that even if there is
enough power that is available, the consumer is often stranded without power due to weakness of the
local distribution grid.
The Secondary Distribution network in Indian utilities will also have to bear the pressure of new
renewable power being injected at a large scale in view of the Government of India’s ambitious plans
for Solar Power. Indian utilities can learn from the experience of German distribution utilities which
went through similar experiences with many surprises. The installation of remote controllable
elements in the Secondary Distribution networks will be critical for ensuring smooth integration of the
resources.
Through use of newer technologies in automation, control and communication, in the hitherto
neglected Secondary distribution network, utilities have the flexibility to consider solutions either in
Centralized, Semi-Decentralized or fully Decentralized configurations. There is a need for the utilities
to develop a comprehensive plan following a step-wise approach:1. Make a study of as-is network. This can be done by a combination of planning office
simulations and by installing intelligence in the network to get actual data of analogs, alarms
and switch/CB statuses.
2. Prepare accurate load forecast in various areas of the licensed area of utility based on city
planners growth models
3. Relook at the as-is network and prepare a ‘should-be’ network plan with redundancies based
on n-1 principle
4. Identify measures for the should-be plan such as new feeders, higher capacity of
transformers, cables, Remote operable RMUs, Automation & Communication requirements
for meeting the future demand.
5. Implement the ‘should-be’ plan for Secondary Distribution Automation
BIBLIOGRAPHY
[1]
Siemens AG, 2016
http://w3.siemens.com/smartgrid/global/en/projects/Pages/Intelligence-replaces-copper.aspx
21
7
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 –on
International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global Trends
the Development
of Power
T&D
including
Smart Grid”
CIGRE-inAORC
Technical Meeting
2016
andSystem
International
Conference
on
INCORPORATING
INTO
DISTRIBUTION
NETWORK
- THE
“Global TrendsINNOVATION
in the Development
of LV
Power
T&D System including
Smart Grid”
CESC PATHWAY
INCORPORATING INNOVATION INTO LV DISTRIBUTION NETWORK - THE
CESCCESC
PATHWAY
KIRIT RANA, DGM (TECHNICAL),
LIMITED, INDIA
ANJAN MITRA, SDM-MAINS (LT CONTROL ROOM), CESC LIMITED, INDIA
KIRIT RANA, DGM (TECHNICAL), CESC LIMITED, INDIA
ARYYABRATA PAUL, DISTRIBUTION ENGINEER (LT CONTROL ROOM),
CESC
INDIA
ANJANLIMITED,
MITRA, SDM-MAINS
(LT CONTROL ROOM), CESC LIMITED, INDIA
Summary
ARYYABRATA PAUL, DISTRIBUTION ENGINEER (LT CONTROL ROOM),
CESC LIMITED, INDIA
CESC Limited is an integrated distribution utility operating in the twin cities of Kolkata and
Summaryover a licensed are of 567 sq. km and having a customer base of nearly 3 million.
Howrah,
Simply put, it is our cable and network equipment that bring power to the home of Kolkatans
CESC Limited is an integrated distribution utility operating in the twin cities of Kolkata and
every day.
Howrah, over a licensed are of 567 sq. km and having a customer base of nearly 3 million.
Simply
it is our cable
and network
bring power
to the
of Kolkatans
In
our put,
continuous
endeavour
to doequipment
our workthat
efficiently,
bring
inhome
improvement
of our
every
day.
performance and to offer our customers quality uninterrupted power at an affordable price,
introducing
innovation
in distribution
is one
of our
key focus
areas.
In our continuous
endeavour
to do our
work
efficiently,
bring
in improvement of our
performance and to offer our customers quality uninterrupted power at an affordable price,
Innovations have many different definitions and interpretations, but we in CESC view
introducing innovation in distribution is one of our key focus areas.
innovation as introducing something novel in to our business processes or distribution
Network
so have
that we
can different
provide Improved
to our esteemed
Customers
terms of
Innovations
many
definitionsServices
and interpretations,
but we
in CESCin view
quality,
costasand
speed. Wesomething
believe that
Innovation
does
not always
have to
path breaking
innovation
introducing
novel
in to our
business
processes
orbedistribution
Network
so thatachieved
we can provide
Improved Services
to our esteemed
Customersasinaterms
and
we have
many considerable
improvements
in distribution
resultof of a
quality,
cost
and
speed.
We
believe
that
Innovation
does
not
always
have
to
be
path
breaking
sequence of small step by step improvements.
and we have achieved many considerable improvements in distribution as a result of a
At
the heart
of ourstep
approach
innovation is our commitment to continuous improvement of
sequence
of small
by step to
improvements.
our Product & Services. This commitment to innovate and improve covers the entirety of
At the heart
of our approach
to innovation
is our
commitment
to continuous
improvement
of
CESC’s
Distribution
services,
including
Customer
Relationship
Processes,
Connection
our Product & Asset
Services.
This commitment
to Automation,
innovate and Safety
improveand
covers
the entiretyRemote
of
Management,
Management,
Network
Sustainability,
CESC’s
Distribution
services,
including
Customer Relationship Processes, Connection
Work
Force
Monitoring
and Back
office functions.
Management, Asset Management, Network Automation, Safety and Sustainability, Remote
Work the
Force
Monitoring
and- Back
functions.
Over
period
of 2009
2013,office
CESC
has made significant improvement in its quality of
supply and performance which was mainly due to focused attention and investment in our
Over the period of 2009 - 2013, CESC has made significant improvement in its quality of
HV network resulting in improved performance and minimisation of failures coupled with
supply and performance which was mainly due to focused attention and investment in our
HV network resulting in improved performance and minimisation of failures coupled with 1
Email id: kirit.rana@rp-sg.in
Email id: kirit.rana@rp-sg.in
1
22
introduction of Remote Control of HV network feeders. However, performance of LV
network of CESC continued to be an issue. With the above contextual factors CESC has
initiated several projects to investigate and implement innovative approaches for performance
improvement in managing LV network.
The paper delineates in details successful developments of new technologies by CESC in LV
distribution relating to Compact LV Distribution Cabinets, LV jointing techniques, LV
compact substation, LV remote changeover, and LV network visibility.
In addition to this, the innovative process changes relates to trouble call management and
new connection processing which also forms part of CESC’s overall innovation portfolio.
We expect that from the deployment of innovative techniques and processes, we would
realise the benefits of improved customer service, improved quality of supply, improved
network visibility, increased operational safety and better network management.
While CESC has made a conscious decision to be a leader in the field of innovation in
distribution amongst all the distribution utilities in India, we believe that organisational
environment conducive to innovation should essentially incorporate the freedom to fail. This
position is also key to our vision to make CESC a great place to work for young engineers by
fostering the spirit of relentless quest for improvement in the organisation.
Key Words: Identification of Pain Areas, Consultation with Partners & Customers,
Realisation of Need and requirement, Scouting Technology and solution, Trials &
Pilots, Horizontal deployment, Sustenance.
Introduction
CESC Limited is an integrated distribution utility operating in the twin cities of Kolkata and
Howrah, over a licensed are of 567 sq. km and a customer base on nearly 3 million.
Like any other Distribution Utility, CESC Ltd. also had a focussed approach towards
betterment of its HV & EHV Network which serves as the backbone of the Distribution
System. In the process the entire gamut of LV & MV system which constitutes of around
12000 circuit km of Network was in the back seat of the improvement story. This was the
situation till 2009-10. Though Losses and other performance parameters in both HV & MV
system were well above regulatory requirements, the essence of value added service offerings
to the esteemed customers was somehow missing. What the company needed was Innovative
approaches in its Product & Processes for a better customer centricity.
The Push to Innovate: Pain Points
With the thrust of the organisation shifting to its LT system in 2011-12, the outlook towards
the LT system underwent a sea change. The operation, maintenance and improvement of the
LT system, whilst remaining within the bounds of economic viability, was seen as the
pathway for further improvement of Consumer Service The change in approach and the
constant drive to improve on current performances, lead to the identification of key
Email id: kirit.rana@rp-sg.in
23
2
challenges and implementing the ideas of improvement. These challenges could not be
satisfactorily solved remaining within the bounds of traditional practises thus creating the
drive to innovate. Hence, like all innovations, the innovations in CESC related to the LT
network were motivated by pain points.






One of the major obstacles faced was due to the vast spread and diversity of the LT
network, the monitoring of the same was difficult through a single window. The
operations on LT network were supervised locally and there was no practise of
Centralised Monitoring or Documentation of ongoing operations. Breakdowns in the
LT network was monitored locally and was a reactive system, relying chiefly on
customer complaints to identify breakdowns.
Fuse protection in CESC system was by means of re-wireable copper fuses at pillar
boxes, pole cut outs and service cut-outs. Consumer interruptions due to fusing at
pillar boxes were frequent and formed a major portion of the supply interruptions
encountered by the consumers. Due to inherent nature of the re wireable fuses, the
fusing current for such fuses depend on a variety of factors such as condition of fuse
contacts, the skill of the workman installing the fuse, fuse material and in service age
of the fuse wire etc. In many cases it was found that the fuse had blown without any
actual fault or overloading and the supply to the affected consumer was restored
simply by replacing the fuse.
Reducing another major cause of interruption in LT systems, namely LT cable faults
were another pain point. The LT cable is laid at a much lower depth as compared to
HT cables. Moreover, there are numerous joints, predominantly tee joints for
providing services along LT distributors, thus creating a number of points prone to
fault at these joints throughout the length of the cable. Thus, LT cables are more
prone to faults as compared to HT cables due to external interference as well as due to
internal failure.
An age old problem associated closely with LT distribution network is the elimination
of low voltage pockets. The problem becomes even more involved when the pockets
have to be eliminated while limiting the investments within a pre specified CAPEX
target.
Specific targets have been set for reducing number of interruptions as well as
turnaround time for restoration of each interruption due to break down for sensitive
LT consumers.
Being an urban utility, CESC faces the problem of paucity of space, especially for
installing pillar boxes which necessarily have to be erected near load centres. The cost
of road restoration that has to be paid to civic authorities for any excavation work
undertaken is quite high for urban areas.
The CESC Pathway of implementing innovations
CESC has a well-defined structure for introducing innovations into its system. The initial
concept, stemming from the urge to alleviate a pain point, is discussed in detail with all stake
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24
3
holders- vendors, personnel from other concerned departments and front end implementers,
following which a pilot project is undertaken. The outcome of the pilot is analysed minutely,
with stress on frontend user feedback, and issues thus thrown up are addressed in
collaboration with partner vendors. Finally, after ensuring that the solution is bug free in a
general sense, it is implemented in full scale
Innovations Introduced
In the following sections, the innovations, encompassing both technical modifications and
process re-engineering is enumerated.
LT CONTROL ROOM: The centre of innovation
In line with CESC’s ardent initiatives to offer the best in class service experience for its
valued retail LT consumers and to continuously improve upon the operational processes for a
better tomorrow, a LT Control room operational 24X7, has been set up at the commercial hub
of Kolkata at B.B.D Bag 132kV Substation, which was inaugurated on 2nd June 2015.
The LT Control Room manned by selected domain experts monitor the operations in the LV
System and ensures that the Turn Around Time (TAT) for each critical process in trouble call
management is adhered to all across the CESC operational area.
The LT Control also acts as a Centre of Excellence by ushering in the latest technology and
innovation in the LV system by regularly scouting the technology space and after proper
trials and experimentations embed them in form of Business as Usual in the system. A few
such examples are delineated below.
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Email id: kirit.rana@rp-sg.in
GIS & GPS integrated Consumer complaint management system:
At the LT Control Room, CESC has innovatively blended the GPS based mobile crew
tracking system and the GIS based mapping of its consumer for better monitoring of the LT
trouble call management. It’s in the same line as OLA & UBER cabs. When a LT complaint
is logged in our CRM system it is visualised in the LT Control Room on the GIS map. On the
same map the mobile maintenance vehicles which are equipped with GPS system are
available on screen. Thus the Control room engineer could take decision and guide the crew
for a better and faster complaint resolution.
CESC installations on GIS
GPS and GIS integrated call response system
Continuous monitoring of essential installations on LT network to ensure swift response
AMR in DTR integrated with GIS
All the 8000+ Distribution Transformers (DTRs) are provided with on line metering which
captures all the electrical parameters and stores the average value over cycles of 30 minutes.
The innovative piece was depicting all these DTRs with these online readings on the GIS
map with color coding to indicate the load profile.
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Email id: kirit.rana@rp-sg.in
Smart pillar box:
Version-1:
Re-engineered Pillar Box
CESC has re-engineered the conventional pillar box, replacing the rewire able copper fuse
units by Fuse Strips fitted with HRC fuses. During last three fiscals more than 10000 number
of modified pillar box has been installed.
Analysis of repetitive fuse failure revealed that 80% of repetitive fusings are contributed by
roughly 20% of the total pillar boxes. Hence for the initial replacements, the pillar boxes to
be replaced were selected by Pareto analysis. Later on, analysing the immense benefits
reaped due to replacement of conventional pillar boxes by re-engineered ones, a corporate
decision has been taken to go for the replacement of all conventional pillar boxes by reengineered ones using a top down approach that is replacing all feeder pillar boxes, then
moving pillar boxes in the downstream network.
Three pronged benefit has been reaped because of this change in design in terms of reduced
fusing, reduced thermal losses and opportunity loss and reduced space requirements.
The number of pillar box fusings has reduced drastically over the years. Compared to the
base figures of 2012-13 till date we have been able to reduce the pillar box fusing by 75%.
There has been substantial cost savings in the form of reduced thermal loss & opportunity
loss by installing this modified design pillar boxes.
There is also lesser space requirement by this modified design pillar boxes.
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Email id: kirit.rana@rp-sg.in
Earlier Design
Modified Design
Item
Features




Rewire able type of Cu fuses
Open Design
Prone to Electrical Hazards
Easy to Pilfer parts




Vertical Fuse strips with HRC fuses
Closed Protected Design
Endures high degree of Safety
Not susceptible to pilferage of parts.
Pillar Box Fusing
100000
75000
71931
75 %
Reduction
78247
72589
56935
55764
50000
34474
19352
25000
0
2009-10
2010-11
2011-12
2012-13
2013-14
2014-15
2015-16 (till
Dec)
Version-2:
Automated Pillar Box:
Customer complaint management is one of the most important functionality of any Power
utility. In today’s world, while customer satisfaction has given way to customer’s delight and
adding wow factor to the bouquet of service offerings by organizations is the need of the day,
In CESC we also have to think differently for the same good old job of complaint
management which we have been doing for more than a century. Customer call management
everywhere is a reactive process and is based on a complaint from the consumer.
Email id: kirit.rana@rp-sg.in
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7
By adding an automated module to the pillar box a process has been developed where in a
SMS is triggered by the automation module to some predefined numbers during any outages
like fuse failure, supply off due to fault etc. Based on such SMS, technicians are sent directly
to the fault site with pin pointed knowledge of the failure which has taken place to attend the
same. Thus we could easily reduce the process cycle time for restoration of supply in the
event of failure. Also once the supply is restored we could proactively give a courtesy call to
the affected consumers (available in our database vide consumer indexing data) seeking
apology for the interruption of supply.
The project of automated pillar boxes in undergoing trial in the system and would be taken up
for larger development based on the performance of the solution under different service
conditions.
Version-3:
LT Remote Monitoring using Pillar Boxes
In pursuit of our journey towards excellence we have travelled a few more miles and utilising
our Optical Fibre Network we have been able to monitor the loading of different units of the
Pillar Boxes. For this job standard CT’s have been installed on the cable cores and MFM
(Multi-function Meters) have been used to capture the Electrical parameters of the Pillar Box
outgoing load units. The data thus captured is transmitted using the RTU to the LT Control
Room and is made available to the engineers on a web page. This helps us to take proactive
decisions and in the event of any abnormality or outages alarms and SMS is available, so that
the LT retail consumers need not call up to log any complaint of supply failures, and our
cherished goal of proactive action in events of supply failure is achieved.
LT Compact Substation (LTCSS):
Quite a few numbers of low voltage complaints are received every year by CESC. The
complaints received are analysed and grouped for identification of low voltage pockets. The
reasons for low voltage are generally:
Email id: kirit.rana@rp-sg.in
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8
a) Overloaded Distribution Transformers
b) Long distributors leading to unacceptable voltage drops. This is especially prevalent
in OH networks.
c) High concentration of reactive loads.
Conventionally, such low voltage pockets were eliminated by re-organisation of LT network
or by installation of a distribution transformer. Both these resolution mechanisms involve
significant amount of CAPEX and are not viable for small pockets. Such low voltage
complaints are now being resolved, where ever possible, by installation of LTCSS, thus
reducing the CAPEX significantly.
LTCSS essentially comprise of two components, namely a Voltage Regulator and a Capacitor
bank, installed individually or in a combination at strategic points in the LT network.
The Voltage regulator is essentially an Autotransformer which is used to boost up voltages at
points where it falls below the threshold value. This is used in areas where the low voltage
problem is solely due to long distributors and the feeding transformer is not overloaded. In
areas with low power factors, voltage regulators are introduced in conjugation with 10 KVAR
capacitor banks to compensate for the reactive power requirement of the transformer.
Capacitor banks of 50 KVAR are also installed in low voltage pockets having a large
concentration of reactive loads. The capacitor bank modulates the reactive power requirement
of the system, in turn reducing the reactive component of the line current effectively leading
to reduced IR drops. It also reduces line losses.
By installing LTCSS at 9 locations in the network, CAPEX deferment to the tune of
Rs. 270 lakhs has been achieved.
LT Compact Substation
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Email id: kirit.rana@rp-sg.in
Re engineering LT able joints:
The breakup of various reasons of LT cable faults in the financial years 2013-2014 and 20142015 is as follows:
5000
4563
4355
4000
2880
2827
3000
2000
1000
0
964
715
108
40
CABLE GLAND
CABLE RUN
TEE JOINTS
3
SLEEVE JOINTS
SPIKE
STRAIGHT
THROUGH
CUM TEE
JOINT
STRAIGHT
THROUGH
JOINT
TERMINATION WORKING END
TOTAL NO OF FAULTS
As can be seen from the data, joint faults accounts for about 59% of the total faults. Hence,
modification of traditional jointing techniques emerged as a pressing need.
Traditional tee joints, by soldering technique, required high degree of skill were prone to
faults due to poor workmanship, contributing to about 26% of the total faults. The traditional
jointing technique has been replaced by Insulated Piercing Connector jointing. The Insulation
piercing Connector, which was a standard accessory for AB network was innovatively
adapted for the underground Tee joint thus simplifying the jointing procedure and making it
skill independent. The modification has resulted in bringing down the number of faults in tee
joints by nearly 20 %.
Another major contributor to LV cable faults is ingress of moisture into cables. Re- designed
LV straight through joints, employing hot melt adhesive coated heat shrink tubes for
conductor encapsulation instead of mastic patches, has been tested as a pilot and has been
10
Email id: kirit.rana@rp-sg.in
31
proved to provide better resistance to moisture ingress. The re- designed joints will be
employed in full scale from the next financial year.
Remote LT Auto change overs
Outages of essential LT consumers have been reduced by introducing LT auto change-over
modules. Such consumers are provided with two supply mains, one main and one stand by
which are being fed from different distribution transformers and where ever practicable from
different power transformers as well. In the event of failure of the main supply, the module
automatically switches the service over to the standby supply without any observable delay.
Once the main supply becomes healthy post repairing, the service is switched back to the
main supply.
LT Auto changeover
New Service Re engineering
CESC being a socially aware utility has always strived to reach a wider spectrum of
consumers and reach them as fast as possible. Stemming from this desire to illuminate homes
faster and cheaper, Overhead service with armoured cables has been initiated as a pilot in
order to speed up the process of providing services and decreasing the cost of new
connections that has to be borne by the consumer.
This method addresses the concerns of susceptibility of OH service cables to mechanical
damages by using armoured cables while eliminating the labour cost and restoration costs
11
Email id: kirit.rana@rp-sg.in
32
borne due to excavation works related to underground services. Such services are being
provided by cables of two cross sections: 50 sqmm and 25 sqmm.
Eliminating Tee joints
Tee joints are an inherent point of weakness in the cable and also restrict the use of fault
pinpointing instruments which delays fault repair. In order to eliminate tee joints different
types of service cabinets have been developed:
a) Turret type pillar boxes
b) 2 way pillar boxes
They have been introduced in fault prone networks. Both these pillar boxes have a very small
footprint and can be erected in congested locations since squeezing out space in a built up
city is a major problem for a Utility. These cabinets sectionalise the LT network and provide
tapping off facilities for 6 service connections.
Two Way Pillar Box & Turret type Pillar box
Crew Management System:
The consumer complaint redressal mechanism has seen a major upheaval in its process flow
in the last few years. Over the years, operations of frontline personnel responding to
consumer complaints were centred on depots located at strategic locations. The personnel
would report at corresponding depots and complaints would be assigned to them for
redressal. After attending every complaint the front end personnel would communicate to the
depot Technician his findings over phone and he in turn would communicate it to Regional
reporting centre to close the call. On finishing the entire batch of complaints assigned to him
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33
12
he would be assigned fresh set of complaints. In this process, time is lost at two junctures,
namely, during providing feedback to the depot personnel and further relaying of the same to
Regional reporting centre.
The need for multiple telephonic conversations has been done away with by introducing the
Crew Management System in Consumer Complaint Redressal Mechanism. The frontend
personnel have been supplied with tablets with are equipped with pre-installed menu driven
Mobile Applications which enable them to accept new assignments and provide feedback at
the tap of a finger on the go thereby reducing the average time for attending consumer
complaints.
Process Flow of Crew Management
Conclusion
While CESC has made a conscious decision to be a leader in the field of innovation in
distribution amongst all the distribution utilities in India, we believe that organisational
environment conducive to innovation should essentially incorporate the freedom to fail. The
projects of Mobile distribution board and Underground link boxes for LT cables have been so
called failures. This position is also key to our vision to make CESC a great place to work for
our young engineers by fostering the spirit of relentless quest for improvement in the
organisation.
34
Email id: kirit.rana@rp-sg.in
13
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
on
ADVANCED
METERING
- THE
PERSPECTIVE
of Power
TransmissionINFRASTRUCTURE
& Distribution Systems including
SmartCESC
Grid, 24-26
Feb. 2016, New Delhi, India
on
UDAYAN GANGULY,
“Global Trends in the Development
of Power T&D System including Smart Grid”
CESC Limited
“Global Trends in the Development
Indiaof Power T&D System including Smart Grid”
ADVANCED METERING INFRASTRUCTURE - THE CESC PERSPECTIVE
ADVANCED METERING INFRASTRUCTURE
- THE CESC PERSPECTIVE
UDAYAN GANGULY,
UDAYAN
CESC GANGULY,
Limited
CESC
Limited
India
India
SUMMARY:
The oldest private power utility of India, CESC, has the history of embracing technological
advancements, promptly, with an eye on improving operational effectiveness & customer satisfaction.
The organisation looked for value additions beyond just AMR and reaped huge benefits in the DT &
high-end consumer segments. For the whole current segment, the choice is Smart meters, compared to
AMR meters, as the focus, additionally, is on remote manageability and greater functional visibility of
the meters. Despite the clarity on the drivers for AMI, CESC is focussed only on mitigating its current
SUMMARY:
pain
& gain triggers. The requirement of deploying Smart meters, in a scattered manner, has thrown
SUMMARY:
up
some
challenges
in theutility
technological
& operational
fronts,
which of
a hybrid
communication
The oldest private
power
of India,
CESC, has
theforhistory
embracing
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network is envisaged. Meter manufacturers are expected, to supply detachable communication
The
oldest private
power
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CESC,
has the effectiveness
history of embracing
advancements,
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with
an eyeofonIndia,
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modules, catering to various technology offerings, to suit the deployment need. CESC wishes to have
advancements,
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eye
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and
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as
the
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on
remote
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and
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of
sharing of communication network provider’s NIC, between meters of different manufacturers. CESC
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onfor
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CESC
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CESC
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of
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inintegration
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aa Governmental
pushthrown
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forinwhich
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compatibility
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push
or a Regulatory nudge shall trigger a “win-win” situation for all in AMI deployment
or a Regulatory nudge shall trigger a “win-win” situation for all in AMI deployment
udayan.ganguly@rp-sg.in
1
35
KEYWORDS
Outage Detection, Proactive, Self –healing, visibility beyond meter reading, blindly aping the West,
remote manageability, drivers, pain & gain triggers, communication woes & learnings,
interoperability, holistic view, smart city, bandwidth, OTA upgrade, smartphone app, least life cost,
win win for all.
AMR & BEYOND:
Looking back, CESC had always been one of the forerunners in the country in adopting smarter
technology, as and when, these were available for use. A fully computerised billing system, for all
categories of consumers, in the early seventies, speaks volumes of such foresight.
If only migrating to an AMR regime took a little bit of time, compared to some of its peers among the
private utilities, it was essentially because of the fact that, CESC had, since 1995, built a robust
integrated billing system, based on HHU based meter readings, for its HT & LT CT consumers, with
data analytics as the main bulwark for efficient customer centric operations.
However, ever since the organisation built, owned, operated & maintained its AMR system, the
primary focus shifted to value additions, looking beyond the meter reading success rate of 99.6% or
more, on a sustained basis.
No wonder, features like outage detection for all categories of high-end consumers & DTs could be
extracted from the vanilla AMR system to reap extensive operational dividends, through home-grown
efforts. The DT analytics tool, developed in-house, has transformed an open-ended & reactive
distribution system to a proactive & close-ended system, beyond just energy audit.
WHOLE CURRENT METERS -JUST REMOTE READINGS OR MORE:
Having tasted success with AMR in the high-end consumer & DT segments, it is only natural, for
utilities to explore, extending AMR in the vast ocean of whole-current metering segment.
AMR in this segment, ruled by sheer numbers of meters, is a difficult proposition, because,
maintaining a separate meter & a modem configuration, for point-to-point communication, unlike the
high-end segment, is not only impractical, but also, an expensive proposition, operationally.
Additionally, multi-point-to-point communication with built-in meter-modems, with Data
Concentrators further complicates the communication mechanism.
AMR meters on offer, have a basic communication design, in order to optimise on cost of the meters
and lacks the reliable “self-healing” features of the communication, as a result of which, the success
rate of remote reading is not up to the levels expected & obtained in the high-end system.
Additionally, this technology does not have any further visibility beyond the meter readings, hence,
shall silently remain in the system, incapable of meeting future expectations of the utility.
The developed countries have gone through this cycle & now, when we have an improved choice, in
the Smart meters, we need to decide on, whether we blindly ape the west, or learn from their
experience.
udayan.ganguly@rp-sg.in
36
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TODAY’S METER:
Customers’ expectations are ever-changing and so are operational expectations of the utility.
Imminent changes in the Electricity Act shall necessitate a radical shift in Distribution operation.
A meter procured and installed today, needs to be equipped to meet contemporary expectations, for at
least 10 years, down the line & need to have remote manageability features.
If a Smart meter installed in circuit does not support features like TOU tariff based billing, bidirectional metering, pre & post-payment functionality on the same metering hardware, load control,
customer portal then, it would become a stranded asset for the utility, with the possibility of no further
value additions.
KEY DRIVERS FOR THE NEXT LEVEL:
Some of the key drivers, for migrating to the next level smarter metering, for the organisation are
improvement of power network performance, customer centricity & outage management, containing
meter reading overheads & improving reading efficiency, distribution loss management, analytics &
BI, reigning in R&M expenditure, improving operational efficiency & supporting value added
services.
THE RESTRAINT:
Unlike most of the utilities in developed countries, the organisation does not envisage a roll-out of
Smart meters, for the entire 3 million meters in circuit, in one go, primarily because of economic
reasons and prefers a segmented approach of deployment, by slowly scaling up, progressively, over a
period of time, instead, depending upon its pain & gain triggers, existing from time to time.
This restraint, in a way, shall help, in trying out technologies & products best suited for deployment,
in its area of operation.
THE PAIN & GAIN TRIGGERS:
Metering all upcoming high-rises with multiple metering points, pump-houses & no-access
consumers, all net-metering requirements, meters of meter pillar boxes in loss prone areas, VVIP
consumers for outage detection & consumers having average monthly consumption of 200/500 units
or more are some of the pain & gain triggers for the organisation, for Smart meter deployment, as of
now.
DEPLOYMENT CONSTRAINTS:
In order to walk a tight rope in introducing Smart meters, for specific target segments, meters need to
be deployed, in a highly scattered manner, except, those in multi-storied housing or meter pillar
boxes.
udayan.ganguly@rp-sg.in
37
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Therefore, there is not only a “planned but scattered” deployment need, but a “random & scattered”
need, as well, in addition to some “clustered” deployment needs, making it difficult to choose the
communication technology, to be deployed, in each case, for Smart metering to be operational.
SUPERIMPOSED COMMUNICATION WOES & LEARNINGS:
To compound the Smart meter installation pains, unlike the favourably located of HT, LT CT & DT
AMR locations, point-to-point GPRS signal, at the meter boxes, located inside the nook & crannies of
households, mostly under stair cases, is not adequate enough, in many installations, hampering
performance.
On the other hand, both for PLC & RF-Mesh technologies, the stability of communication of which,
largely depends on the formation of mesh, with help of the presence of adjoining Smart meters,
themselves, are throwing up deployment challenges, owing to the very scattered nature of meter
installations, those, that are needed now.
PoC / trials, carried out by us, with PLC technology has met with noise-related communication-nonavailability issues in both underground & overhead network. However, performance at clustered
deployment sites has been found in order.
Also, various PoCs / trials with RF-Mesh indicate that, strategic locations for network devices may
not be readily available for use in reality and concrete density in the heart of Kolkata is also an
impediment. Furthermore, extended antenna & repeaters are necessary to increase signal strength at
some areas. Locating RF-Mesh repeaters and powering these up are also a challenge.
We envisage, with RF-Mesh communication, network devices have to be increased in numbers
initially, to attain the desired communication levels and later on some of these may have to be
“harvested” again, as the meter density picks up later, causing network erection costs to increase.
HYBRID COMMUNICATION MEDIUM:
CESC has a rich optical fibre network, spread across its licensed area, which shall be leveraged for the
primary backhaul of AMI communication purposes, with GPRS as the backup.
Apart from the point-to-point communication modalities used on hired network of the communication
service provider, the last-mile communication, is to be primarily utility owned, & can either be
“wired” e.g. PLC or “wire-less” e.g. RF-Mesh, thus rendering the entire communication network,
essentially hybrid, suiting specific deployment modalities.
Initially, it is expected that, meters with point-to-point communication, shall gain momentum. This
would die down with time, with the deployment finally, remaining confined to fringe areas, where
privately owned network is not strong or the Smart meters are in randomly distributed pockets.
With the passage of time, probably “wire-less” communication will be the principal communication
channel, with PLC being a close second, primarily, in clustered deployment of Smart meters.
38
udayan.ganguly@rp-sg.in
4
DETACHABLE COMMUNICATION MODULES IN METERS:
With a flexible hybrid bouquet of communication medium envisaged, catering to the deployment
need, CESC expects, Smart meter manufacturers to come up with their own compatible “point-topoint”, “wired” & “wire-less” communication modules, to meet the utility’s flexible deployment
requirement, so that, a particular make of meter shake hands with different communication technology
needs at site.
Internally, the power supply of the Smart meter needs to be designed in a manner, so as to
accommodate this change in communication module.
THE INTEROPERABILITY TANGLE:
The organisation is on the lookout for achieving perfect interoperability at the Smart meter level, with
different makes of the meter, as well as, at the field communication device level too.
However, despite all the debate on interoperability, such a system is yet to see the light of the day,
worldwide, because of purely competitive reasons.
For all practical purposes, Smart meters, of different makes, are expected to achieve working
interoperability, through the sharing of NIC (Network Information Card) as has been the case abroad.
This presupposes that, the communication network provider, is automatically the supplier of the HES
& the network devices, may be a Smart meter manufacturer or an independent entity, is operating in
an enviable monopolistic position and the performance of the NIC inside various Smart meters of
different makes, determines, the final performance of the end-to-end system.
Also, this NIC based inter-operability solution largely depends on how effectively the utility is able to
rope in Smart meter vendors into accepting a third party NIC, with customised form-factor, after
successful technical trials and the strength of the commercial agreement between the NIC sharer &
NIC acceptor (Smart meter manufacturer).
THE HOLISTIC VIEW BEYOND SMART METERS:
When a utility decides on owning a communication medium for AMI, it is important to take note of
the fact that, the other facets of Smart Grid, like Feeder Automation, Volt-Var Optimisation,
Conservation Voltage Reduction & Fault Location, Isolation & System Restoration (FLISR), need to,
preferably, hang from that network as well, in order to optimise on the built network OPEX, else
maintaining various different networks, for different purposes, may turn out to be an issue by itself.
With the Smart City concept catching up in India, the utility has the option to extend value added
services, like traffic signalling, street light-control etc. riding on the common, multipurpose
communication canopy erected, on a rent.
However, in the developed countries, utilities have chosen either of the two possible models and have
managed their system well.
39
udayan.ganguly@rp-sg.in
5
THE BANDWIDTH PARADOX:
People are taking sides, almost in equal numbers, on the debate of the sufficiency of the 2 MHz band
width on offer in the 865-867MHz de-licensed band for “wire-less “communication for AMI.
For AMI this bandwidth may not be an issue for smooth operation, however, on a shared
multipurpose common canopy, running bandwidth guzzling applications, like video-surveillance, may
be an issue.
Alternatively, in order to avail a higher bandwidth, one may tend to choose 2.4 GHz, as the
communication frequency for AMI, which, in a congested city like Kolkata, may pose serious “lineof-sight-issues” to grapple with, especially for AMI applications.
This is certainly not an issue to overlook, with an eye on the future.
SMART METER – THE KEY EXPECTATIONS:
A Smart meter needs to be designed with a horizon of 15 years of life, and consequently, should have
adequate memory space inside, for firmware upgrades in future, as, newer generations of firmware,
usually, take up more memory space inside the meter, as well as, adequate precautions need to be
taken so that, the firmware upgrade needs to happen in a fail safe manner.
MULTIPLE METER VENDOR ISSUES:
Any utility would certainly not like the idea of investing in one smart meter vendor, essentially to
infuse quality & price competition. Experience from developed countries warns us against the fact
that, the process of an Over The Air (OTA) firmware upgrade, throws up lot of challenges in two
different makes of Smart meters.
This is essentially, because of fact that, even though the two Smart meters have the same
specification, they are not necessarily manufactured in the same way, causing issues during firmware
upgrades. Therefore, more the number of Smart meters types, more are the chances of an unsuccessful
upgrade OTA.
COMMUNICATION REDUNDANCIES:
A careful design of the communication system too assumes importance for a Smart meter deployment,
as clogging of network devices, particularly during mass supply outages, may render the entire system
unreliable, if not planned adequately in advance.
All communication network devices needs to be loaded up to a maximum of 50% of their respective
capacities, so that, in the event of an outage of one device, the adjoining network device can cater to
the additional load to be shared for seamless operation.
Also, sufficient battery backup, for such communication network devices is a must for reliable
operation during power outage, a small, but important aspect, may get overlooked in pursuit of
striking the cheapest deal in the Indian context.
udayan.ganguly@rp-sg.in
40
6
IHD OR SMART PHONE APP:
These days the use of “In Home Display Unit” is gradually losing out to a feature rich Mobile APP on
a Smart Phone, giving the consumer, a host of interact-able interfaces to take advantage from.
However, IHD is still necessary in the consumer segments, where the Smart Phone penetration is not
that great. Therefore, it is important that, the Smart meter procured, has this provision of an Add-on
communication module, which may be plugged in later, should there be a request from the consumer.
ANTI-TAMPER FEATURES IN METERS:
Smart Meters come with near real time alerts and have an effective data driven surveillance tool. No
longer is the utility, entirely, at the mercy of the unscrupulous consumers, fiddling with the
registration of the meters.
Going slow on the fortification of the Smart meter, with anti-tamper features, hitherto, unthinkable for
the vanilla Static meters, would be a welcome idea.
Moreover, the presence of the switch & the communication modules inside the Smart meters makes
the testing of some anti-tamper features in the meter & operation of the meter in certain conditions,
difficult.
MDM, HES & INTEGRATION:
MDM is essentially the heart of Smart Grid, in the sense that, most of the information is fed to the
smart system through the MDM by the Smart meters at site.
While the versatility of this software is to be carefully assessed, with its capability & scalability,
integration of the MDM, with the various on-going and new processes of the utility, assumes critical
importance for the smooth running of the Smart Grid. If not planned adequately, the integration costs
may become considerably higher.
Utilities, may explore multiple Head End Systems, talking to one MDM, especially, in a Hybrid
communication scenario, through readymade or custom-built Adaptors.
A complete IT vision of the utility needs to be chalked out prior to settling for the MDM software.
LEAST COST OR LEAST LIFE COST OF OWNERSHIP:
India has not bought meters with warranty beyond 5 years since long, but, things are set to change,
with the advent of Smart meters, when, we have a vision to continue with the meter for 10-15 years.
Quality, capability & upgradability of a Smart meter are very important.
Cost of ownership of a Smart meter for the utility is high compared to static meters. Cost of
replacement of a meter from circuit is significant too.
It is important for us, therefore, to try & look at the probable total ownership cost of a Smart meter
during procurement itself.
udayan.ganguly@rp-sg.in
41
7
A WIN-WIN FOR ALL:
AMI / Smart Metering is the pivotal piece of Smart Grid intervention in India.
It has the capability to touch all the stake holders, the consumer, the utility & the Government /
Regulator, be it through customer empowerment, reduced operational costs or through reliable,
quality power & customer satisfaction.
Beyond the declared 14 Smart Grid Pilots, an enabling push in the policy by the Government or a
tariff nudge from the regulator, could impact the distribution scenario significantly, in a manner that
may result in a “win-win” situation for all.
42
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
Transmission
andTransmission
Distribution
Integrated
and
System
for
on Analysis
of Power
& Distribution
Systems
including Smart
Grid,Evaluation
24-26 Feb. 2016,
New Delhi,
India
Distributed
Generation
“Global Trends in the Development of Power T&D System including Smart Grid”
J.SUH
S.Yoon
G.Jang
Korea University
Korea University
Korea University
Transmission and
Distribution Integrated
System for
Korea
KoreaAnalysis and Evaluation
Korea
Distributed Generation
J.SUH
Korea University
Korea
S.Yoon
Korea University
Korea
G.Jang
Korea University
Korea
SUMMARY
As the amount of distributed generation supplied to distribution systems has expanded,
neighboring distribution systems or even transmission systems have been more affected
according to penetration of distributed generation. However, until now, power system analysis
has been conducted separately for the transmission system and distribution system. This way
SUMMARY
of analysis has had no problem in the existing power systems. However, with the rising DG
in the
the need
to reflect
mutual interaction
hashas
elevated
and
Asconnection
the amount
of distribution
distributed system,
generation
supplied
to distribution
systems
expanded,
the
separated
method
became
unable
to
do
it
properly.
Transmission
and
distribution
neighboring distribution systems or even transmission systems have been more affected
integrated
analysis aims
to enablinggeneration.
mutual interaction
analysis.
this system
paper, analysis
a new
according
to penetration
of distributed
However, until
now,Inpower
methodology
to
evaluate
the
effect
of
distributed
generation
in
the
integrated
transmission
has been conducted separately for the transmission system and distribution system. This and
way
distribution
systems
using
on-line
data.
And
by
simulating
mutual
interaction,
which
could
of analysis has had no problem in the existing power systems. However, with the rising DG
not be observed in previous system, case study results shows the need for transmission and
connection in the distribution system, the need to reflect mutual interaction has elevated and
distribution integrated systems with distributed generation.
the separated method became unable to do it properly. Transmission and distribution
integrated
analysis aims to enabling mutual interaction analysis. In this paper, a new
KEYWORDS
methodology to evaluate the effect of distributed generation in the integrated transmission and
distribution
systemsPSS/E,
using SCADA,
on-line data.
And DAS,
by simulating
mutual interaction, which could
DG, Distribution.
SOMAS,
Transmission
not be observed in previous system, case study results shows the need for transmission and
distribution integrated systems with distributed generation.
KEYWORDS
DG, Distribution. PSS/E, SCADA, SOMAS, DAS, Transmission
Jaewans87@korea.ac.kr
43
Jaewans87@korea.ac.kr
1. Introduction
Recently as distributed generation (DG) has increased, the distributed power
generation has increasingly affected power systems. Large-scale DGs in distribution system
can affect transmission and other adjacent distribution system. However the monitoring,
analysis and evaluation associated with DG have been performed separately until now. In this
separate method, DG could be connected and operated to local power system without
considering its effect on other distribution feeder and transmission system. This paper
presents a new methodology to evaluate the effect of DG and recommend the optimal
operation of DG in the integrated transmission and distribution systems. In order to analyze
the effect of DG in the on-line environment, transmission and distribution integrated system is
connected to distribution automation system (DAS) and supervisory control and data
acquisition (SCADA). When Transmission and distribution integrated system analyze DG
connected power system, both SCADA and DAS system date is integrated automatically.
Case study, which is performed by using the real-time data of Jeonnam region, shows
effectiveness of integrated method.
2. Transmission and Distribution integrated System
In Korea power system, transmission system is monitored in real-time by SCADA
system. And Substation Operating results Management System (SOMAS) records and
provides the real-time data (Main transformer, transmission line, breaker, etc.) of the Korea
Electric Power Corporation (KEPCO) system from SCADA every 30 seconds. DAS monitors
and provides the operating conditions of the distribution system in real-time [1-2]. Feeder
remote terminal units, which are installed in distribution system, send the state data of
equipment to the main server via communication device. Transmission and distribution
system had been analyzed and operated separately in Korean power system. However, as
installed DG has increased, the necessity of transmission and distribution integrated analysis
is occurred [3-5]. Transmission and distribution integrated system acquires monitoring data
from SOMAS and DAS to process transmission and distribution integrated monitoring and
analysis. Fig. 1 shows the architecture of transmission and distribution integrated monitoring
and analysis system.
Fig. 1. System diagram of transmission and distribution integrated system
44
1
There are two types of transmission and distribution integrated system such as network
version and stand-alone version. In stand-alone version, operator has to install the
transmission and distribution integrated analysis program to stand-alone computer for
monitoring and analysis. And this version uses the power system data file which is extracted
from DAS and SOMAS. In network version, integrated sever acquire and store power system
data from SOMAS and DAS automatically. And every PC, which is connected in KEPCO
network, can run transmission and distribution integrated monitoring and analysis function
without installation of software. By using this network version, system operators in regional
headquarters can use transmission and distribution integrated monitoring and analysis system
easily.
A. Power system analysis
Transmission and distribution integrated monitoring and analysis system uses PSS/E engine
for power flow and fault current calculation. The system compares automatically with Korean
power system regulation and gives a violation warning to user. Following analyses, which are
hard to be performed with the conventional system which analyzes transmission and
distribution separately, can be possible in the transmission and distribution integrated system.
• Automated preliminary evaluation of DG connection
• DG connection impact on neighboring distribution system or transmission system
• Transmission system fault current contribution of DG in distribution system
• Phase angle information for distribution system normally open switch movement
B. Preliminary evaluation of DG connection
Main purpose of transmission and distribution integrated monitoring and analysis system is
to analyze DG connection impact. Before DG connection, System operator have to consider
the effect of DG on power system. In conventional system, operator evaluate the effect of DG
manually before it connected [6]. And the operator only consider the effect of DG on
distribution line which connected to DG and they ignore effect of DG on transmission and
other distribution system. However, in real operation, DG affects power quality of other
distribution or transmission system. As the DG penetration increase, those effect become a
considerable problem in Korean power system. When system operator receive request the
permission of new DG installation from electricity suppliers, transmission and distribution
integrated monitoring and analysis system evaluated the impact of new DG connection and
gives a warning to operator when violation of regulation is predicted. In this preliminary
evaluation transmission and distribution integrated analysis makes more accurate evaluation
possible by covering the entire power system and previously installed DG. And prevent the
DG installation which causes problem. This automated preliminary evaluation process
considers voltage fluctuation, short-circuit capacity, possibility of violation of voltage
regulation, and capacity regulation.
C. Determination of area of vulnerability
45
2
Voltage sag is one of the most significant problem for power system. And it can causing
damage to sensitive equipment in power system [7]. Transmission and distribution integrated
monitoring and analysis system can determine the area of vulnerability for voltage sag in
entire power system. In separated analysis, distribution system fault could not be considered
for area of vulnerability in transmission system. However those faults, especially in high DG
connected system, can cause the voltage sag in transmission system or other distribution
system. Transmission and distribution integrated monitoring and analysis system uses fast
method to determine an area of vulnerability [8] and integrated analysis results. By using
integrated analysis for area of vulnerability determination, unlike conventional system, area of
vulnerability in entire power system can be determined.
D. Application
Transmission and distribution integrated monitoring and analysis system is used for
distribution system optimization platform. Following applications, which are based on
transmission and distribution integrated analysis result, are included in the system.
 Optimal placement of ESS/FACTS
 OLTC Control
 Distribution system reconfiguration
More applications will be developed and applied to the transmission and distribution
integrated monitoring and analysis system by further study.
3. Case studies
For the case studies, real distribution network data of Jeollanam-do province and whole
transmission network date of the KEPCO systems are used. There are about 70 substations in
Jeollanam-do province. Seven major substations became targets for case study simulation.
Fault current, power flow, voltage fluctuation, preliminary evaluation of DG are simulated.
Simulations focused on the problems which had not been seen through previous
methodologies. The power flow simulation was performed in order to compare the difference
between conventional method and integrated method. In the analysis for only one distribution
system, the effect of DG in other distribution system couldn’t reflect to the power flow. This
makes difference of two analyses. The results for the fault current and voltage fluctuation
show that the effect of DGs was considered to other distribution system and transmission
system.
Simulation focused the problems which had not been seen through previous methodologies
to demonstrate the need for transmission and distribution integrated monitoring and analysis
system where DG input rose.
4.1 Comparison of power flow analysis result
The simulation was performed with same transmission system data in order to see the
difference between conventional method and integrated method. In conventional transmission
monitoring and analysis system, effect of DG in distribution system couldn’t reflected to
transmission analysis result. This makes difference of two analysis result. And in
conventional distribution analysis, substation which connect between distribution system and
transmission system is assumed as slack bus. Usually slack bus’s voltage is assumed as 1∠0°
46
3
which neglect effect of transmission system or other distribution system. Especially voltage
angle difference is huge because voltage angle is relative value.
Table 1 Comparison between conventional transmission analysis and integrated method
Substation
Transmission and distribution
integrated analysis
Magnitude
Conventional transmission analysis
Angle
Magnitude
(P.U)
Angle
(P.U)
Hwasun
1.0293
-16.39
1.03
-16.54
South Gwangju
1.0279
-17.58
1.029
-17.78
Songjung
1.0211
-15.97
1.0315
-17.13
Naju
1.0262
-16.81
1.0291
-17.2
Maewol
1.0216
-17.51
1.0223
-17.66
Hwajeong
1.0205
-17.93
1.0213
-18.09
Nogseong
1.0201
-18.03
1.0209
-18.19
Table 2 Comparison between conventional distribution analysis and integrated method
Automatic switch
number in
distribution system
Transmission and distribution
integrated analysis
Magnitude
(P.U)
Angle
Conventional distribution analysis
Magnitude
(P.U)
Angle
160028
1.025
-19.27
0.997
-0.77
160029
1.025
-19.28
0.997
-0.78
160030
1.024
-19.28
0.996
-0.78
160031
1.023
-19.29
0.995
-0.79
160032
1.021
-19.3
0.993
-0.8
4.2 DG impact on neighboring distribution system and transmission system
The Korea Electric Power Corporation (KEPCO) conducted influence assessment only on
each feeder when determining DG connection. However, if large scale distributed generation
is connected in distribution system, other neighboring distribution systems or transmission
systems would have a higher risk of a voltage problem. Previously, as the distribution system
was analyzed separately, such a problem had never been considered. In this case study, the
occurrence of a voltage problem in neighboring distribution systems or transmission systems
according to distribution system DG connection is simulated. Fig. 2 and Fig. 3 show the
voltage profile of Hwasun and South Gwangju distribution system regarding DG on Whasun
distribution system. The simulation result shows that if DG was supplied to the feeders below
Hwasun substation, then the feeders below Hwasun substation did not have a voltage problem
but the feeders below South Gwangju substation could have a voltage problem due to DG on
Hwasun distribution system. Such a possibility has not been noticed in previous analysis,
demonstrating the need for distribution and transmission integrated monitoring and analysis
system for DG supply consideration.
47
4
Fig. 2 Voltage profile of Hwasun distribution system
Fig. 3 Voltage profile of South Gwangju distribution system
4.3 Phase angle difference at both ends of normally open switch
Currently, KEPCO’s distribution system is structured in connection with other feeder in the
same substations or other substations via the normally open switches on the end of the
distribution line. By controlling such a switch, distribution systems can be more efficiently
operated or supply power during system failure or maintenance. But in closing the normally
open switches, the difference of phase angles on both overhead transfer buses are important.
If the phase angle difference becomes larger than a certain level, the switches become
impossible to connect. Through conventional distribution analysis method, which is
performed by each substation individually, it is possible to figure out both phase angles above
the switches in same substation but impossible to measure both phase angles above the
switches between different substations. In transmission and distribution integrated analysis,
such switch phase angles can be measured and phase angle changes according to different DG
supply can also be identified. Case study is performed by using the real data of distribution
systems below South Gwangju and Hwajeong substation. Table 3 shows information of the
distribution and normally open switch. Baekun distribution feeder is belong to South
Gwangju and Daemyung distribution feeder is belong to Hwajeong substation. And those two
distribution feeder is connected with normally open switch to supply electric power in
abnormal condition.
Table 3 Information of switch between two substations
Substaion 1
Bank No.
Feeder name
Substaion 2
Bank No.
Feeder name
South Gwangju
3
Baekun
Hwajeong
1
Daemyung
Table 4 shows the voltages and phase angles of both switch sides when DG output and
location is changed. Before DG connected, there is only slight difference exist between both
48
5
ends of switch. However DG output and location make increase of phase difference which
Table 4 Phase angle difference between both ends of switch
Baekun feeder
Magnitude
Daemyung feeder
Magnitude
Angle
(P.U)
Angle
(P.U)
Difference
Magnitude
(P.U)
Angle
Without DG
1.0164
-19.37
1.0062
-19.74
0.0102
0.37
9MW DG in South Gwangju
distribution
1.0273
-17.62
1.0097
-18.86
0.0176
1.24
30MW DG in South
Gwangju distribution
1.0302
-16.88
1.0112
-18.44
0.0190
1.56
9MW DG in Hwajeong
distribution
1.0200
-18.48
1.0179
-17.89
0.0021
-0.59
interrupt the close of normally open switch. As DG penetration has increased distribution
system operator has to consider the phase difference between both ends of normally open
switch before it close. And this case study shows the effectiveness of verifying the phase
difference changes due to DG output and location.
4.4 Contribution of DG to transmission system fault current
In the previous SCADA system, it was impossible to figure out the fault current
contribution of DG to transmission system when DG is connected on distribution system.
However, the transmission and distribution integrated monitoring and analysis system makes
possible to find out such fault current contribution. Table 5 shows the result of comparing the
sizes of transmission system’s fault current as 27MW distributed power was connected to
South Gwangju substation systems. In this case study result, not all substations showed a huge
increase in fault current but fault current largely increased in substations, which have large
amount of DG in distribution line, such as South Gwangju substations and Hwasun substation.
Table 5 Fault current comparison
Substation
Fault current
without DG (A)
Fault current with
DG (A)
Hwasun
18572.8
20033.1
South
Gwangju
17437.8
19879.5
Songjung
24416.4
24858.8
Naju
24332.7
25626.7
Maewol
17439.1
18748.6
Hwajeong
17029.2
18432.7
Nongseong
16969
18411.7
4. Conclusion
In conventional radial distribution system, the necessity of transmission and distribution
integrated analysis was less than DG connected distribution system. However, as DG
penetration has increased, DGs have a large impact on power systems. Those DGs make hard
49
6
to analysis and operate the power system, especially in distribution system. This paper
introduced a methodology to evaluate the effect on DGs in the transmission and distribution
integrated system on South Korea’s power systems. In addition, cases study which has been
impossible with the existing separated method was conducted. Case study results show the
necessity and effectiveness of transmission and distribution integrated analysis. More
applications such as distribution system reconfiguration, optimal placement of ESS/FACTS
and OLTC control based on transmission and distribution integrated analysis will be
developed by further research.
BIBLIOGRAPHY
Jaewan Suh received a B.S degree from the School of Electrical Engineering, Korea University, in
2011. He is currently pursuing Ph.D. degree at Korea University.
Yoon-Sung, Cho received a Ph. D. from Korea University, Korea in 2008. He worked a senior
engineer at LS Industrial Systems Co. Ltd from 2005 to 2012. He is presently an assistant professor in
the Department of Electric and Energy Engineering, Catholic University of Daegu. His research
interests include power system stability analysis, modeling, and energy management systems.
Gilsoo Jang received his B.S. and M.S. degree from Korea University, Korea. He received his Ph. D.
degree from Iowa State University in 1997. He worked in Electrical and Computer Engineering
Department at Iowa State University as a Visiting Scientist for one year and at Korea Electric Power
Research Institute as a researcher for 2 years. He is presently a Professor of School of Electrical
Engineering at Korea University. His research interests include power quality, power system dynamics
and control.
[1]
The development of optimal operating system in distribution networks based on distribution
automation. Final Report, Korea electric power corporation, Daejeon, Korea
[2] Photovoltaics, Dispersed Generation. (2011). IEEE Guide for Design, Operation, and Integration
of Distributed Resource Island Systems with Electric Power Systems.
[3] Song, Chong-Suk, Suh, Jae-Wan, Jang, Moon-Jong, & Jang, Gil-Soo. (2013). Development of a
Transmission/Distribution Integrated Analysis Hybrid Algorithm for System Operation Platform
Including Distributed Generation. Journal of the Korean Institute of Illuminating and Electrical
Installation Engineers, 27(1), 35-45.
[4] Sun, HB, & Zhang, BM. (2005). Global state estimation for whole transmission and distribution
networks. Electric power systems research, 74(2), 187-195.
[5] Sun, Hongbin, & Zhang, Boming. (2008). Distributed power flow calculation for whole
networks including transmission and distribution. Paper presented at the Transmission and
Distribution Conference and Exposition, 2008. T&# x00026; D. IEEE/PES.
[6] Corporation, Research Center of the Korea Electric Power. (2012). A study on the new technical
guidelines for interconnection capacity of distributed generations in distribution system.
Daejeon: Korea Tech.
[7] Goswami, AK, Gupta, CP, & Singh, GK. (2008). Area of vulnerability for prediction of voltage
sags by an analytical method in indian distribution systems. Paper presented at the India
Conference, 2008. INDICON 2008. Annual IEEE.
[8] Park, CH, & Jang, G. (2005). Fast method to determine an area of vulnerability for stochastic
prediction of voltage sags. IEE Proceedings-Generation, Transmission and Distribution, 152(6),
819-827.
50
7
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016on
– International Conference on Global Trends in the Development
GIS-BasedofDecision
Support
for Distribution
System
Improvement:
A Case
Power Transmission
& Distribution
Systems including
Smart Grid,
24-26 Feb. 2016, New
Delhi, India
“Global TrendsStudy
in the in
Development
of Power T&D
System including Smart Grid”
the PEA N1 Chiangmai
Thailand

GIS-Based Decision Support for Distribution System Improvement: A Case
1
, Dr.Titti
Saksornchai
, Siwapornpat
Tirapong Kasirawat
Study in1the
PEA N1
Chiangmai
Thailand Chomchavalit1
1. Provincial Electricity
 Authority (PEA)
THAILAND

Tirapong Kasirawat1, Dr.Titti Saksornchai1, Siwapornpat Chomchavalit1
1. Provincial Electricity Authority (PEA)
THAILAND

SUMMARY
Planning and designing for electrical substation, transmission and distribution to meet
the electrical demand from residential, commercial and industrial customers is one of the
greatest challenges faces by utilities. The system must provide a good quality of supply to the
users including safety and efficiency. In addition, it must be able to cover an emerging
SUMMARY
demand from new customers in the coming future.
In a large city with high growth and expansion rate, the utility has to solve a variety of
electrical
supply
i.e.for
high
peak demand,
qualitytransmission
of supply, voltage
drop, distribution
Planning
andproblems,
designing
electrical
substation,
and distribution
to meet
size upgrade,
network expansion,
etc. and
Thisindustrial
paper presents
a case
the transformer
electrical demand
from residential,
commercial
customers
is study
one ofofthe
Provincial
Electricity
AreaThe
1 (North)
Province
(PEA
N1) having
24,000
greatest
challenges
facesAuthority
by utilities.
systemChiangmai
must provide
a good
quality
of supply
to the
cct-km
of
22
kV
distribution
line,
50,000
cct-km
of
low
voltage
circuit,
and
43,800
installed
users including safety and efficiency. In addition, it must be able to cover an emerging
distribution
transformers
MVA
capacity)
to supply a total of 1,800,000 customers. From
demand
from new
customers(6.6
in the
coming
future.
thisIn
very
largecity
figure
of high
PEA growth
N1 network,
voltage andrate,
loadthe
measurement
collection
for of
a large
with
and expansion
utility has data
to solve
a variety
system improvement engineering requires excessive resources and is time consuming process.
electrical supply problems, i.e. high peak demand, quality of supply, voltage drop, distribution
As a result, timely system improvement to meet customer demands will be a very difficult
transformer
upgrade, network expansion, etc. This paper presents a case study of
task to be size
achieved.
Provincial From
Electricity
Authority
1 (North)
Chiangmai
Province
(PEA
N1) having
the above,
PEA Area
N1 has
developed
a GIS-based
decision
support
system24,000
for
cct-km
of 22 kVand
distribution
line,
50,000planning
cct-km and
of low
voltage
circuit, system
and 43,800
installed
transmission
distribution
networks
design.
The support
will import
distribution
supply meters
a total and
of 1,800,000
customers.
From
customertransformers
energy usage(6.6
dataMVA
from capacity)
SAP into to
customer
distribution
transformers
this database
very large
figure
of PEA
N1 network,
voltage
andarea
load
data collection
in GIS.
Each
distribution
transformer
service
canmeasurement
be shown graphically
by usingfor
system
engineering
requires
excessive
is time consuming
process.
Arcimprovement
GIS. Then, the
gathered energy
usage
data isresources
applied toand
determine
load condition
of
transformers
electrical density
in the interested
Based
on
As adistribution
result, timely
system and
improvement
to meetconsumption
customer demands
will bearea.
a very
difficult
this
derived
and
practical
information,
engineers
can
quickly
and
efficiently
make
a
decision
task to be achieved.
on From
systemthe
improvement
andN1
electrical
network and
substation decision
expansion,support
to copesystem
with afor
above, PEA
has developed
a GIS-based
changing
demand
in
any
service
area.
transmission and distribution networks planning and design. The support system will import
customer energy usage data from SAP into customer meters and distribution transformers
t_kasirawat@yahoo.com
database in GIS. Each distribution transformer service area can be shown graphically by using
Arc GIS. Then, the gathered energy usage data is applied to determine load condition of
distribution transformers and electrical density consumption in the interested area. Based on
this derived and practical information, engineers
51 can quickly and efficiently make a decision
on system improvement and electrical network and substation expansion, to cope with a
changing demand in any service area.
In conclusion, GIS-based decision support system is a great tool for distribution
system improvement planning and design. The support system will help a utility in reducing
cost, error and time usage in field data collection. As a result, utility can promptly respond to
growing demand and increase customer satisfaction.
KEYWORDS
GIS(Geographic Information System),Distribution System Improvement,Transformer Load
Analysis
52
1
1. Introduction
The Provincial Electricity Authority (PEA) is a government enterprise. PEA has 12
regional offices in four different regions, covering approximately 510,000 km or 99% of
nationwide service area. PEA mission is to supply electricity to end customers in a safe, high
quality and efficient manners. PEA has a total of 18 million customers and a maximum
demand of 18,596 MW consisted of residential (23%), commercial (25%), industrial (48%)
and others (4%). The electrical demand growth is about 4% annually in past 5 years (20112015)
Chiangmai is one of the largest cities in northern part of Thailand and is located in PEA
N1 service area. The PEA N1 distribution network contains 24,000 cct-km of 22 kV
distribution line, 50,000 cct-km of low voltage circuit, and 43,800 installed distribution
transformers (6.6 MVA capacity) supplying 1,800,000 customers. Chiangmai city has a very
high growth rate of customers and electrical demand. In Chiangmai city, the total customer is
250,000 approximately, which are supplied by 8,662 distribution transformers or equal to
1,959,730 kVA in capacity. In addition, an increase in private business in the city and air
conditioning load in business building and residential in summer can cause high loading
condition in distribution transformers. These may result in transformer overloading and
damage to distribution circuits which can cause power quality problem to customers and
customer complaints. To solve the problem, PEA N1 performs field measurements of peak
loadings on many distribution transformers, which have been selected randomly. However, it
is a very tedious and impractical practice to identify the overloaded transformers because just
a few percentages of transformers have been selected from several thousands. It also takes
time in investigation process and requires high resources in measurement activity. PEA N1
had been studied on DGA online and real time current/voltage monitoring project, however
the project including communication system for inspection and monitoring is very costly.
These all together put an effect on system planning, efficient operation, substation
construction and distribution system expansion.
Several researches have been made on Transformer Load Management (TLM). A
systematic methodology has been proposed to estimate the peak loadings of all distribution
transformers according to the energy consumption of customers served [1, 2], and display the
loading factors of all transformers on digital mapping [3–7]. In this way, the distribution
transformers with potentially overloading problems can be identified for loading reduction to
achieve preventive strategy of transformer damage. To achieve TLM more effectively, the
customers served by each distribution transformer have to be determined. An automated
distribution routing approach for rural areas was presented in [8], where the area studied to
build a new electric line was divided into different cost regions according to the difficulty of
building in each region. The obstacles or regions with high constraints to the construction of a
new line were treated as infinite cost regions. A further approach with the same methodology,
but using GIS, was presented in [9]. The automated mapping/facility management/geographic
information system (AM/FM /GIS) has been widely used in utilities for several years.
Because of the increasing demand for engineering design and operational analysis software, it
has become more and more important that AM/FM/GIS generate and maintain an engineering
analysis database [10-14].
2. GIS Based Decision Support System Design for Distribution System Improvement in
PEA N1 Chiangmai City
53
2
Nowadays, distribution network becomes more complex from many components and
variables getting involved in system study and analysis. System planning becomes a
challenging and difficult task in determining substation location and construction, transformer
sizing, number of supplied feeders and feeder routing. Recently, an extensive application of
geographical information systems (GIS) has enabled the representation of distribution systems
in more details. Therefore, the application of GIS can be a noble tool for supporting PEA
distribution system planning in order to obtain optimum result in both operation and planning.
The annual growth rate of economic development in Chiangmai city has been
continuously high for years. The distribution system is difficult to expand due to urban
physical characteristic, social and environmental concerns in the big city area. Therefore, it
becomes important for PEA N1 to investigate and build the decision based system for
distribution planning, system improvement and transformer load management. The support
system that is based on AM/FM/GIS will be more effective for load management of
transformers and help PEA engineer in analyzing transformer loading condition to avoid
transformer overloading or low utilization of less than 20%, and accelerate electrical system
expansion process to catch up with the increase in customer demand.
PEA N1 has been studying and designing GIS based decision support for distribution
system improvement in Chiangmai City. To become more productive and economical, the
development of the system must integrate IT platforms across many utility platforms. These
integrations typically involve both new IT systems and legacy systems and can include
standard mapping systems, GISs, customer information systems (CIS), outage management
systems (OMS), computer-aided design (CAD), transformer load management (TLM), and
others. These integrations with the aim of making the planning function more efficient and
effective can be achieved by importing useful information from customer database, metertransformer connection, electrical network diagram and mapping/facilities
management/geographic information system (AM/FM/GIS) database, customer billing data
from SAP system. The information platform of TLM is formulated by the integration of
customer energy consumption in SAP ,CIS, transformer and customer mapping in
AM/FM/GIS system and typical load patterns of customer classes. The peak loadings of all
distribution transformers are therefore estimated in a very effective manner based on the
service class and monthly energy consumption of all customers served by each distribution
transformer.
PEA GIS (Geographic Information System) database can be divided into 4 main layers
as follows.
1. High Voltage Transmission System (HV) – Transmission system and equipment in 69115 kV.
2. Medium Voltage Distribution System (MV) – Distribution system, transformers and
equipment in 22-33 kV.
3. Low Voltage Distribution System (LV) – LV system, meters and equipment in 220230 V.
4. Land base – Geographical information such as water resources, transportation,
boundary line, landmarks etc.
54
3
Fig 1 The composition of PEA GIS LAYERs
3. Structure and Major Function in GIS Based Decision Support
The GIS Based Decision Support for PEA N1 Distribution System Improvement and
Planning provides graphic functions for electrical network viewing including zoom-in/zoomout, system component details, searching of transformers including their location and other
electrical equipment. Four layers of the digital map are used in the application. The main
system function are described as following.
1. Distribution System Information
The distribution system information includes sub-functions as
1) customers data supplied by a transformer
2) customers data supplied by a feeder
3) transformers data in a feeder
4) transformer data for spot load
5) leading conductorsize and type data of a transformer
6) medium voltage electrical system data
2. Distribution Transformer Loading and Forecast of Transformer Overloading includes
sub-functions as below
1) forecast of overloading of transformers in a feeder;
2) forecast of overloading of transformers inside a substation
3) display present transformer loading condition and classified to 4 levels which are
0-20%, 20-80%, 80-100%, and overloading
55
4









Monthly electricity consumption
Transformer
Low voltage conductor
Meter
PEA’s service area

Fig 2 – Structure and work flow of GIS Based Decision Support System
The function provides PEA N1 engineers an easy way to understand and identify
possibly overloaded or light-loaded transformersat present and in the future.The function
accounts for the forecasting results from various types of customers. The peak load of a
specific transformer is evaluated by accumulating the loads of the customers that it serves,
and then judging if it is overloaded or light-loaded. The information involves transformer
rating, transformer loading, location, transformer ID, number of serving customer and
overload or light-load of transformers. This function gives PEA N1 engineers an effective and
convenient way to determine possibly overloaded transformers before they fail and possibly
light-loaded transformers to redesign LV electrical supply network or upgrade distribution
transformer size to become more effectively. The function offers distribution engineers a
friendly interface to set the overload and light-load values for transformers based on the
experiences of engineers.
56
5
Fig 3 - Sample display of GIS and distribution transformer load
Load factor and Maximum load of transformer can be calculated from
by m: month and k: customer type
3. Load Density and Service Area Map
The load distribution map overview function includessub-functions as listed below.
1) Display load density over the area
2) Display supplied area of a transformer, feeder, or substation
3) Display energy usage of customer and customer type in feeder or substation
57
6
Fig 4 Load density calculated in GIS Based Decision Support for Distribution System
Improvement
By using GIS based decision support, it is found that there are 693 distribution
transformers in the electrical supplied area of Chaingmai city that are currently more than
80% loading condition. In this number, 355 has been overloaded. Therefore, distribution
system improvement including transformer upgrade/replacement and circuit expansion are
required in some area. Besides, it is found that there are 782 distribution transformers in the
area that are less than 20% loading condition which requires a change and improvement on
electrical supply network to increase transformer utilization.
4. Conclusion
The design of the GIS Based Decision Support for Distribution System Improvement
application program, implemented on Chiangmai’s AM/FM/GIS system, with intranet
database system, has been introduced in this paper. The program not only provides detailed
information on facilities, but also offers loading behavior analysis of transformers.
Additionally, it will help electrical engineers on system evaluation and improvement on
distribution network, transformer and operation. The GIS Based Decision Support for
Distribution System Improvement also provides a friendly man-machine interface which
permits users to operate it more easily and conveniently than the old one. The program can
forecast the peak load of transformers and send an alarm before an overload or light-load
event does occurs. In addition, the improved GIS Based Decision Support for Distribution
System Improvement program adds several new sub-functions and modifies the others to
enhance its performance and operation efficiency. This application program has been running
and operating by distribution engineers in Chiangmai City district with rather encouraging
results. Operation experience shows that the program developed in this study can help
distribution engineers to manage and design a distribution system more efficiently and
conveniently. Especially, it provides quick and correct inquiry information to increase repair
efficiency and reduce outage time for maintenance engineers .The GIS Based Decision
Support for Distribution System Improvement not only support the distribution engineers
performance on distribution system planning, design and operation, but also provide essential
data for enabling application programs to do calculation and analysis.
58
7
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
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CHEN C.S.,T.T KU, C.H LIN ‘‘Implementation of a systematic distribution
transformer load management in Taipower’’(IET Generation Transmission &
Distribution, 2009, Vol. 3, Issue 3, pp. 286–295)
CHAO Y.T., LEE S.T., CHANG H.C., CHEN T.H.: ‘‘An improvement project for
distribution transformer load management in Taiwan’’( IEEE Trans. Power System.,
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J. XIO. Y. Yixin, C. Wang, S. Ji, and H. Jia, “A study and implementation of
distribution information management & analysis system” ( Proc.Power Syst. Technol.
Conf., 1998,vol. 2, pp. 1246–1250)
Yen-Ting Chao, Sheng-Ta Lee, Hong-Chan Chang, and Tsai-Hsiang Che ‘An
Improvement Project for Distribution Transformer Load Management in Taiwan”(
IEEE Trans. Power System, 2003,Vol. 18, No. 2, pp 875-881)
N. A. West, B. Dwolatzky, and A. S. Meyer, “Terrain based routing of distribution
cables”( IEEE Comput. Appl. Power, vol. 10,1997, pp.42–46)
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electrification planning tool,” ( Proc. IEEE Power Eng.Soc. Transmission Distribution
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for optimal planning in large distribution networks”( IEEE Trans. Power
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R. Ranjan, B. Venkatesh, D. Das,” A new algorithm for power distribution system
planning”( Electric Power Systems Research 62,2002,pp. 55–65)
H.L. Willis’’Spatial Electric Load Forecasting’’ 2nd ed., New York, MarcelDrekker
Inc, 2002.
Joel D. Melo, Edgar M. Carreno, Aida Calvino, Antonio Padilha-Feltrin, “Determining
spatial resolution in spatial load forecasting using a grid-based model”( Electric Power
Systems Research 111,2014,pp. 177–184)
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planning in the modern power systems era: Models, methods and future research”(
Electric Power Systems Research 121,2015,pp. 89–100)
8
59
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
CIGREAORC
Technical
Meeting
2016Smart
andGrid,
International
Conference
on Systems
of Power
Transmission
& Distribution
including
24-26 Feb. 2016,
New Delhi, India
on
“Global Trends in the Development of Power T&D System including Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
Demand
Response
Programin
in Thailand:
Thailand:
Demand
Response
Program
Practical Experiences and Lessons Learned
Practical Experiences and Lessons Learned
A. SODE-YOME
Electricity
Authority of Thailand,
A. Generating
SODE-YOME
System Control and Operation Division, THAILAND
Electricity Generating Authority of Thailand,
System Control and Operation Division, THAILAND
SUMMARY
Demand Response (DR) can play an important role by allowing customers to reduce load
consumption during critical periods. This paper presents demand response program that has
SUMMARY been implemented in Thailand in 2015. The paper firstly presents backgrounds of gas field
shutdown in Myanmar and in JDA-A18 together with their impacts to generation capacity.
Details of DR program including implementation procedure, target MW, timing, incentive
Demand Response
(DR)
play are
an described
important
role Performance
by allowing
customers
to reduce
load
price and
targetcan
customers
in details.
of DR
is then measured
by
using
the
actual
reduction
in
the
consumption
compared
to
the
baseline,
which
is
classified
consumption during critical periods. This paper presents demand response program that has
based on Time of Use electricity rate. The paper also discusses pros and cons of the present
been implemented
in Thailand in 2015. The paper firstly presents backgrounds of gas field
DR program together with future work. This information may be useful for electric power
shutdown in Myanmar
and toinimplement
JDA-A18
together
with
their impacts to generation capacity.
utilities who wish
DR program
in the
future.
Details of DR program including implementation procedure, target MW, timing, incentive
price and target
customers are described in details. Performance of DR is then measured by
KEYWORDS
using the actual reduction in the consumption compared to the baseline, which is classified
Response,
Gas Fieldrate.
Shutdown,
Baseline.
based on TimeDemand
of Use
electricity
The Incentive,
paper also
discusses pros and cons of the present
DR program together with future work. This information may be useful for electric power
utilities who wish to implement DR program in the future.
KEYWORDS
Demand Response, Gas Field Shutdown, Incentive, Baseline.
arthit.s@egat.co.th
60
1
Introduction
To ensure security and reliability on the electricity grid, electricity supply and demand
have to be matched at all time. Traditionally, electric utilities have called upon peaking power
plants to increase power generation to meet rising demand. In some cases, however, the
generation from these power plants cannot be increased due to some constraints such as the
shortage of fuel supply, transmission limits, instability of the power system, etc. Accordingly,
demand response which is one of demand side management can play an important role to
secure the power system by allowing customers to reduce load consumption during critical
periods, such as gas supply shortage, etc.
Demand Response (DR) is one of Demand Side Management (DSM) that is used to
promote the efficient use of electricity at end-users by changing load patterns of customers in
short-term in response to price incentive or a price signal from the electricity hourly market
[1],[2]. According to the Federal Energy Regulatory Commission, Demand Response (DR) is
defined as: “Changes in electric usage by end-use customers from their normal consumption
patterns in response to changes in the price of electricity over time, or to incentive payments
designed to induce lower electricity use at times of high wholesale market prices or when
system reliability is jeopardized” [2]. DR use the flexibility of load demand that customers
are willing to modify their consumption patterns of electricity by altering the timing, level of
demand, and the total electricity consumption. In short term, DR can be used when security
of generation supply are the major concern. In long term, it can be used to reduce investments
in building additional generation capacity to serve the load demand at peak hours (few days in
summer in case of Thailand).
This paper presents Demand Response Program in Thailand that has been implemented in
2015. The paper is structured as follows: Section 2 briefly describes Thailand power system.
In Section 3, DR program in 2015 are presented in details including organization,
implementation procedure, baseline calculation and compensation rate. An example of
practical DR is also presented. Finally, in Section 4 a summary of the main conclusion is
presented.
2
Thailand Power System
2.1 General Information
Thailand is a country located in the southeastern region of Asia. Electric Supply
Industry (ESI) in Thailand is a single buyer consisting of three utilities, namely the Electricity
Generating Authority of Thailand (EGAT), Metropolitan Electricity Authority (MEA) and
Provincial Electricity Authority (PEA). EGAT is responsible for generation and transmission
grids of high voltage levels, while MEA and PEA are responsible for distribution levels. ESI
is regulated under Energy Regulatory Commission or Regulator [3],[4]. Figure 1 shows ESI
of Thailand including Generation, Transmission, distribution and Regulator. From Figure 1,
EGAT is the only buyer of the electricity from Independent Power Producers (IPPs), Small
Power Producers (SPPs), while PEA and MEA are distribution utilities. Regulator or Energy
Regulatory Commission is the independent authority who regulates the electricity market in
Thailand. Power Stations and 230/500 kV Transmission Lines are distributed throughout
system. In the following subsections, Generation System, Transmission System, Load
Demand, gas supply infrastructure are briefly presented.
61
1
Regulator
Generators
EGAT Owned
EGAT
Transmission
System
IPP
MEA
MEA’s Customers
PEA
PEA’s Customers
Ring-Fenced
System
Operator
Imported
SPP
EGAT’s Direct Customers
SPP’s Direct Customers
Figure 1: Market Structure of Thailand Power System.
2.2 Generation System
Electrical power system of Thailand is a medium size power system, compared to
those in US, China, Japan, etc. As of December 2014, the total installed capacity of system is
34,668.03 MW [3] including generation from EGAT power plants, IPPs, SPPs and power
neighboring countries i.e. Lao and Malaysia. Major fuel resource used in Thailand is gas
which shares about 69.80% of fuel consumption of electricity supply in the country. Figure 2
illustrates the fuel diversification of Thailand [2].
EGAT and IPPs are major contributors of generation in Thailand. In 2014, EGAT is
the major supplier of the generation for the whole country about 44.66%, whereas IPPs, SPPs
and purchased power share 37.98, 10.43 and 6.93 percent, respectively [3]. Most of IPPs are
combined cycled and thermal plants. SPPs are the third contributors in generation with only
27.46% (10.43/37.98) in generation compared to IPPs. Thailand imports power from Lao via
230 and 500 kV transmission lines with maximum capacity of about 3000 MW through the
Northeast region of the country. Thailand exchanges power in the south, via HVDC
transmission system with the maximum transfer capacity of 300 MW, both directions.
Hydro Fuel Oil
9.50% 0.93%
Diesel
0.13%
Coal
17.60%
Renewable
Energy
2.32%
Gas
69.80%
Figure 2: Fuel Diversification of Generation in Thailand in 2014.
62
2
2.3 Transmission System and Load Demand
The transmission system of Thailand is a fully connected system having the highest
voltage level of 500 kV. These 500 kV transmission lines are designed to carry bulks of
power from generation sources located in the North, East and West to the major load centers
located in the capital city and central area. The 230 kV lines are distributed throughout the
country. The system may have a problem of angle stability in the south due to lack of
generation facilities in the region. Figure 5 shows load in each Region in Thailand. It is
observed that Central region are the source while Bangkok and vicinity area is the major load
of Thailand.
The highest load demand of Thailand occurred on April 23rd 2014 during the summer
season. The maximum electrical demand was 26,942.10 MW, occurred at 14.26 hrs[1].
Figure 6 shows monthly peak energy in 2013 and 2014. The peak energy in Thailand is
occurred in summer season. The maximum daily energy consumed for Thailand is 574.384
GWh occurred on April 23rd, 2014 and the energy demand for the 2014 is 177,580 GWh [1].
Figure 3 shows Generation/load demand in each region and gas pipelines in Thailand.
Generation is concentrated in central regions of Thailand where the gas pipelines are
distributed.
In Thailand, gas is supplied from three main sources from: 1) Gulf of Thailand, 2)
Myanmar and 3) JDA-A18 located in the border between the south of Thailand and Malaysia.
Figure 3 shows the gas pipeline in Thailand. From Figure 3, it is noticed that there are three
gas wells in Myanmar: Yadana, Yekakun and Zawtika. These gas wells however have
different gas heating values. Shutting down one of these gas wells may impact overall
heating value of gas from Myanmar. These heating value may exceed the operating limit of
heating values at power stations, thus they may have to shut down to avoid damage to
equipment. Gas source in JDA-A18 will impact the generation in the south of Thailand,
where the generation is matched the load demand. If the gas in the south is shutdown, some
generators in the south may have to change the fuel to Diesel.
In order to cope with emergency situation during gas field shutdown and the high
generation cost of diesel fuel, DR response has been introduced since 2015. In the next
section, implementation of DR program is summarized.
3
Demand Response Program in Thailand
3.1 Details of DR Program in Thailand
The main objective of DR in Thailand is to increase reliability and security of the
electricity supply during gas field shutdown in Myanmar (shared about 40% of total gas
supply) and in Thailand-Malaysia Joint Development Area (JDA-A18). Before activating DR
program, potential of Demand Response in Thailand is studied first. In the study funded by
EGAT, it is found that the reduction of power consumption in industrial and business sectors
are 300-960 and 230-1100 MW, respectively. This information has confirmed the possibilities
of load reduction at large consumers.
In order to activate DR program, the Energy Regulatory Commission (ERC) has set up
working committee that is composed of EGAT, PEA, MEA and ERC. This committee is a
policy maker who helps ERC in making decision to activate DR. EGAT, PEA and MEA acts
as load aggregator who collect amount of MW from their own customers. Figure 4 shows the
structure of organization for DR program.
63
3
Yadana
Zawtika
Yetagun
JDA
Figure: 3 Generation/Load Demand in each Region and Gas Pipelines in Thailand.
Policy Maker
ISO
Operator
Participant
Aggregator
Aggregator
MEA’scustomer
PEA’scustomer
Aggregator
EGAT’s
customer
Figure 4: Organization Structure of DR in Thailand.
64
4
Procedure of DR is summarized in Figure 5. From Figure 5, the study is carried out in
advance to confirm the need of DR (about 4 month before the shutdown dates). Campaign of
the DR program is done by ERC and load aggregators. Target MW, timing, baseline
calculation and compensation rate are proposed by working committee before getting
approval from ERC. During the DR program, load decrease is computed and illustrated at the
end of the day by load aggregator. After the program, baseline and compensation are
calculated by load aggregators.
3.2 Examples of DR Program in 2015
In order to understand the implementation of DR program in Thailand, example of DR
program during gas field shutdown in Myanmar in 2015 is given. The purposes of Demand
Response program are 1) to decrease power demand to avoid high generation costs from
diesel fuel and 2) to continue DR program from 2014. The detail of DR program is as follows:
Date of operation:
Period of operation:
Goal:
Compensation Rate:
Costumers:
Application
submission:
Application Period:
Application Result:
10, 17, 18 and 20 April 2015
10.00-12.00, 14.00-17.00 and 19.00-22.00 Hrs
500 MW per period (Application is between 450-700 MW)
3 baht/kwh but not exceed 48 million baht totally
Type 3, 4 and 5 which have AMR meter and reduce more
than 100 kW each period.
EGAT, MEA and PEA
23-31 March 2015
3 April 2015
The gas field shutdown is scheduled before and after the long holiday “Songkarn day”.
During the program, many customers are interested to participate in DR program as it can be
seen from the application during 12 periods (4 days, 3 periods a day), which is higher than the
target. The first day after the long holiday is the most interested day as the customers may
extend their holiday in order to join the DR program.
3.3 Baselines Calculation and Compensation
Baseline is the normal MW use of the load demand for each customer. It is calculated by
averaging the load value by gathering data every 15 minutes 10 days before DR program.
During the DR program, actual MW and the value of Baseline are compared for each
customer every 15 minute to compute the compensation for DR program. Net energy
reduction (kWh) during 4 hours of each customer on the day is used to compute the
compensation. Total energy reduction is compensated if it can reduce more than 50% of
agreement. (reduce energy from 50% to 150% of the baseline).
65
5
Study the shutdown plan of Yadana Field whether it affects the
reliability of power system.
NO
Not Proceed
YES
4 months before
shutdown
Campaign for Demand Response Implementation
Define DR Target Group
3 months before
shutdown
Define baseline calculation and data collection
Liaise with related sectors for discussing with target group
Define compensation rates and conditions
2 months before
shutdown
Provide the system for monitoring demand decrease
Monitor and make a report on demand decrease
Summarize the achievement and pay compensation
END
During shutdown
Within 3 months
after shutdown
Figure 5: Procedures of DR in Thailand.
Figure 6: Application of DR from Day 1 (Period 1-3) to Day 4 (Period 10-12).
66
6
Profile energy use of each
participant for 10 days before
Demand Response program.
Average
Baseline
Compare profile baseline and
actual use since the first day
of program.
Actual Use/Demand
Figure 7: Base Line and Actual Use for DR Program.
4
Conclusion
Demand Response program is officially implemented in Thailand since 2015 by DR
working committee comprising of ERC, EGAT, PEA and MEA. The DR program is
publicized in advance by informing the goal and date of the program to the public and target
customer. EGAT, PEA and MEA are gathering data of energy use, monitoring and calculating
compensation for energy reduction. Demand Side Management division may be the center of
information and service to customers.
BIBLIOGRAPHY
[1]
[2]
ERC, “Development of Demand Response in Thailand”, (2014)
Balijepalli Murthy, Pradhan Khaparde "Review of Demand Response under Smart Grid
Paradigm", (IEEE PES Innovative Smart Grid Technologies. 2011).
[3] Statistical Report, “System Control and Operation Division”, (2014).
[4] Statistical Report, “System Control and Operation Division”, (2013).
[5] Tempo Electricity Tariff –France, “Review of Load Management and Demand Response in
Australia” , P. 45-46.
[6] Review of Load Management and Demand Response in Australia, ETSA Utilities Residential
Direct Load Control Trial –Australia, P. 38.
[7] SCE, Time of Use Base Interruptible Program, Commit to reduce electricity use in time of
critical need, www.sce.com. link
[8] PG&E, Base Interruptible Program, BIP, www.pge.com.
[9] FLORIDA POWER & LIGHT COMPANY, Commercial Industrial Demand Reduction Rider,
CDR, www1.eere.energy.gov/femp/financing/eip_fl.html, P. 82-84.
[10] NYISO, 2013, Emergency Demand Response Program Manual, version 7.1.
[11] Rahimi et al., 2010, Overview of Demand Response under the Smart Grid and Market
Paradigms.
7
67
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global
Trends
in
the
Development
Power T&D
System
including
Grid”
CIGRE- AORC Technical Meeting 2016 – of
International
Conference
on Global
Trends Smart
in the Development
ofCIGREPower Transmission
Systems
including2016
Smart Grid,
Feb. 2016, NewConference
Delhi, India
AORC& Distribution
Technical
Meeting
and24-26
International
on
Smart Grid
Scheme
Intelligent Load
Prioritization
for Industries
“Global
Trends
in theusing
Development
of Power
T&D System
including Smart Grid”
Muhammad Ehsan, Kevin Ark Kumar, K Gnanasekaran, V Ratchanniya Samuel
Bharat Heavy Electricals Limited, Tiruchirappalli
India Load Prioritization for Industries
Smart Grid Scheme using Intelligent
Muhammad Ehsan, Kevin Ark Kumar, K Gnanasekaran, V Ratchanniya Samuel
Bharat Heavy Electricals Limited, Tiruchirappalli
India
SUMMARY
Several industries have implemented grid connected solar PV power generation systems to
fulfil their SPO and as a co-yield, they are meeting their partial power demands. Today smart
grid systems are reliable and improve efficiency and security of electrical networks by making
the grid controllable with continuous monitoring and automation. The smart grid system
schedules and manages electrical demand in a reliable, economic, and sustainable manner.
SUMMARY
The smart grid system also possess demand response capacity to support and stabilize
electrical consumption with electrical supply. The smart grid system has the potential to
Several
industries
have implemented
connected
solar PVandpower
generation
to
integrate
new technologies
to enablegrid
energy
storage elements
the large-scale
usesystems
of
fulfil electrical
their SPO
and as a co-yield,
they are meeting
their
demands.
Today smart
installations,
including transportation
systems
likepartial
electricpower
vehicles.
Proper control
grid systems
are reliable
and improve
efficiency
andthe
security
of electrical
networks
by making
and management
schemes
are imperative
to utilize
available
electricity in
an efficient
manner
and to avoidwith
overdrawing
powermonitoring
beyond the contractual
demand. Through
this paper,
the grid
controllable
continuous
and automation.
The smart
grid system
a novel
grid scheme
withdemand
intelligent
prioritization
method
proposed formanner.
schedules
andsmart
manages
electrical
in aload
reliable,
economic,
andis sustainable
industries with grid integrated PV plants. A simulated smart grid scheme is proposed for
The smart grid system also possess demand response capacity to support and stabilize
implementation on an experimental basis in Tiruchirappalli unit of Bharat Heavy Electricals
electrical
consumption
with
electrical
The smartandgrid
system hasenterprises,
the potential to
Limited
(BHEL), one
of the
largest supply.
Indian engineering
manufacturing
integrate
new
technologies
to
enable
energy
storage
elements
and
the
large-scale
catering to the needs of energy, industry and infrastructure sectors. This paper presents the use of
electrical
installations,
including
transportation
systems
electric vehicles.
Proper control
design
aspects, operational
features
and various
controllike
methodologies
with simulation
results.
Such
a
smart
grid
scheme
enables
industries
to
have
a
greater
control
over
theirefficient
and management schemes are imperative to utilize the available electricity in an
electricity
consumption
and also
ensure
compliance
to demand-side
regulations.
manner
and to avoid
overdrawing
power
beyond
the contractual
demand.
Through The
this paper,
simulation results prove the proposed scheme is feasible and reliable for large scale
a novel smart grid scheme with intelligent load prioritization method is proposed for
integration in industries.
industries with grid integrated PV plants. A simulated smart grid scheme is proposed for
implementation
on an experimental basis in Tiruchirappalli unit of Bharat Heavy Electricals
KEYWORDS
Smart
Grid;
Load
Prioritization;
Systems;
Renewable
resources and manufacturing enterprises,
Limited (BHEL), one
of the Fuzzy
largest
Indian
engineering
catering to the needs of energy, industry and infrastructure sectors. This paper presents the
design aspects, operational features and various control methodologies with simulation
results. Such a smart grid scheme enables industries to have a greater control over their
electricity consumption and also ensure compliance to demand-side regulations. The
simulation results prove the proposed scheme is feasible and reliable for large scale
muhammad@bheltry.co.in
integration
in industries.
KEYWORDS
Smart Grid; Load Prioritization; Fuzzy Systems; Renewable resources
68
1. INTRODUCTION
Growth of manufacturing sector is a key indicator of socio-economic development and
prosperity of a country. As such, better energy infrastructure and its growth are important to
sustain the pace of industrial development. Use of solar photovoltaic power in industries is
seen to be growing in a rapid pace from different case studies [1-3]. Increase in power
demand, power reliability, reduction in greenhouse gas emission etc., are the main reasons for
using solar power. Apart from that, industries are also mandated by central and state
electricity regulatory commissions for solar purchase obligations (SPO) to promote solar
energy across the state and to reduce their carbon footprint. Several industries have
implemented grid connected solar PV power generation systems to fulfil their SPO and as a
co-yield, they are meeting their partial power demands. BHEL Tiruchirappalli, one of the
major engineering enterprises in India has also initiated the use of solar photovoltaic power
through various grid connected projects to meet more than one-third of its maximum demand.
Presently the industrial power distribution network has an abundant accord of intelligence and
these network forms a beginning for the development of Smart Grid schemes. In the literature,
the smart equipment are provided with localized programs, minimum processing capacity,
and local data and measurement results are obtained from the equipment for the process.
Smart devices in multi-vendor systems communicate and operate industry-wide with each
other [4, 5]. Most of the features of Smart Grid concept are also desirable in an industrial
power supply network, which can form part of a wide Smart Grid [6-8]. Power density inside
the factory site is often very high and the distribution network is heavily loaded. It is built on
an advanced architecture and regulated to facilitate the integration of all involved energy
resources. Power demand in the industrial distribution network may be considerable large (in
a range of hundreds of MW). Most of the features of Smart Grid concept are also desirable in
an industrial power supply network, which can form part of a wide Smart Grid. Power density
inside the factory site is often very high and the distribution network is heavily loaded. A
novel smart grid scheme with intelligent load prioritization method is proposed for industries
with grid integrated PV plants. The schematic of the proposed smart grid networking scheme
for Industries is shown in Fig.1.
Fig. 1. Smart grid scheme for Industries
69
1
The proposed smart grid scheme continuously compares the industry’s demand with PV
power generation and grid. Whenever there is a reduction in PV power generation and an
increase in demand is simultaneously envisaged by the scheme, load prioritization program is
activated and production centres are made to curtail certain percentage of their loads. This
will help the industries to utilize the solar PV power to a maximum extent and to avoid penal
charges for crossing the sanctioned maximum demand. Due to high level of nonlinearity in
the system, a model-free optimization algorithm is used. Fuzzy systems solve problems with
imprecise and incomplete data, and can model nonlinear functions of random complexity.
Fuzzy systems has the advantage of effortless programming and provide stable results. The
flow chart of the load shedding process is shown in Fig.2. For load shedding prioritization,
fuzzy logic system is used and this will prioritize the loads for shedding to avoid overshooting
the contractual demand. The loads will be resumed back using the optimization algorithm,
once PV power generation improves. This scheme helps to integrate the existing and
upcoming grid connected PV generation systems for smart power scheduling operations of the
unit. This paper presents the fuzzy approach for load prioritization methodologies with
simulation results.
Fig. 2. Flow chart for load prioritization
2. FUZZY BASED LOAD SHEDDING PRIORITIZATION
The load prioritization consists of resource allocation to production activities that optimizes
the production performance measures. When scheduling production activities there are some
resource conflict and in order to solve this conflict, a priority is calculated for the activities
considering time, electrical power rating of the machinery and criticality of the production
70
2
activity. Mapping these parameters with load prioritization is highly non-linear and models
could become uncertain. Considering the non-linearity and model uncertainty, a fuzzy based
load prioritization approach is proposed in this paper. In this paper, three important
production centres of tubular shop of a boiler manufacturing industry is considered. The three
important work centres are 1) auto welding machines; 2) CNC tube bending machines and 3)
tube preparation machines, which are very essential in the boiler manufacturing process. The
time of the operation is critical input parameter to decide on the load prioritization. For
example in the start hours of the shift, importance will be given to tube preparation rather than
welding functions. Similarly during peak hours of operation welding work centres and CNC
tube bending machines will be given top priority as compared to tube preparation machines.
Yet another parameter that affect the decision making process in load prioritization is the
criticality of the production. The criticality of the production depends on the availability of
job materials and scheduled loading of work centres. The criticality can be fed online to the
system though enterprise resource planning (ERP). Apart from that, the maximum power
demand needs to be monitored continuously and it should be taken as an input for load
prioritization.
Fig. 3 Fuzzy architecture for load prioritization
The architecture of the fuzzy logic controller used in this proposed system are shown in Fig.
3. The crisp values of inputs such as time, maximum demand and activity are fuzzified into
corresponding fuzzy values by input fuzzification. Fuzzy rules are established with the
knowledge of relationship between inputs and outputs based on a set of IF-THEN rules. The
fuzzy values of input and fuzzy rules are fed to the fuzzy inference engine, which consists of
computational algorithms based on the fuzzy inputs and fuzzy rules and compute the output
truth values. The output truth values are defuzzified into real time values in output
defuzzification. The real time values of production load priority are then processed by the
microcontroller to control the proposed system. To design a fuzzy controller, the range of
possible values, universe of discourse, of the real time input variables and real time output
variables are to be detailed. In fuzzy set theory, the membership functions are used to map the
universe of discourse into fuzzy values in the range 0 to 1. In general, the shape of the
membership function is triangular, trapezoidal, Gaussian or sigmoidal.
The fuzzy
membership functions of the input and output variables are shown in Figures 4, 5, 6, 7, 8 and
9. The rules establish a relationship between the input domains and output domain. The
71
3
relationships are defined using IF-THEN statement, based on a proper analysis on the input
numerical values and expert’s opinion. The rule base of the proposed system is tabulated in
table I.
Fig. 4 Input variable ‘Time of the day’
Fig. 7. Load Priority of Welding machines
Fig. 5. Input variable ‘Maximum Demand’
Fig. 8. Load Priority of Bending machines
Fig. 6. Input variable ‘Production Activity’
Fig. 9. Load Priority of Tube Preparation
INPUT
START
MAX.
DEMAND
VERGE
START
TABLE 1 FUZZY RULE BASE
OUTPUT (PRIORITY)
AUTO WELD
CNC BENDING
CRITICAL
LEAST
MODERATE
TUBE
PREPARATION
TOP
VERGE
NON-CRITICAL
LEAST
MODERATE
TOP
START
ALARMING
CRITICAL
MODERATE
LEAST
TOP
START
ALARMING
NON-CRITICAL
MODERATE
LEAST
TOP
PEAK
VERGE
CRITICAL
TOP
MODERATE
LEAST
PEAK
VERGE
NON-CRITICAL
MODERATE
TOP
LEAST
PEAK
ALARMING
CRITICAL
TOP
MODERATE
LEAST
PEAK
ALARMING
NON-CRITICAL
MODERATE
TOP
LEAST
OFF PEAK
VERGE
CRITICAL
TOP
LEAST
MODERATE
OFF PEAK
VERGE
NON-CRITICAL
TOP
MODERATE
LEAST
OFF PEAK
ALARMING
CRITICAL
MODERATE
TOP
LEAST
OFF PEAK
ALARMING
NON-CRITICAL
TOP
LEAST
MODERATE
TIME
ACTIVITY
72
4
3. RESULTS AND DISCUSSIONS
The input values provided by the appropriate sensors are processed using the rule base to
determine the load priority. The response surface of the input-output relations are shown in
Fig.10 (a) to (i).
(a)
(b)
(c)
(d)
(e)
(f)
73
(g)
(h)
(i)
Fig. 10. Surface plots of input-output variables
The figures shows the way the proposed system will respond to different working conditions,
for instance if the operation is done during 8:30 hrs and the activity is non critical, then the
load scheduling priority proposed by the fuzzy logic control (FLC) is 15% of welding
machines, 50% of CNC bending machines and 84% of tube preparation machines. This means
most of the auto welding machines can be switched OFF and this clearly shows that during
the start of the shift, material preparation should be of prime importance and hence during
load shedding, material preparation will be given the least priority. Thus the simulation results
prove that the proposed fuzzy system is capable of generating reliable and stable control
signals.
5. CONCLUSION
A smart grid scheme enables industries to have a greater control over their electricity
consumption and also ensure compliance to demand-side regulations. This paper outlined a
scheme for optimizing power demand in industries through soft computing technique. The
load prioritization of different work centres is carried out using fuzzy logic system. The
simulation results prove the proposed scheme is feasible and reliable for large scale
integration in industries.
74
6
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Tariq Samad and K. Sila. “Smart grid technologies and application for the industrial
sector” (Computers and Chemical Engineering 47 July 2012 pages 76-84).
K.A. Kumar, K. Sundareswaran, P.R. Venkateswaran. “Performance study on a grid
connected 20kWp solar photovoltaic installation in an industry in Tiruchirappalli
(India)” (Energy for Sustainable Development 23 December 2014 pages 294-304)
K. Sundareswaran, KA Kumar, PR Venkateswaran. “Dual input autonomous solar
photovoltaic powered motor drive system for industrial applications” (Journal of
Renewable and Sustainable Energy 7 (1), January 2015 pages 013128 1- 7)
ABB working group. “Smart Grid in Industrial Networks” (ABB Industrial Smart Grid
February 2011)
Enrique Santacana. “The Importance of Standardizing the Smart Grid” (Electric-lightpower. Volume-87. Issue 4)
Manuela Sechilariu, Baochao Wang and Fabrice Locment." Building-integrated
microgrid: Advanced local energy management for forthcoming smart power grid
communication” (Energy No. 59 January 2013 pages 236–243)
Konark Sharma and Lalit Mohan Saini. "Performance analysis of smart metering for
smart grid: An overview" (Renewable and Sustainable Energy Reviews No. 49 May
2015 pages 720–735)
M. Welscha,M. Howells, M. Bazilian, J.F. DeCarolis, S. Hermann, H.H. Rogner.
"Modelling elements of Smart Grids Enhancing the OSeMOSYS (Open Source Energy
Modelling System) code" (Energy 46 September 2012 pages 337-350)
75
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC
Technical
Meeting 2016 –of
International
on Globalincluding
Trends in the Development
“Global Trends
in the
Development
PowerConference
T&D System
Smart Grid”
Smart Grid Deployment in CESC Transmission and Distribution System
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
SANTANU SEN
CESC Limited
INDIA
Smart Grid Deployment in CESC Transmission and Distribution System
SANTANU SEN
CESC Limited
INDIA
SUMMARY
“Smart Grid” is being talked about around the world now a days. Definition of Smart Grid is
ever changing. Smart Grid has a huge range of areas where electric utility can participate. The
basic requirement is to provide electricity with enhanced efficiency, low waste, low cost, low
impact on environment pollution, involving consumers in the process for better world of the
future generations with enhanced life of the earth. Conversion of conventional utility to a
Smart Grid compliance is a journey which requires Efficiency on Strategy, Management,
Regulator’s & Consumers participation, Grid Operations, Work & Asset Management, Value
SUMMARY
Chain integration, Technology, Social & Environment etc.
“SmartCESC
Grid”Limited
is being
talked
about
around
the world
Definition
of Smart
is the
oldest
Electricity
Utility
in India.now
Cityaofdays.
Kolkata
was powered
with Grid is
ever changing.
GridYork
hasand
a huge
range
of areas
where electric
utility canCompany
participate. The
ElectricitySmart
after New
London.
CESC
is transforming
from a Technology
to Service Company,
whereelectricity
Customer centricity
is at the
focal point.
Thewaste,
century
basic requirement
is to provide
with enhanced
efficiency,
low
lowoldcost, low
company
has
many
legacy
systems
in
both
technology
and
HR
front.
Smart
Grid
migration
impact on environment pollution, involving consumers in the process for better world of the
would be harder than the Utilities which are much younger than us with green field projects.
future generations
with enhanced life of the earth. Conversion of conventional utility to a
Over the years, we have implemented many high end projects to cater to the basic
Smart requirement
Grid compliance
is a journey
which requires
Efficiency
Strategy, Management,
of our customers
i.e. uninterrupted
quality power
supply.on
Modernisation
of the
Regulator’s
&
Consumers
participation,
Grid
Operations,
Work
&
Asset
Management,
Grid has been the priority. SCADA & Automation has yielded good results through
robust Value
optical fibre based
communication
AMR of DTs
Chain integration,
Technology,
Socialsystem.
& Environment
etc.& HT consumers have yielded a
localised OMS. Our in-house IT expertise has developed many customer centric applications
including
andElectricity
internet based
services.
There isCity
major
area was
is to powered
reduce
CESC Limited mobile
is the apps
oldest
Utility
in India.
of thrust
Kolkata
with
AT&C loss through application of technologies. The OT applications have applied with basic
Electricity
after
New
York
and
London.
CESC
is
transforming
from
a
Technology
Company
security features. We are in the process of IT & OT convergence. Smart Grid feasibility study
to Service
Company,
centricity
is at survey.
the focal
point.
century old
has been
completedwhere
by US Customer
based consultant
with SGMM
We have
plan The
to deploy
smart
AMIsystems
system. in
Weboth
are technology
working on digital
engagement
of consumer
company
hasmeter
manywith
legacy
and HR
front. Smart
Grid migration
programme.
As
a
part
of
DR/DSM
programme
we
are
in
the
process
of
carrying
out
pilotprojects.
would be harder than the Utilities which are much younger than us with green field
projects
on
DELP,
utilisation
of
captive
DG
sets
of
Consumers,
control
of
consumer
loads
Over the years, we have implemented many high end projects to cater toetc.
the basic
through various eminent vendors. Smart Grid control centre is being considered as our next
requirement
our will
customers
i.e. uninterrupted
quality
supply.
Modernisation
project of
which
be implemented
very soon in which
wepower
are going
to include
GIS centric of the
Grid has
been the
SCADA
& Automation
hasplanning,
yieldedenergy
goodaudit
results
workflow
/ LTpriority.
OMS / asset
management
/ FFM / network
etc. through robust
optical fibre based communication system. AMR of DTs & HT consumers have yielded a
santanu.sen@rp-sg.in
localised
OMS. Our in-house IT expertise has developed many customer centric applications
including
mobile apps and internet based services. There is major thrust area is to reduce
KEYWORDS
AT&C loss through application of technologies. The OT applications have applied with basic
securitySGMM
features.
We Grid
areMaturity
in theModel
process of IT & OT convergence. Smart Grid feasibility study
:
Smart
DSM
/ DR:
Demand
Side
Management
/ Demand
Responsewith SGMM survey. We have plan to deploy
has been
completed
by
US
based
consultant
AMI :
Advanced Metering Infrastructure
OT :
Operational
smart meter
with
AMITechnology
system. We are working on digital engagement of consumer
OMS :
Outage Management System
programme.
As aGeographical
part of Information
DR/DSM
programme we are in the process of carrying out pilot
GIS :
System
DELP
:
Domestic
Efficient
Lighting
Programme
projects on DELP, utilisation of captive DG sets of Consumers, control of consumer loads etc.
through various eminent vendors. Smart Grid control centre is being considered as our next
76 which we are going to include GIS centric
project which will be implemented very soon in
workflow / LT OMS / asset management / FFM / network planning, energy audit etc.
santanu.sen@rp-sg.in
History
CESC Limited is a flagship company of RP-Sanjiv Goenka Group. It is a fully integrated
power utility with its operation spanning the entire value chain: from mining coal, generating
power, and the distribution of energy. CESC is the sole distributor of electricity within an area
of 567 sq. km of Kolkata and neighbouring areas serving nearly 3 million consumers, which
includes domestic, industrial and commercial users, delivering safe, cost-effective and reliable
energy. Starting as India’s first fully integrated electric utility, CESC has been generating and
distributing electrical energy since 1899.
Generation System
The aggregated generating capacity of the 4 Generating Stations is 1125MW. The Maximum
Demand is 2042MW. Power is being imported from other agencies and also via Haldia
Energy Limited with capacity of 600MW. HEL belongs to RP-SG group of companies.
The Power from Generating Stations are being evacuated through transmission lines / cables
at various voltage levels of 400kV, 220kV, 132kV, 33kV. The power is being distributed to
the consumers through 11kV, 6kV and LT networks.
The Generating Stations are equipped with state of the art DCS for smooth control &
monitoring of the Station. SCADA system is being provided for the outdoor yards with feed
from the Generating Station for operational convenience from Central control Room.
Transmission System
There are 18 Receiving Stations / Substations for transfer of power to the city heart. These
comprise of conventional outdoor yards to indoor GIS / Switch boards. We have state of the
art 220kV GIS at our New Cossipore Substations. The cable system have N-1 redundancy
without interruption. New Stations are being covered with online PD measurement system.
The stations have Numerical Protection system, Disturbance Recorders, Optical Fibre based
communication system. All the transmission lines are protected with Unit Line Differential
Protection with Fibre as carrier. In case of tripping of Machines at Generating Stations,
equivalent load is being shed at the required location through fast acting contact transfer
system riding over our own optical fibre communication system.
These stations are under the purview of SCADA system.
The Numerical Relays (around 1100 in numbers) and Disturbance Recorders (14 nos) are
connected to a Central Office for Management of Protection system and fault analysis.
77
2
Distribution System
There are 108 Distribution Stations / Switch Houses which receives power at 33kV and
Distributed through 11 / 6kV & LT network to the Consumers. The Distribution Stations are
with GIS, 20MVA Transformers, AIS etc. The system is N-1 redundant with interruption.
Most of the Stations are unmanned and are remotely monitored & controlled through SCADA
system. At present 92 Stations are Automated. These Stations are being controlled from 6
RCCs (Regional Control Centre) in Distributed architecture. The remaining Stations will be
will be ready with SCADA system by end of FY 2016-2017.
The new stations are equipped with Numerical protection relays which are once again
communicable and are connected to the Central Office for Protection management and fault
analysis.
The Feeders at 6 / 11kV side are with RMUs (Ring Main Unit) with FPIs (Fault Passage
Indicator). 5000+ RMUs are in operation. RMU Automation has been major thrust of actions
in recent past in CESC. 380+ RMUs have been fully automated with motorisation, FRTUs,
communication connected to SCADA DMS. 50+ RMU sites are with semi-automation where
FPI signals are being connected to SCADA DMS. The device has been developed in-house.
This innovative work is based on SMS services from service provider. We have aggressive
target of fully automating another 50% RMUs in next 3 years.
LT System
We have around 8000 Distribution Transformers to cater to nearly 3 million consumers. AMR
is present in such DTs. The AMR last gasp helps us in outage management.
LT outage are being monitored through Smart Meters and through PFI (Phase Failure
Indicators), an in-house developed sms based product.
The Automation of VIP LT consumers are being made through LT Auto-Changeover
arrangement.
The Automation of Pillar Boxes are being done as a pilot case in 25 Pillar boxes to monitor
voltage outage / fuse blown cases.
Several pilots for customer centricity have been developed such as
 HT consumer end point supply availability monitoring
 Temperature alert for Pillar Box
 Video streaming in case Pillar Box door is opened.
78
3
The Network with Automation status
DC, DR, MCC, BCC
CESC has own Data Centre with Back-up Disaster Recovery System. The Enterprise
application covering email, Billing information, CRM (Customer Relationship Management
System), SOS (Site Office System), LTFMS (LT Fault Management System), DTLMS
(Distribution Transformer Fault Management System), HRMS, ERP etc. are riding on this.
The RTUs / FRTUs of different locations reports to BCC for redundancy in addition to
reporting at MCC.
79
4
Communication System
CESC owns around 1400km optical fibre cable. All the Substations and 90% Distribution
Stations are connected over Fibre. The voice with intra-office EPABX connectivity is
provided. Enterprise applications and DS SCADA are riding over CESC GB Ethernet
Network. Transmission SCADA and RMU Automation data are riding on SDH STM4
network.
IT Initiatives
CESC’s in-house IT group has developed many consumer centric web based / Apps based
services where facility has been provided for new connection application to bill payment.
Meter readings are being taken on Tabs. Cable sketches are also being drawn on Tab. Crew
Management system has also been under implementation based on Apps. Several new
initiatives are being considered regularly for efficiency improvement and consumer delight.
80
5
Some system & performance parameters of CESC is summarised below:
81
6
The above trend indicate that we are in the path of making the Transmission &
Distribution system including LT system to a Smarter / Efficient system.
Smart Grid Feasibility Study
CESC has been surveyed by US Consultant for Smart Grid Feasibility study. The report is
encouraging. The report indicates potential areas of improvement and areas of strength.
CESC’s 4 year Smart Grid aspiration has also been plotted. Conversion of conventional utility
to a Smart Grid compliance is a journey which requires Efficiency on Strategy, Management,
82
7
Regulator’s & Consumers participation, Grid Operations, Work & Asset Management, Value
Chain integration, Technology, Social & Environment etc. SGMM survey report covers the
same. The Consultant has suggested 15 years Smart Grid road map. A no of projects have
already been initiated based on the recommendations.
RF Mesh Pilot / Communication Trials
Several trials on communication technologies for AMI and RMU Automation carried out. The
GPRS / CDMA / 3G wireless trials for automation was found not to be technically suitable,
due to low availability factor. However, service provider’s wired MPLS solution was found to
be suitable for automation. RF Mesh pilot in 865-867MHz has shown good results both in
Smart Meter and Automation than 2.4GHz & 5.8GHz RF mesh systems.
A pilot is being undertaken with 25000 Smart Meters and 8 RMU Automation in 2 pockets in
Kolkata where RF Mesh communication technology will be utilised. The implementation will
be completed in 2016.
Smart Grid Control Centre
The Smart Grid Control Centre will convert the existing SCADA network control centre to a
unified control centre covering EMS, OMS, ADMS and CIS, AM. DSM & DR, EV, Storage
will be part of the system. We are in the process of implementation of the same in near future.
83
8
Customer Engagement Programme
We have engaged US based organisation for digitally connecting Consumers with the
understanding of engaging the customers with us in the competitive market.
GIS
We do have GIS system which need to be revamped with newer system where main focus are
Consumer Indexing for Energy Audit, Network Planning, OMS. The existing GIS is not fully
blown up. However, many services are riding on GIS. Vehicle Tracking system, Fault data
Management, Asset Management, Optical Cable etc. are riding on this system. HT & EHT
cable will be plotted soon on GIS.
Demand Response
Demand Response programme is being conducted for which order has been placed on US
base Company for participation of Consumers in DR programme. The programme is in the
verge of implementation. This will facilitate 1.5MW DR through DG synchronisation and
Chiller & Lighting control on demand. Regulators permission for synchronisation is in the
process.
84
9
DSM
Demand Side Management by utilising captive Diesel Generators of the Consumers have
been considered. A pilot project has been initiated. Regulators permission awaited. In this
project consumers will be directly participating in the programme.
BI / BA
CESC is working hard on this front for analysing data of various system ranging from energy
loss – customer call – Bills etc. Several pilot projects have been initiated in this area.
Environment
9MW Solar and 50MW Wind Generation is in service from the Group. Another 54MW
renewable will be in service very soon. Hydel projects are also under consideration by the
group.
CESC has installed solar system for Street Lighting of a few Substations. Roof top Solar have
been commissioned in few Substations.
Future plan
CESC is in the process of deployment of Smart Grid modules. The journey has begun. The
various aspects of Smart Grid are under consideration as per the CESC Smart Grid feasibility
study report by a renowned US Smart Grid consultant. Here, the consumers will be the focus
of all the activities covering environment & society.
85
CIGREAORC
Technical
Meeting
International
Conference
CIGREAORC
Technical
Meeting
2016 – International
Conference
Global Trends inConference
the Development
CIGREAORC
Technical
Meeting2016
2016and
andon
International
of Power Transmission & Distribution Systems
including
Smart
Grid,
24-26
Feb.
2016,
New Delhi, India
onon
“Global
Trends
in the
Development
ofofPower
SmartGrid”
Grid”
“Global
Trends
in the
Development
PowerT&D
T&DSystem
System including
including Smart
DESIGN
OF INTIGRATED
TRANSMISSIONAND
ANDDISTRIBUTION
DISTRIBUTION NET
NET WORK
DESIGN
OF INTIGRATED
TRANSMISSION
WORKFOR
FOR
A
GREEN
FIELD
SMART
CITY
A GREEN FIELD SMART CITY
S. TAKALKAR,
M. TAKALKAR,
K.G.
GAIKWAD,K.N.
K.N.VELANI
VELANI
S. M.
K.G.
GAIKWAD,
TAKALKAR POWER ENGINEERS & CONSULTANTS PVT. LTD.
TAKALKAR POWER ENGINEERS & CONSULTANTS PVT. LTD.
INDIA
INDIA
SUMMARY
SUMMARY
The Dholera Special Investment Region (DSIR) will be a major smart city cum new industrial
The Dholera
Special
(DSIR) state
will be
a major
smart
cum new industrial
hub located
on aInvestment
Greenfield Region
site of Gujarat
in India.
The
site city
is strategically
situated
between on
the amain
industrial
centres
of Ahmedabad,
Vadodara,
and Bhavnagar.
hub located
Greenfield
site
of Gujarat
state in India.
TheSurat,
site isRajkot
strategically
situated
The the
aimsmain
of itindustrial
is the creation
of of
an Ahmedabad,
economically Vadodara,
and sociallySurat,
balanced,
newand
ageBhavnagar.
City with
between
centres
Rajkot
worldof
class
quality of life.and
Adoption
of balanced,
a sustainable
approach
across
The aims
it isinfrastructure
the creationand
of high
an economically
socially
new
age City
with
key
components
such
as
transportation,
industries,
overall
urban
development
and
resource
world class infrastructure and high quality of life. Adoption of a sustainable approach across
efficiency form
the as
basis
of this Plan. industries, overall urban development and resource
key components
such
transportation,
efficiency form the basis of this Plan.
Phase-I of DSIR will be developed first in five years from now. Town planning schemes, TP1
and TP2 are part of Phase-I. Town planning scheme 2 is divided in to two part, TP2E and
Phase-I
of DSIR will be developed first in five years from now. Town planning schemes, TP1
TP2W.
and TP2 are part of Phase-I. Town planning scheme 2 is divided in to two part, TP2E and
TP2W.
Power demand and power network of TP2E, are focussed in the paper. Methods which are
adopted to calculate maximum power demand, transmit the bulk of power to distribution
Power
demand distribute
and powertotal
network
TP2E,atare
focussedend,
in the
paper.for
Methods
which
are
substation,
powerofdemand
consumer
operation
the entire
power
adopted
to
calculate
maximum
power
demand,
transmit
the
bulk
of
power
to
distribution
network for TP2E one of the Activation zone of Dholera SIR, etc. all covered in the paper
substation,
distribute total power demand at consumer end, operation for the entire power
here under.
network for TP2E one of the Activation zone of Dholera SIR, etc. all covered in the paper
KEYWORDS
here under.
Smart city, Town Planning, Max. Power Demand, Transmission Lines, Distribution Lines,
Gas Insulated Substation, Power Cable, Auxiliary Supply, System Study, SCADA and Smart
KEYWORDS
SmartGrid
city,System
Town Planning, Max. Power Demand, Transmission Lines, Distribution Lines,
Gas Insulated Substation, Power Cable, Auxiliary Supply, System Study, SCADA and Smart
INTRODUCTION
Grid 1.0
System
1.1
The concept of Smart Cities and towns is gathering a momentum in India as well as in
many parts of the world. High quality of life, international trade and industrial growth
1.0 INTRODUCTION
are at the core of development of such smart cities and towns.
1.1 The concept of Smart Cities and towns is gathering a momentum in India as well as in
1.2 It may be interesting to indicate that such smart cities will need huge quantum of power
many parts of the world. High quality of life, international trade and industrial growth
with a very high reliability tag. Quality power supply is one most important aspect of
are atpower
the core
of development
of such smart cities and towns.
supply
for such cities/towns.
1.2 1.3
It may
interesting
to indicate that
smart cities
will need
of power
Thebe design
of transmission
andsuch
distribution
network
for huge
such quantum
application,
need
with integration
a very high
reliability
tag.
Quality
power
supply
is
one
most
important
aspect
with the existing power system of utility/state grid as well as, system studyof
1.3
power supply for such cities/towns.
The design of transmission and distribution network for such application, need
integration with the existing power system of utility/state grid as well as, system study
smtakalkar@tpec.in
smtakalkar@tpec.in
1
86
1
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
and planning. The task becomes more difficult when a green field smart city is planned
with power demand projections which are based on the town planning.
A rationale has to be developed for working out power requirement per square meter of
plot for different usages like Residential, Industrial, High Access Corridor, Costal
Region Zone, Recreation and Sports, Tourism & Resorts, Village Buffer, River/Water
Body, Public Facility Zone, Roads and Strategic Infrastructure.
Power demand in KW for each and every plot has then to be worked out. The lumping
of loads and creation of load centers is the next task, which ultimately leads to
integrated transmission and distribution network of such smart city/town.
The paper here under presents an interesting case study of part of such a green field
smart city of Dholera SIR taking shape in the state of Gujarat, India.
The preliminary design report covers power system of approximately 550 MW from 400
kV to 415 Volt. The system comprise underground cabling, GIS substations and ring
main sourcing at each voltage level (i.e. 400 kV, 220 kV, 66 kV, 11 kV & 415 V).
The smart city necessarily means reliable and quality power. The design has therefore to
ensure 24x7 power at proper voltage and stable system.
To achieve the provisions of 1.8 above, the power system from 400 kV to 415 V, is in
ring mains. All the substations are GIS and transmission and distribution network is
underground.
BRIEF OF SMART CITY OF DHOLERA
Dholera is a sleepy town between the major cities of Ahmedabad and Bhavnagar on the
west side of bay of cambay (Khambat). In Harappan era Dholera used to be a
flourishing port but as of now it is almost a barren area of approximately 920 Sq.km.
Figure: 1 Location Plan – Dholera SIR
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2
Figure: 2 Development Plan – Dholera SIR
Figure: 3 Town Planning Scheme – Dholera SIR
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3
2.2
There are small villages in this 920 Sq.M. When the smart city is developed, these
villages will also be covered and developed. The entire 920 Sq.km. area will be
developed in various phases. Area under development will be 422 Sq.Km. It is divided
into 6 town planning schemes. Out of them, the town planning scheme Number 2 (TP 2)
is sub divided into TP 2 east and TP 2 west. This division is done with reference to the
highway from Ahmedabad to Bhavnagar. TP2 east is on the east side of the road and
TP2 west is on the west side on the road. The balance out of 920 Sq.Km. (after
developing 422 Sq.Km) will be a green field meant for public purpose which is actually
a green corridor.
2.3
Out of the 422 Sq.kM under development, the first phase comprise 153 Sq.kM (TP1 &
TP2). Again out of this, the immediate development to be taken on hand is 22.54
Sq.kM. This is actually a high industrial corridor and an industrial hub of International
Standard. (TP1 & TP2 Photo)
Figure: 4 Development Phase Plan Scheme
Figure: 5 Town Planning Scheme
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4
2.4
The area under TP2 is 57 Sq.kM. Out of this the activation area (industrially active) is
17.54 Sq.kM. Again out of TP4, about 5 Sq.kM. will be added to the activation area.
Thus the total activation area will be 22.54 Sq.kM. (TP2E Photo)
Figure: 6 Formation of Town Planning Scheme (Geographical Representation)
2.5
While the power requirement for 57 plus 5 Sq.kM (total 62 Sq.kM) is being considered,
the high density consumers will be in 22.54 Sq.kM. (Activation Area)
Figure: 7 Formation of Activation Area (Geographical Representation)
3.0
3.1
3.2
NORMS FOR ARIVING AT THE POWER REQUIREMENT
The 62 Sq.kM area (TP2E + part of TP4) has a varied power requirement depending
upon the approved town planning scheme.
The types of load considered are Residential, High Access Corridor, Industrial,
Recreation & Sports, Strategic Infrastructure, Roads, Public Facility Zone, Tourism and
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5
3.3
3.4
Resorts, Village Buffer, Original village (Gamtal) River/Water Body & Coastal Region
Zone.
It is worth mentioning that all the above usages are not solitary. In many plots there will
be mix usages. They are described hereunder :
i.
Residential Usage – This may include residential buildings, commercial
establishment, community facilities, open space, roads etc.
ii. High Access Corridor – This may include the usages indicated in (i) above.
iii. Industrial – This may include general manufacturing units, electronics,
automobiles, agro and food processing, heavy engineering, metal & metallurgical
products, pharmaceutical & biotechnical and logistic. This may also include the
loads described in (i) above.
iv. Recreation, Entertainment and sports – This may comprise leisure, hospitality,
sports complexes, movie and entertainment theaters. This may also include the
loads described in (i) above.
v.
Strategic Infrastructures – This may include the plots meant for utilities,
information and technological hubs. The water supply, drainage system, street
light and other public facility operating centers, etc.
vi. Roads – They may include the main roads, sub roads and lane roads. This may
also include the loads described in (i) above.
vii. Public facility Zone – This plots are reserved for educational institutions and
public facilities.
viii. Tourism & Resorts – This may include hubs of tourism, leisure, hospitality and
public facilities, including the roads.
ix. Village Buffer – This may comprise the space for residential, public/community
facilities and roads.
x.
Original Village (Gamtal) – This plots will be completely reserved for residential
purpose and will include roads, street lights etc.
xi. River/Water Body – This space will be used for water sports, public open space,
recreation, and sports/entertainment. This may also include the loads described in
(i) above.
xii. Coastal Region Zone – This will comprise only local roads. Since Dholera is on
the sea coast such plots assume good significance.
After ear marking the plots for different usages (independent and mix), the following
methodology is adopted for working out the power requirement for each plot.
i.
Keeping in view, the usage of the particular plot, it is necessary to assume power
requirement in Watts/Sq.M. based on the requirement of illumination, fans, air
conditioners, common house hold appliances, industrial equipment, street light,
flood lights, utility equipment load etc. This is done keeping in view the local life
style as well as international/national norms on design of power system.
ii. After going through available national and international document is related to
energy consumption for various usages & practical energy consumption in existing
industries, the following quantum of load in Watts/Sq.M has been arrived at for
different categories of utilization. This is exhibited in the table below: Table 1
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6
Table 1
iii.
Type
Total Wattage (Watt / m2)
Residential
58.3
Commercial Offices/Retail
133.4
Leisure/Hospitality
64.8
Light Service Industry
32.3
Industry
164.2
Education
63.5
Public Facility/ Community Facility
25.3
Local Public Open Space
1.1
Recreation Sports & Entertainment
36.5
Roads
1.1
Utilities
1.1
It is clear from the contents of 3.3 above that most of the plots are having mixed
usage. In such circumstances it is necessary to take a weighted average and arrive
at load in Watt/Sq.M. This is exhibited in the tables below – Tables 2 & 3.
Table 2
Residential Area (Mix Plot)
Area under consideration
% area occupation
Watt/Sq.m
Residential
54%
58.3
commercial offices
2%
133.4
leisure hospitality
1%
64.8
Community facilities
10%
25.3
local public open space
10%
1.1
local roads
22%
1.1
Utilities
1%
1.1
Total
100%
Uniform Watt/sq.m by
means of Weighted
Arithmetic mean (WAM)
=
(54%*Y*58.3 +2%*Y*133.4 + 1%*Y*64.8 +
10%*Y*25.3 + 10%*Y*1.1 + 22%*Y*1.1 +
1%*Y*1.1)
Y
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7
Table 3
Type
Total Wattage (Watt / m2)
Residential
37.66
High access corridor
37.85
Industrial
130.68
Recreation Sports and Entertainment
25.65
Strategic Infrastructure
1.08
Roads
1.08
Public facility zone
3.30
Tourism & resorts
28.31
Village Buffer
33.26
Gamtal
58.25
River / water body
1.08
Coastal region zone
0.06
iv.
3.5
It can be seen that while working out the usage in Watt/Sq.M. in a mixed usage
plot. It is necessary to precisely work out each category of usage as a percentage of
total plot area and multiply the same with the actual Watt/Sq.M. requirement for
that category of load. Thus, after summing of such fraction of power requirement
for each category of load, we will be able to arrive at the requirement of power in
Watt/Sq.M. for a mixed usage.
After working out the power requirement for each plot, the next step is to work out the
total demand for the entire area under development. In case of Dholera SIR, the total
requirement has been worked out as shown in the table below: Table 4.1 & 4.2
Areas
Power Consumption
(MW)
Table 4.1
00:00 08:00 11:00 18:00
----08:00 11:00 18:00 00:00
Hrs
Hrs
Hrs
Hrs
Group Diversity factor
Considered
Residential Zone
High Access Corridor
Industrial Zone
Recreation Sports and
Entertainment
Strategic Infrastructure
Roads
Public facility Zone
111.65
6.23
379.35
92.98
0.6
0.5
0.5
0.2
0.8
0.8
0.9
0.7
0.7
0.6
0.9
0.4
0.8
0.8
0.6
0.8
0.50
3.48
1.48
0.6
0.4
0.2
0.8
0.2
0.9
0.8
0.2
0.9
0.6
0.8
0.6
Load Cycle
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8
Tourism & Resorts
Gamtal
Village buffer
River / Water Body
Costal Region Zone
Total Wattage (MW)
METRO Rail & Other
Miscellaneous Power
Consumption (MW)
55.62
7.84
11.26
0.04
0.06
0.3
0.5
0.3
0.6
0.8
Residential Zone
High Access Corridor
Industrial Zone
Recreation Sports and
Entertainment
Strategic Infrastructure
Roads
Public facility Zone
Tourism & Resorts
Gamtal
Village buffer
River / Water Body
Costal Region Zone
Total Wattage (MW)
METRO Rail & Other
Miscellaneous Power
Consumption (MW)
0.4
0.9
0.6
0.4
0.6
0.8
0.8
0.5
0.6
0.9
670
25.00
Load Cycle
Areas
0.9
0.7
0.5
0.4
0.6
Power
Consumption
(MW)
111.65
6.23
379.35
92.98
Table 4.2
00:00 08:00 11:00 18:00
----08:00 11:00 18:00 00:00
Hrs
Hrs
Hrs
Hrs
Demand after considering group
Diversity factor
66.99
3.12
189.67
18.60
89.32
4.99
341.41
65.09
78.15
3.74
341.41
37.19
89.32
4.99
227.61
74.38
0.50
3.48
1.48
55.62
7.84
11.26
0.04
0.06
0.30
1.39
0.30
16.69
3.92
3.38
0.03
0.05
0.40
0.70
1.33
50.06
5.49
5.63
0.02
0.04
0.40
0.70
1.33
22.25
7.06
6.76
0.02
0.04
0.30
2.78
0.89
44.49
6.27
5.63
0.03
0.05
670
25.00
304
564
498
456
Considering Peak Power Consumption, 565 MW after applying Group
Diversity Factor from above table.
Total Power Consumption for TP2E is 590 MW.
i.
The total power requirement of Dholera SIR is categorized in separate part TP2E
(power demand 608 MW for 57 Sq.kM) & TP4 (power demand 88 MW for 5
Sq.kM).
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9
Figure: 8 Formation of TP Scheme of Load (Geographical Representation)
ii.
The total power requirement of Dholera SIR is categorized in separate part for
activation area (power demand 429 MW for 22 Sq.kM) & remaining area (power
demand 267 MW for 40 Sq.kM).
Figure: 9 Formation of Activation Area of Load (Geographical Representation)
3.6
Once the total demand for the area under development, is worked out, it becomes
necessary to lump the loads and form a cluster. This is done keeping in view the
maximum power which can be supplied from a load center with a particular voltage
level. The cluster formation in the present case, has been done keeping in view the
power system prevailing in the state of Gujarat. It may be necessary to indicate the
present practice of the utilities of the state of Gujarat (India), for supplying the power at
different voltage level with different levels of power demand. This is given in Table 5.
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10
Details of Distribution Network
Connected Load
Type of
Consumer
Upto 6kW
Residential
Upto 6kW
Commercial
Above 6kW
Residential
Above 6kW
Commercial
Upto 99kW
Industrial
100kVA to 400
HT Industrial
0kVA
EHT Industrial 4000 kVA to 35000
kVA
EHT Industrial Above 35000 kVA
3.7
Table 5
Prescribed Nominal Voltage Level for
Supply
230V, 1 Phase
230V, 1 Phase
400V, 3 Phase
400V, 3 Phase
400V, 3 Phase
11KV, 3 Phase
66KV, 3 Phase
220KV, 3 Phase
Thus, the 66 kV substation is ear marked for each cluster of load. In case of Dholera
SIR, total 28 clusters have been formed as indicated in table below – Table 6
Figure: 10 Formation of Cluster of Load (Geographical Representation)
Cluster - 1
Cluster - 2
Cluster - 3
Load in
MW
39.8
50.71
29.61
Load in MVA at
0.85 PF
46.82353
59.65882
34.83529
Cluster - 4
Cluster - 5
Cluster - 6
Cluster - 7
56.86
91.92
51.24
34.86
66.89412
108.1412
60.28235
41.01176
Cluster No.
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Type of Loads
Table 6
Industrial & Water body.
Industrial & Residential
High access corridor, Industrial and
Water body.
Industrial
Industrial
Industrial
Residential & Public Facility
11
Cluster - 8
7.15
8.411765
Cluster - 9
4.47
5.258824
Cluster - 10 2.23
2.623529
Cluster - 11 8.53
10.03529
Cluster - 12 8.67
10.2
Cluster - 13 4.35
5.117647
Cluster - 14 12.78
15.03529
Cluster - 15 12.98
15.27059
Cluster - 16 4.63
5.447059
Cluster - 17 10.91
12.83529
Cluster - 18 42.32
49.78824
Cluster - 19 15.48
18.21176
Cluster - 20 13.7
16.11765
Cluster - 21 11.7
13.76471
Cluster - 22 18.17
21.37647
Cluster - 23 13.69
16.10588
Cluster - 24
Cluster - 25
Cluster - 26
Cluster - 27
Cluster - 28
Total
3.8
24.8
36.31
31.74
33.97
21.87
695.47
( Say 696 )
Residential, CRZ, Recreation&
Sports, Tourism and Water body
CRZ, Recreation & sports and
Tourism
CRZ, Recreation & sports and
Tourism
Infrastructure, CRZ, Recreation &
sports and Tourism
Recreation & Sports, Tourism and
Water body
Recreation & Sports, CRZ, Tourism
and Village buffer boundary
Recreation & Sports, CRZ, Tourism
and Village buffer boundary
CRZ, Recreation & sports and
Tourism
CRZ, Recreation & sports and
Tourism
CRZ, Recreation & sports and
Tourism
Residential, Village buffer boundary,
Water body and Tourism
Residential, Village buffer boundary,
Water body and Recreation and
Sports
Residential, Village buffer boundary,
CRZ and Tourism
Residential, Recreation & Sports,
CRZ and Tourism
Recreation & Sports, CRZ, Tourism
& Village buffer boundary
CRZ, Recreation & sports and
Tourism
Recreation & sports and Tourism
Metro, Roads and Gamtal
Industrial
Industrial
Industrial
29.17647
42.71765
37.34117
39.96470
25.72941
818.1765
( Say 818 )
After formation of cluster, the next agenda is to form zones. In case of Dholera SIR,
seven zones have been created. The details of the clusters which have been grouped
together in a particular zone, have been indicated in the table 7 below.
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Figure: 11 Formation of Zone of Load (Geographical Representation)
Table 7
Zone No.
Zone - 1
Zone - 2
Zone - 3
Zone - 4
Zone - 5
Zone - 6
Zone - 7
Total
4.0
4.1
4.2
4.3
Clusters considered in
zone
1, 2 , 19 & 20
3,4, 5, 18& 25
6, 7, 16 & 17
8,9,10,11,&12
13,14 &15
21, 22, 23 & 24
26,27,& 28
Load in
MW
119.69
257.02
101.64
31.05
30.11
68.36
87.48
695.35
( Say 696 )
Load in MVA at 0.85 PF
140.8118
302.3765
119.5765
36.52941
35.42353
80.42353
102.92
818.06127
( Say 818 )
SOURCING THE POWER
It can be seen that the total power requirement of Dholera SIR is of the order of 696
MW (818 MVA). This is quite huge considering the area of usage (62 Sq.kM).
It is planned to avail power at 400 kV voltage level. There will be two independent
double circuit lines from two different substations of local utility called “Gujarat Energy
Transmission Corporation Ltd. (GETCO)”. These substations are Chorania & Fedra.
400 kV double circuit transmission lines are proposed to be connected to the above
mentioned substations with overhead configuration and are proposed to be terminated to
switching substation at boundary of Dholera SIR. From switching substation to Main
Receiving Substation (MRSS), 400 kV transmission line will be with underground EHV
cables. This is for the fact that in Dholera SIR no overhead network is envisaged.
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Figure: 12 Power Sourcing Diagram (Geographical Representation)
5.0
5.1
5.2
POWER DISTRIBUTION NETWORK
After charging of MRSS from 400 kV double circuit transmission lines, Power
distribution of Dholera SIR is done by stepping down the power with ring main
configuration at each voltage level.
Depending upon the power demand of different zones, the locations of 220/66 kV
substations has been finalized. Each 220/66 kV substation will be fed from the MRSS
(400/220/66 kV Substation) through the 220 kV underground cables with appropriate
size. All 220/66 kV substations will be connected through appropriate size of the cables
to form a ring main configuration. Demand of load and installed capacity of 400/220/66
kV Substations are indicated in table below. Table 8
Sr.
No
1
2
3
4
5
5.3
Table 8
Load Requirement
Installed Number of 160
of Substation in
MVA Three Phase
MVA
Transformer
400/220/66kV MRSS
258
3
Location-1
220/66kV Substation
120
2
Location-2
220/66kV Substation
105.5
2
Location-3
220/66kV Substation
128.5
2
Location-4
MVA
612
1440
220/66kV
Substation location
Depending upon the power demand of different clusters and independent demand of the
industrial plots, the location of 66/11 kV substations are finalized. Each 66/11 kV
substation will be fed from the nearby 220/66 kV substation with underground cables
with appropriate size. Again all 66/11 kV substations will be interconnected through
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14
appropriate size of the cables to form a ring main. Demand of load and installed
capacity of 66/11 kV Substation is indicated in table below. Table 9
Sr.
No
66/11kV Substation
location
1
66/11kV substation S7
66/11kV substation –
S10
MVA
66/11kV substation –
S6
66/11kV substation –
S11
MVA
66/11kV Substation
location
2
1
2
Sr.
No
1
2
3
Sr.
No
1
2
3
4
5.4
66/11kV substation –
S1
66/11kV substation –
S4
66/11kV substation –
S4
MVA
66/11kV Substation
location
66/11kV substation –
S2
66/11kV substation –
S3
66/11kV substation –
S8
66/11kV substation –
S9
MVA
Load Requirement
of Substation in
MVA
15.27
Table 9
Installed Number of 20 MVA
Three Phase Transformer
2
16.11
2
31.38
23.04
80
2
22.17
2
45.21
Load Requirement
of Substation in
MVA
27.78
100
Installed Number of 30 MVA
Three Phase Transformer
29.95
2
28.85
2
86.58
Load Requirement
of Substation in
MVA
32
2
180
Installed Number of 40MVA
Three Phase Transformer
2
38.2
2
34.34
2
35.14
2
139.68
320
Depending upon the power demand of lumped loads of different plots for the clusters
and independent demand of the small industrial plots and other utilities, the location of
each 11/0.415 kV distribution Ring Main Unit (RMU) is finalized. All RMUs will be
fed from the nearby 66/11 kV substation with underground cables of appropriate size.
Each RMU will be interconnected with appropriate size of the cable through ring main
configuration.
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Figure: 13 Power Distribution Diagram – Ring Main System
Figure: 14 Power Sourcing Diagram (Geographical Representation)
6.0
6.1
POWER CABLING
The power cables to be used for different applications are described below.
i. The power cable up to 66 kV shall be of copper conductor and those of 11 kV, 415 V
& 230 V will be of aluminum core.
ii. For 400 kV, 220 kV & 66 kV nominal voltage level, the cables to be used will be
single core. They shall be standard copper, super clean XLPE insulated. They will
be provided with aluminum armor and an overall outer sheath of PVC. They shall
comply with IEC 60228.
iii. The 11 kV cables shall be single core or three core depending upon the load to be
fed. They shall comprise stranded and compacted aluminum conductor, extruded
semi conducting screen over conductor, XLPE insulation, armor and overall FRLS
PVC outer sheath conforming to IEC 60502 or IS 7098 (part II).
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6.2
iv. LT power cable shall be 1100 V graded. They shall be single or multi core
(depending upon the quantum of power to be fed). They shall be stranded
aluminum conductor, insulated with XLPE insulation with inner sheath of FRLS
PVC compound which shall generally conform to IS 7098 (part II).
v. The cables for DC system shall be single core type. Minimum conductor cross
section will be 10 sq.mm. & for copper they can be below 10 sq.mm.
The sizes of various cables shall be decided on the following basis.
i. Continuous current rating
a. The power cable shall be rated to carry full load current continuously under the
atmospheric conditions prevailing in Dholera SIR. The design parameter for
cable shall include a maximum temperature of 50 deg. C in air. All the cables
shall be laid in the cable trench.
b. Derating factor shall be considered as per relevant IS/IEC. It will also depend
upon the condition of installation like ambient temperature, grouping of cables
on racks, variation in ground temperature, depth of laying, bonding of armors
and formation of laying.
ii. Voltage Drops
a. Cables connecting RMU and 415 V switch gear, shall have a voltage drop of
not more than 1%.
b. Cables connecting 415 V switchgear & feeder pillars (415 V), shall have a
voltage drop of not more than 2%.
c. The cables connecting the feeder pillars or motor control centers (public utility
pumps etc.), shall have a voltage drop of not more than 10% at starting and 3%
at full load, at rated voltages.
d. The cables connecting the distribution transformer (secondary) to the motor
terminal, shall have a voltage drop of not more than 5% at full load and rated
voltage.
iii. Short circuit withstand capacity of cables
a. The cables shall have fault current withstand capability for the duration which
is not less than the maximum time required for the backup protecting system to
respond and isolate the fault.
iv. Voltage grade of cables
a. Cables shall be rated to UE voltage for resistance earthed system & U0 for
solidly earthed system.
v. Cable Termination, Cable Laying & Cable Joints
a. All the cables are proposed to be laid in the trenches on cable trays except 400
kV and 220 kV. The termination & jointing shall be heat shrinkable type.
b. Inside the control room also laying will be done in the trenches.
c. XLPE cable in the GIS shall be terminated in the respective terminal boxes of
GIS equipment.
d. The single phase cables shall have bonding of metallic screens to maximize the
current flow cable conductor. Cross bonding method of bonding metallic
screen/sheath shall be adopted.
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7.0
7.1
7.2
7.3
8.0
8.1
8.2
8.3
9.0
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
AUXILIARY SUPPLY
It is proposed to load the tertiary winding of 220 kV/66 kV transformers and avail the
auxiliary supply for all the GIS substation up to 220 kV.
The auxiliary supply for GIS substations of 66/11 kV rating shall be obtained by
providing a station transformer of suitable size having voltage ratio of 11 kV/415 V.
Auxiliary power requirement will include yard lighting, control room lighting, ACDB,
DCDB, substation utility etc.
SYSTEM STUDY
As indicated here before, the entire sub transmission and distribution network is through
underground cables only, it is utmost important to carry out system study covering load
flow analysis and contingency analysis.
Due to the large quantity of cable network, the rise in voltage at different voltage levels,
cannot be ruled out. Every substation and every individual consumer has to be protected
against very high voltage or very low voltage.
The system study done for Dholera SIR indicates that there is no over voltage or under
voltage in the system.
RELIABILITY OF POWER SUPPLY THROUGH SCADA AND SMART GRID
SOLUTIONS
The concept of smart city leads to an understanding that the power control shall be
totally automatic having minimum response time, self-healing and smart operations.
The smart transmission means good connectivity and availability as well as real time
data acquisition and monitoring of transmission lines from the source (GETCO
substations at Chorania & Fedra).
The energy received and sent out in the transmission network has to be precisely
accounted and monitored.
The N -1 criteria has to be fulfilled at every voltage level of transmission line and
substation network. As already stated, there is a ring main at 400 kV, 220 kV, 66 kV and
11 kV. Normally each cable will carry 50 % or less load. The transformer capacities and
their numbers have been fixed for maximum of 70% loading and N-1 criteria. A typical
tabulation of transformer capacity for 400 kV, 220 kV, 66 kV substation is already
given in table number 8 & 9.
The distribution system shall also be with the smart applications such as centralized
remote metering system, fault location monitoring and response logistic as well as
maintenance scheduling.
24 x 7 quality power has to be ensured by Ring Main Units (RMU) at distribution level.
The system study and voltage profiles lead to a conclusion that the tail end consumer
receives power at proper voltage all the time.
The frequency will depend upon the state power system stability, regional power system
stability and the national power system stability. It is difficult to maintain 50 Hz in
Dholera SIR in isolation. If it is to be achieved, independent and standalone type power
system is required. However, for the present this has been ruled out.
The harmonics cannot be controlled from sending end. The consumers will therefore
have to maintain harmonic filters at their end. Regular measurements of harmonics of
high load consumers in person or through SCADA will be able to control the harmonics
in the smart city power system to an acceptable level.
smtakalkar@tpec.in
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18
9.9
All the smart grid gadgets and SCADA will work on fiber optic network. It may start
from consumer end & lead to 400 kV MRSS.
10.0 CIVIL WORKS
10.1 The high standard of living in the smart city of Dholera, necessarily mean that all the
power structures have to be very reliable. In addition to this, there will be an aesthetic
view to every civil structure including GIS building, control room, transformer yards &
cable trenches.
10.2 The power system in the Dholera SIR has to ensure that there is absolutely no loss of
power to the public utilities such as water supply, drainage, sewerage, street light,
Information & Communication Technology.
10.3 While maintaining high standards of quality of civil works, it will also be necessary that
the utilization of space is bare minimum.
10.4 The power system shall be flexible to accommodate changes and extensions at the later
date.
11.0 CONCLUSION
11.1 The power system in Dholera SIR has to be highly reliable and therefore lot of care has
been taken in the Preliminary Design Report (PDR). The detailed system study,
providing sufficient redundancy in the network as well as following N -1 criteria in the
system from 400 kV to 415 V, are some of the measures to ensure 24 x 7 power supply.
11.2 For better reliability entire power system is under ground and all the substations are Gas
Insulated Switchgear (GIS).
11.3 Quality & 24 x 7 power supply is bound to attract large scale industries in Dholera SIR.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
Dholera SIR Final Development – DSIRDA | Report – 1
Technical Assesement Report
Design Basis Report
Preliminary Design Report
smtakalkar@tpec.in
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19
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016on
– International Conference on Global Trends in the Development
CIGREAORC
Technical
Meeting
2016
and
International
Conference
of Power
Transmission
& Distribution
Systems
including
Smart
Grid,
24-26 Feb. 2016,
New Delhi, India
“Global Trends in the Development
onof Power T&D System including Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
Smart Grid Technologies – Microgrids, Demand Response and Communication
Smart Grid Technologies
– Microgrids,
Demand network
Response and Communication
Systems
in Distribution
Systems in Distribution network
S.R. Vijayan
S.R. Vijayan
ABB India Ltd.
ABB India Ltd.
India
India
Rishi Mishra
Rishi Mishra
ABB India Ltd.
ABB India Ltd.
India
India
SUMMARY
SUMMARY
TheThe
modern
dayday
power
over the
the recent
recentyears
yearsfrom
fromthethe
traditional
modern
powersystem
systemisistransforming
transforming over
traditional
unidirectional
(Generation
to
Distribution
to
Consumers)
power
flow
to
an
inter-connected
unidirectional (Generation to Distribution to Consumers) power flow to an inter-connected
distributed
generationinjecting
injecting power
power into
(sometimes
grid,grid,
withwith
distributed
generation
into the
the grid
gridatatdifferent
differentlevels
levels
(sometimes
even
at
the
consumer
point)
within
the
system.
Variability
of
solar
and
wind
power
in
even at the consumer point) within the system. Variability of solar and wind power ainsmall
a small
geographical
domaincalls
callsfor
forquickly
quickly controllable
controllable back
such
as as
geographical
domain
back up
up generation
generationororstorage
storage
such
battery
systems
to
fill
in
shortfalls.
In
urban
scenario,
the
loads
may
peak
during
morning
and
battery systems to fill in shortfalls. In urban scenario, the loads may peak during morning and
evening hours when there is no solar generation. It also makes sense to encourage shifting the
evening
hours when there is no solar generation. It also makes sense to encourage shifting the
loads to a time of the day when there is surplus energy available in the system through
loads to a time of the day when there is surplus energy available in the system through
‘Demand Response’.
‘Demand Response’.
As the percentage or penetration of renewables increase in a power system, it becomes
As imperative
the percentage
penetration
of balancing
renewables
increase
in a power
system,
it becomes
to haveorgrid
level power
using
energy storage
systems.
Microgrids
are
imperative
to
have
grid
level
power
balancing
using
energy
storage
systems.
Microgrids
expected to form an inherent component in the grid system with localized generation and are
expected
inherent
component
in theThey
gridcan
system
with localized
storagetoasform
close an
to the
load centers
as possible.
be differentiated
from generation
major powerand
storage
to thethat
loadthey
centers
as possible.
Theyatcan
differentiated
from
power
gridsasinclose
the sense
are usually
integrated
thebe
distribution
system
of major
the power
system,
limited
to
integration
at
low
or
medium
voltage
levels
of
the
grid.
They
are
limited
in
grids in the sense that they are usually integrated at the distribution system of the power
geographical
reach
unlike
power
grids,
and
they
lack
bulk
power
transmission
capabilities.
system, limited to integration at low or medium voltage levels of the grid. They are limited in
Microgridsreach
are thus
morepower
localized
where
generation
andpower
consumption
happenscapabilities.
within a
geographical
unlike
grids,
andthethey
lack bulk
transmission
small
area.
Microgrids are thus more localized where the generation and consumption happens within a
small area.
Another technique that can be used to assist power balance would be Demand Response
(DR), which encourages customers to shift the load from one time of the day to another. This
Another
technique that can be used to assist power balance would be Demand Response
helps in reducing the peak demand during particular times of a day. As peak shave off is more
(DR),
which encourages
customers
to shifttothemaintain
load from
time ofconditions
the day toofanother.
This
important
from the utilities
perspective
theone
operating
the grid,
helps
in
reducing
the
peak
demand
during
particular
times
of
a
day.
As
peak
shave
off
is
more
incentive payments are normally included to encourage end customers to volunteer and
important
from
the
utilities perspective to maintain the operating conditions of the grid,
subscribe
to the
program.
incentive payments are normally included to encourage end customers to volunteer and
subscribe
the program.
While to
distributed
generation is changing the traditional grid connectivity, the distribution
system needs implementation of technologies to improve its operational efficiency like energy
availability,
power
quality and
responsiveness.
To achieve
this, a smart the
utility
has to
While
distributed
generation
is system
changing
the traditional
grid connectivity,
distribution
not
only
monitor
the
system
components
at
every
location
of
the
distribution
system
but
system needs implementation of technologies to improve its operational efficiency like also
energy
plan ‘automatic’
of disconnected
customers,
technically
within
a to
availability,
power reconnection
quality and system
responsiveness.
Towhen
achieve
this, a feasible,
smart utility
has
time. The
solutions atinclude
applications
likedistribution
SCADA/DMS,
not short
only monitor
the automation
system components
every location
of the
systemOutage
but also
1 a
plan ‘automatic’ reconnection of disconnected customers, when technically feasible, within
105 applications like SCADA/DMS, Outage
short time. The automation solutions include
1
Management System (OMS), Advanced Metering Infrastructure (AMI), Smart Metering and
advanced applications like Demand Response etc. For implementation of such Distribution
Automation (DA) systems, communication network is the backbone to interconnect the field
devices to the control system applications. There are different communication technologies
that are available today, with each one having its advantages and limitations. While it is
comparatively easier to select a particular technology for transmission grid automation, the
distribution grid automation faces a challenge of choosing a right and reliable technology.
KEYWORDS
Microgrid, Distributed Generation, Storage, Demand Response, GPRS, wireless, AMI,
Communication
Microgrids
The share of renewable energy is small in India today but is expected to grow rapidly in the
near future. Renewable Energy Futures Study done by National Renewable Energy
Laboratory of the U. S. Department of Energy focuses on this area and analyses the impacts
of renewable penetration levels as high as 80% by 2050. While Power Grid of India’s report
Desert Power India-2050 touches upon impact of major centralized solar power generation
from Rajasthan, Gujarat, J&K, and broadly outlines the grid systems possible by that time
(Figure-1), it does highlight that distributed generation could be potentially 45GW. The report
also highlights that the cost of PV generation would fall below that of conventional generation
between 2016 and 2018. India is thus at the threshold of a major solar power growth phase.
Figure 1. Projected installed capacity over the years: Power Grid report ‘Desert Power
India-2050’
While renewable energies such as wind and solar are the most desirable from environment
perspective, the variable nature of the source needs special approach while integrating them
with the power system.
The penetration levels of renewables in Indian power system are expected to increase
significantly, especially with the goal set for solar plants of 100GW by 2022. The variations
of renewable energy over a wide geographical region within a band of accuracy are better
predicted today but drastic variations in the outputs of both wind and solar cannot be ruled
out. Since the generation and load balance has to be maintained at every given instant of time,
variations in generation of renewable can be balanced somewhat by the other generations,
especially gas, hydro etc. The base load power generation from coal and nuclear are best left
undisturbed for technical and economic reasons. As the percentage or penetration of
106
2
renewables increase in a power system, it becomes imperative to have grid level power
balancing using energy storage systems (ESS) such as batteries, pumped storage schemes,
solar thermal power with storage etc.(Figure 2). Note however that some of the centralized
grid level power storage, such as pumped storage situated away from load centers, comes at
the cost of transmission and distribution losses. Where economically viable, it is imperative to
have energy resource as well as storage embedded within the distribution systems as much as
possible.
Figure 2. Adding Energy Storage Systems (ESS) in a power system help balancing power and
load and maintain frequency
One may visualize microgrid as a part of a power system with generation, having a mix of
renewable and conventional, with storage elements for grid stabilization added (if a high
penetration of renewable has to be achieved within the microgrid so formed) enabling
independent operation to be achieved with or without provision to be connected to a grid as
indicated in Figure-3 below:
Figure 3. Typical Microgrid and its electrical schematics
107
3
Microgrids being smart themselves, can operate independently in remote communities but
when multiples of them get integrated with the powergrids, they form the basic building
blocks of a smart grid at distribution level forming smartgrids.
They are limited in geographical reach unlike power grids, and they lack bulk power
transmission capabilities. Microgrids are thus more localized where the generation and
consumption happens within a small area.
Figure 4 shows the common features and differences between a power grid and a micro grid.
Figure 4. Common features and differences between Power Grids and Microgrids
The motivations for installing and operating a microgrid vary depending on the segment in
which the power system is applied. Figure-5 below provides an overview of when and where
a microgrid could be considered depending on various factors.
Figure 5. Some main driving forces in applying Microgrids
108
4
Demand Response
AMI is a complete infrastructure which includes smart meters, communications, meter data
management system (MDMS). In the implementation of AMI, the communication is
bidirectional, which means that this facility enables monitoring the consumption of the
customer connected as well as controlling of the meter/appliances. The smart meter
component of an AMI system also has a display unit either within the meter or separately
mountable unit, which displays information about the energy usage. With this information
customer can make choices of running the home appliances selectively and efficiently based
on the consumption pattern and the price at the time of use.
AMI, which enables bi-directional communication between the utility system and the
consumer devices/appliances, can be extended to a full fledge Demand Response program.
Demand Response is a program to control and change the end customer energy consumption
pattern depending on the factors like time of use price, peak shave-off incentives. Peak shave
off is reducing the consumption to reduce and bring down the peak levels, so that the
electrical network can deliver without any disturbances arising due to overloads. Figure 6
depicts the demand curve when a DR program is implemented.
Figure 6. Peak shaving by shifting consumption pattern
As peak shave off is more important from the utilities perspective to maintain the operating
conditions of the grid, incentive payments are normally included to encourage end customers
to volunteer and subscribe to the program. The time-of-use consumption will trigger selfinterest in the end customer to use the appliances based on the tariffs fixed at different time of
the day. DR opens up a disciplined usage of energy by intentionally altering the time of usage
of home appliances. Demand Response is a voluntary program where the end customer
“participates” in helping the utilities to manage the energy distribution.
The implementations of Microgrids and AMI systems are widely viewed as enabling
technologies for demand response that will permit greater and more effective use of demand
response strategies. These technologies will allow for demand response programs to be more
extensive and more efficient. Demand response programs built on these technologies will not
only promote increased participation by commercial and industrial customers, but will foster
the integration of residential customers into demand response programs.
109
5
Communication technologies for Distribution Automation
A Smart Grid is expected to improve the power system operations, like –






Optimize asset utilization and operating efficiency.
Provide power quality
Anticipate and respond to system disturbances in a self-healing manner.
Operate resiliently against physical and cyber-attacks
Enable active participation by consumers.
Address Distributed Generation and energy storage options
While SCADA is the basic platform of an automation system, the applications for the
distribution network widely known as Distribution Management System (DMS) is a key
component of smart grid (or) distribution automation.
Communications between the field devices and the control center executing the automation
applications is critical to a power system because it serves as a backbone for the real time
information exchange. Combined with distributed intelligence, telecommunications make it
possible to report and resolve grid issues in real time (self-healing). In addition, the
information communicated by intelligent electronic devices alerts operators about an
abnormality and take corrective action. It is thus important to evaluate the system’s reliability,
security and availability, as well as technology cost, when choosing telecommunication
methods. The applications like FLISR used for reducing the outages and affected consumers
by remote operation of Ring Main Units (RMUs) and the volt-var optimization are
predominantly used applications in the Distribution Management System.
Scalability is another important consideration in choosing telecommunications technologies.
With smart metering, an advanced infrastructure of interval meters and two-way
communication systems serves as a gateway for distribution company-customer interaction.
This integration brings with it an exponential growth in the amount of data that must be
gathered, stored, and transformed in near real-time for intelligent responses and decision
support. Besides the AMI, even the RMU automation can be taken up in a phased manner to
increase the network visibility at the control center. The ability to scale up the communication
network becomes an important parameter.
Thus we see that the Distribution Automation covers not only the primary distribution
substations (33/11kV), but includes field networking devices like the RMUs, Smart Meters
etc. From the communication perspective, the entire chain between the control center, the
substations, RMUs, the smart meters and the Home Area Network (HAN) the communication
layer can be tired into 4 basic layers to cater to the Distribution Automation needs. The figure
7 below indicates these 4 layers.
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6
Figure 7. Communication tiers in a DA system
As Tier 3 and Tier 4 becomes more distributed as the geographical reach is spread across,
providing a robust tier 1 and tier 2 network becomes a key factor in highly enhancing the
reliability and availability of the DA system. While it is comparatively easier to choose a fiber
optic or a Microwave radio network for the tier 1, it is difficult to choose the right technology
for tier2.
A comparison between the various communication technologies for the tier 2 is given below :
Technology
Capability
Infrastructure
available in India
Land Line
Remote area
connectivity
not available
everywhere.
Cost of transferring Low
data
Reliability
Risk involved
Scalability
Wireless Telecom
Depends on the
service provider in a
particular location.
Low
(based
on
transmission during
off-peak time)
Low (due to High,
however
risk of physical depends
on
the
damage).
service provider in a
particular location.
Physical
High traffic during
damage
day-time
High
(major Low (bandwidth in
investment
wireless domain is
needed)
limited)
Power Line Carrier
Dependent on the
reliable distribution
network. Not widely
used in India until
now.
Low
(different
standards must be
implemented first so
initial cost may be
high)
Low (due to use of
newer and untested
technologies).
Private Radio Mesh
Mesh networks can
be established based
on the needs
Free
High
Newer,
relatively Onsite support
untested technology
High
(major High (technology is
investment needed)
not a barrier)
7
111
Application bundling Not possible
in
the
existing
network
Cyber Security
Secured
Not
possible Not possible
(bandwidth
in
wireless domain is
limited)
Public network - Secured
VPN required
Very High
Secured
From the above comparison establishing a private radio mesh network apart from the initial
costs involved, seems to be an option looking on the long term benefits it stands to deliver.
Conclusion
The basic concept of microgrid and its application in evolving Indian power scenario is
highlighted. Microgrids are expected to form an important component of smart grid. They
improve the operational efficiency as well as the reliability of the overall power system even
during emergency scenario, enabling maintenance of life line of power and communications
with a great portions of affected systems.
Demand Response program provides a technical solution to the saying ‘Energy saved is
energy generated’. While it provides the power system with the required energy to meet the
demand without a feeder level load shedding, it also a leaves a satisfied customer due to the
incentives and the availability of power to meet his critical requirements. Thus, the
implementation of DR is mutually beneficial to the utilities and the consumers.
Communications is the backbone of the successful implementation of Distribution
Automation solutions and choosing the right one for today ’s and future requirements is the
key for an efficient and cost effective implementation. With choices of technology available,
choosing the right one has to consider the long term plans in implementing solutions in phases
and weigh the pros and cons of each technology. While the popularly used GPRS network is
easy for implementation and involves less intial costs, a wireless mesh indicates a highly
reliable, scalable and secured network for real time data transfer for the tier 2 network.
8
112
Transformers & HV Equipment
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
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123
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
CIGREAORC& Technical
Meeting 2016
and International
Conference
Power
Transmission
Distribution
Systems including
Smart Grid,
24-26 Feb.
2016, New
Delhi, India
On the Roleofof
Power
Transformer
Design
for Resilient
Future
Electric
Energy
on
Systems
“Global Trends in the Development of Power T&D System including Smart Grid”
Tobias Haring*, Martin Stössl**
*Siemens AG, **Siemens AG Austria
On the Role of Power Transformer
Design**Austria
for Resilient Future Electric Energy
*Germany,
Systems
Tobias Haring*, Martin Stössl**
*Siemens AG, **Siemens AG Austria
*Germany, **Austria
SUMMARY
Power transformers play a key role in electricity systems as long as alternating current (AC)
grid infrastructure is the preferred technical solution for transmission and distribution of
electric energy. Further, the world-wide demand of electric energy is going to grow steadily in
SUMMARY
the next decades, and new challenges have arisen in terms of grid operation, and asset
management. First, financially supported intermittent feed-in of renewable energy sources,
Power
transformers
play
a keySecond,
role in electricity
long
alternating
partially
in remote
areas.
different systems
mixturesas of
ACas and
direct current
current(AC)
(DC)
grid
infrastructure
is
the
preferred
technical
solution
for
transmission
and
distribution
technology applied in the grid in addition to a rising share of converter based supply, of
and
electric
Further,
the world-wide
demand
of electric
energy
is going
grow steadily
hence energy.
diminishing
system
inertia. Third,
growing
concerns
about
the to
vulnerability
of in
the
the
next
decades,
and
new
challenges
have
arisen
in
terms
of
grid
operation,
and
asset
electric grid infrastructure to several exogenous system threats.
management.
financially
supported
intermittent
of renewable
energy hence
sources,
However, theFirst,
current
economic
evaluation
of reliablefeed-in
and resilient
infrastructure,
the
partially
in
remote
areas.
Second,
different
mixtures
of
AC
and
direct
current
(DC)
methods to calculate the total cost of ownership (TCO) of power transformers, given the
technology
applied
the grid
in additiondesign,
to a rising
of converter
basedincentives
supply, andfor
advancements
in inpower
transformer
may share
not trigger
the right
hence
diminishing
system reinforcements,
inertia. Third, growing
concerns about the vulnerability of the
investments
in respective
or new technologies.
electric
grid
infrastructure
to
several
exogenous
system
threats.
The aim of this paper is to review some the most recent
advancement in power transformer
However,
the focus
current
evaluation
of reliable
and resilient
henceand
theto
design with
oneconomic
the previously
mentioned
challenges
in powerinfrastructure,
system operation,
methods
to
calculate
the
total
cost
of
ownership
(TCO)
of
power
transformers,
given
highlight the problematic setting of focusing solely on purchase price and loss evaluationsthefor
advancements
in element
power such
transformer
design, may
trigger the
incentives
for
a critical system
as a transformer.
It cannot
be concluded
thatright
further
improvements
investments
in
respective
reinforcements,
or
new
technologies.
in the life cycle costs evaluations, and the design of specifications are needed in order to
The
aim of
paper is gap
to review
some
the most
recent advancement
in power transformer
narrow
thethis
commercial
between
technical
innovations
and its remuneration.
design with focus on the previously mentioned challenges in power system operation, and to
highlight the problematic setting of focusing solely on purchase price and loss evaluations for
a critical system element such as a transformer. It can be concluded that further improvements
in the life cycle costs evaluations, and the design of specifications are needed in order to
narrow the commercial gap between technical innovations and its remuneration.
KEYWORDS
Power Transformers, Reliability, Resiliency, Total Cost of Ownership
E-Mail: tobias.haring@siemens.com
KEYWORDS
Power Transformers, Reliability, Resiliency, Total Cost of Ownership
124
E-Mail: tobias.haring@siemens.com
1. Introduction
Reliable and resilient power systems are of vital interest in any economy worldwide [1] [2]
[3] [4]. On the one hand, the resilience of a power system determines the ability of a system to
recover from a failure into a state, where it is considered functional. On the other hand,
reliability can be defined as the ability of the power system components to deliver electricity
at all times in the quantity and with the quality demanded by the customer [5]. It is clear from
the definition above that a reliable, or robust, grid does not include resiliency, but transitions
are blurred.
In order to quantify the worth of a reliable electricity grid we follow [6], where the metric
chosen is the return on investment (ROI). There, the authors conclude that each US $1
invested in reliability and resiliency of grid infrastructure triggers a return of US $2.80–6 to
the U.S. economy. Moreover, the authors estimate that a stronger grid would reduce the lowend estimate of current outage costs of US $80 billion annually by US $49 billion.
Additionally, it is estimated that the efficiency of the system would increase by about 4.5%
which makes up another US $20.4 billion, annually. In sum, the annual benefit of reducing
outages, and improving efficiency is about US $70 billion.
However, at the same time, current power systems are exposed to several challenges, partially
with tremendous severity in case the system is under stress conditions. First, large scale
renewable energy sources with variable feed-in behaviour are installed in mainly remote
onshore, or offshore, areas [7]. This means more than ever that electric energy has to be
transported reliably over long distances to the load [1]. Second, due to large scale converter
based injection of intermittent energy sources or geomagnetic distortions, diminishing system
inertia, and non-sinus wave voltage penetration of the grid. Third, the installation and
operation of high-voltage power system equipment gets closer to populated areas, or areas
where it is environmentally highly exposed. Fourth, an increasing exploitation of technical
margins in the electric grid infrastructure. All previously mentioned trends account not only
for the system design, but also for component design. In particular, the technical design and
economic assessment of long-serving and established elements like power transformers has to
be revisited.
The reliable, and hence resilient, operation of a power transformer requires a diverse set of
preventive and corrective actions not only for technical disturbances, e.g. electric failures
during operation, but also against non-technical threats. Given the definitions in [2] on grid
resiliency, and summarizing all the previously mentioned tendencies, it is eligible to question
how the design of power transformers as a major element of substations can tackle these
issues, given the cost pressure in terms of investments in electric grid infrastructure, but also
the operation of the grid. Similar to grid operation, with its well-known classification of
preventive, i.e. N-1 criterion, and corrective actions, i.e. generation re-dispatch, a resilience
concept, which comprises “Prevent”, “Protect” and “React” is introduced [8]. “Prevent”
contains all measures, which increase transformer life-time, and help to prevent unplanned
outages. “Protect” comprises all actions and design elements with the aim to protect the
transformer against natural and man-made destruction. However, this term also covers the
protection of the environment of threats coming from the transformer. For example, hazard on
man and the environment due to fire and explosion of a transformer using mineral oil as
insulation medium. The term “React” contains all actions and design elements, i.e. mobile
design at different ratings with adjustable bushings, which enable the fast replacement of a
damaged unit and the re-energization of the affected sub-system.
The aim of this paper is to review on the one hand the term “Protect”, hence design proposals
with the aim to alleviate problems (a) of direct current (DC) penetration of the AC grid
through converter-based injection, close operation of AC and DC grids, or of geomagnetic
125
1
induced currents (GIC), (b) in substituting mineral oil as insulating and cooling medium, (c)
in terms of the ability to handle short-circuits, and (d) in terms of the ability to withstand manmade vandalism. Further, this paper deals with the “React”-phase, which comprises what can
be done in case that protective actions weren´t enough to prohibit the damage of a transformer
and how this may be economically evaluated. On the other hand, the identified technical
challenges, and their impact on the operation of the grid are contrasted with current
approaches in the economic assessment of power transformers.
By the best of our knowledge, no similar literature has been found, which comprehensively
summarizes the upcoming challenges on power transformers in the field between economic
interests and the need for technical innovation.
This paper is structured as follows: Section 2 reviews different challenges that power
transformers are exposed to in modern grids, and how these issues can be tackled with state of
the art technology. Section 3 explains why traditional total cost of ownership approaches may
not be sufficient to capture new requirements on power transformers in a resilient grid.
Section 4 concludes the paper.
2. New challenges for Transformer Designs
Following [9], transformer design is an iterative and interactive process which has to consider
many parameters and boundary conditions in order to find an optimal solution. The
technically sound solution comprises a balance between cost efficiency and,
 Masses and losses,
 Sound level,
 Short circuit strength,
 Winding temperature, hot spots, and cooling equipment,
 Dielectric strength between windings and inside windings.
In the following, major threats and design challenges for transformers, which directly relate to
the previously mentioned design issues are described.
2.1 Direct Current Penetration
AC systems may be penetrated by different sources with DC currents [10] [11] [12] [13].
Those distortions may be due to,
 converter-based system components, i.e. Static Var Compensators (SVC) or High
Voltage Direct Current (HVDC) transmission,
 close operation of AC and DC infrastructure, maybe historically grown, or for
transmission purposes in order to save space,
 geomagnetic induced currents (GIC).
The first two sources of DC penetration are regarded as not critical for the transformer itself,
however they influence tremendously the performance of the transformer. The major effect of
DC is the core saturation during one half of the cycle wave, known as half wave saturation
[12], which results in (a) a higher consumption of reactive power, because during each core
saturation time instant the leakage flux, which penetrates the windings, leads due to the
nonlinearity of the magnetization curve to an increased exciting current with harmonics [11]
[12], (b) a higher noise level including a wider noise spectrum, (c) to increased no-load losses.
The impacts of the last two effects are also non-linear dependent upon the amount of DC
penetration in the grid. Finally, laboratory tests have shown that higher temperatures at the
axial centres of the tie bars and the clamping plates could be identified. Figure 1 shows
hotspot temperature evolvement for different transformer types [11]. Possible effects of
126
2
increased temperature levels can be determined via IEC 60076-2:2011 [14] and IEC 60076-72005 [15].
Figure 1 Hotspot temperatures of critical components in case of GIC penetration for different transformer type T1 T2, T3,
and the IEC Limit (ambient temperature = 30°C), Source: [11].
In order to deal with DC penetration at different levels, various countermeasures can be set.
For example, GIC safe design through the usage of non-magnetic steel inserts in the
transformer and other design specifics. On the other hand, small DC penetrations may be
evened out via in-build compensatory devices. The principle of Direct Current Compensation
(DCC), as well as test results are shown in Figure 2. The challenges are the exact
measurement of small DC currents in the high voltage equipment, the speed of the control
mechanism, and the height of the currents which can be compensated with such a mechanism.
A further discussion about alternative ways of DC compensation outside of the transformer,
and their pros and cons, is out of the scope of this paper.
Control signal from core
Digital
control
loop
DCC
cabinet
Injecting counter DC in
compensation winding
(a)
(b)
Figure 2 a.)Major design principle of direct current compensation, b.) reduction of noise level with direct current
compensation for a 134,4MVA single phase test unit, Source: [12].
2.2 Replacement of Environmentally Critical Materials
One decisive factor of supporting resiliency in grid operation from a power transformers’
perspective is the usage of non-critical substances, which allows the fast recovery, or
replacement of a device in case of failures. Figure 3 illustrates the major motivations for using
alternative insulations and cooling media compared with mineral oil in power transformers
[16] [17].
127
3
(a)
(b)
Figure 3 Illustration of major advantages of alternative insulation and cooling media: a.)Biogradability, and b.)Flashpoint,
Source: [16].
Mineral Oil: Mineral oil is made from fossil oil and consists of hydrocarbon compounds with
various bonds. The main disadvantages of transformer oil are the low fire point, and the very
limited biodegradability characteristic.
Silicone Fluids: Silicone fluids are specially developed for transformer applications and are
fully synthetic coolants and insulation fluids. The very low biodegradability, and the
formation of jelly-like bridges of silicone-oxide under arcing, are disadvantages.
Synthetic Esters: Synthetic esters are derived from chemicals. They are usually the product of
a polyol with synthetic or natural carboxylic acids to give structures, where several acid
groups are bonded to a central polyol structure. Their flash and fire points are higher than
those of mineral oil.
Natural Esters: Natural ester fluids can be classified into saturated, single-, double and triple
unsaturated fatty acids. Saturated fatty acids are chemically stable, but have a high viscosity.
Their flash and fire points are significantly higher compared to mineral oil.
Over time, transformers of different ratings, i.e. rated voltage 238 kV and 135 MVA rated
power, were successfully tested with synthetic ester. In 2013, the worlds’ first power
transformer with natural ester with a rated voltage of 420 kV and a rated power of 300 MVA
has been successfully tested. An in-depth discussion about the dielectric characteristics, aging,
etc. is given in a rich literature and is out of the scope of this paper.
2.3 Robustness against Technical/Natural/Man-made Threats
As mentioned in the beginning, resiliency, reliability, and robustness are terms which are
sometimes used interchangeably.
In the following, we divide the robustness of transformer into two classes,
 Operational Robustness,
 Non-Operational (Disaster) Robustness.
In case of operational robustness, the short-circuit withstand capability is recognized as an
essential characteristic of power transformers [9]. Standard tests are manifested, i.e. IEC
60076-5 [18]. However, the authors of [9] highlight that in past test series up to 28% of the
short-circuit tests failed initially. These failures were observed throughout the complete range
of voltage and power. Therefore, as shown in ref. [19] and [20], the expenses for short-circuit
testing must be weighed against the importance of the function of the transformer, and the
time for repair and replacement.
For non-operational robustness, natural disasters such as earthquakes, and man-made threats
such as vandalism and hence terrorism are of growing concern. With regard to the seismic
requirements, the IEEE 693 [21] provides guidelines for design consideration of a transformer
in order to withstand different grade of seismic activity. However, man-made attacks on vital
128
4
infrastructure require additional considerations which account for the resiliency of the system
and the equipment. Advances on the transformer level have been made in this direction, e.g.
[22], but require also a holistic view on a substation.
3. New Challenges in Terms of Economic Evaluation
All previously mentioned design issues, which improve grid resiliency require an in-depth
knowledge about the whole environment that the transformer is embedded. Hence, they are so
far non-standard and may require additional financial effort for the transformer.
3.1 General Statements on the Total Cost of Ownership
The total ownership cost (TCO) is typically used during a tendering process to compare the
offerings of two or more manufacturers. The aim is to facilitate the best purchase choice
among competing transformers [23]. However, the real cost of a transformer for the owner is
the sum of the initial purchase price plus the cost of running it up to many decades. Therefore,
as probably already intelligible from the previous section, a sole rely on the purchase price
and loss evaluation to determine the total cost of ownership may not be sufficient for the best
choice at all. From the 1960´s on, electric utilities developed loss evaluation formulas [24]
[23]. Following [25], a complete specification evaluating losses should include:
1. The evaluation cost per kilowatt of losses,
2. The percent of rated load for the evaluation.
A general methodology about the economic evaluation of system losses has been done in
[26]. The authors divide the costs into a demand component, which reflects the costs of
serving an additional kW of load, and an energy component, which reflects the cost of
producing the increment of energy required by the losses. The regard to the current practise in
the economic evaluation of a power transformer, several past approaches where evaluated and
the general methodologies follow the respective standardizations, i.e. IEEE C57.120.1991
[27]:
,
Eq. 1
,
Eq. 2
where,
“A”…cost of installing a kilowatt of plant,
“B”…fixed charge rate of a plant,
“C”…cost of a kilowatthour,
“D”…hours per year that transformer is energized.
Parts “A” and “B” make up the yearly cost of the demand portion. Parts “C” and “D” make up
the yearly cost of the energy portion. The numerator shows how much it costs per year to
provide a kilowatt, whereas the denominator determines how much a user can afford to pay
for a more efficient transformer to save that kilowatt.
3.2 Improvement Potential for Conventional Economic Evaluation Methods
Given the previous notion of total cost of ownership, we highlight in the following
supplementary points which show that the sole evaluation based on purchase prices and
electric losses may be insufficient.
The Notion of Losses: In general the electric efficiency of power transformers is regarded as
very high. However, losses in form of waste heat may still be re-utilized as shown in practice
129
5
[28] [29] [30] [31]. Therefore, additional considerations about the worthiness of additional
low process heat sources are valid, in particular for areas with high population density, and
hence energy density.
Market-Driven Approaches vs. Security-Driven Approaches: The authors in [23] and [32]
enhance existing methodologies by including (a) a method of incorporating the contribution
of the user´s operating expenditures to supply life-cycle losses of power transformers, and (b)
the calculation of the projected energy prices per specific fuel used in the generation mix of
the system. This paper already highlights an important additional aspect in the discussion
about the applicability of the conventional TCO calculation. Namely, the involvement of a
decentral market framework, and the ownership status in the loss evaluation process. In a
subsequent paper [33], the authors add probability theory to a decentralized market
framework in order to split the TCO for an independent wind power producer into a “wind
plant element”, and a “market element”. Hence, the evaluation of losses becomes a term of
the form,
,
Eq. 3
where the total value of losses is itself again dependent upon different operating states, and
therefore different pricing schemes. The mean value , and the standard distribution
indicate the probabilistic nature of the considered influential factors. This approach becomes
particularly interesting in case of a locational component for the electricity prices. Locational
marginal pricing (LMP) uses market-based prices for managing transmission congestion.
Following [34], LMPs depict the marginal cost of supplying the next increment of electric
demand at a specific location (node) on the electric power network, taking into account both
supply (generation/import) bids and demand (load/export) offers, the physical aspects of the
transmission system including transmission, and other operational constraints. Thus, two
transformers connected over a congested line with financially supported renewable energy
sources and weak load on the one end, and high load on the other end, may be evaluated
differently. In fact, the market component at the line end where the renewable energy source
is attached would be small, but a market based loss evaluation at the load centre would lead to
strong emphasis on low losses.
Ref. [35] provides a methodology for the economic valuation of transformers considering the
aging loss, the power loss, and the outage risk of a transformer. The authors define a nodal
outage cost function, where the outage costs increase with the amount of load shedding, but
with decreasing marginal cost. The authors can show that their approach clearly shows high
total costs in case of an increasing load level. Clearly, the outage costs are influenced by the
system structure, the flow limits in the branches, and the outage costs of the customers.
, are defined as,
Hence, the total cost of a transformer,
Eq. 4
is defined as the cost of an outage,
are the aging costs, and
are the
where
costs of power losses.
However, the evaluation of consumer outage costs as stated in Eq. 4 is not straight forward. It
leads directly into the debate about the value of lost load, which is not only dependent upon
the classification of the load, i.e. residential or industrial, but also the timing of the day, the
duration, and the repetition rate [36] [37] [38]. Further, the authors in [39] conclude that there
are critical issues related in both power transmission and distribution standards if they are
seen from the perspective of their foundations in risk and reliability. In particular by (a) using
130
6
inconsistent methods of calculation of reliability indices, (b) inconsistent treatment of major
event impacts, (c) reported average indices that hide spots of poor reliability, and (d) a lack of
quantified targets for achieving an acceptable level of reliability. Thus, the risk indices
calculated for transmission system do not completely capture the risks associated with the
transmission system. However, an in-depth treatment of the right use of reliability metrics is
beyond the scope of this paper. The comparison of these different approaches immediately
results into the contrast of economic interests, and the difficulty of market driven approaches
to grasp the technical notion of reliability, and technical constraints which have to be
balanced.
Consideration of Maintenance: The state-of-the-art in maintenance management offers at least
three basic approaches for making maintenance management decisions [40]:
(1) Condition-Based Maintenance (CBM) initiates a maintenance activity when recorded data
from equipment monitors indicates the need for it.
(2) Reliability Centered Maintenance (RCM) prioritizes maintenance activities based on
quantification of likelihood and consequence of equipment failures. Thus, the underlying
principle in RCM is that maintenance scheduling should be related to the failure likelihood so
that a piece of equipment is maintained, when its failure probability increases significantly.
(3) Optimization Techniques (OT) offer methods for maximizing effectiveness of the
maintenance activities subject to constraints on economic resources, available maintenance
crews, and restricted time intervals.
From a temporal perspective, long-term considerations (based on the individual component
performance, the objective is to maximize the residual life of equipment while minimizing the
cost of maintenance), mid-term considerations (the scheduling is based on the forecast of
network and loading condition for a period of time, which is usually one year, with limited
resources to be allocated in the maintenance period), and short-term considerations (impact on
bilateral and nodal priced electricity markets and reliability criteria which cannot be violated)
are identified. A recent example for the combination of mid-term and short-term maintenance
problem is done in [41] [42], where both issues are combined via a Mixed Integer Linear
Program (MILP). A heuristic approach is presented in [43].
Therefore, given the complexity of the timing and the various approaches for maintenance, a
decoupling of the costs of maintenance efforts from the total costs of ownership may counter
the initial savings of low purchase prices.
Consideration of the transformer environment: The initial price of a transformer may not be
always the key to a cost-optimal substation design. For example, ignoring technical features
such as mineral oil substitutes, or in-build equipment to reduce noise impact (which may safes
an additional sound-house) may lead to the paradox situation where the choice of cheap
devices lead in total to a suboptimal and even more expensive total design. As shown in
Figure 4, the transformer is usually one element in an interconnected system. Therefore, when
comparing the total costs of ownership of different transformers, also the changes in the costs
of the total system design such in the grounding expenditures, civil work, environmental
protection, electric protection, etc. of a substation have to be taken into account.
Figure 4 Embeddement of a transformer (TR) in an interconnected system such as a substation with high voltage (HV),
medium voltage (MV), low voltage (LV), and other equipment, Source: own illustration
131
7
Consideration of Resiliency: Despite technical innovation and diverse measure for equipment
protection, the possibility of failures remains [44] [45] [46]. Therefore, in addition to the
purchase of a transformer, considerations about its fast replacement have to be made.
However, respective business models require in-depth financial assessment, are system
specific and therefore are out of the scope of this paper.
4. Conclusions
The aim of this paper was to highlight the gap between a rising demands for technological
innovation in the design of power transformers on the one hand, and the means to financially
assess them on the other hand. The immediate and critical goal is to avoid widespread
network failure, but the longer-term vision is to enable an adaptive, and resilient
infrastructure. Several issues in modern power transformer design have been demonstrated,
which all require close interaction between utilities, system operators, and manufacturers, and
may comprise additional financial effort for the power transformer in terms of the initial
purchase price. However, we have also shown that current methods to evaluate the costs of
ownership of a power transformer may not be sufficient to highlight the importance of
reliable, well-performing, and resilient infrastructure. Further research is needed in the lifecycle cost analysis of power transformer and infrastructure equipment in general in order to
ensure financially sustainable system design.
Acknowledgement
We would like to acknowledge the support of E. Abold, G. Fleck, F. Klammler, G. Leber, G.
Pukel, J. Raith, and E. Schweiger for their kind support during the creation of this paper.
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134
10
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
CIGRE- AORC Technical Meeting 2016 and International Conference
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
on
“Global Trends
the Development
of Power
T&D System
including
Smart Grid”
Challenges
for theinapplication
of Natural
Ester fluids
in extra high
voltage
transformers
Challenges for the application of Natural Ester fluids in extra high voltage
Alan Sbravati John Luksich
Kevin J.
Rajaram Shinde
David
transformers
Cargill
Brazil
Alan Sbravati
Cargill
Brazil
Cargill
USA
John Luksich
Cargill
USA
Rapp
Cargill
USA
Kevin J.
Rapp
Cargill
USA
Cargill
India
Rajaram Shinde
Cargill
India
Bingenheimer
Cargill
USA
David
Bingenheimer
Cargill
USA
SUMMARY
Approaching 20 years of commercial application, natural ester insulating liquids are, by far,
the most successful ‘alternative fluid’, and have reached a relevant market share positioned
beyond a niche product to a mainstream fluid. A significant number of test programs and field
SUMMARY
applications have shown that natural ester liquids are an effective alternative to mineral oil.
Currently the two initial motivations for its development (improved fire and environmental
Approaching
20 years of commercial application, natural ester insulating liquids are, by far,
safety) are increasingly considered as a “bonus”, overshadowed by the life extension of the
the cellulose
most successful
‘alternative fluid’, and have reached a relevant market share positioned
based materials immersed in natural ester liquid. The possibility of increasing the
beyond
a nichetemperature
product to aofmainstream
number
of test
programs
and field
operational
transformersfluid.
by upAtosignificant
20 degrees,
associated
with
the increased
applications
have
shown
that
natural
ester
liquids
are
an
effective
alternative
to
mineral
reliability enhanced by the continuous process of water removal from the solid insulation,oil.
is
the primary
motivator
the accelerated
of natural (improved
ester liquid filled
transformers.
Currently
the two
initialformotivations
for adoption
its development
fire and
environmental
safety)
areofincreasingly
considered
as a “bonus”,
overshadowed
by the class,
life extension
of the
Years
validation were
required before
increasing
the range of voltage
reaching the
245kV
class
ten
years
ago.
Five
years
ago,
the
application
at
extra
high
voltage
units,
at
the
cellulose based materials immersed in natural ester liquid. The possibility of increasing the
level of temperature
420kV and 550kV,
gained serious
first extra
high
operational
of transformers
by up consideration.
to 20 degrees,The
associated
with
thevoltage
increased
transformer,
420kV/300MVA,
is
in
operation
for
over
two
years.
Higher
voltage
equipment
reliability enhanced by the continuous process of water removal from the solid insulation, is
and HVDC
are currently
receiving
attention.
the primary
motivator
for the
accelerated
adoption of natural ester liquid filled transformers.
The baseline for dielectric validation has always been side-by-side comparison with mineral
Years
of validation were required before increasing the range of voltage class, reaching the
oil. However, because of fundamental differences between natural ester liquids and mineral
245kV
class ten years ago. Five years ago, the application at extra high voltage units, at the
oil, testing procedures may require modifications to achieve reliable results.
level of 420kV and 550kV, gained serious consideration. The first extra high voltage
This paper420kV/300MVA,
presents several studies
and tests conducted
by renowned
institutions
around
the
transformer,
is in operation
for over two
years. Higher
voltage
equipment
world.
Differences
between
the
liquids
and
application
conditions
have
been
identified,
which
and HVDC are currently receiving attention.
have an impact on the dielectric design and the insulation system of a transformer. There are
Theno
baseline
dielectric
validation ofhas
always
been
side-by-side
comparison
with mineral
apparentfor
barriers
for application
natural
ester
liquids
in extra high
voltage equipment,
thatbecause
design and
testing are conducted
properly.
oil. provided
However,
of fundamental
differences
between natural ester liquids and mineral
oil, testing procedures may require modifications to achieve reliable results.
ThisKEYWORDS
paper presents several studies and tests conducted by renowned institutions around the
Natural
ester liquid,
dielectric
high voltage conditions
transformershave been identified, which
world.
Differences
between
the design,
liquidsextra
and application
havealan_sbravati@cargill.com
an impact on the dielectric design and the insulation system of a transformer. There are
no apparent barriers for application of natural ester liquids in extra high voltage equipment,
provided that design and testing are conducted properly.
135
KEYWORDS
Natural ester liquid, dielectric design, extra high voltage transformers
alan_sbravati@cargill.com
INTRODUCTION
The adoption of natural ester liquid application is accelerating. After an initial period of application as
a more cost-effective (in comparison to other K class liquids) niche product for fire and environmental
sensitive locations, the early 2000’s represents the early acceleration period. In those early years,
several users converted their new distribution transformer specifications to natural ester liquid filled
units. This was achieved based upon payback calculations considering life extension and increased
reliability. The scientific basis for the calculations was accelerated life testing, which identified a
significant reduction of the cellulosic material degradation rate when immersed in natural ester liquids.
Some of these utilities now have a history of more than 10 years of successful experience, indicating
that the payback calculations were very reliable. The validation of reduced failure rate and life
extension, associated with the cost reduction of the transformers filled with natural ester liquids,
provides confidence in the technology.
A few years ago, based on many additional studies and field experience, the benefits of the
interactions between natural ester fluids and cellulosic material have been included in standards. The
IEEE C57.154 [1], published in October 2012, and the IEC 60076-14 [2], published in September
2013, have a very comprehensive review of the aging studies and suggests higher thermal classes for
kraft and thermally upgraded paper in their Annexes (B and C, respectively). The same table can be
found in both standards:
Table 1 – Partial reproduction of Table included in IEEE C57.154 – Annex B and IEC 60076-14 – Annex C,
supporting the use of higher thermal classes for papers immersed in Natural Ester in comparison to Mineral oil.
Constant
Temperature Thermal Thermal
a
(°C)
index
class
Mineral oil/thermally upgraded kraft paper
9.80 × 10-18
110.0
110
120
Natural ester fluid/thermally upgraded kraft paper
7.25 × 10-17
130.6
130
140
In [1] and [2] temperature rise limits for solid insulation materials of different thermal classes are
indicated (see Table 4 of [1] and [2]). As the thermal class of cellulosic materials is increased when
they are immersed in natural ester liquids, the simple replacement of the insulating liquid allows
increasing the temperature rise limits of the transformer up to 30K. This may allow some increase of
transformer rating, estimated up to 20% extra power, or, in the case of new transformers, optimization
of core and coils to the new set of limits, saving materials and reducing total cost. As clearly indicated,
the increase of the thermal class of cellulosic based materials is only valid for natural ester liquids.
Using other dielectric liquids requires the use of solid insulation materials reaching the required
minimum thermal class.
CHALLENGES FOR APPLICATION IN POWER TRANSFORMERS
The adoption time of any new technology includes several development phases, which lengthens the
required time for a smooth transition toward long term use. Initial application of natural ester liquids at
lower voltages and power was important, both to minimize impact to the end customers and the costs
of the trial orders and prototypes.
After gaining experience in distribution transformers, several new questions arose that pertained to the
use in larger equipment. A renowned consultant, Mr. Harold Moore [1], developed a matrix of tests
and baseline conditions for applying natural ester liquids in larger power. These tests were completed
through 2010. Some of the main questions referred to oxidation stability, the cooling impact of higher
viscosity, and the dielectric withstand capacity.
The oxidation stability of natural ester liquids is now better understood, especially considering the
extensive list of about 26,000 power transformers in service with excellent performance in all climatic
conditions and maintenance policies around the world.
Viscosity of Natural Ester Liquids
The viscosity of natural ester liquids is higher than mineral oil. Considering the properties of the most
widely used brand, Envirotemp™ FR3™ liquid, the effective difference is from a typical value of
136
1
9 cSt for mineral oil to 32 cSt, at 40C, which is still a relatively low viscosity value. For comparison,
the viscosity of a synthetic ester transformer liquid is about 28 cSt, while a high molecular weight
hydrocarbon is about 110 cSt.
Tracking the top oil temperature of mineral oil power transformers retrofilled with natural ester liquid
or, restated, units designed for mineral oil, but filled with natural ester liquid, shows an average
increase of 5K.
Dielectric Behavior
The dielectric behavior of natural ester liquids, as well as their physical and chemical properties, may
be different when the base oil is changed. The complexity of the breakdown process involves
electronic phenomena as well as aspects of the gaseous phase, which makes extrapolation of behaviors
very difficult from one fluid to another. It is important to have test data from the actual fluid under
consideration, preventing eventual problems due to assumptions like “it is almost the same”. Data
presented in this paper refers to the natural ester FR3 fluid produced by Cargill.
TESTING NATURAL ESTER FLUIDS
A very long list of tests have been performed, starting from ASTM D1816 and IEC 60156. Even for
such widely applied standard tests, there are some differences between the fluids which must be taken
into consideration. When testing a sample of natural ester liquid directly from the tote there are two
aspects to be considered: the fluid has a high nitrogen gas concentration, both due to shipment and
manufacturing processes, and the higher viscosity increases the required time for bubbles to dissipate
due to the pouring procedure. Because of this, it is recommended to increase the resting time to about
30 minutes between pouring the fluid and starting the application of voltage. This behavior is clearly
identified in the chart presented at [5], from where Figure 1 has been taken.
The blue curve in Figure 1 shows a clear tendency of improved breakdown voltage with successive
shots increasing in time after the pouring process. As a comparison, the red curve shows constant test
results using 30 minutes between shots. Using the average of the data plotted by the blue curve would
lead to wrong conclusions. The very same process will affect other non-standardized dielectric tests. It
may be even worse, since some electrodes are designed with oil wedges and regions that can entrap
bubbles. A carefully designed electrode should take this into consideration.
The next essential aspect is the targeted region that is to be evaluated. The design and construction of
the testing electrode will, very often, allow the discharge to happen in different regions as depicted in
Figure 2, taken from [6]. Another particularity of the natural ester liquid affecting this is the higher
permittivity, closer to the value of impregnated paper. This causes the electrical field to be shifted
towards the solid insulation, in comparison to the same structure filled with mineral oil. The result is
an increase of the voltage concentration on edges and small constructions, requiring additional care for
the use of shielding structures.
The presence of sharp edges and regions of highly concentrated electrical field may lead to disruptive
discharge in regions outside of the focus zone. This particular condition may be identified when
analyzing one of the tests from [6]. As described in the paper, test results had a high variability, whose
root cause was the occurrence of disruptive discharge in regions out of the target area. Clearly the
target gap, which would be the path A, is not the only region affecting test results. In this case the
Figure 1 – Influence of the waiting time on test.
137
Figure 2 – Three different breakdown paths for
model with paper insulated conductor.
2
obvious conclusion is that the test is not valid for determining the breakdown voltage of gap A. It may
be valid for evaluating other phenomena, but any result for this gap is questionable. Statistical analysis
can be applied to anything, but the physical sense is completely lost in this case, since different
phenomena are affecting the spreading of results. Even if the standard deviation of the data population
is low, it is possible that 95% of the breakdowns have happened in regions B or C, which is not the
gap under investigation. A well designed test and test specimen should avoid all these issues.
PERFORMED TESTS – HOMOGENEOUS FIELDS
The same difficulties were encountered when testing the three electrodes shown in Figure 3. As the
repetition of the complete development of design curves for natural ester liquids would require
hundreds of tests, the initial test program was combined with the expertise of Weidmann insulation
experts at that time [7-8] for defining the critical tests to ensure the design curves from mineral oil
could be used for natural ester fluids.
Electrode 1 in Figure 3, designed for representing a gap turn-to-turn or coil-to-coil in a real winding,
was expected to be sufficient for testing up to 25mm gap, but it had unreliable results at 12mm.
Electrode 2, targeting gaps from 12mm to 25mm was only useful for 12mm, due to creep breakdowns
outside the test gap area of the 25 mm specimen. Electrode 3 was a much more robust construction
with a shielding disc at the fixing points of the electrodes. With this construction it was possible to
obtain results up to a 50mm gap distance. However, as the gap distance increases more of the
breakdowns take place at the radial ends similar to gap B in Figure 2, which increases dispersion.
The shielding and shape of the cable was aimed to ensure the disruptive discharge was always at the
target area between the two conductors, but, as a scientific test, including a large number of repetitions
of breakdowns, the construction is not sufficient for long gaps. It is essential to understand the
difference between an electrode designed for hundreds of breakdowns and a real construction of a
winding, which should never see a breakdown. Final results for this round of tests are presented in 0.
The results presented in [10], always at a direct comparison (side-by-side) to mineral oil, confirms the
breakdown voltage of natural ester liquids is statistically equivalent to mineral oil. The side-by-side
comparison is essential, since different test setups may lead to a large variation in results.
Tests for creepage may be found in [7] and [8], also reinforcing the same conclusion of equivalency
between the dielectric strength of natural ester liquid and mineral oil.
Electrode 2
Electrode 1
Electrode 3
Figure 3 – Different designed electrodes for testing different gaps, representing the region between discs or coils.
Table 2
– Results of dielectric tests of electrodes presented in Figure 3. NE = Natural Ester; MO = Mineral Oil
Electrode
Electrode 1
Oil Gap
Fluid
Average gap
(mm)
U50% (kV)
3mm
NE
5mm
MO
NE
Electrode 2
8mm
MO
NE
12mm
MO
NE
12mm
Electrode 3
25mm
50mm
MO
NE
MO
NE
MO
NE
MO
3
3
5
5
8
8
12
12
10.3
12.3
23.3
24.1
48.1
48.0
139
U50% (kV/mm) 46.3
Std Dev.(kV) 18.5
122
40.7
20.3
175
35
44.5
156
31.2
21
211
26.4
21
209
26.1
16.9
266
22.2
38.8
275
22.9
17.3
352
34.2
8.3
404
32.8
13.9
611
26.2
116
695
28.8
139
712
14.8
97.8
846
17.6
79.4
138
3
PERFORMED TESTS – INHOMOGENEOUS ELECTRICAL FIELDS
One of the main activities of a transformer designer is to verify the electrical field distribution,
spending significant time and material to make this distribution as homogeneous as possible.
However, there are some regions of a transformer where it is necessary to deal with inhomogeneous
fields. In such regions the challenge is to minimize the field concentration, as higher values of voltage
gradient can lead to partial discharges and, eventually, disruptive discharges. Accordingly, the tests of
inhomogeneous fields can be divided in two main groups: transformer like electrodes and breakdown
mechanism studies.
The electrodes identified as “transformer like” are designed to represent specific regions of a power
transformer. As a sequence of the H. Moore matrix, the structure considered as most critical was the
bushing electrode, which was chosen to be represented in the tests described in [9], [10] and [11]. A
stainless steel disc 216 mm diameter × 38 mm thick with a top and bottom edge radius of 4.3 mm was
installed at the bottom of a 550kV (AC) / 1850kV (BIL) bushing and the distance between this disc
and the bottom of a test tank was the tested gap. For distances up to 150mm, reaching impulse level up
to the limits of the bushing, the resultant curves confirm again an equivalency between dielectric
strength of natural ester liquid and mineral oil.
A second set of “transformer like” electrodes were chosen to be the contacts of a tap selector rod from
an actual on-load tap changer, supplied by MR (Maschinenfabrik Reinhausen) as the most critical gap
inside the LTC equipment. This testing was quite challenging, as the complex structure is very
favorable for micro gas bubble entrapment and the laboratory does not reproduce completely the
filling procedure of a real power transformer. However, testing the gap between contacts and to the
tank, to the limits of the testing setup, again confirmed a dielectric strength of natural ester liquid
equal or superior to mineral oil. These results can also be found in detail in [10].
Streaming Electrification
Still within the group of “transformer like” studies is the comparison of streaming electrification. This
is a concern for transformers with forced or driven oil flow, where the velocity of the liquid in contact
with the insulation material may generate static charges. The generation of static charge and charge
accumulation can lead to static or partial discharge in transformers having high oil flow rates. Because
the resistivity of natural esters and fatty acid esters is lower than mineral oil, electrical charge moves
more easily compared to mineral oil, especially at elevated temperature when flow due to pumping is
most prevalent. Tests using the “ministatic” method as in [12] to [15], “spinning disk” method [16],
and Kerr-optic oil filter method [17] show higher charge density for natural esters compared to
mineral oil, while static charge generated using a PTFE filter method shows a higher charge density
for mineral oil compared to natural ester liquid [18].
The balance between the two mechanisms may create some difference in behavior, which is expected
to be positive. However, just as a safety margin, some manufacturers apply a reduction on the
velocities considered as critical. While in mineral oil values in the range of 300cm/s are considered are
critical, for natural esters some consider about 200cm/s. As the effective value inside the coils are,
typically, much lower than this, such safety margins are not really impacting the design.
Partial Discharge Inception Voltages
The investigation of partial discharges (PD) is in the transition between the two types of tests.
Electrodes creating highly concentrated field are applied to create high voltage gradients without
requiring too high voltages. The voltage is then increased to the level where disturbances on the wave
shape are identified, indicating the occurrence of PD.
As deeply studied in [19] and [20], the level of PD inception voltage of natural ester liquids is superior
to mineral oil at several different temperatures and moisture saturation conditions.
Other studies, such as [5], identified that the level of PD when the applied voltage is superior to the
inception level, will be higher in natural ester than in mineral oil. Despite generating interest, this type
of study is no longer a “transformer like” investigation, since no transformer is designed at voltage
levels above partial discharge inception. This difference will be further discussed in this paper.
4
139
Breakdown Investigation
The transition between the “transformer like” tests and the “breakdown investigation” tests is not very
clear. This is a specific topic we are currently investigating further. As evidenced by the needle-tosphere tests, which are clearly “breakdown investigation”, the behavior of the fluid is not the same at
such highly concentrated fields. The breakdown mechanism of the natural ester liquids are different
from mineral oil, certainly due to the differences in the molecular structure. While mineral oil is nonpolar, with molecules very well charge-balanced, the natural ester molecule has six atoms of oxygen
as the ester group, which is electronegative and creates a slightly polar behavior. This is a major
reason for the higher moisture saturation of natural esters, but, somehow, must also be related to the
differences of the breakdown mechanism. Possibly the presence of double bonds in the long-chain
molecules is also a relevant factor. These parameters should influence differently the volumetric effect
in mineral oil, described in [21] and in natural ester, still under investigation.
On-going investigations yet unpublished have shown that for electrodes defined as “blunt point” (3mm
diameter) to a 25mm diameter sphere, at testing gap of 50mm, the breakdown voltage is the same for
both liquids.
A second application of the highly concentrated field tests would be a “scale-test” for the large gaps.
Some laboratories, aimed to test larger gaps without applying extremely high voltages, which may not
be possible in their test facilities, have used the needle-to-plate test and a mathematical extrapolation
procedure to estimate the breakdown voltage of larger gaps, as described in [23]. However, since the
behavior of the natural esters under highly concentrated fields are different and the volumetric effect is
also expected to be different, it is evident that the extrapolation procedure will also lead to incorrect
results. The comparison of the resultant chart presented in [23] (figure 18 of the paper), shows a large
deviation between the extrapolated results to the effectively measured values on real gaps. So, the only
possible conclusion is that the results of the extrapolation are not valid for natural ester liquids.
Streamers
The dielectric breakdown mechanism and the breakdown intermediate streamers have a history of
study. For uniform and quasi-uniform fields, the streamer inception voltage is close to the breakdown
voltage, and variations in streamer speed and length have little impact on the breakdown voltage.
However, in non-uniform fields, streamer inception occurs at a much lower voltage. Variations in
streamer speed and length have a greater influence on breakdown. In natural esters, the streamer speed
and stopping length are both higher than for mineral oil, therefore producing a lower breakdown
voltage [22].
In an effort to translate such investigations into clearer concepts, the effective difference due to quick
evolution to fast streamers, is that the voltage increase between the partial discharge inception and the
disruptive breakdown will be smaller for the situations of highly concentrated fields. Taking in
consideration that the PDIV of natural ester liquids is higher than mineral oil, and the transformers are
designed to be “partial discharge free”, there should be no effective impact of this difference on the
design of the transformer. In fact, there should even less chance of PD, as the inception is higher.
As a safety margin, it may be possible to keep some safety margin for the design of transformer leads,
as this would be the region where more inhomogeneous fields could be present. Undergoing
investigations should clarify how high the field concentration can be while behavior is equivalent.
DIELECTRIC DESIGN OF POWER TRANSFORMERS
The main aspect to take into consideration for designing a power transformer using natural ester
liquids is the higher permittivity. Detailed values can be found in [8], showing the permittivity of the
fluid and impregnated paper at different temperatures. The electrical field distribution is affected by
this difference, increasing the voltage drop at the solid insulation and reducing at the liquid gap.
As described in [7] and [8], the use of the design curves developed for mineral oil should be on the
safe side for natural ester filled equipment. The design curves are essentially applied for the design of
the windings and winding assembly, regions were the electrical field is very much homogeneous.
When a transformer is designed to the traditional temperature rise limits, due to higher viscosity, it
may be necessary to increase the radial dimension of the cooling ducts. However, if the enhanced
140
5
properties of the insulation system formed by cellulosic material and natural ester are explored,
allowing higher temperature rise limits, the cooling ducts may be reduced or some of them may be
removed, saving conductors and reducing the total weight.
For the design of the internal leads connecting the windings to the bushings and tap changers,
performed tests (not yet published) have already shown that there would be no difference in the
breakdown voltage limits for test electrode down to 3 mm.
CONCLUSION
The following table represents the relative conclusions from a large number of studies around the
globe, designed and performed taking into account the particularities of natural ester liquids instead of
doing “as it was for mineral oil”, including true side-by-side comparison, depicted as pluses and
minuses:
Transformer Design
turn-to-turn
coil-to-coil
bushing-to-tank wall
creep
tap changer selector rod
streaming electrification
bubble formation
Electrode Geometry – Oil Gap
uniform
mildly divergent
strongly divergent
Electrode Geometry – Creep
mildly divergent
strongly divergent
Envirotemp FR3 Fluid
Mineral Oil
=
=
=
=
=
++
+++
=
=
=
=
=
----
=
=
-
=
=
+
=
-
=
+
So, except for highly inhomogeneous field distribution, the results of breakdown voltage of natural
ester and mineral oil, for AC, lightning impulse (negative and positive polarity), switching impulse
(negative and positive polarity), chopped wave, both in oil gap and creep indicate a very high level of
equivalency between the fluids. For the extremely divergent field generated by the needle to plate
configuration, the results are not the same. Test results clearly indicate a higher value of PD inception
voltage for natural ester liquid, increasing the safety margin when design criteria from mineral oil are
applied for a “partial discharge free” transformer. Increasing the voltage above PD ignition (which
should not be a real condition in any well-designed power transformers), the required increment to
reach breakdown will be lower in natural ester liquids than in mineral oil.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
IEEE C57.154:2012 IEEE Standard for the Design, Testing, and Application of Liquid-Immersed
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Operating at Elevated Temperatures, October 2012
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H. R. Moore, Requirements and Expectations of Natural Ester Fluids for Application in Power
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Juan, PR
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[12]
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[16]
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[21]
[22]
[23]
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T. A. Prevost, M. Franchek, K. Rapp, “Investigation of the dielectric design criteria for pressboard/natural
ester interfacial stress”, 75th Annual Intl. Doble Client Conf., April 6-11, 2008, Boston, USA
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Dec. 2009
K. J. Rapp, C. P. McShane, J. Vandermaar, D. Vuković and S. Tenbohlen, ”Long gap breakdown of
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2010, New Orleans, USA.
K. J. Rapp, J. Vandermaar, M. A. Franchek, “Switching impulse of long oil gaps of natural ester fluid”,
Intl. Conf. on High Voltage Engineering and Application (ICHVEA), Sept. 17-20, 2012, Shanghai, China
C. Perrier, A. Beroual, "Experimental investigations on insulating liquids for power transformers:
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P. K. Poovamma, V. V. Pattanshetti, T. R. Afzal Ahmed, A. Sudhindra, "Charging tendency of mineral
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Trondheim, Norway, Paper 63
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T. Paillat, Y. Zelu, G. Morin, C. Perrier, "Ester oils and flow electrification hazards in power
transformers", IEEE Trans. Dielectrics and Electrical Insulation, Vol. 19, No. 5, Oct. 2012
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oil for power transformers", IEEE Intl. Conf. on Dielectric Liquids (ICDL), June 30 - July 3, 2008,
Futuroscope-Chasseneuil, France
K. Yasuda, S. Arazoe, T. Igarashi; S. Yanabu, G. Ueta, S. Okabe, "Comparison of the insulation
characteristics of environmentally-friendly oils", IEEE Trans. Dielectrics and Electrical lnsulation, Vol.
17, No.3, June 2010
E. Gockenbach, H. Borsi, B. Dolata, “Research project on the comparison of electric and dielectric
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(Partial discharge behavior, permittivity and dissipation factor tan d)”, Institute of Electric Power
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Sept.-Nov. 2005
T. C. Wei. T. R. Blackburn, “A Report of the Partial Discharge Test Conducted on Envirotemp FR3Fluid
for Cooper Power Industries”, Engineering Bachelor work, South Wales University, Australia, June 2004
Yu. V. Torshin, “Prediction of Breakdown Voltage of Transformer Oil from Predischarge Phenomena”,
IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 10, No. 6; December 2003
X. Wang, Partial Discharge Behaviors and Breakdown Mechanisms of Ester Transformer Liquids Under
AC Stress, Doctoral Thesis, School of Electrical and Electronic Engineering, University of Manchester,
2011, Manchester, UK
Q. Liu, Z. D. Wang, “Streamer characteristic and breakdown in synthetic and natural ester transformer
liquids under standard lightning impulse voltage”, IEEE Trans. Dielectrics and Electrical Insulation, Vol.
18, No. 1, Feb. 2011, pp. 285-294
142
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
on including Smart Grid, 24-26 Feb. 2016, New Delhi, India
of Power Transmission & Distribution Systems
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRETechnical Meeting
International Conference
on Global
Trends in the Development
Residual
LifeAORC
Assessment
and2016
Life– Extension
Technique
of Transformer
M.L. SACHDEVA
Skipper Seil Ltd
India
POONAM SACHDEVA
Skipper Seil Group
Dubai
Residual Life Assessment and Life Extension Technique of Transformer
M.L. SACHDEVA
Skipper Seil Ltd
India
POONAM SACHDEVA
Skipper Seil Group
Dubai
SUMMARY
The vertically integrated power utilities, existed over later half of twentieth century in India, has
transitioned to horizontal organisations of ‘Gen Cos’, ‘Trans Cos ’ and ‘Dist Cos’. The deregulation
allowed private sector participation within laid down frame work in all the activities of Generation,
Transmission and Distribution.
The power equipment have mostly exhausted their serviceable life. The continuous running of these
assets itself a challenge.Utilities thru System Management are estimating the residual life of the
equipment and making the system available with assured continuous power supply free of ripples,
SUMMARY
dynamic over
voltages
etc. Power
Transformer
is half
a major
and vital component
of supply
The hormonics,
vertically integrated
power
utilities,
existed
over later
of twentieth
century in
India, has
system and its reliability and availability shall be of comparatively higher than others in a S/S. Most of
transitioned
to
horizontal
organisations
of
‘Gen
Cos’,
‘Trans
Cos
’
and
‘Dist
Cos’.
The
deregulation
the Grid S/Ss configurations so planned that their components either physically duplicated or provided
allowed
participation
within
laid
work inAny
all transformerr
the activities
of ends
Generation,
with private
duplicatesector
operational
accessories
except
fordown
powerframe
Transformer.
fault
up
partly/ full loss
S/S power depending upon network condition.A power utility suffering unplanned
Transmission
and of
Distribution.
loss of power transformer depending upon network criticality loses revenue as also put to penalty for
Theloss
power
equipment have
mostly
serviceable life. The continuous running of these
of power/system
stability
as perexhausted
Regulatorytheir
Policies.
assets itself a challenge.Utilities thru System Management are estimating the residual life of the
Most of and
the existing
transformers
havewith
reached
near their
useful lifepower
completion
under
equipment
makingpower
the system
available
assured
continuous
supply
freenormal
of ripples,
operation
or
subjected
to
accelerated
ageing
on
their
exposure
to
operational
stresses
(full
faults, of supply
hormonics, dynamic over voltages etc. Power Transformer is a major and vital component
insulation degrading, mechanical stresses, etc.) and such fleet is required to be evaluated for residual
system
and its reliability and availability shall be of comparatively higher than others in a S/S. Most of
life and life extension.
the Grid S/Ss configurations so planned that their components either physically duplicated or provided
withCondition
duplicateassessment
operational
accessories
Transformer.
Any transformerr
fault ends up
is performed
thruexcept
analysisfor
of power
historical
data and performing
dielectric tests,
partly/
fulldischarge
loss of S/S
depending
network
condition.A
powerofutility
unplanned
partial
testspower
, vibration
tests, oil upon
analysis
and checking
serviceability
major suffering
accessoriesloss OLTC
of power
transformer
depending
network
criticality
loses revenue
as also
put to penalty
for
contacts,
PRV, Bushings,
LAs,upon
Valves,
etc. These
studies facilitate
assessment
of residual
life
any modification
/ replacement
out with
latest devices result into life extension. A Tradeloss and
of power/system
stability
as percarried
Regulatory
Policies.
off between life enhancement and investment or go for replacement with new one and use this
at somepower
other location
needing
low reached
operational
duties
left for life
decision
under Asset
Mosttransformer
of the existing
transformers
have
near
theiris useful
completion
under normal
Management Plan.
operation or subjected to accelerated ageing on their exposure to operational stresses (full faults,
insulation
degrading,
mechanical
etc.) andquantities,
such fleet
is required
to bethe
evaluated
for residual
The paper
includes types
of gasesstresses,
& their allowable
types
of fault inside
transformer
life and
life
extension.
winding causing liberation of those gases, deposit and damage of winding insulation and advanced
diagnosis tools to ascertain present winding condition before un-tanking the transformer for repair.
Power Transformer
at works
site aredata
characterised
for Controlled
Condition
assessment manufacturing
is performed facilities
thru analysis
of and
historical
and performing
dielectric tests,
Environment(Cleanliness
and Orderliness),Heavy
Lifting
Equipmentserviceability
for detanking of
andaccessoriescoil
partial
discharge tests , vibration
tests, oil analysis
and checking
ofcore
major
assembly,
Manufacturing
of winding
application
of insulation
andfacilitate
dried andassessment
oil impregnated
OLTC
contacts,
PRV, Bushings,
LAs,and
Valves,
etc. These
studies
of residual life
followed by
packing in positive
dryout
airwith
pressure
maintain
moisture
Core andA Tradeand operation
any modification
/ replacement
carried
latest
deviceslow
result
into content,
life extension.
coils subsequent to assembly and placed in the tank for final drying and during On-site Drying
off between life enhancement and investment or go for replacement with new one and use this
transformer at some other location needing low operational duties is left for decision under Asset
Management Plan.
1
The paper includes types of gases & their allowable
143 quantities, types of fault inside the transformer
winding causing liberation of those gases, deposit and damage of winding insulation and advanced
diagnosis tools to ascertain present winding condition before un-tanking the transformer for repair.
Power Transformer manufacturing facilities at works and site are characterised for Controlled
process, the moisture is reduced to below 1%. High Voltage testing including applied voltage &
induced voltage testand PD measurement, of assembled transformer.
Other add ons (old / new for capcity uprating) are fitted at Client site / repair site as the situation arises
In Brazil, Italy, Spain and Nigeria, stationary transformer manufacturing / servicing hubs have been in
operation by some manufacturers and a few other suppliers/ manufacturers have mobile shops for
servicing / repair of transformers.
Start typing here with the summary (about 500 words; Times or Helvetica, size 11 or 12 only, from
4.8” / 12 cm from the top). Do not remove or shift the title “SUMMARY”, as Papers must have the
same presentation for the CD ROM issue.
KEYWORDS
Power Transformer, Residual life Assessment, Life extension, Oil & Winding Analysis, Oil
Gases Liberation & solid insulation polymerisation Limits, Factory and / or Site Repairs, Site
Drying and Testing Process.
3 to 10 words or phrases (Times or Helvetica, size 11 or 12 only).As for “SUMMARY”, please keep
the title “KEYWORDS”.
All pages after title page must start from this line, i.e. 1” (2, 5 cm) margin from the top (Times or
Helvetica, size 11 or 12). Pages will be automatically numbered.
1.
INTRODUCTION
The vertically integrated power utilities, existing over later half of twentieth century in India, have
been transitioned into horizontal ‘Gen Cos’, ‘Trans Cos ’ and ‘Dist Cos’. The deregulation allowed
private sector participation too within the laid down frame structuree in all the activities of Generation,
Transmission and Distribution. Power Utilities, unlike in the past, have lost their monopolistic hold.
They are striving for optimal operational cost thru modern technical & management solutions by best
utilisation of existing resources and adapting best practices and transforming work culture.
Today’s Power Systems are facing new challenges and are racing for pollution free (ripple free,
harmonic free) and more reliable /sustainable interruption free grid in the face of growing electricity
demand. It is imperative to adapt existing infra structures to new technologies.
The integration/ extension of digital technology into old infrastructures ensures improve reliability,
high investment with fast recovery and enhanced asset management.
Substations are now upgraded as Smarter (provided with facilities conforming to IEC 61850) with
condition monitoring, SCADA & automation and analysis system. In addition to converting into
smarter S/Ss, associated networks are also provided with intelligent infrastructure allowing efficient
asset management (asset operations optimisation, condition based maintenance, repair and
replacement strategies). Investing in quality & innovative equipment optimises electrical infrastructure
and heightens return on investment.
In this time changing scenario, the time honoured/ scheduled maintenance is giving place to
conditioned based /predictive based maintence/ reliability centered base maintenance resulting into
following:
- Reduce the probability of failures and ensure the reliability of network
144
2
-
Increase asset life, increase productivity and in turn return on investment
Optimise field engineers reactivity for remote substations
Most of the power transformers in the existing system have reached nearing completion of their useful
life under normal operation or subjected to accelerated ageing of having been exposed to operational
stresses (full faults, insulation degrading, mechanical stresses, etc.) due to weak system. Such fleet is
required to be evaluated for residual life and life extension.
2.
Power Transformer
Power transformer is a critical and higest cost item in a Grid S/S. Its life continues depreciating being
in operation unless preventive measures (continuous monitoring & real time data collection and not on
time interval basis, conditioned based maintenance, etc) are implemented to reduce rate of ageing as a
result of extended maintenance cycle & less costing and experience controlled loading. The
transformers which have aged and beyond refurbishment to full rating be shifted to other suitable
locations and replaced with transformer of proper rating keeping in view prevalent SC level.
Alternatively, measures to control SC level are to be implemented.
Transformer Failure Statistics (Germany, Austria, Switzerland, Netherland)
S.N
o/
Ref
No
1
Winding
Lead
Exit
37.69%
5.78%
2
32.1%
3
45.0%
Transformer Failure Statistics (CigreA2.37 Report) (Ref 1)
Bushin
Tap
Core &
Insulat
Flux
Tank
g
Change Mag. Cct
ion
Shunt
r
31.16%
2.61%
8.9%
17.16
%
11.6%
33.9%
7.1%
7.0%
17.0%
26.0%
3.0%
2.43%
0.37%
0.75%
Cooling
Unit
Elect
Screen
1.12%
0.56%
0.9%
0.9%
4.5%
1.0%
1%
S.No.1Ref : Tenhohlen et-al: Development and Results of a World Wide Transformer Reliability Survey’ CIGRE SC
A2 Collouquam 2015, Shanghai
rd
S.No2:Total Transformer Failures in Germany, Austria, Switerzerland, Netherland as per INMR Jan 23 2016
S.No3:Total Transformer Failures above 100kV in Germany, Austria, Switerzerland, Netherland as per INMR Jan,16
External Effects of Bushing Failure (Ref 1)
Type of Failure
Explosion
Fire
Leakage
Colleteral
Others
None
Burst
Damages
% Failure
10.45
30.43
5.22
0.87
7.83
45.22
Ref: Tenhohlen et.al: ‘Development of Results of a World Wide Transformer Reliability Survey’
CIGRE SC A2, Colloquaum 2015,Shanghai
Transformer associated with Non-conventional Resources of power (PV Solar & Wind
Generators) - Special Features:

High Harmonics :Transformer core to be designed suitable for handling harmonics
created by inverter

Transients: Ramp rates and voltage control from renewable energy sources can be
rapid and need to be accommodated
3
145

Interface with Inverters: Short circuit performance of inverters is significantly
different from that caused by Synchronous rotating generators and varies from
supplier to supplier. The transformers have to be designed to cater for specific
inverter used.
Operation of a Transformer depends on moisture accumulation and ageing contaminants in the space
of main insulation resulting in reduction of reconvertible dielectric strength and non-convertible
deterioration of insulation due to partial discharges. The oil barrier insulation system dielectric
strength reduces dramatically though oil measured characteristics meet all the traditional criteria.
Accordingly, utilities have been installing monitoring systems that perform remote dissolved gas
analysis (DGA) on a near-real-time basis and transmit results to central monitoring stations.
Transformer Monitoring affords benefits such as ‘Prevent unexpected failures up to 70%’, ‘Service
cost reduction up to 30%’ and ‘Defer capital expenditure’.
Moisture in Transformer ‘Limits loading capability due to decreased bubbling inception temperature’,
‘Decreases dielectric strength of oil & decreases PD inception voltage’ and ‘High temperature and
moisture dramatically accelerates ageing that lowers mechanical strength of cellulose insulation’.
Typical moisture content in paper/pressboard for i) New transformer: < 1%, ii) Aged transformer: 2 4% and iii) Normal increase of water content is typically 0.05-0.2%/year
Cigre Technical Brochure 248 "Guide-on Economics of Transformer Management" June 2004
concludes that deployment of on-line monitoring is cost effective as compared to non monitoring. It is
intended to provide an early warning for any type of fault developing in the main tank to allow
operator to take further action to evaluate the severity of the situation. Monitoring devices have to be
simple, dependable and cost effective. Experience has shown that a combined reading of hydrogen and
carbon monoxide fulfills that need successfully.
Transformer Bushings (Ref 2 & 3& 10)
Out of Transformer Busings in the order of superiority, Resin Bonded Paper (RBP), Oil Immersed
Paper (OIP), Resin Imprenated (RIP) and Resin Impregnated Synthetic (RIS), the most commonly used
bushings are OIP condenser type but on failure do cause casatrophic damage thru bursting and
causing fire.
For Europeon Power Utilities (Germany, Austria, Switzerland and Netherlands), CIGRE SC(A2.37)
revealed that about 12% of transformers failures is due to bushing failures and this failure rate grows
to 17% considering transformers of voltage rating greater than 100kV.
Factors Leading to Ageing of Transformer Bushing
High ambient temp and temp changes, High & frequency load cycles, Over voltage / transients,
Leakage and Moisture ingress, Oil leakage & Corrosive contaiminant oils (OIP only) and loss of
insulation / dielectric Properties, Capillary cracks (RBP type) and partial discharge and Partial
discharge.
Proportioning of Damage to Bushing
80%leakage (Only for oil within insulation), 13% deterioration of Insulation and 7% mechanical
damage (mainly due to porcelain) is approx.distribution of identifiable root causes requiring overhaul
replacement of a bushing.
146
4
Voltage Class and Change of Capacitance for Condenser type Bushings (Ref 1)
Bushing Voltage (kV)
123
245
420
550
Nos of Layers
14
30
40
50
% Capacitance Change
7.1
3.3
2.5
1.8
Ref: Tenhohlen et.al: ‘Development of Results of a World Wide Transformer Reliability
Survey’ CIGRE SC A2.34 Colloquaum 2015, Shanghai
3.
Residual Life Assessment
The present status of transformer is to be ascertained before taking up any remedial measures
(refurbishment, life extension) as follows:
Grouping of Transformers
All transformers during certain period have mostly similar designs, but differences do exist between
models and manufacturers. A typical assessment should include an evaluation of the unit ratings
(nameplate), tank design, core/coil de-sign, load tap-hanger (OLTC)/de-energized tap-changer (DETC/
OLTC) design, oil thermal expansion design, bushing design, arrester design, and known common
mode failure mechanisms.
Further to above, they are grouped not only from the period in service but also as per year of
manufacture and manufacturer wise. Though the technical specifications at that time may be same but
each manufacturer has its own manufacturing model and built in factor of safety as also manufacturing
capabilities (Quality & testing).
As such transformers in the same group have to be handled intelligently and carefully as far as
possible on individual investigation as per finding from the following
3.1Visual Inspection
A thorough external visual inspection of all add on items / fitments
3.2Maintenance Record Review
The maintenance history to be re-viewed to help determine its condition.
3.3 Operating Record Review
The operations and loading history to be re-viewed to establish benchmark data for a thermal analysis
of the unit in an effort to determine loss of life. This shall also be noted that the equipment
commissioned in later years may have less safety margins due to past superior perfoemance and
available updated designs tools for effecting economy and competitiveness.
3.4 Status of Live Transformer Performing Non- Intrusive Tests
After all the documents have been thoroughly studied as also a good practice to perform Balance life
assessment of a transformer after it has run about half of its life provided no major repairs / overhaul
has been performed, the present status of transformer is ascertained as under:
Infrared Camera for measuring High temperature of heated external component.
Partial discharge detection (100 to 200 kHZ band) existing in transformer thru use of an
acoustic emission sensor coupled to suitable electronics high speed oscilloscope.
 Portable Hydran unit measures hydrogen concentration as indication of partial discharge
arcing in Transformer.
 Acoustic and Vibration detection equipment {Vibration transducer, mounted on transformer
surface, suitable for measuring Sub-harmonic (below 50/60Hz) random vibrations} is used to
detect transformer core looseness and core misalignment.
 Doble Hand held PD Detector is a commonly used instrument for measuring PD and has the
capability of segregating the background noise out of the real PD


147
5
 Doble’s LCM possess the ability to measures hormanic and store data for upto 1000
LAs. It also capable of continuous on-line surveillance of any arrester with use of modem
communication to a PC.
3.5 Internal Analysis of Transformer
In addition to checking the documents, the Transformer dissection using the tools, the chemical,
mechanical and electrical diagonistic of transformers is carried out. The oil drained, bushings
demounted and the transformer is detanked and following is inspected:
i) Inspection of Core for core sheet burning, sheet insulation damage and loose core clamps;
ii) Check for arcing signs on winding insulation, loosening of winding, shorting of winding;
iii) Arcing signs on leads, deforming of leads, in case of non availability of design of winding,.
iv) Checking of bushings for leakge, surface damage, DP, etcAll these tests indicate condition of
solid and liquid insulation and winding.
v) Analysis of oil
vi) Checking tank for leakage and external corrosion
vii) Check cooling system for damage, leakage, working of air fans/ oil pumps / water pumps
viii) Check On-Load Tap Changer for its workability
xi) Check operationability of other BOPs
x) Repair of damaged Civil Work (Foundation, sump, burnt oil storage tank)
3.5.1 Detailed DGA of the Transformer
The detailed DGA is got carried out from a reputed Testing Laboratory or test results of 8 DGA
mounted on the transformer are reviewed by competent Authority in the light of published / standard
data and suitable decision taken for further necessary action (Stripping off and reworking or declared
Unserviceable / Salvage).
The recent version of Hydran with provision of Transformer Models provides measuring facilities as
given in Table -1
OMNICRON’s Dhirana instrument is used for determining moisture in the solid insulation inside the
transformer
3.5.2 Standard Norms / Parameters
The findings from various Investigation are compared with the permissible values mentioned and
corrective measures are suggested for performing:
i) Residual life of a transformer can be derived from Dielectric Power Factor (Ref 4)
EPRI Guidelines for Residual Life Extension
DP Value (Tandelta)
1000 to 1400
500
300
200
Balance Life (%)
100
60 to 66
30
0
Guidelines for Life Extension of S/Ss 2000 Upside, EPRI, California, USA
ii) DGA Analysis Requirement
Table2 Most Recommended Tests in Service Transformers (Ref 5)
Table3 Categories of the Key Gases and General Fault Conditions in the Transformer
Diagonistic of Insulation (Ref 6)
Table 4 Space(Location), Defects, Componentsand Probability of Detection (Ref 7)
iii) Electrical Diagonoistic
Table 5 gives indication of faults as a result of performing electrical related tests (Ref 8)
iv) Relative Thermal ageing of Cellulose Insulation as per IEC 354(Section 1.2) (Section 2.6.2)
148
6
based on 20°C ambient + 78°C hot spot rise = 98°C.
θh (° C)
92
98
104
110
134
Relative Ageing rate
0.5
1.0
2.0
4.0
64
V= 2(����� )/6
v) Tansformer Oil Classification ( Ref 4)
Class A
Class K
Mineral oil (Inhibited or Un-inhibited oil).
Silicon oil, Synthetic ester and Hi-Temp
natural liquid (seeds).
Hot spot factor normally presented between 1.1 to 1.5 depending on
winding design
105° C
120°C
3.6 Transformer Bushings (Ref 9)
Bushing Defects and Associated Indicators
Partial breakdowns
Voids, cracks
Bushing Defects
Associated
Indicators
Capacitance
Partial discharge
Capacitance
Partial discharges
Ageing
moisture
by-products,
Dissipation/power factor
Metod of Measurement of Bushing Capacitance in the order of ‘Higest Uncertainty’ to ‘Lowest
Uncertainty’
Relative measurement(bushing-to-bushing) ii) Dual transformer comparison and iii) Absolute
Measurement ( VT reference)
The Partial discharge in the Bushings is detected by following methods :
i)Chemical (DGA)

An indicator that there can be PD.

Can be performed without shutting down the transformer.

Cannot quantify the amount of PD.
ii)Electrical (narrow band or wide band) according to IEC 60270

The only means of quantifying the amount of PD.

PD may be localized to a particular phase or winding.

Requires a shutdown of the transformer.

External noise can be a problem in the field.
i) Acoustical

Can be performed without shutting down the transformer.

PD can be localized to within a few inches.

Cannot quantify the amount of PD.
ii) UHF

May not be necessary to shut down the transformer.

Steel tank of the transformer acts as a faraday cage.

Requires a gate valve or some type of pre-manufactured access.
149
7
Cannot quantify the amount of PD.

On- Line Monitoring of Capacitance and Dissipation Factor
i).Reference method (When group of VT is available) ii).Comparison methods (when
a group of two sister transformers with the same type of the bushings are close each
other and work in parallel) and iii) Sum-of-current method (Bushing to Bhusing of
same Transformer)
Partial Discharge Detection
-
PD detection is the early indicator of defects in dielectric insulation
-
In typical field environments of transformers, electrical PD detection suffers from a
high noise level originated from out side the transformer,like corona
-
The system monitors PD at the bushing taps and inside the transformer tank, usinga
UHF sensor
-
The sensor inside the tank is not affected by outside noise
-
Synchronous multi-channel recording enables UHF gating
-
Using the UHF signals to distinguish between PD events in side and out side the
transformer at the bushing tap sensors
-
Further advanced noise suppression technologies are available:
3-Phase Amplitude Relation Diagram (3PARD)
3-Center Frequency Relation Diagram (3CFRD)
4.
Performing Refurbishment and Life Enhancement
4.1
Refurbishment
Subsequent to performing conditioning monitoring and knowing the health of solid & liquid
insulation, core & winding, Bushings and other accessories, SC rating and present SC level, decision
is to be taken whether to go for Refurbishment or refurbishment and life extension and work is to be
performed at Site, Principal Works or both at Principal Works cum Site. The decision of any of the
alternative will depend upon the importance of the unit, facilities available for repair at site, period for
repair, testing facilities available at site, time for dismentalling and re-erection, transportation cost and
its duration, etc
4.2
Life Extension
Life extension / Capacity Up-rating of Transformers is performed as follows
- Replace with Plate-fin type radiators with symmetrical arrangement. ONAN , ONWF
cooling arrangement be changed with ODAF with Zig-Zag path using oil barriers after
review original Heat-run test reports
- Change OIP bushings with RIB or preferably Dry Type Bushings epending upon
availability
- High Pressure Water Sprinkler/ Mulsifyre Fire fighting with Nitrogen Injection Fire
Protection system( NIFPS)
- Change Explosion vent with PRV
- Change conventional conservator with Membrane type of Conservator/ Drycol
breather
- Provide two air breathers instead of single air breather
150
8
-
Provide On-Line oil filteration pump in the oil circuit of the transformer
Use Oil directed air natural in place of Oil Natural Air Forced Cooling Vacuum
Vacuum OLTC instead of Oil OLTC where available
Use of High temp Insulation paper and board (150°C) instead of Cellulose paper and
spacer (115°C)
-
Use of Synthetic Ester oil (average winding Temp 95 to115°C) in place of Mineral Oil
(Average winding 65°C)
Replace Non- Linear resistortype LA with ZnO Lighting arrestor and provide In-series
current meterr instead of conventional surge counter and leakage current meter for
continuous monitoring 3rd harmonic in the grounding lead to avoid damage.
Change OIP bushings with RIB or preferably Dry Type Bushings epending upon
availability
Provide sensors for monitoring partial discharge, hydran, LA condition Monitoring
eqpt, etc. for real time monitoring.
-
-
5.
Manufacturing Facilities
Power Transformer manufacturing factories and workshops are charcterised by their cleanliness and
well control atmosphere which are prerequisite for manufacturing and repair of High Voltage grid
transformers. The establishment are also to be equipped with heavy lifting equipment, special tools &
plants and high voltage test equipment set with highly trained and expert staff for each process.
For Site repair, the requisite are
Controlled environment in terms of cleanliness and orderliness
Heavy Lifting Equipment for detanking of core and coil assembly
Manufacturing of winding and application of insulationand dried and oil impregnated. For
transportation and storage in positive dry air pressure, windings are packed to maintain low
moisture content.
Core and coils subsequent to assembly and placed in the tank for final drying. On-site
Drying process, the moisture is reduced to below 1%. The Vapour phase drying process
/heating of whole transformer with oil & withdrawing oil on achieving desired temp,
succeded by vacuum cycles cum spray of hot oil over the active part / Low Frequency (1 Hz)
Current heating and conventional hot oil spary method.
High Voltage testing including applied voltage & induced voltage testand PD measurement,
of assembled transformer
Part of above facilities, if available on Client site / service bay, are made use for removing and
treatment of oil and detanking of Core, coils, and winding blocks.
Balance Work requiring Controlled environment is performed at the earmarked area. The test
equipment and oil treatment plant are available on wheel and can be easily transportated at locations
where manufacture permanent site repair facilities are not available.
Other add ons (old / new for capcity uprating) are fitted at Client site / repair site as the situation arises
6.
Conclusion
Residual life assessment and life extension of Power Transformers and their accessories / fitments
including busings & LAs and their conditioned / risk management under the present scenerio of Power
supply has become vital. The Power system are provided with real time data monitoring devices to
ascertain their health to operate the system reliably and economically ensuring meeting regulatory
norms. The paper lays down collection of data from the first test signatures/ supply test record,
maintenance records, the latest test results and make comparison with permissible limits for planning
151
9
repair at Client site, manufacturer principal works and Semi Work shop set up Centrally to the major
transformer population.
The repair facilities shall be with controlled environment with Cleanliness and dust free air, heavy
lifting facility, transformer assembly drying process and testing facilities (static/ mobile) and well
qualified repair and quality control staff.
For Life extension and capacity up rating, use of high temp soil insulation, synthetic easter oil,
radiators & uprating of cooling fans/ pumps, conservator system & air breaters, LA & ground current
metering device instead of surge counter and current leakage meter, Bushings, etc.
152
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
on including Smart Grid, 24-26 Feb. 2016, New Delhi, India
of Power Transmission & Distribution Systems
CIGRE- AORC Technical Meeting 2016 and International Conference
“Global Trends in the Development
on of Power T&D System including Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
Global trend in health index estimation and validation on generation
transformer fleet management
Global trend in health index estimation and validation on generation
ARADHANAfleet
RAY and
V. SHRINET
transformer
management
Laxmi Associates, VADODARA
INDIA
ARADHANA
RAY and V. SHRINET
E: mail: rayaradhana@yahoo.com
Laxmi Associates, VADODARA
INDIA
E: mail: rayaradhana@yahoo.com
SUMMARY
With an aging fleet of transformers and limited maintenance budgets, the assumption that all
are in good condition for an extended working life can be dangerous. When it comes to
transformer asset management, utility’s main objective is to reduce the risk of a failure and
minimize the impact, if a failure does occur. Comprehensive fleet management approach
SUMMARY
provides just the support utility need to make intelligent maintenance decisions to face these
challenges.
With an aging fleet of transformers and limited maintenance budgets, the assumption that all
are in good
working islife
bescanner,
dangerous.
When
comes to
Thecondition
well-knownfor
bathan
tub extended
shape life distribution
nowcan
under
particularly
for it
power
transformer
asset management,
main
objective
is rate
to reduce
riskearly
of aage)
failure
transformers.
It has been utility’s
reported that
infant
mortality
(failure the
during
is and
significantly
reduced
may
be
due
to
matured
design,
better
manufacturing
capabilities,
minimize the impact, if a failure does occur. Comprehensive fleet management approach
improved
materialsutility
performance
andmake
good commissioning
practice. A survey
carriedtoinface
the these
provides just
the support
need to
intelligent maintenance
decisions
year 2000 on 300,000 substation assets among 13 European countries reveals that 93% of
challenges.utilities had historically replaced less than 10% of their assets and 70% had replaced less than
5%. Such observations indicate that there is need to develop comprehensive transformer fleet
management
In case
large number is
of now
transformers
(transformer
fleet) effortsfor
are power
The well-known
bathstrategy.
tub shape
lifeofdistribution
under scanner,
particularly
being
made
to
evolve
reliable
ranking
(often
called
as
Health
index)
structure.
These
ranking
transformers. It has been reported that infant mortality rate (failure during early age) is
are primarily governed by the significance of various diagnostic parameters. Such index
significantly
reduced may be due to matured design, better manufacturing capabilities,
enables utility to screen degree of attention needed by individual transformer.
improved materials performance and good commissioning practice. A survey carried in the
year 2000During
on 300,000
assets
among
13 been
European
countries
thatof93% of
last onesubstation
decade several
attempts
haves
made to
estimate reveals
health index
transformers.
Health
index less
estimation
is in of
evolving
phase and
has replaced
constitutedless
a than
utilities had
historically
replaced
than 10%
their assets
andCIGRE
70% had
working
group
on
this
subject.
However,
there
are
various
aspects
such
as
index
range,
order
5%. Such observations indicate that there is need to develop comprehensive transformer fleet
of ranking, weightage factor assigned to different parameters, large number of parameters
management
strategy. In case of large number of transformers (transformer fleet) efforts are
(sometimes more than two dozen) considered etc., that can be improved. Further more
being made
to evolveallotted
reliable
calledneeds
as Health
index)
structure.
These
significance
to aranking
particular(often
health index
clarification
so that
a utility shall
ableranking
are primarily
governed
by the
of various diagnostic parameters. Such index
to make
any inference
from significance
the available score.
enables utility to screen degree of attention needed by individual transformer.
In this paper an effort have been made to review various health index approaches, their
advantages, limitations and suggested an improved methodology for the same. The proposed
During last
decade
severalonattempts
haves
been transformers.
made to estimate
health are
index of
newone
procedure
is validated
twenty four
Generation
These transformers
transformers. Health index estimation is in evolving phase and CIGRE has constituted a
working group on this subject. However, there are various aspects such as index range, order
of ranking, weightage factor assigned to different
parameters, large number of parameters
153
(sometimes more than two dozen) considered etc., that can be improved. Further more
significance allotted to a particular health index needs clarification so that a utility shall able
to make any inference from the available score.
installed at five power stations, have service age ranging from more than three decades to less
than a decade, manufactured by fifteen manufacturers, of various rating but all of them are
still in service.
KEYWORDS
Generation transformer, Health index, Transformer fleet management, Asset management,
1.0 INTRODUCTION
There is increasing pressure on all owners and operators of
Transformers to develop asset management strategies that are effective and cost efficient.
Ensuring a corporately acceptable failure rate, prolonging the life of the assets and planning
for appropriate replacement are of paramount importance.
CBRM involves four sequential steps. Firstly, define asset condition by deriving ‘heath
indices’ for individual assets and build health index profiles for asset groups. Secondly, link
current condition to performance by calibrating the health index against relative probability
of failure (POF) as shown in Figure 1. The health index profile is matched with current
failure rate to determine health index/POF relationship. Thirdly estimate future condition and
performance by using knowledge of degradation processes to ‘age’ health indices, ageing
rates dependent on initial health index and operating conditions. Future failure rates are
calculated from aged health index profiles (Figure 2) and previously defined health
index/POF relationship. Lastly evaluate potential interventions in terms of POF and failure
rates by factoring in the effect of potential replacement, refurbishment or changes to
maintenance regimes, modify future health index profiles and recalculate future failure rates.
Figure 1: The relationship between Health Index and POF
154
Figure 2: Heath Index distribution- Yn&Y0
The first parameter and the foundation for the rest of the CBRM process is the definition of
asset condition in the form of a health index (HI) derived for individual assets. Health index
is key link between diagnostic or condition monitoring and asset management. CIGRE has
realized importance of health index therefore constituted a working group on the subject. It is
needless to say that correct health index only able to manage asset optimally. There is no
universally accepted methodology for health index is available so far. However, several
attempts have been made to evolve suitable methodology for calculation of health index of
transformer (8, 9, 10, 11, 12). Various authors suggested different methods and vary in
following terms:
1. Range. Some author reported health index from 1-100 but several follows range from
1-10. (9)
2. Sequence of ranking. Healthiness increases with number and vice versa.
3. Weightage factor assigned to different parameters or tests.
4. Number of tests considered and degree of significant provided to tests
5. Sometimes a similar but new terminology indicated such as Age index (9)
Furthermore several tests (sometimes about two dozen diagnostic tests) are considered for
health index for which often results are not available with most of the utilities (8, 9, 10).
Apart from these limitations, there is need to elaborate usefulness, significant and simple
meaning to health index numbers to make it relevant. In this paper an attempt has been to
address above issues, suggest a simple and practical methodology and finally the proposed
methodology is validated on a generation transformer fleet of 24 numbers.
2.0 PROPOSED METHOD
Various key parameters to estimate health index and their
relevance is discussed below:
2.1 Range and sequence-
The health index is still in evolving stage. Therefore a range from
1-100 is too large to assign. Although such wide range can provide higher resolution about
health status but perhaps today it is premature. Because there is some element of subjectivity
involved but this will improve with experience and become precise. Hence a range of 1-10 is
appropriate at this stage. Psychologically higher number is linked with better performance
155
like in any academic examination report card. Similarly, assigning lowest number to new
healthy asset and highest number to worst, need to be reversed.
2.2 Relevance to health index number-
To provide more clarity to health index number
and its relevance a specific condition is suggested to each number as follows:
H
index
10
9
8
7
6
5
4
3
2
1
Key word
Condition
Suggested action
Good
All parameters are good
Acceptable degradation
Moderate degradation
High degradation
High degradation closely watch
Minor criticality suspected
Moderate criticality suspected
Higher criticality found
High criticality found
Very critical
Routine monitoring
Watch
Increase frequency
Trending
Online monitoring
Preventive measure
Identify fault
Quantify fault
Corrective measure
Replacement/ Refurbishment
Average
Poor
Bad
Critical
Above table provides a broad idea about usefulness of each health index number. Utility can
take first step based on the health index then later on experts can go in detail, if needed.
2.3 Number of diagnostic tests for health index-
There are several on-line and off line
diagnostic tools are available. It is desirable to have as much as data of all possible
diagnostics tests available for health index. Some authors have suggested two dozen tests.
But there is practical limitation. Most of the utility have limited data. The historically only
following test results are usually available:
I.
Transformer oil test result
II.
Dissolved Gas Analysis result
III.
Furan content
IV.
Operating history, Maintenance and age
Considering this situation, health index based on above four parameters are proposed as fleet
screening and Tier 1 approach.
2.4 Weightage factor for diagnostic tests-
Different authors have suggested several weightage
factors for various diagnostic tests. Effect of weightage factor on health index for twenty four
generation transformer fleet is discussed next.
3.0 CASE STUDY- GENERATOR TRANSFORMER FLEET-
Following assumptions
are made to develop a simple, practical and effective health index methodology:
156
1. Health index of transformer is cumulative indices of its key parts namely liquid
insulation (transformer oil), Solid insulation (cellulosic paper) and service age.
2. Several parameters of transformer oil is measured periodically such as moisture
content, volume resistivity, dielectric dissipation factor, break down voltage, flash
point, sludge etc, but they are reversible. Preventive maintenance on oil can change
the results. However, interfacial tension and acidity (neutralization value) are
important tests to access the quality of oil. Oil quality index is considered to quantify
oil quality.
3. DGA is another parameter considered for health index. It provides fairy accurate
information about health of transformer. In DGA also several gases such as hydrogen,
lower hydrocarbons, carbon oxides and atmospheric gases are analyzed. But only key
gases namely hydrogen, methane, ethane, ethylene, acetylene, carbon mono oxide,
carbon di oxide, total dissolved gas content and ratio of carbon oxides are significant.
The permissible limits (in ppm) of these gases are taken from IEEE C.57.104-2008
and two new criteria on TDG and CO2/ Co is also considered:
Hydrogen Methane
Ethane Ethylene Acetylene CO TDG CO2/Co
100
120
65
50
>1
350 700
3-10
4. DP (Degree of polymerisation) of paper is more accurate test to quantify extent of
degradation of cellulosic paper. But sampling of paper from transformer in service,
needed for DP test, is not practical. The popular alternative is furan content in oil as
furans get dissolved in oil. Therefore, furan content is another parameter considered
for health index.
5. Finally, service age of transformer is also considered. It is desirable to include hot
spot temperature, winding temperature, load etc but availability of these data are main
concern.
From above four individual categories namely oil quality, DGA, furan and age, composite
health index of transformer is estimated as follows:
Conditions
Oil quality index DGA (No. of violations) Furan content (ppm) Age (Years)
<50
>4
>10
>50
50-100
4
5-10
41-50
101-200
3
1-5
36-40
201-500
3
0.5-1
31-35
501-1000
2
0.1-0.5
25-30
1001-1500
2
0.05-0.1
21-25
1501-2000
1
0.01-0.05
16-20
2001-3000
1
0.005-0.01
11-15
3001-4000
0
0.001-0.005
6-10
>4001
0
<0.001
<5
Following eight weightage options were considered for cumulative health index estimation:
I.
Option A- Equal distribution to all, 25% (Oil)+ 25% (DGA) +25% (Furan)+ 25%
(Age) on 0 to 4 scale
II.
Option B- Equal distribution to all, 25% (Oil)+ 25% (DGA) +25% (Furan)+ 25%
(Age) on 1-10 scale
157
III.
IV.
V.
VI.
VII.
VIII.
Option C- Higher preference to DGA, 20% (Oil)+ 40% (DGA) + 20% (Furan)+ 20%
(Age) on 0 to 4 scale
Option D- Higher preference to DGA, 20% (Oil)+ 40% (DGA) + 20% (Furan)+ 20%
(Age) on 1-10 scale
Option E- Higher preference to Furan, 20% (Oil)+ 20% (DGA) + 40% (Furan)+ 20%
(Age) 0 to 4 scale
Option F- Higher preference to Furan, 20% (Oil)+ 20% (DGA) + 40% (Furan)+ 20%
(Age) 1 to 10 scale
Option G- High but equal preference to DGA and furan, 20% (Oil)+ 30% (DGA) +
30% (Furan)+ 20% (Age) on 0 to 4 scale
Option H- High but equal preference to DGA and furan, 20% (Oil)+ 30% (DGA) +
30% (Furan)+ 20% (Age) on 1 to 10 scale
To identify optimal weightage factor option, health indices through above eight options for
selected twenty four generator transformers are estimated. It was observed that those
transformers which are either healthy (having health index more than 7) or those are
unhealthy (having health index less than 4.5), the spread of health index estimated from
above eight options have lower and easily can be identified. However, in case of moderate
transformers (having health index between 4.5 and 7) are not clearly identified and varies
considerably with above options. It was also found that scale of 0- 4 does not provide distinct
information and 1-10 scale is more useful. It may be interesting to report that higher
weightage factor (more than 40%) to any one category from above four, gives skewed results.
Therefore, either equal (option A) or slight higher weightage factor (say 30%) to key
categories (Options H) such as DGA and Furan is suggested. From this exercise option H was
selected for interpretation of the health of twenty four generation transformers.
4.0 DISCUSSION
Details of transformer, observed results of various diagnostic tests and
estimated health indices of twenty four generation transformers are mentioned in table 1 and
Figure 3 & 4. To correlate health index with observed results these transformers are grouped
in following three categories:
4.1 Healthy-
Five transformers of S No 7, 8, 17, 18 and 21 are having health indices
(more than 7) 7.1, 8.6, 8.5, 7.5 and 9.5 respectively. Furan content of S No 7, 8 and 18
are not measured resulting into lesser health index. DGA result of transformer of S No
7 indicates presence of electrical fault which was identified as defective bushing.
Bushing is replaced and transformer is now working satisfactorily. These five
transformers do not require any special attention and normal monitoring shall be
conducted.
4.2 Unhealthy-
Based on health index (less than 4.5), seven transformers can be
identified as unhealthy. Transformers of S no 2, 3, 13, 14, 15, 16 and 22 are having
health index 4.2, 4.4, 3.7, 4.3, 4.3, 3.9 and 4.1 respectively. Among these seven
transformers, three are more than three decade old. S No 2 and 3 are of 38 years and S
158
No. 22 has completed 31 years of service. There health index is lower due to normal
aging. They are close to end of their expected designed life and shall be planned for
replacement. On the other hand remaining four transformers namely S No 13, 14, 15
and 16 are 24 years old but oil quality is poor and furan content is marginally on
higher side. These transformers need attention and after detailed diagnostic tests
appropriate corrective actions shall be planned.
4.3- Moderate-
Remaining twelve transformers are having health index within 4.5 to
7. Specific attention is required to each transformer. S No 5 and 6 indicates poor oil
quality and moderately high furan content. Whereas DGA result of S No 11 shows
development of internal fault. The other transformers are under normal aging and
routine diagnostics shall be conducted to monitor rate.
HI scores
10
8
6
HI scores
4
2
0
0
5
10
15
20
25
30
35
Figure 3: Heath Index distribution of GTs
No of Tx
Generation Txs - Age Profile
16
14
12
10
8
6
4
2
0
6-10
11-15
16-20
21-25
26-30
31-35
Age Bin
Figure 4: Age distribution of GT
159
36-40
Outcomes of fleet screening exercise may lead to review of condition assessment
methods/technologies/programs and also focusing of remedial /corrective asset solutions on highly
critical asset sub-groups or classes within entire population.
Apart from providing more focused and prioritized asset strategy and solutions, overall gaps and
opportunities in fleet management will be made more transparent and understood for more conscious
or integrated development of holistic fleet management capabilities of critical assets.
• Standardizing the definitions of condition states, failure modes, specifications
• Establishing useful long term data collection procedures by standardized norms
• Calibrating test protocols and developing relationships between test outcomes and
asset condition .
• Conducting on-going failure cause analysis of selected equipment recovered form the
field
• Undertaking statistical analysis of the data and comparing with the results of expert
judgment.
Complicating matters further is the complexity of evaluating and assessing the risk with new
tools designed to test health , increasing volume of available data and a shortage of
experienced maintenance engineers.
5.0 CONCLUSION
This study reveals that health index of transformer fleet can provide
useful information about current status, preventive or corrective actions needed. However,
following points need attention:
1.
2.
3.
4.
Scale of 1-10 is desirable than lower scale.
Advisable to arrive a consensus of decreasing health index with deteriorating health.
Weightage to any category more than 40% gives skewed information.
At the outset three categories, healthy, moderate and unhealthy can be identified.
6.0 REFERENCES
1. “Development of a Plant Health Index for Eskom Distribution Substations”, Elton
Brand, Eskom Distribution and Ulrich Minnaar, School of Electrical Engineering,
Cape Peninsula University of Technology, www.nersa.org.za
2. “Asset Stewardship Report” Ian Butler, 2014 ,
3. “The Transmission Asset Condition Assessment Project” Project Charter Reference
No. BCTC003, British Columbia Transmission Corporation, April 2004
4. “Transformer health assessment and techno-economic end of life evaluation” AEB
Abu Elanien, Waterloo, 2011
5. “Asset Health- Predict Failure, Initiate Action” VENTIX, May 2013
6. “Asset risk management” TRANSPOWER New Zealand, Nov 2013
7. “Asset Management Plan-3.2-01, Substation transformers 2014-2025” SA Power
network, Oct 2014
160
8. “An Approach to Power Transformer Asset Management Using Health Index” Ali
Naderian Jahromi, Ray Piercy, Stephen Cress, Jim R. R. Service and Wang Fan, IEEE
Electrical Insulation Magazine, Vol. 25, No. 2, March/April 2009.
9. “Aging Assessment of Power Transformer Using Multi-parameters” Yuan Li, MingJie Tang, Feng-Jiao Wu, Guan-Jun Zhang, Shu-Hong Wang, Suwarno, International
Journal on Electrical Engineering and Informatics - Volume 5, Number 1, March
2013
10. “Emerging Trends in Diagnosis and Condition Assessment of Power Transformers
Based on Health Index” Priyesh Kumar Pandey, Harmendra Singh, M Rao, and R K
Jarial, 2nd International Conference on Emerging Trends in Engineering and
Technology (ICETET'2014), May 30-31, 2014 London (UK)
11. “Calculation of power transformers health indexes” Bogdan GORGAN1, Petru V.
NOTINGHER1, Laurentiu V. BADICU1, Gabriel TANASESCU2. Annals of the
university of Craiova, Electrical Engineering Series, No 34, 2010
12. “Systems and methods for asset condition monitoring on electric power substation
equipment” Brian David Sparlmg, Bazzocchi er, Claude Beauchemin, Fantana et al.;
Jacques Aubin, US 8,484,150 B2, July 2013.
BIBLIOGRAPHY
A. Dr Aradhana Ray
[1]
[2]
Recipient of "Dr Vikram Sharabhai Young Scientist Award" by Department of Science &
Tech. India, in 2005.
Published more than Fourty technical & research papers
[3] Served on technical committees of national and international conferences including IEEMA ,
CIRED Conferences
[4] 20 years working experience with Consulting, third party inspection and Asset Management
project in the field of Electrical power equipment in several countries such as India, Dubai, OMAN,
North America, South Africa Malyasia and Australia.
[5] 2Conducted many workshops worldwide over the last five year and trained approx. 3,000
managers, engineers
B. Dr V Shrinet
[1]
[2]
[3]
[4]
[5]
[6]
Chairman of BIS sectional committee of ETD 2
Recipient of Gujarat state “Dr Vikram Sarabhai award” National “NRDC award” and
international “WIPO Gold medal” for best invention of the year
Published more than hundred research papers
Filed more than thirteen patents.
Guided two Ph D students.
Conceived, developed and commercialized more than ten technologies
161
162
Trf
asset
code
DG1
DG2
DG3
DG4
GTG5
GTG6
Main #1
Main #2
#1 Main
#2 Main
#3 Main
#4 Main
GT1
GT2
GT3
GT4
GT5
GT6
GT7
GT8
STG9
GT10
IB T1
IB T2
S
No
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
16
16
16
17.5
45
45
160
160
63
63
45
45
45
45
45
45
45
45
15.7
12.5
15.5
45
45
45
Rating
(MVA)
1977
1977
1977
1982
1993
1993
2007
2007
1996
1996
2002
2002
1991
1991
1991
1992
1996
1996
1998
1998
2008
1984
1984
1984
0.08
0.12
0.06
0.01
0.23
0.2
0.01
0.01
0.04
0.04
0.04
0.04
0.22
0.23
0.2
0.15
0.01
0.04
0.01
0.03
0.01
0.13
0.08
0.08
Acid
ity
25.9
23.4
29.1
30
20.5
20.7
41
47
44
39
37.2
38
17
17
18
18
41
NM
43
NM
47
19
30.3
24.5
IFT
5
5
5
5
5
4
34
5
0
144
140
0
88
56
64
29
24
0
5
0
19
6
0
5
Hyd
roge
n
2
2
2
2
4
3
47
1.3
22
23
15
27
43
7
22
5
14
2
25
25
8
1
4
4
Met
hane
2
2
2
1
2
2
11
1
4
11
2
3
36
4
14
3
4
0
8
8
2
1
3
2
Eth
ane
9
12
12
3
9
6
69
1
3
10
6
2
15
7
11
3
12
9
4
4
1
22
44
1
Ethy
lene
0.5
0.5
0.6
0.3
0.6
0.3
43
0
0
0
0
0
0.7
0.8
0.7
0.6
0.3
0
0.4
0.4
0.2
0.6
0
0.3
Ac
etyl
ene
144
192
170
108
340
247
841
35
841
247
1111
919
613
568
584
362
283
191
898
748
245
252
265
258
CO
1180
3130
2570
1740
2330
1940
4273
427
4273
4764
3845
3569
3540
4740
4370
3970
1720
1418
7260
6027
1070
2774
3013
2850
CO2
163
214
192
119
361
262
1047
43.1
870
435
1274
951
796
643
696
403
337
202
940
785
275
283
316
270
TDG
0.482
0.802
0.706
1.31
1.23
1.22
NM
NM
0.0018
0.0018
0.001
0.0027
2.56
2.63
2.5
1.62
0.018
NM
0.026
NM
0.002
1.264
0.15
0.09
Furfura
l
content
323
195
485
3000
89
103
4100
4700
1100
975
930
950
77
73
90
120
4100
--4300
--4700
146
378
306
Oil
quality
index
11
NM-Not measured, #-One bushing failed and replaced, @Higher particle count found
Commissi
oning
year
Table 1-Observed results of generation transformer
0
1
1
1
0
0
4
1
2
2
3
2
2
1
1
2
0
0
2
2
0
1
1
1
# of gases
violates
38
38
38
33
22
22
8
8
19
19
13
13
24
24
24
23
19
19
17
17
7
31
31
31
Age
5.6
4.2
4.4
5.3
5.5@
5.7@
7.1#
8.6
6.5
6.3
5.9
6.5
3.7
4.3
4.3
3.9
8.5
7.6
6.7
5.8
9.5
4.1
4.6
5.2
Cumulative
Health
index
CIGREAORCMeeting
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CIGREAORC Technical
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including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“GlobalCIGRETrends in
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T&D System
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AORC
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“Global Trends in the Development of Power T&D System including Smart Grid”
Mitigation of the Effect of Magnetizing Inrush Due To Switching of Distribution
Transformers in HT Power Distribution System of a Typical Chemical Plant
MitigationDR.
of the
Effect of Magnetizing InrushDEBNIL
Due ToCHAKRABORTY
Switching of Distribution
J. K. DAS
Transformers
in
HT
Power
Distribution
System
of
a
Typical
ChemicalLtd
Plant
Tata Consulting Engineers Ltd.
Calcutta Electric Supply Corporation
India
DR. J. K. DAS
Tata Consulting Engineers Ltd.
India
India
DEBNIL CHAKRABORTY
Calcutta Electric Supply Corporation Ltd
India
SUMMARY
Very often it is noticed that complete black out takes place in an industrial plant for
occurrence of an abnormal condition in the power system. Generally restoration of power is
SUMMARY
done through available Emergency Diesel Generator (EDG) sets in the plant to ensure power
supply to the critical loads. It is observed that during initial load pick up phase switching
Very
often
it isdistribution
noticed that
complete
black
out takes
placeininsynchronisation
an industrialofplant
inrush
of the
transformers
creates
enormous
difficulty
EDG for
sets resulting
secondarycondition
collapse which
again
delay Generally
the entire process
of emergency
occurrence
of aninabnormal
in themay
power
system.
restoration
of power is
restoration.
This
delay mayDiesel
create Generator
irreversible (EDG)
damagesets
to the
power
sensitive
critical
donepower
through
available
Emergency
in the
plant
to ensure
power
loads.
such loads.
situationIt was
faced in that
a typical
large
chemical
plant up
andphase
was studied
supply
to Similar
the critical
is observed
during
initial
load pick
switching
further
to overcome
the transformers
situation through
cost effective
measures.
inrush
of the
distribution
creates
enormous
difficulty in synchronisation of EDG
sets resulting in secondary collapse which may again delay the entire process of emergency
power restoration. This delay may create irreversible damage to the power sensitive critical
loads. Similar such situation was faced in a typical large chemical plant and was studied
further to overcome the situation through cost effective measures.
KEYWORDS
Mitigation of Effect of Magnetizing Inrush, Emergency Diesel Generator (EDG), Safe Emergency
Power Restoration.
KEYWORDS
Mitigation of Effect of Magnetizing Inrush, Emergency Diesel Generator (EDG), Safe Emergency
Power Restoration.
jkdas@tce.co.in
163
I.
INTRODUCTION
Switching of transformers is considered as a critical event in the operation of an Industrial power
system. When a transformer is energized, due to momentary saturation of transformer core during
magnetising process, it generates very high value of transient current known as inrush current. This
inrush current has tremendous stress on system equipment, protection co-ordination and
synchronisation etc. The voltage dip in the bus reaches beyond acceptable limit due to high surge
current, sometimes 9/10 times the full load current and the same may de-synchronize EDG sets just
connected with the system for emergency power restoration. Due to involvement of switching of
several load transformers in large power distribution, successful synchronisation and load pick up of
EDG units during black out condition is really a challenging task. This system criticality is generated
due to the aforesaid unpredictable system transients followed by energization of transformers. In the
subsequent sections we will attempt to focus on phenomenon, reasons, effects and mitigation plans of
the effect of inrush current to ensure steady synchronisation of EDG and load pick up through
transformer switching. A case study with simulation results have also been incorporated for a large
chemical plant where delay in restoration of power supply for some critical loads may create
irreversible damage and jeopardize the production process.
II.
MAGNETIZING INRUSH - CAUSE & EFFECT
Transformer Inrush is generated due to the nonlinear relationship of flux and magnetizing current as
transformer core enters into saturation mode. It is not only the high magnitude of inrush current but its
composition (high DC component and harmonics) and duration also are the causes of concern which
severely affects the stability of the system.
This disturbance can be severe enough to carry the transient swing of rotor angle beyond 180° which
in turn results in the slipping of poles for the connected generators and create loss of synchronism with
the power system.
Inrush current is found to be a function of several factors like magnitude of remnant flux in
transformer core, Nonlinear magnetizing characteristic during saturation, Magnitude of source voltage
and impedance, the switching instant and short circuit power of the source including VAR absorption
capacity .
The general equation that gives the amplitude of inrush current as a function of time can be expressed
as
i(t ) 
2Vm
* Sw * Ks * Sint     e
Ze
 t  t 0 

* Sin
Where,
Vm – Maximum r.m.s voltage across the transformer primary;
Ze – Equivalent impedance under inrush;
θ – Angle of energization;
t – Time of enerzization;
t0 – Time at core saturation;
τ – Transformer winding time constant during inrush;
φ – Function of t0;
Sw – constants for 3 phase winding connection;
Ks – constants for short-circuit power of network.
164
1
III.
CASE STUDY
A case study of loss of synchronism for the plant EDGs as encountered during switching of
transformers in a reputed large chemical plant in India have been carried out and is described below.
The subject plant is a renowned producer of Purified Terephthalic Acid (PTA). The plant has been
categorized into three (3) different processes, namely HP Plant, DP plant and CHH Plant.
The plant is getting main power supply from the state utility at 132kV level. Afterward, it is stepped
down to 6.6kV via two (2) nos 35MVA transformer. There are three different 6.6kV switchgears for
HP Plant, DP plant and CHH Plant. HP plant is connected with DP and CHH plant at 6.6kV via tie
lines. During normal operation one transformer is connected at HP plant and another is connected with
DP pant. CHH plant is connected with HP plant through the tie cable of 6.6kV. The tie between HP
and DP plant remains open in normal condition.
The power distribution philosophy for all the three plant is described as below:
6.6/0.433kV transformers of different sizes have been found for downstream distribution. Motor
feeders above 150kW are fed from 6.6kV Board while rest are fed from 415V Board. Total plant load
comes to the tune of 45MW out of which critical survival load is around 5.5 MW.
A block diagram for the power system of the chemical plant up to 6.6 KV level has been shown below
in the Fig 1.
Fig. 1: Block Single Line Diagram of the Plant
It is observed recently that due to grid disturbances 132kV grid power failed and became isolated
resulting complete black out and tripping of the process plant loads. For resuming the process, critical
loads were to be restored within 60 sec as per the requirement of the plant.
The plant is having 2x 6 MW EDG sets at HP plant to run the critical loads to cope up with such
situation.
On occurrence of complete black out / islanding from grid, the HP plant DG sets needed to be
synchronised one after another and the critical load buses were energized. It was found that the load
side 6.6/0.433kV distribution transformers were switched on almost simultaneously for quick
restoration of critical loads.
There is total twenty four (24) nos. distribution transformer in the range of 0.8MVA to 2 MVA,
6.6/0.433kV which are fed from the DG supply during emergency condition.
It was found that the DG sets went out of step and failed to pick up the loads upon switching on the
distribution transformers.
While analysing the root cause of the failure, the study team collected all the data and gathered the
sequence of operation followed for switching all the emergency loads.
165
2
Based upon the data collected the critical power system was modelled in PSCAD and represented as
shown in the Fig. 2 below.
Fig. 2: Emergency Power System of the subject plant
The simulation results of the transformer magnetizing inrush current for the operating sequence
followed has been shown in Fig. 3 below. The highest amplitude of magnetizing inrush current of a 2
MVA, 6.6/0.433kV transformer appears to be 1.7kA at 6.6kV side which is almost 10 times of the full
load current.
Fig 3: Simulation result of magnetizing inrush current (typical) of 2MVA, 6.6/0.433kV Transformer
The simulation result of frequency analysis of the inrush current has been shown in Fig 4 below. It is
found that after fundamental, 2nd harmonics is predominant which matches with the typical nature of
the inrush current.
166
3
Fig 4: Simulation result of 'R' phase frequency component (typical) of 2MVA, 6.6/0.433kV
Transformer, (fundamental – top, 2nd harmonic – middle, 3rd harmonic – bottom)
The simulation result of voltage profile of 6.6 bus after connecting the EDG is shown in Fig. 5 below.
It is found that severe bus voltage collapse due to voltage drop for magnetizing inrush effect of the
transformers.
Fig 5: Simulation result of voltage profile of EDG bus (6.6kV)
The simulation result of rotor angle of the EDG sets has been shown in Fig 6 below. It is found from the
result that DGs are going out of step with rotor angle variation more than 3c.
Fig 6: Simulation result of Rotor Angle output of EDGs
167
4
IV.
MITIGATION PLAN
The phenomenon of transformer inrush is dynamic in nature and largely depends on system
configuration. Some of the mitigation methods are as follows [1]
 Pre Insertion Resister in circuit breaker
 Low Impedance Charging
 Load the transformer to its minimum possible load prior to proceeding with energization [2], [3]
With the above mitigation plan, new components are required to be introduced which has cost and
time involvement.
So the solution has been thought of in a different way without involving any additional investment for
any new equipment or parts.
Change of operating sequence has been thought of and studied with simulation model with different
possible sequences. It is observed that the final suggested pattern of switching sequence works out
successfully to reduce the inrush causing out of step of EDGs. The operating sequence is described
below:
First one 6 MW DG is started and the loads in HP and DP plants are switched on sequentially as per
the Table - 1 described below.
Table 1: Suggested sequence of operation for restoration of critical loads
The effectiveness of the proposed technique is checked by the simulation results which are produced
below:
168
5
Fig 7: Simulation result of active power outputs of EDGs
Fig 8: Simulation result of reactive power outputs of EDGs
Fig 9: Simulation result of voltage profile of EDG bus (6.6kV)
169
Fig 10: Simulation result of Rotor Angle output of EDGs
It is found that the maximum internal phase angle (Fig 10) has reduced to 1.14c and after
synchronization of 2nd EDG the same has reduced to less than 1c.
V.
RECOMMENDATIONS
Due to change of switching sequence it has been observed that the rotor angle swing during
magnetising inrush is coming within the acceptable limit thereby reducing the threat for going out of
step. [4] The situation improves after synchronisation of the 2nd EDG and load pick up becomes
smooth. Active and reactive power outputs (Fig 7 & 8) from both the machines are also found well
within the EDG capability curve.
Voltages at 6.6kV buses are found within ± 10% during switching operation of Transformers, HT
motors (Fig - 9).
As per IEEE 399 stipulation, the transient overshoot of the rotor angle should never exceed 2c or if the
root cause of rotor swing is quickly removed, the machine may continue with the system in
synchronised condition. The rotor angle then oscillates with gradually decreasing swings until it settles
to its final steady value (less than 90°). The oscillations are damped by electrical load and mechanical
& electrical losses in the machine and system, especially through the damper windings of the machine.
The result of internal phase angle depicts that the transient overshoot of the rotor angle never exceeds
2c and finally settles at around 0.8c.
Hence, the suggested operation philosophy for restoration of critical loads of the plant after black out
satisfy the requirement of controlling the effect of magnetising inrush without additional cost
involvement and without violating the condition for process requirement.
The same sequence has also been vetted by the process people for implementation.
VI.
CONCLUSION
In this paper a cost effective method for controlling the effect of overall magnetising inrush current
due to switching of load transformers during start up time of EDG sets has been proposed. The
proposed scheme aims to prevent the EDG sets going out of step and failing in emergency load pick
up by changing only the switching sequence. This strategy on the basis of the reducing peak load is
quite different from other standard approaches of inrush current reduction. This control strategy is
easy to implement because the operating sequence is effective in reducing the overall start-up inrush
current. This is achieved without any additional hardware and without the need for a separate source.
The same philosophy may be followed for any such industrial plant facing the similar problem
provided that the simulated switching strategy fulfils the process requirement.
170
7
VII.
ACKNOWLEDGEMENT
Author 1 is working in Tata Consulting Engineers Ltd (TCE), Kolkata and Author 2 is working in
Calcutta Electric Supply Corporation Ltd (CESC) and they carried out the studies on the power
systems of the chemical plant situated in Eastern India. The study is the basis of formulating this
technical paper. We thankfully acknowledge the contribution of the technical team of the client while
completing the study successfully.
VIII. BIBLIOGRAPHY
Type here the bibliography at the end of your text, according to this presentation (see sample
references below). Font to be used is always Times or Helvetica 11 or 12.
[1]
[2]
[3]
1.Saurabh Shrivastava, Ashfaque Khan, Amita Mahor, Transformer Inrush Current and Related
Challenges, International Journal of Emerging Technology and Advanced Engineering (ISSN
2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 12, December 2014).
L. Prikler, G. Banfai, G. Ban and P. Becker, Reducing the Magnetizing Inrush current by means
of Controlled Energization and de-Energization of Large Power Transformer, International
Conference on Power System Transients, IPST 2003.
Salman Kahrobaee, Marcelo C. Algrain, Sohrab Asgarpoor, ―Investigation and Mitigation of
Transformer Inrush Current during Black Start of an Independent Power Producer Plantǁ
Electric Power Division, Caterpillar, Inc., Peoria, USA.
171
8
CIGRE- AORC Technical Meeting 2016 and International Conference
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Technical
Meeting 2016on
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Development
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Technical
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and on
International
Conference
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global Trends in the Development of Power
on T&DSystem including Smart Grid”
“Global Trends in the Development of Power T&DSystem including Smart Grid”
Power Quality Improvement through Smart Control & Diagnostics of Power
Transformer Load Tap Changer
Power Quality Improvement through Smart Control & Diagnostics of Power
Transformer
Load Tap
Changer
KuldeepKumar Jain,
Raj Kumar Sharma,
Yogesh
Gupta, Alokadri Basu.
Tata Power Delhi Distribution Limited
KuldeepKumar Jain, Raj Kumar India
Sharma, Yogesh Gupta, Alokadri Basu.
Tata Power Delhi Distribution Limited
India
SUMMARY
Post Delhi reforms in 2002, Tata Power Delhi Distribution Limited (erstwhileNDPL) has been
consistently able to meet and overachieve its performance target related to utility business in terms of
SUMMARY
operational excellence, consumer services and other key stakeholder expectation. This has been
possible through unique design and deployment of strategy, process, and technology vis-à-vis
commitment
of TPDDL
Reliability
and Quality
of supply
is critical component
Post consistent
Delhi reforms
in 2002,
Tata workforce.
Power Delhi
Distribution
Limited
(erstwhileNDPL)
has been
of
consumer
satisfaction
and
needs
continuous
engagement
and
innovation
from
Planning,
consistently able to meet and overachieve its performance target related to utility business in terms of
Engineering,
Execution,
Operation services
& Maintenance
functions
organization.
operational
excellence,
consumer
and other
keywithin
stakeholder
expectation. This has been
Over
the
year,
Sub-transmission
system
in
TPDDL
has
seen
phenomenal
growth
in terms vis-à-vis
of
possible through unique design and deployment of strategy, process,
and both
technology
network expansion and technological interventions. Sub Transmission grid substation have increased
consistent
commitment of TPDDL workforce. Reliability and Quality of supply is critical component
from 38 No’s with 1635 MVA capacity to 68 No’s with 3838 MVA as on date. Smart Grid
of consumer
andsolarneeds
continuous
and
innovation
frommore
Planning,
technologiessatisfaction
& Roof top PV
integration
in comingengagement
times will make
existing
power system
Engineering,
Execution,
Operation
&
Maintenance
functions
within
organization.
dynamic, interactive and complex. PV Solar Integration, Electronic Appliances and Dynamic loading
Overscenario
the year,
Sub-transmission
system
in TPDDL
seen makes
phenomenal
growth
in terms
of
considering
industrial and
residential
growth has
in Delhi,
the system
more both
complex
to
ensure
Quality power
to Consumers.interventions.
It has been a Sub
common
practice in grid
mostsubstation
of transmission
network
expansion
and technological
Transmission
have and
increased
in India
Power Transformers
operated
fixed as
taps.onHistorical
data Grid
fromdistribution
38 No’s industries
with 1635
MVAthat
capacity
to 68 No’sare
with
3838onMVA
date. Smart
clearly
indicates
that
40%
of
transformer
failures
are
attributed
to
OLTC
faults
as
OLTC
is
the
only
technologies & Roof top PV solar integration in coming times will make existing power system more
moving
part of transformers.
Requirement
of Integration,
frequent specialized
periodic
maintenance
also one ofloading
dynamic,
interactive
and complex.
PV Solar
Electronic
Appliances
andisDynamic
the major reason because of which OLTC’s are kept out of service in most of transmission and
scenario
considering industrial and residential growth in Delhi, makes the system more complex to
distribution utilities. Same was the case in Delhi Vidyut Board till its unbundling in 2002. This paper
ensure
Qualitybroadly
powerhow
to TPDDL
Consumers.
It has
common
practiceandinprocess
most of
transmission
illustrates
designed
and been
adopt asmart
technological
innovation
and and
distribution
industries
in
India
that
Power
Transformers
are
operated
on
fixed
taps.
Historical
data
latest maintenance strategy to ensure Quality Power Supply to its valuable 1.4 million consumer base.
clearly indicates that 40% of transformer failures are attributed to OLTC faults as OLTC is the only
moving
part of transformers. Requirement of frequent specialized periodic maintenance is also one of
KEYWORDS
the major reason because of which OLTC’s are kept out of service in most of transmission and
Power Quality,
OLTC,
Changer,
Capacitor
Bank,
IEDs,Board
Logics,
Diagnostic, in
Vibroacoustic,
distribution
utilities.
SameTap
was
the case
in Delhi
Vidyut
tillOLTC
its unbundling
2002. This paper
Envelops,
MaintenanceStrategy.
illustrates broadly how TPDDL designed and adopt smart technological and process innovation and
latest maintenance strategy to ensure Quality Power Supply to its valuable 1.4 million consumer base.
KEYWORDS
Power Quality, OLTC, Tap Changer, Capacitor Bank, IEDs, Logics, OLTC Diagnostic, Vibroacoustic,
Envelops, MaintenanceStrategy.
alokadri.basu@tatapower-ddl.com
172
1. INTRODUCTION
Being a consumer conscious utility, TPDDL decided to regulate the secondary voltage of its 66/33/11
kV power transformers within band of ±4%; much better than mandated by regulator of ±6%. A
systematic and planned project has been started with automatic OLTC operation in unmanned grids to
get the desired voltage regulation in the power transformers. The task of operating the fleet of around
175 no’s power transformers with OLTC’s not only includes the initial repairs but also proper upkeep
by preventive maintenance.
As per different established studies, On-load Tap changers are major contributor in power transformer
failures and most of utilities prefer fix tap or off-load tap changing operation. This practice results in
poor quality of supply and adversely impacts consumers’ satisfaction. Further for industrial consumer,
fluctuating voltage supply can result in manufacturing and associated high revenue loss. The advent of
reactive power penalty under IEGC further created concern for utility due to heavy monetary penalty
associated with voltage violation.
To mitigate OLTC failure vis-à-vis ensuring quality power supply and healthy reactive power
management, TPDDL took two significant initiatives. In first phase, TPDDL has completed 100%
Automatic Voltage Control at 11kV Bus by AVR integration. TPDDL has more than 175 nos. of Tap
Changers of Different makes, design (In-tank or Flange mounted), age and different operational stress.
TPDDL commenced Integration of 11 kV Shunt Capacitor Banks over Tap Changer Operations.
Logics and coding has been developed within Transformer Monitoring Unit which will first put
Capacitor bank on operation for certain band of voltage violation from reference voltage. This
intervention has resulted in significant reduction of Tap Changer Operation and associated risk of
failure in old Tap Changers. Integration of tap parameters with SCADA further enabled remote
monitoring and functionality of tap changers. Over The period Un Utilized Shunt Capacitor Banks at
33kV and 66kV level are integrated to this system by self-developed logics in IEDs. This Paper
describes the phase wise logic development and implementation with schematic diagrams.
On Load Tap changers are the only moving part in Power Transformers and historical data reveals that
40% of Power Transformer failure is caused by failure of Tap Changers. To overcome this problem,
smart mixing of Condition and Risk Based Maintenance Strategies are introduced in TPDDL. In “Asis” scenario, DC Winding Resistance and Turns Ratio are popular diagnostic tools used for OLTC. But
these tools can only diagnose contact looseness, contact Wear & Tear and Wrong connections. We
cannot detect Sluggish operation Problem, Shaft Alignment, Energy Accumulator/ Bearing Assembly
problems through DC Winding Resistance & Transformer Turns Ratio. To plug the subject gap it was
imperative to adopt more advanced diagnostic tool to identify these types of defects in load tap
changer. Post pilot, TPDDL has adoptedVibro-Acoustic diagnostic Techniques to identify Sluggish
operation issue, Alignment and other issues based on Signature analysis at different taps. The paper
will elaborate on subject technology and utility operational experiences for diagnostic maintenance of
Load Tap changers.
2. VOLTAGE AND REACTIVE POWER CONTROL:
The desired voltages are obtained by directly controlling the voltage and also by controlling the
reactive power flow which, in turn, will affect the voltage drop. Thus two methods were mainly used.
2.1Voltage Control with On-Load Tap Changer
A transformer equipped with on load tap changer(OLTC) can adjust its voltage ratio with respect to
the present or expected load, to compensate the voltage drop over the transformer and upstream lines.
The representation of a transformer equipping an OLTC and its equivalent diagram is shown
below.The OLTC controller keeps the substation secondary bus voltage constant within the range.
173
Fig.1. Automatic Voltage Control through OLTC
2.2Reactive Power Control with Shunt Capacitors
Shunt capacitors inject reactive power to the system. The reactive power pumped by the capacitor
compensates the reactive power demand and thereby boost the voltage, according to the following
voltage drop approximation:
ΔU = U1 – U2 ≈ RP+XQ/U2
With U1 and U2 as the sending and receiving voltage, respectively; R and X as the resistance and
reactance of the line, respectively; and P and Q as the active and reactive power flow, respectively.
Reactive power-controlled capacitors are effective when the capacitor is intended to minimize the
reactive power flow. We have 11/33/66 kV Capacitor banks in our Power network and are operated to
meet reactive requirement and voltage control. TPDDL has graduated from manual control to a
systematically designed Voltage and Reactive control of Switching of Capacitor Banks.
2.3Voltage and Reactive Power Control – TPDDL Methodology
Voltage and reactive power control involve proper coordination among the OLTC and all capacitor
banks in the distribution system to obtain an optimum voltage profile and optimum reactive power
flows in the system according to the objective function and operating constraints.
Many researchers have addressed the problem of voltage and reactive power control in distribution
systems. Recently, most of them focused on automated remote dispatch, either by using one-day-ahead
daily dispatch schedules or real-time control.
The main obstacle of the implementation of this method is its dependency on communication links and
remote control to all capacitors. Real-time control requires an even higher level of distribution system
automation.
In TPDDL, the available OLTC and capacitor banks are controlled using Transformer monitoring
units (TMU) based on predetermined set point values, without requiring communication links among
equipment involved in the voltage and reactive power control.
3.TRANSFORMER MONITORING UNITS
TPDDL has replaced all its Remote Tap Changer Control(RTCC) panels with TransformerMonitoring
Units, these TMU’s are latest Intelligent Electronic Devicesthat not only serve the purpose of reactive
power and voltage control but also acts as backup protection and monitoring device for transformers.
174
Till 2006, TPDDL was engaged in building/revamping the infrastructural backbone of its sub
transmission network by replacing the old equipment and augmentation of network. Afterwards the
thrust grow to provide quality powerto its consumers. First of all, all the make & types of OLTCs
available in TPDDL were identified and the Spare requirements for the various types of OLTCs were
procured.
Before making OLTC operation automatic, following checks were performed:
A. Internal Checking of OLTC including replacement of spares etc.
B. Operational Checking of OLTC
C. Testing of OLTC
D. Initializing and commissioning of the AVR
E. Integrating the OLTC with our Transformer Monitoring Units
Every solution comes with a problem, and that’s the exact case that arises after making the OLTC’s
operational. Tap operations increased drastically with automation of OLTC’s and it followed high
maintenance cost and even equipment breakdown. We have overcome on many problems after finetuning the settings and implementation of improvised programs of Transformer monitoring units based
on field inputs and Operational Experience.
In TPDDL, Transformer Monitoring Units found their widespread usage in control, monitoring,
protection, tripping analysis.
Fig 2. Voltage Control Using TMU (unutilized Capacitor Bank)
Control is the most important function of TMU that ensures Reactive Power/Voltage control through
integration of both OLTC and Capacitor Banks. Initially when OLTC were taken into service, there
was a potential threat of underutilized capacitor banks meant for reactive power compensation under
the ABT regime. There were more than 80 nos. of 11KV Capacitor Banks that became underutilized
after integration of OLTC s with TMU s.
175
Fig 3. Capacitor control using TMU
Fig 4.OLTC Operation optimization
It has been seen in summer time in NCR region that voltage dip goes beyond 20%. As our metering is
on 66 kV Bus at DTL and capacitor bank switch-on logic is on 11 kV Bus; Capacitor banks went OFF
at 11 kV because of local correction by OLTC without a fact of low incoming voltage in the greater
scenario.
Thus new logics were developed that integrates the operation of OLTC’s along with Capacitor banks
and provide maximum voltage regulation/reactive power control along with maximum utilization of
Cap Banks. Thus it not only controls the no. of operations of OLTC but also control switching of
capacitor banks for reactive power compensation/11 kV bus voltage regulation. The underlying logic
is as follows:
176
Fig 5.Smart Logic for Integration of Capacitor bank and OLTC with IEDs
5. RECORD DATA ANALYSIS AND LOAD TAP CHANGER MAINTENANCE STRATEGY
Transformer Monitoring Units maintains exhaustive record of tap positions, current and voltage
profiles along with alarm/trip histories of Bucholz, OSR, SPR, PRV, WTI, OTI, etc. It also preserves
temperature trends of oil and windings. Thus, it plays very important role in scheduling preventive and
predictive maintenance of transformers and OLTC.
Fig 6. Statistical Data of Tap Changer
Based on the Above Statistical Data, OEM recommendations and rich operational experience
Maintenance Strategy of Tap Changers are finalized in every year. This database also helps us to
maintain critical spares of Tap Changers at the time of Maintenance.
6. DIAGONOSTIC METHODS OF TAP CHANGER
TPDDL follows Smart approach of Online/Off line Condition and Risk Based Maintenance Strategy
of Tap Changers by using ERP Applications.
177
6.1 On Line Inspection
a. Tr. Oil Analysis: Oil BDV, Moisture Content etc. ( BDV should be High and Moisture Should be
less for quicker arc extinction)
b. Drive Mechanism Inspection:
 Tightness of control wiring
 Setting of Heater
 MCB/Fuse
 Illumination
 Contactor cleaning
 Door locking, Gasket etc.
 Counter Operation
c. OLTC Tank Leakage, Dirt, Rust etc.
d. Conservator leakage, Oil Level, Breather
e. AVR operation, Manual Handle Operation
f. Tap Position Indication and Statistics in AVR
g. AVR and OLTC Electrical Connections.
6.2 Off Line Inspection (During Shutdown of Tr.-Freq: 5000 Operations or Two Years
whichever is earlier)
a. Diverter Switch
 Contact Cleaning
 Contact wear check
 Contact replacement if required
 Winding Resistance/ Turns Ratio Measurement.
b. Correct Stopping of OLTC after One Operation
c. Step by Step Operation
d. OSR test
But there are several instances we found where Transformer Tripped due to OLTC sluggish Operation,
Contact wears, Shaft misalignment, and Energy Accumulator slip. To diagnose these problems
Winding Resistance, Turns Ratio and Oil analysis are not sufficient. With the Help of one Tap
Changer manufacturer in India we started VibroAcoustic based OLTC diagnosis on identified tap
changers. We found that this equipment is capable to detect following problems which other can’t:
Tap Changer Problems:
A.
Diverter/Selector Switch
B.
Motor Drive
1.
Contact Wear
1.
Motor
2.
Overheating/Coking
2.
Brake
3.
Transition Time
3.
Lubrication
4.
Contact Alignment
4. Control /Relays
5.
High Arcing
5.
6.
Timing/Sequence
6. Energy Accumulator/Spring
Linkage/Gears
Accelerometer is fitted on the Transformer main tank and the Vibrations during tap change are
captured by the Equipment and graphs are displayed on laptop.
178
Fig 7.VibroAcoustic OLTC Diagnostic set up.
There are two traces in Vibro-Acoustic Output.
1. Graph of g (acceleration) and
2. Motor Current Waveform
Based on the Software these charts are converted into “envelops” (Low Frequency and High
frequency).
Fig 8.Raw Traces of Vibroacoustic Output
The Principle Behind this technology is that a stable OLTC produces a consistent chart. By comparing
the charts the unstable OLTC can be identified at early stage.
Analyzing further we can superimpose one envelop on another for comparison. As the X axis of the
chart gives the time in milliseconds, the timing and sequence of various incidents in OLTC operation
can also be identified. So by comparing the time the magnitude of g (acceleration) and Shape of charts
we can easily identify stability of OLTC.
Fig 9 : LF and HF Envelops
179
LF: Low frequency signature gives information on LF acoustics produced by Tap change mechanism
and associated process. Normally the amplitude is high when contacts are new and it reduces with
wear and tear.
HF: High frequency signature gives information on HF acoustics produced by Tap change mechanism
and associated process. Normally the amplitude is low when contacts are new and it increases
withwear and tear and arcing.
In new contacts HF/LF ratio is approximately one but may vary on design and batch. When the
change is more than 30% from a new one or last record it becomes an anomaly.
6.3 Case Study:
Location: PP 2 Grid; 20 MVA Tr. No. 2.
OLTC Details: Make: CTR; Type: FDF; Sr. No. 3161685.
Date: 28.12.2012 Time: 15:16 hrs
a. Tap Position: +5 (4 to 5)
Fig 10. Vibro Acoustic Analysis (Case 1)
Observations:
•
•
Motor current brakes before TAP changing which is a major anomaly.
Contact making is poor and shows synchronism of contact make and motor break
does not exist.
b. Tap Position: +5 ( 4 to 5)
Fig 11.Vibro Acoustic Analysis (Case 2)
180
Observations:
•
•
Tap change completes after motor current braking is a major anomaly.
Motor current shows some looseness in spring.
c. Tap Position : -4 (5 to 4)
Fig 12.Vibro Acoustic Analysis (Case 3)
Observations:
•
•
Motor starts and breaks for 0.5 sec.
There is no tap change due to Tap contact Stuck Up.
7. CONCLUSIONS:
In this paper, we have presented success story of effective use of OLTC’s of power transformers in
utility. We have deliberated our efforts with initial focus of voltage control to meet the consumer
satisfaction by providing desired voltages. The paper matured to the next level where we have
achieved Voltage and reactive control in distribution system using latest SCADA Compatible IEDs.
We have highlighted the features of the Transformer monitoring units which have been used
successfully in our network. Evaluation of the Logics and programs for effective voltage and Reactive
control has also been presented to give insight how we have progressed in the area with help of site
inputs. We have also presented how we are using TMU data in our Maintenance practices.This paper
also describes the use of latest Vibro-Acoustic based Diagnostic methods in parallel to conventional
CBM and Time Based Testing to identify the problem of Tap changers. This is a presentation of one
more achievement of Power utility to make best use of available technology focusing Reliability,
capacity building, predictive approach towards maintenance, and contribution in Grid Stability and
more importantly Consumer delight by providing quality power supply.
BIBLIOGRAPHY
[1]
[2]
TAP 4 –OnloadAnalyzer: Zonsole.com.
New technologies for monitoring transformer tap-changersand bushings and their
integration into a modern IT infrastructure”, CIGRE 2012, Paper A2-101- P. PICHER, S.
RIENDEAU, M. GAUVIN, F. LÉONARD, L. DUPONT, J. GOULET, C. RAJOTTE
[3] REG DA, A EberleUser Manual.
[4] J & P Transformer Book-Martin J Heatcote.
181
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Performance Monitoring of Power Transformer : A novice approach
Dr.ShashikantBakre
Superintending
(Training): A novice approach
Performance Monitoring
of PowerEngineer
Transformer
Maharashtra State Electricity Transmission Co. Ltd , Mumbai , India
Dr.ShashikantBakre
Superintending Engineer (Training)
Maharashtra State Electricity Transmission Co. Ltd , Mumbai , India
ABSTRACT
Condition monitoring and diagnostic testing is a vital task in front of a power system
engineer. He has to monitor various parameters such as breakdown voltage (Bdv), Parts Per
Million (PPM), DGA, Furan analysis, Partial discharge, tan delta, SFRA, winding resistance,
polarization index etc quite frequently. The deviation from standard results may affect
performance and health of the transformer. However many a times it so happens that the
results are within permissible limits but the trend of results over last 2-3 years indicate a
ABSTRACT
deterioration. It is therefore important to monitor the trend for last 2-3 years in order to
ascertain healthiness of transformer. This paper recommends a novice approach to monitor
performanceand
of transformer.
For testing
this purpose
simpletask
database
is system
Condition the
monitoring
diagnostic
is a, a vital
in using
frontJava-Netbeans
of a power
prepared. Using Structured Query Language (SQL) it is ensured whether the parameters are
engineer. He
has to monitor various parameters such as breakdown voltage (Bdv), Parts Per
within permissible limits or otherwise. The method is so simple that the knowledge of Java
Million (PPM),
DGA,isFuran
discharge,
tan delta,
windingfrom
resistance,
programming
not at analysis,
all required Partial
.Using simple
SQL commands
theSFRA,
data is retrieved
is however
required to update
as and
when
the measurements
are affect
polarizationdatabase.
index Itetc
quite frequently.
The database
deviation
from
standard
results may
conducted.
performance and health of the transformer. However many a times it so happens that the
results are KEYWORDS
within permissible limits but the trend of results over last 2-3 years indicate a
deterioration.
It isMonitoring,
thereforeDatabase,
important
to monitor
the trend
for Per
lastMillion
2-3 (PPM),
years in order to
Condition
Structured
Query Language(
SQL), Parts
Total Gas
Contents(TGC)
Dissolve Gas Analysis(DGA),
ascertain healthiness
of transformer.
This
paper recommends a novice approach to monitor
the performance
of transformer. For this purpose , a simple database using Java-Netbeans is
INTRODUCTION
prepared. Using
Structured
Query
Language
(SQL)
is ensuredobserving
whetherparameters
the parameters
are
The condition
of power
transformers
is checked
byitcontinuously
such
within permissible
limits
or (Bdv),
otherwise.
The
method
is Dissolve
so simple
the (DGA),
knowledge
as breakdown
voltage
Parts Per
Million
(PPM),
Gas that
Analysis
Furan of Java
analysis,
Partial
discharge,
tan delta,
SFRA,
winding
resistance,
polarization
index is
etcretrieved
. These
programming
is not
at all
required
.Using
simple
SQL
commands
the data
from
parameters are required to be monitored frequently.In case some deviations with respect to
database. Itstandard
is however
required to update database as and when the measurements are
values are observed, the corrective action is taken thereby enhancing performance
conducted.and life of power transformer.The deviation from standard results may affect performance and
health of the transformer. However many a times it so happens that the results are within
permissible limits but the trend of results over last 2-3 years indicates a deterioration. It is
KEYWORDS
therefore important
to monitor
the trend
for lastLanguage(
2-3 years and
thereby
observe
the condition
Condition Monitoring,
Database,
Structured
Query
SQL),
Parts
Per Million
(PPM),
of transformer.
Dissolve Gas
Gas Contents(TGC)
In Analysis(DGA),
order to monitor theTotal
performance
, the power system engineer has to maintain the record
of measurements noted during last 2-3 years. Based on these , he has to prepare a comparative
chart. He finds this task difficult, particularly when number of transformers in his jurisdiction
INTRODUCTION
is large.
The condition
of power transformers is checked by continuously observing parameters such
as breakdown voltage (Bdv), Parts Per Million (PPM), Dissolve Gas Analysis (DGA),
Furan
1
analysis, Partial discharge, tan delta, SFRA, winding
resistance, polarization index etc . These
182
parameters are required to be monitored frequently.In case some deviations with respect to
standard values are observed, the corrective action is taken thereby enhancing performance
and life of power transformer.The deviation from standard results may affect performance and
THE JAVA NETBEANS DATABASE
Java Netbeans is the solution over a problem. We can create a simple database using Java
Netbeans and monitor various values using Structured Query Language(SQL). Now let us talk
a few words about Java[1]. Java was deceloped by James Gosling at Sun Microsystems in
early nineties. Later it was owned by Oracle Corporation. Java is robust , object oriented
[2], web enabled , platform independent programming language. It supports significant
programming features such as code reuse , abstraction , polymorphism and
encapsulation. Therefore it is Java is widely used in number of fields such as desktop
applications , internet applications , web applications , database management systems , mobile
computing , artificial intelligence , assembly language , Android systems , graphics and
animation , smart device programming etc. About 3000 billion electronic devices in the
world work on Java platform, including numeric relays and numeric meters.Therefore , Java
is generally used as a substation configuration language[3].
THE NETBEANS PACKAGE
Earlier , programmers had to run Java programs on command prompt. This was tedious and
time consuming task. Now, Netbeans and Eclipse have developed Integrated Development
Environment (IDE) for running and developing Java programs. The IDE offers user friendly
environment for Java developers for editing and debugging. The Netbeans package is easily
downloadable from Oracle website , oracle.com.
Java is used as a front end tool and database as backend. Java controls database through the
program called Java Database Connectivity (JDBC). Through JDBC, Java is connected to
DBMS/RDBMS packages such as Oracle , Microsoft Access, SiBase etc[4]. We can also use
internal database of Netbeans called JavaDB. The JavaDB is provided in-built with Netbeans
package.
We can easily create a database from JavaDB and enter measurements of transformer
parameters. For example, the measurements of 167 MVA, 400/220 KV , R phase transformer
unit for last four years (2011-12,2012-13,2013-14 and 2014-15) have been recorded as
shown in Table1.
Table 1
Measurements of 167 MVA, 400/220 KV , R phase transformer unit for four years
183
2
THE STRUCTURED QUERY LANGUAGE (SQL)
The Structured Query Language(SQL) is a simple programming language to interact with the
database. It is case insensitive language provided inbuilt in database package.
The basic command to display all data is given in a following format.
SELECT * FROM tablename;
Where * indicates all records against all columns for the given tablename.
For instance , the data for PPM as per PPM of Table I will be displayed by giving following
command. In this case , Table I indicating only PPM is taken in consideration and not other
fields.
SELECT * FROM SLG.DGA;
Where SLG is the name of table.
The results of the above SQL command would be displayed as shown in Figure I.
Fig 1
SQL Command to display all records.
Now , let us see how to retrieve specific records as per our requirement. The format for
conditional SQL statement is as followsSELECT * FROM tablename where column = Condition;
Again let us understand this with the example given in PPM ofTable I. If the abnormal values
of PPM are to be detected the following command would be given.
SELECT * FROM SLG.DGA WHERE PPM>20;
184
3
Fig 2
SQL Command to display specific records.
On execution of the above SQL command the abnormal values of PPM (more than 20) have
been detected.
The above procedure can be applied over a wide range of data and for more number of
transformers to have a quick access to the deviation in permissible limits. Different SQL
commands for examining trend would be given.
This is illustrated with the example of 167 MVA, 400/220 KV , R phase transformer. The
DGA results were monitored continuously. The Total Gas Contents(TGC) indicated a rising
trend as shown in Table I. Therefore the detailed DGA was conducted by sending oil sample
in laboratory. The results indicated general overheating involving cellulose insulation. Hence
the Furan Test was conducted. The Furen content in transformer oil was measured. The
Furan values above 2500 ppb indicate that the solid insulation has deteriorated. Under this
situation , the Degree of polymerization test (DP test) is conducted. The DP test ascertains
the extent of degradation of paper insulation [5].
Fig 3
SQL Command to display all records of TGC.
185
4
Fig 4
SQL Command to display specific records of TGC
Fig 3 and Fig 4 show the Total Gas Contents under general and specific conditions.
Fig 5 shows a graph showing DP verses Remnant Life of a transformer. The remaining life
of transformer in percent is ascertained from the corresponding value of DP.
For example , the average DP value of thin paper insulation of one of our transformers was
measured as 600 . As seen from graph , it corresponds to remaining life of nearly 79 %
,indicating normal ageing of the paper insulation. It confirms that the solid insulation still has
79% of remaining life. As such , the transformer can provide a useful service life for many
more years.
Fig 5
DP verses Remnant Life
CONCLUSION
This paper recommends a novice approach to monitor the performance of transformer using
Java-netbeans-SQLbased method. Using Structured Query Language (SQL) it is ensured
whether the parameters are within permissible limits or otherwise. The method is so simple
that the knowledge of Java programming is not at all required.Using simple SQL commands
the data is retrieved from database. It is however required to update database as and when the
measurements are conducted.
From the results obtained from Java-netbeans-SQL based method , it is possible to conduct
Residual Life Assessment(RLA) of the transformer . For example, from DGA it can be
186
5
decided to conduct the Degree of polymerization (DP) test and the remnant life of the
transformer is ascertained.
ACKNOWLEDGEMENTS
The author desires to acknowledge the support given by Dr. Mrs. P.N. Gokhale , Professor , Electrical
Engineering Department , JSPM College of Engineering , Pune , while writing this paper. The author
is also thankful to Mrs. Geeta Mandhare , Asst. Professor , Electrical Engineering Department , Trinity
College of Engineering , Pune.
BIBLIOGRAPHY
Dr. Shashikant M. Bakre completed
his
bachelor’s
degree
in
Electrical
Engineering
from Govt Engineering College Amravati (Nagpur University) , followed by master’s degree in
engineering from COEP (Pune University).He also completed MMS , master’s degree in management
from Pune University . Later , he completed his doctorate from Bharati Vidyapeeth Deemed University
, Pune in the year 2011. He is the author of ten books on various subjects .Some of his books are
Computer Fundamentals , Computer Master , Build your own website , OOPS and Core Java , Object
Oriented Analysis and Design and Supply Chain Management. He has published abut 35
research papers . His research work is focused on applications of Information Technology in
Power Systems . At present, is working with Maharashtra State Electricity Transmission Company as
a Superintending Engineer at Training Section, Corporate office , Mumbai.
REFERENCES
[1]
[2]
[3]
[4]
[5]
S. M. Bakre, ‘Object oriented design and basic Java’, Everest Publishing House, 2003.
Shubha Pandit, S.A.Soman, S.A. Khaparde, ‘Object Oriented Design for
Applications, Ieeexplore.ieee.org/iel5/67/18980/00876870. Oct 2000.
S. Chen and F.Y. Lu, ‘Web-based simulations of power systems’, IEEE Computer
Applications in Power, Jan 2002, pp 35-40.
Dongyuan Shi, Yinhong Lee, Xianzhong and Q.H. Wu, ‘Power system data
warehouses’, IEEE Computer Applications in Power, July 2001, pp 49-55.
S.G. Patki, S.G. Patil, J.S.Wadhwa, ‘Assessing Remanant Life of Transformer based
on Furen Content in transformer oil and degree of polymerisation of soild insulation’ ,
Fifteenth National Power System Conférence (NPSC), IIT Bombay, Dec 2008
187
6
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016on
– International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global Trends
in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
Development of 420 kV Gas Insulated Switchgear with One–break Spring
Operated Gas Circuit Breaker
Development of 420 kV Gas Insulated Switchgear with One–break Spring
Circuit Breaker
M. Kawahigashi, M. Operated
Fujioka,Gas
H. Kajino,
D. Yoshida and H. Koyama
Mitsubishi Electric Corporation (Japan)
SUMMARY
M. Kawahigashi, M. Fujioka, H. Kajino, D. Yoshida and H. Koyama
Mitsubishi Electric Corporation (Japan)
SUMMARY
Reduction of life-cycle cost of high-voltage electric equipment including installation and
Reduction of life-cycle cost of high-voltage electric equipment including installation and
maintenance
costs iscosts
an isincreasing
need
electricpower
power
utilities.
In general,
gas insulated
maintenance
an increasing
needfor
for electric
utilities.
In general,
gas insulated
switchgear
(GIS), (GIS),
whichwhich
is one
of of
thethehigh-voltage
electric
equipment,
be and
compact and
switchgear
is one
high-voltage electric
equipment,
should should
be compact
have high-reliability
that enables
reduction ofofinstallation
period
and maintenance
work.
have high-reliability
that enables
thethereduction
installation
period
and maintenance
work.
420
kV
GIS
with
one-break
spring
operated
gas
circuit
breaker
(GCB)
has
been
developed
to
420 kV GIS with one-break spring operated gas circuit breaker (GCB) has been developed to
meet the growing demand for substation construction together with the demand for reduced
meet the installation
growing demand
for substation
with
for reduced
and maintenance
costs. The construction
paper presents together
key benefits
andthe
theirdemand
supporting
installation
and maintenance
costs. The
technologies
applied to the developed
GIS.paper presents key benefits and their supporting
technologies
applied
to the developed
GIS. by the compact design of GIS with concentrated
Reduced
installation
period is achieved
Application of one-break GCB enables reduced size of GCB and contributes to
Reducedconfiguration.
installation
period is achieved by the compact design of GIS with concentrated
the concentrated configuration of the primary circuit of the GIS connected to both sides of the
configuration.
Application
of one-break
enables
reduced
size
of GCB
contributes to
GCB. Operating mechanism
for GCB GCB
is arranged
in front
of GIS,
which
resultsand
in lower
the concentrated
configuration
of the primary
circuitthan
of that
the for
GIS
connected
to both sides of the
height of GCB
and easy accessible
for maintenance
existing
GIS. Concentrated
configuration
enables
single
transportation
per
GIS
unit
and
reduction
of
installation
to in lower
GCB. Operating mechanism for GCB is arranged in front of GIS, which work
results
60 % because many gas compartments assembled in factory can be installed without assembly
height ofwork
GCB
and easy accessible for maintenance than that for existing GIS. Concentrated
on site. Compactness also reduces the installation footprint of switchgear to 60 % of that
configuration
enables
singleand
transportation
per GIS
unit and
reduction
of substation.
installation work to
for existing
switchgear,
results in the reduction
of building
cost
for the whole
60 % because
many
gas
compartments
assembled
in
factory
can
be
installed
without assembly
Reduced maintenance work is achieved by GCB with torsion-bar spring operating
work on site.
Compactness
also
reduces
thetoinstallation
of switchgear
60 % of that
mechanism
and flexible
linkage
applied
disconnectorsfootprint
(DS) and earthing
switches to
(ES).
Operating
mechanism
torsion
bar reduction
spring possesses
enough capability
for existing
switchgear,
andwith
results
in the
of building
cost for to
theapplied
wholeonesubstation.
break GCB while also providing benefits of increased mechanical reliability and reduced
Reducedmaintenance
maintenance
is achieved
by GCB
with
torsion-bar
spring
work. It work
also enables
to design a compact
operating
mechanism
with large
stored operating
energy,
higher interrupting
capability
be achieved with
simple
mechanism
andand
flexible
linkage applied
to can
disconnectors
(DS)
andmechanical
earthing puffer
switches (ES).
interrupter.
Flexible
linkage
using
metallic
wires
is
applied
to
DS
and
ES
to
achieve
Operating mechanism with torsion bar spring possesses enough capability to easy
applied oneaccess for maintenance work. Metallic wires transmit operating force from the operating
break GCB
while toalso
mechanical
and reduced
mechanism
the providing
moving partsbenefits
of DS orofES,increased
while enable
the flexible reliability
location of the
maintenance
work.
It
also
enables
to
design
a
compact
operating
mechanism
with
large stored
operating mechanism. They also contributes to concentrated configuration of all operating
mechanisms
in front capability
of the GIS unit,
results in enables
single location
for
energy, and
higher located
interrupting
can that
be achieved
with simple
mechanical
puffer
maintenance
of
the
GIS
unit
and
reduction
of
the
maintenance
work.
interrupter. Flexible linkage using metallic wires is applied to DS and ES to achieve easy
environmental
impact
is achieved
by the
compact design
of the force
developed
GIS.the
SF6 operating
access forReduced
maintenance
work.
Metallic
wires
transmit
operating
from
gas is reduced to 60 % compared to existing GIS. Use of material can also be reduced to 50 %.
mechanism to the moving parts of DS or ES, while enable the flexible location of the
tests were carried out on prototype GIS in accordance with IEC standard.
operating Type
mechanism.
They also contributes to concentrated configuration of all operating
mechanisms
located in front of the GIS unit, that results in enables single location for
KEYWORDS
Gas insulated
switchgear,
Gasreduction
circuit-breaker,
Torsion-bar
spring operating
maintenance
of the GIS
unit and
of the
maintenance
work. mechanism,
Flexible linkage
Reduced environmental impact is achieved by the compact design of the developed GIS. SF6
gas is reduced
to 60 % compared to existing GIS. Use of material can also be reduced to 50 %.
Kawahigashi.Masato@ak.MitsubishiElectric.co.jp
Type tests were carried out on prototype GIS in accordance with IEC standard.
188
KEYWORDS
Gas insulated switchgear, Gas circuit-breaker, Torsion-bar spring operating mechanism,
Flexible linkage
1. Introduction
Reduction of life-cycle cost of the high-voltage electric equipment including installation cost
and maintenance cost is a growing demand for electric power utilities.
420 kV gas insulated switchgear (GIS) has been developed to meet the growing demand of
the substation construction together with the demand for reduced installation and maintenance
cost.
Key features and benefits to reduce life-cycle cost of the developed 420 kV GIS and their
supporting technologies are presented.
2. Basic specifications and structure
Major ratings for developed GIS are shown in Table 1. International standards are
considered and the ratings are determined in accordance with IEC-62271-100, 102 and 203.
GIS
GCB
DS
Fast Earthing Switch
(FES)
Table 1 Ratings of 420 kV GIS
Rated voltage
Rated normal current
Rated short time withstand current
Rated frequency
Lightning impulse voltage
Dielectric
Switching impulse voltage
Power frequency voltage
Rated breaking current
Rated breaking time
Bus transfer current switching
Electromagnetically induced current
switching
Electrostatically induced current switching
420 kV
up to 5000 A
63 kA
50 / 60 Hz
1425 kV
1050 kV
650 kV
63 kA
2 cycles
20 V / 1600 A
10 kV / 160 A
20 kV / 18 A
Application of one-break GCB and concentrated main bus configuration enables compact
structure of GIS. Figures 1 shows comparison of internal structure of existing and developed
GIS. Reduction of the size of GCB contributes to the concentrated configuration of the
primary circuit connected to both sides of the GCB.
Horizontal arrangement of operating mechanism and interrupter enables lower height of
GCB compared to two-break GCB where operating mechanism is arranged beneath the
interrupter. Three-phase double main bus arranged horizontally in the developed GIS so that
the total height of the GIS can be reduced, while they are arranged vertically in existing GIS
resulting in tall configuration.
Table 2 shows comparison of the footprint, cubic content and total height between existing
GIS and the developed GIS. They are reduced to 50 %, 30 % and 50 %, respectively.
Table 2 Comparison typical size of existing and developed GIS
Developed
Existing GIS
GIS
Footprint
100%
50%
Cubic content
100%
30%
Height
100%
50%
189
1



















3. Features of developed 420 kV GIS
3.1 Reduced installation period
3.1.1 Single package transportation(1)
Site construction work can be minimized because whole unit can be transported with single
package, whereas each unit is required to divide into five packages for existing GIS. Figure 2
shows difference of transportation packages for one unit of existing GIS and developed GIS.
Transportation with single package results in the reduction of the on-site installation period to
60 % when developed GIS is applied. Reliability is also improved because many gas
compartment assembled in clean factory is installed without assembly work on site.





3.1.2 Integrated DS with the main bus
Number of parts and length of DS for main bus are reduced to 40 % and 50 % respectively,
because moving side of DS is integrated with the main bus. Figure 3 shows comparison of
configuration between DSs for existing and developed GIS. Moving side of DS constitutes a
190
2
part of the main bus in developed GIS whereas DS is separated with the main bus in existing
GIS.







Compact structure contributes the reduction of land and building cost for substation. Figure
4 shows comparison of top view of the typical whole switchgear construction between
existing GIS and developed GIS. The footprint of the total construction of developed GIS is
60 % of that of existing GIS.

࣭
࣭


3.2 Reduced maintenance work
3.2.1 Torsion-bar spring operating mechanism (2)(3)(4)
Spring operating mechanisms have been used to develop higher interrupting capabilities
while also providing benefits of increased mechanical reliability and reduced maintenance
work.
A spring operating mechanism stores mechanical energy in the solid spring. Since the
operating characteristics of a spring operating mechanism are less affected by the change of
ambient temperature and loss of mechanical pressure, which often occurs in hydraulic
mechanisms due to hydraulic leakage, spring mechanisms are inherently superior in long-term
reliability as compared with a pneumatic or hydraulic operating mechanism. Lubricating
material, such as sulfur molybdenum, is thermally applied on the sliding parts to optimize
long-term mechanical performance by reducing friction and preventing rust.
191
3
The use of a torsion-bar spring divided into two bars makes it possible to design a compact
operating mechanism with large stored energy. A picture of a torsion spring operating
mechanism is shown in Figure 5. The mechanisms have been verified by extensive testing
programs. The programs include the
normal mechanical endurance tests of
2,000 operations where the stored
energy is 120 % of the normal value,
special mechanical endurance tests to
confirm the change of operating
characteristics when greases are
removed, as well as extended
mechanical endurance tests of up to
30,000-50,000 operations. A highspeed motion analyzer was also used
to detect any changes during these

mechanical endurance tests.
3.2.2 Improved accessibility to operating mechanism
Concentration of the mechanism for GCB, DS and ES to the front of GIS unit enables easy
access during maintenance. Introducing a one-break GCB makes it possible to arrange the
operating mechanism and the interrupter horizontally. All the operating mechanisms for DS
and ES can be also located in front of the GIS thanks to an application of flexible-linkage
system. Figure 6 shows structure of linkage system for DS and ES in existing GIS and
developed GIS together with the direction of access for maintenance. All the maintenance can
be done in front of developed GIS. Detail construction of flexible linkage system is also
shown in the figure. Metallic wires are used to transmit operating force from the operating
mechanism to the moving part of DS or ES, and ensure flexible location of the operating
mechanism. Since all the maintenance can be done on the mechanism side where the motor is
located, concentrated configuration of the mechanism location is essential to reduce the time
for maintenance work. On the other hand, maintenance needs to be done in three places for
existing GIS because their rigid linkage system limits the location of mechanism.
























192
4
3.3 Reduced environmental impact
Reduction of SF6 gas and reduced use of materials are achieved due to the compact design of
developed GIS. Table 3 shows a summary of the comparison of environmental impact
between existing and developed GIS. Use of SF6 gas and material weight are reduced to 60 %
and 50 %, respectively.
Table 3 Reduction of environmental impact
Existing GIS
Developed GIS
SF6 gas weight
100%
60%
Material weight
100%
50%
4. Testing
Type test to verify the performance of developed GIS were carried out in accordance with
IEC 62271-100, 102, 203 and other related standards. Table 4 shows performance verified
with test items. Figures 7, 8 and 9 show pictures of dielectric test, short-circuit making test
and interruption test with prototype GIS. All the tests finished with successful results.
Table 4 Items included in type test accordance with IEC
Items
Lightning impulse voltage tests
Switching impulse voltage tests
Dielectric strength
Power frequency voltage tests
Partial discharge tests
Temperature rise tests
Current carrying
Short time withstand current and peak withstand current tests
Transportation tests
Mechanical endurance
Seismic analysis
Bus transfer current switching tests
Induced current switching tests
Making and breaking current
Short-circuit making tests
Bus charging current switching tests
Satisfactory operation at temperature limits tests
Operation
Satisfactory operation and mechanical endurance tests
Short-circuit tests
Short-line fault tests
Interruption
Out-of-phase making and breaking tests
Capacitive current switching tests
Performance

193
5




5. Conclusions
420 kV GIS with one-break GCB has been developed considering the reduction of the cost
imposed on the utility during installation, operation and maintenance. The following benefits
are presented.
1) Reduced installation cost
Transportation with single package per unit reduces on-site construction work. Compact
structure reduces substation footprint resulting in the reduction of land and building cost.
2) Reduced maintenance cost
Maintenance work and replacement of parts reduced because of the application of onebreak GCB. Concentrated mechanism location in front of the GIS unit enables easy access
and reduction of time for maintenance.
3) Reduced environmental impact
Reduction of SF6 gas and reduced use of materials are achieved due to the compact design
of developed GIS.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
S. Nakauchi, et al., “Development of compact type 550 kV GIS”, IEEJ Power and Energy 7-291
(2015).
Y. Yoshitomo, et al., “Development of 362 kV 63 kA spring mechanism GCB”, IEEJ National
convention 6-221 (2010).
T. Mori, et al., “Development of 550 kV 63 kA Spring Operated Gas Circuit-Breaker”, CIGREAORC-E-3-0005 (2013).
H. Wilson, et al., “Development of GCBs with a torsion bar spring operating mech-anism and
their applications to severe SLF duty and non-standard reactor switching”, CIGRE SC A3 & B3
Joint Colloquium 105 (2005).
194
6
CIGREAORCMeeting
Technical
2016
and International
Conference
CIGREAORC Technical
2016 –Meeting
International
Conference
on Global Trends
in the Development
on
of Power Transmission & Distribution Systems
including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global
Trends for
in the
Development
of Power
T&DPhase
System
including Smart Grid”
Methodology
Lightning
Impulse Testing
of Three
Combined
Instrument Transformers
DHARMESH YELAMANCHI
CentralImpulse
Power Research
Institute
Methodology for Lightning
Testing
of Three Phase Combined
India
Instrument Transformers
DHARMESH YELAMANCHI
Central Power Research Institute
India
SUMMARY
Instrument transformers are broadly classified into two groups as current transformers and
potential transformers. They are high accuracy class electrical devices used to transform
voltage or current from high values in the power system network to low values that can be
utilized by low voltage measuring, control and relay devices. Combined Instrument
transformers comprise both current transformer and potential transformer in one unit. Three
phase combined instrument transformers are in use for metering purpose upto 33kV voltage
SUMMARY
level distribution systems in India. They have complex design and manufacturing process but
are economical and compact. Generally, the three phase combined instrument transformers
Instrument
transformers
broadly
classified
intowhich
two stresses
groupsitsasinsulation.
currentHence,
transformers
and
are outdoor
type and are
are exposed
to natural
lightning
the
strength They
of this are
equipment
should be evaluated
against the
standardused
stipulated
potentialinsulation
transformers.
high accuracy
class electrical
devices
to transform
lightning
impulses.
The
Indian
national
standards
and
International
standards
for
instrument
voltage or current from high values in the power system network to low values that can be
do not provide guidelines for lightning impulse testing of this equipment.
utilized transformers
by low voltage
measuring, control and relay devices. Combined Instrument
Various testing laboratories practice different test procedures due to non-availability of
transformers
comprise
currentThe
transformer
and potential
transformer
in one
unit. Three
standard
stipulatedboth
procedure.
lightning impulse
test procedures
are of two
types,
phase combined
instrument
transformers
are in use for metering
upto 33kV voltage
Deterministic
procedures
and Statistical/Probabilistic
procedures.purpose
The deterministic
procedures are
generally
to They
test thehave
lightning
impulsedesign
voltageand
withstand
strength of the
level distribution
systems
in used
India.
complex
manufacturing
process but
internal
non-self-restoring
insulation.
In
this
procedure
the
test
object
shall
be
subjected
to
a
are economical and compact. Generally, the three phase combined instrument transformers
predefined number of lightning impulse voltage applications and declared as pass only if there
are outdoor
and are
exposed
natural/probabilistic
lightning which
stresses
its insulation.
Hence, the
is no type
disruptive
discharge.
The to
statistical
procedures
are generally
used to test
insulation
of thisvoltage
equipment
against theinsulation.
standardInstipulated
the strength
lightning impulse
withstandshould
strengthbe
of evaluated
the external self-restoring
procedure The
also aIndian
predefined
numberstandards
of lightningand
impulse
voltages shallstandards
be applied for
to the
lightningthisimpulses.
national
International
instrument
test
object
and
is
declared
as
pass
by
allowing
fixed
number
of
disruptive
discharges.
The
transformers do not provide guidelines for lightning impulse testing of this equipment.
three phase combined instrument transformer insulation includes both external self-restoring
Various insulation
testing and
laboratories
practice different test procedures due to non-availability of
internal non-self-restoring insulation. This paper discusses about the different
standardlightning
stipulated
procedure.
The lightning
impulse
testinstrument
procedures
are ofand
two types,
impulse
testing practices
of three phase
combined
transformers
proposes aprocedures
new test methodology.
As per the proposed test methodology,
the test
shoulddeterministic
be
Deterministic
and Statistical/Probabilistic
procedures.
The
performed
on
individual
phase
terminals
separately
by
connecting
primary
terminals
of
a
procedures are generally used to test the lightning impulse voltage withstand strength
of the
single phase to source and grounding all other terminals of the equipment. In this case the
internal non-self-restoring insulation. In this procedure the test object shall be subjected to a
predefined
lightning
impulse
and declared as pass only if there
Typenumber
here the of
email
address of
the mainvoltage
author asapplications
a footnote.
is no disruptive discharge. The statistical /probabilistic procedures are generally used to test
the lightning impulse voltage withstand strength of the external self-restoring insulation. In
195
this procedure also a predefined number of lightning impulse voltages shall be applied to the
test object and is declared as pass by allowing fixed number of disruptive discharges. The
three phase combined instrument transformer insulation includes both external self-restoring
phase to phase insulation of three phase combined instrument transformer will be tested three
times which will lead to undesirable deterioration of the insulation. Hence, the number of
impulse applications per series is reduced to tolerable number. The proposed Impulse test
methodology for three phase combined instrument transformers is very effective and will not
result in unwanted degradation of the insulation. The proposed test methodology can be
adopted by national and international standard bodies to bring uniformity in testing procedure
of three phase combined instrument transformers.
KEYWORDS
Lightning impulse, Three phase combined instrument transformer.
INTRODUCTION
Instrument transformers are used in power system to scale down the high voltage and current
signals to lower levels that can be used by low voltage metering and protection relay devices.
The three phase combined instrument transformer is a single equipment comprises both the
potential transformer and current transformers as shown in Fig.1. The three phase combined
instrument transformers are complex in design and manufacturing. They are in use in India
upto 33kV voltage level distribution systems due to their compactness and economical.
Figure.1.Circuit diagram of three phase combined instrument transformer
PA1, PA2: Primary terminals of phase A of three phase combined instrument transformer.
PB1, PB2: Primary terminals of phase B of three phase combined instrument transformer.
PC1, PC2: Primary terminals of phase C of three phase combined instrument transformer.
PA1, PA2: Primary terminals of phase A of three phase combined instrument transformer.
Sa1, Sa2: Current transformer secondary terminal corresponding to the phase A of three phase
combined instrument transformer.
Sb1, Sb2: Current transformer secondary terminal corresponding to the phase B of three phase
combined instrument transformer.
196
1
Sc1, Sc2: Current transformer secondary terminal corresponding to the phase C of three phase
combined instrument transformer.
a, b, c, n: Potential transformer secondary terminals of the three phase combined
instrument transformer
The three phase combined instrument transformer use different materials (air, porcelain, craft
paper, insulating oil) as insulating media to isolate the live parts at different potentials as well
as live parts and earth. Generally, three phase combined instrument transformers meant for
outdoor usage and these are exposed to natural lightning. Hence, the insulation strength of this
equipment should be evaluated against the standard stipulated lightning impulses. The Indian
national standards and International standards for instrument transformers do not provide
guidelines for lightning impulse testing of three phase combined instrument transformer [1].
This paper proposes an admissible methodology for impulse testing of three phase combined
instrument transformers.
TEST CONNECTIONS
The test connection plays significant role in lighting impulse test as it defines the lightning
impulse stress distribution across the equipment insulation. Figure.1 shows the c i r c u i t
diagram of three phase combined instrument transformer. PA1, PA2, PB1, PB2, PC1, PC2,
Sa1, Sa2, Sb1, Sb2, Sc1, Sc2, a, b, c & n terminals are available to make connections.
The test connection for impulse testing of any instrument transformer shall simulate the worst
possible filed condition [2-5]. When the lightning strikes on one phase terminal while other
phase terminals operate at normal voltages (which are negligible in magnitude compared to
the lightning impulse peak voltage). In this case, the phase to phase, phase to earth and
primary to secondary insulation of three phase combined instrument transformer should
withstand the stresses due to lightning impulse. The test connection shown in the Fig.2
simulates the above situation.
Figure.2.Proposed test connection for phase A of three phase combined instrument
transformer
197
2
To simulate the more severe conditions, it is required to test the each phase separately. For
impulse test on phase “A”, the primary terminals of phase “A” shall be connected to impulse
source, primary terminals of other phases and all secondary terminals shall be earthed along
with frame as shown in Fig.2. Under this condition, the insulation between primary terminals
of phase A to primary terminals of other phases, primary terminals of phase A to earth and
primary terminals of phase A to secondary terminals will be stressed. The terminal
connections (for performing test on phase A) of primary and secondary terminals are shown in
the below photographs (Fig.3 & 4.)
TEST CONNECTIONS
The test connection plays significant role in lighting impulse test as it defines the lightning
impulse stress distribution across the equipment insulation. Figure.1 shows the c i r c u i t
diagram of three phase combined instrument transformer. PA1, PA2, PB1, PB2, PC1, PC2,
Sa1, Sa2, Sb1, Sb2, Sc1, Sc2, a, b, c & n terminals are available to make connections.
The test connection for impulse testing of any instrument transformer shall simulate the worst
possible filed condition [2-5]. When the lightning strikes on one phase terminal while other
phase terminals operate at normal voltages (which are negligible in magnitude compared to
the lightning impulse peak voltage). In this case, the phase to phase, phase to earth and
primary to secondary insulation of three phase combined instrument transformer should
withstand the stresses due to lightning impulse. The test connection shown in the Fig.2
simulates the above situation.
Figure.2.Proposed test connection for phase A of three phase combined instrument
transformer
To simulate the more severe conditions, it is required to test the each phase separately. For
impulse test on phase “A”, the primary terminals of phase “A” shall be connected to impulse
198
3
source, primary terminals of other phases and all secondary terminals shall be earthed along
with frame as shown in Fig.2. Under this condition, the insulation between primary terminals
of phase A to primary terminals of other phases, primary terminals of phase A to earth and
primary terminals of phase A to secondary terminals will be stressed. The terminal
connections (for performing test on phase A) of primary and secondary terminals are shown in
the below photographs (Fig.3 & 4.)
Figure.3.Photograph of primary terminals connection for test on Phase A of three phase
combined instrument transformer.
Figure.4.Photograph of secondary terminals connection for test on Phase A of three phase
combined instrument transformer.
199
4
For impulse test on phase “B”, the primary terminals of phase “B” shall be connected to
impulse source, primary terminals of other phases and all secondary terminals shall be
earthed along with frame. Under this condition, the insulation between primary terminals
of phase B to primary terminals of other phases, primary terminals of phase B to earth and
primary terminals of phase B to secondary terminals will be stressed. For impulse test on
phase “C”, the primary terminals of phase “C” shall be connected to impulse source,
primary terminals of other phases and all secondary terminals shall be earthed along with
frame. Under this condition, the insulation between primary terminals of phase C to
primary terminals of other phases, primary terminals of phase C to earth and primary
terminals of phase C to secondary terminals will be stressed [1].
TEST PROCEDURE
The National and International standards stipulated procedure is fifteen number of lightning
impulse applications with specified voltage level shall be applied to the test object. There
should not be more than two disruptive discharges in the self-restoring part of the
insulation (external air insulation) and no indication of failure in the non-self-restoring
insulation (internal oil and craft paper) to pass the withstand test [2-6]. By using the
proposed test connections, the test shall be repeated for the individual phase terminals
which will lead to more number of impulse stresses on phase to phase insulation. This may
lead to unwanted deterioration of the insulation strength. To avoid unwanted deterioration of
the insulation the number of impulse applications per sequence can be reduced to five without
allowing any type of discharge.
The standard stipulated procedure of fifteen number of impulse applications per sequence is
meant to verify both internal and external insulation. With respect to the external insulation
the procedure is statistical (probabilistic) [6, 7]. The proposed five number of impulse
applications per sequence is also meant to verify both internal and external insulation and it is
a deterministic method. The severity of the standard stipulated and proposed procedures with
respect to external is shown in Fig.5. [7, 8]. The proposed test methodology with standard
stipulated procedure (fifteen number of applications) will stresses the phase to phase
insulation by 45 times, may causes unnecessary deterioration of the internal insulation. The
proposed five number of impulse applications procedure stresses the insulation maximum
fifteen number of times (can be allowed). Total number of impulse applications on the various
insulation sections of the three phase combined instrument transformer with respect to
internal insulation are tabulated in Table.1.
Figure.5. Characteristics of proposed and standard test procedures with respect to the external
air insulation
200
5
Table.1. Total number of impulse applications as per proposed test procedure (0/5) and
standard test procedure
Insulation Primary& Earth
Primary &
Phase to Phase
of
Secondary
Test
2/15
0/5
2/15
0/5
2/15
0/5
procedure
CTs
15
5
15
5
30
10
PTs
15
5
15
5
45
15
CONCLUSION
The lightning impulse test of three phase combined instrument transformer is complex as
it involves the evaluation of phase to phase, phase to earth and primary to secondary
insulation. The Indian national standards and International standards for instrument
transformers do not provide guidelines for lightning impulse testing of three phase combined
instrument transformer. Various testing laboratories practice different test procedures due to
non-availability of standard stipulated procedure.
As per the proposed test connection, the primary terminals of the phase which is under test
shall be connected to source and all other terminals of the equipment shall be connected to
earth along with frame. The test should be repeated on all the three phases individually. The
proposed test connection is effective in simulating the worst filed condition. In this case the
phase to phase insulation of three phase combined instrument transformer will be tested three
times which will lead to undesirable deterioration of the insulation. Hence, the number of
impulse applications per series is reduced to tolerable number (five). The proposed Impulse
test methodology for three phase combined instrument transformers is very effective and will
not result in unwanted degradation of the insulation. result in unwanted degradation of the
insulation.
BIBLIOGRAPHY
[1] Yelamanchi, D.; Annabattula, J.; Aradhya, R.S.S., "Lightning impulse testing of three
phase combined instrument transformer," in International Conference on Science
Engineering and Management Research (ICSEMR), 2014, vol., no., pp.1-4, 27-29 Nov.
2014
[2] Instrument transformers Part 1: General requirements, IEC 61869-1: 2007, Edition 1.0.
[3] Instrument transformers Part 2: Additional requirements for current transformers, IEC
61869-2:2012, Edition 1.0.
[4] Instrument transformers Part 3: Additional requirements for inductive voltage
transformers, IEC 61869-3/2011, Edition 1.0.
[5] Instrument transformers Part 4: Additional requirements for combined transformers, IEC
61869-4:2013, Edition 1.0.
[6] High-voltage test techniques Part 1: General definitions and test re- quirements, IEC
60060-1:2010, Edition 3.0.
[7] Andrew R. Hileman, Insulation Coordination for Power Systems, CRC Press, 1999.
[8] Sheldon Ross, A First Course in Probability (9th Edition), Pearson Education Ltd.
publications.
201
6
Substations
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission &
Systems including
Grid, 24-26
Feb. 2016, New
Delhi, India
Reliable, Resource-saving
&Distribution
Maintenance-free
Air Smart
Insulated
Substation
(AIS)
with High Voltage Hybrid (Mixed Technology) switchgear
CIGRE- AORC Technical Meeting 2016 and International Conference
RAJDEEPAK
on PANDEY
ABB India Limited
“Global Trends in the Development of Power T&D System including Smart Grid”
India
Reliable, Resource-saving & Maintenance-free Air Insulated Substation (AIS)
with High Voltage Hybrid (Mixed Technology) switchgear
RAJDEEPAK PANDEY
ABB India Limited
India
SUMMARY
While designing a new Air insulated substation (AIS) or extending an existing AIS substation,
the substation designers / planners increasingly faces challenges in terms of huge space
requirements for building a new substation or unavailability of space for extension in an
existing one, cumbersome land acquisitions process, long project completion time and an ever
increasing demand for reliable and available power 24x7 from end users.
While the planners have generally used full Gas insulated substation (GIS) to tackle these
challenges,
SUMMARY another technology, Hybrid Switchgear, could be a possible solution to address
these challenges for AIS substation. It is steadily getting acceptable and being used in the
Global & Indian power sector. The main drivers of its growth are possibility to build a techno
While
designingAIS
a new
Air insulated
substation
extending
an existing
substation,
economical
substation
, saving on
premium (AIS)
space, or
faster
land clearances
due toAIS
reduced
the substation
designers
/
planners
increasingly
faces
challenges
in
terms
of
huge
space needs, quicker installation time and improved reliability and performance due to critical space
requirements
for building
a new
substation
or unavailability of space for extension in an
substation equipments
being
enclosed
in a SF6 environment.
existing one, cumbersome land acquisitions process, long project completion time and an ever
The Hybrid
switchgear,
positioned
in between
insulated
substation
increasing
demand
for reliable
and available
powerAir24x7
from end
users. (AIS) and Gas
insulated substation (GIS), contains all the switchgear functionality such as Circuit breaker /
disconnector
/ earthing
/ current
inside SF6
gas atmosphere,
while
the these
While
the planners
have switch
generally
usedtransformer
full Gas etc
insulated
substation
(GIS) to
tackle
Bus bars still remain open in the air. So this way Hybrid switchgear combines the advantages
challenges,
another technology, Hybrid Switchgear, could be a possible solution to address
of AIS & GIS technology – GIS reliability & space saving with AIS cost advantage. IEC
these62271-205
challenges
for dedicated
AIS substation.
It is for
steadily
acceptable
andandbeing
is the
IEC standard
Hybridgetting
switchgear
technology
as perused
this in the
Global
&
Indian
power
sector.
The
main
drivers
of
its
growth
are
possibility
to
build
a techno
standard this technology is referred as MTS (Mixed technology Switchgear).
economical AIS substation , saving on premium space, faster land clearances due to reduced
space needs, quicker installation time and improved reliability and performance due to critical
KEYWORDS
substation
equipments being enclosed in a SF6 environment.
Mixed Technology Switchgear, Space Saving substation, faster execution, no HV tests at site,
The Lower
Hybrid
switchgear, positioned in between Air insulated substation (AIS) and Gas
life cycle costs, minimum maintenance, Reliability, High Pollution performance.
insulated substation (GIS), contains all the switchgear functionality such as Circuit breaker /
disconnector / earthing switch / current transformer etc inside SF6 gas atmosphere, while the
1
Bus bars still remain open in the air. So this way Hybrid switchgear combines the advantages
of AIS & GIS technology – GIS reliability & space saving with AIS cost advantage. IEC
62271-205 is the dedicated IEC standard for Hybrid switchgear technology and as per this
standard this technology is referred as MTS (Mixed
technology Switchgear).
205
KEYWORDS
INTRODUCTION
All substation designers today have to cope up the ever increasing demand of load in urban,
semi-urban & industrial areas. While designing a new air insulated substation (AIS) or
extending an existing AIS substation for such areas, the substation designers increasingly
faces challenges in terms of huge space requirements, cumbersome land acquisitions process,
long project completion time and an ever increasing demand for reliable and available power
24x7 from end users. Generally these designers / planners have following expectations from
the technology they would eventually select to tackle these challenges:
 Reliable solution meeting application
The selected solution should be reliable, proven and meet the ever growing substation
load & application requirements.
 Space saving solution enabling faster land Acquisition process
Nowadays the land is getting costlier day by day due to the increasingly heavy
pressure on resources. The space is at a premium. Further the land acquisition process
itself is quite challenging and time consuming under present prevailing rules and
regulations. The designers are looking for compact solutions which require lesser
space for construction of a substation and thereby also has inherent potential, since
design/planning stage, to get faster land acquisition due to lesser land requirements.
 High Performance in site environment
The conventional AIS substation are air insulated which means that all the equipment
in the substations , such as Circuit breaker / Disconnector / Earth switch / Instrument
transformers , are exposed to extremities of atmosphere such as rain , pollution etc.
This generally impacts the performance of the equipment and disconnector / earthing
switch are the most impacted based on general field experience. The designers look
for solution which provides strong performance in field.
 Low Civil works / Fast Installation
The conventional AIS substations require huge civil works as each equipment has its
own support structure and hence it’s associated civil works. This also increases the
overall project execution time as one has to install all the support structure and
construct its foundations. The designers need a solution which saves civil works and
improves the project execution time.
 Less Maintenance / low total cost of ownership.
As often experienced in AIS substations, disconnectors get jammed and do not work
when they are expected to perform. Similarly current transformers are with OIL and
carry the risks associated with oil. So generally these equipment need some
maintenance. The designers need solution which are virtually maintenance free and
have low cost of the ownership.
206
2
While the planners have generally used full Gas insulated substation (GIS) to meet these
expectations, another technology which is called Hybrid Switchgear also exists and finds
merit globally in several typical substation and application. Such Hybrid switchgear could be
a possible solution to address the challenges faced by substation designers in building a new
substation or extending an already existing substation to address cost, maintenance and time
criteria in a limited available space.
WHAT IS HYBRID SWITCHGEAR
Substations can be built by two technology which are in use since quite some time and
proven.
1) Air Insulated Substation (AIS)
2) Gas Insulated Substation (GIS)



AIS
Installation : Outdoor
High Space & Civil requirements
Several Live exposed parts,
connected by ACSR conductor / Al.
Pipe.



GIS
Installation : Indoor
Very low Space however
special Civil requirements
Switchgear parts within SF6
, including the Bus bars
Figure 1. Typical AIS & GIS substation
The third option to make similar substation is using Hybrid switchgear technology. The
hybrid switchgear encapsulates the main functions of a substation bay (such as circuit breaker,
disconnector, earthing switch, current transformer) in a metal enclosed chamber consisting of
SF6 gas however the Busbar are of conventional air insulated type. SF6 to AIR polymer
bushings are provided on the hybrid switchgear to facilitate connection between the hybrid
switchgear and the substation Busbars.
Hybrid / MTS




Figure 2. Typical Hybrid substation
Installation : Outdoor
Moderate space & low Civil
requirements
Main Switchgear
funtionalities within SF6 gas.
Busbar is Conventional type
IEC 62271-205 is standard for Hybrid switchgear and as per this standard this technology is
defined as “Mixed Technology Switchgear “as it has Mix of AIS and GIS technology. So this
207
3
way it could be observed that Hybrid switchgear offers the reliability of GIS and cost benefits
of AIS.
ADVANTAGES & VALUE PROPOSITIONS OF HYBRID SWITCHGEAR
SPACE SAVING SOLUTION FOR AIS SUBSTATIONS
For AIS substation, one has to maintain the mandatory clearances between individual
equipment such as Circuit breaker, disconnector, current transformer, earthing switch etc.
Hence the site area required is more because the bay length is more. However in case of
Hybrid switchgear , the bay length is reduced since most of the functions like circuit breaker ,
disconnector , earthing switch , current transformer etc. are enclosed within a metal enclosed
gas module , this reduces the site area required to make substation with Hybrid switchgear
because the bay length is reduced.
Figure 3 shows a typical 220 KV AIS substation bay for Double Busbar configuration which
requires following area – 18 x 66 = 1188 square meter. (18 meter is typical bay width for 220
KV AIS substation). If the same bay is made with Hybrid switchgear then this will need 18 x
29.5 = 531 square meter site area, space saving of 55 % as compared to AIS substation.
Figure 3 – A typical 220 KV AIS Bay for DBB (Double Bus Bar) Configuration
Figure 4 – A typical 220 KV Hybrid Bay for DBB (Double Bus Bar) Configuration
208
4
The reduction in land area leads to following benefits –
1) Lesser space required to build new AIS substation.
2) Extension of an existing substation could be made if space is constraint for extension.
3) More bays could be added in same area to meet local load growth.
4) Old existing substations could be upgraded to next higher voltage substation utilizing
the same space & infrastructure / manpower.
Another example is shown below for a typical four bays substation wherein incoming /
outgoing lines are terminating through overhead gantries. Since the required bay width needs
to be maintained for line termination with overhead gantries, this bay width might govern the
site area required for substation. Under such situations, Hybrid substation could be a more
optimized & faster solution considering lesser civil works (no GIS building).
AIS switchyard
Hybrid switchyard
GIS switchyard
Figure 5 – A typical comparison between AIS / Hybrid /GIS for substation with overhead line entry.
HIGH OPERATIONAL RELIABILITY, MINIMUM MAINTENANCE
The disconnector and earthing switch in AIS substation are exposed to atmospheric affects
such as rain, humidity, pollution etc. Continuous exposure lead to fasters aging and corrosion
of these equipment. The increase in contact resistance & burn-out are generally observed for
such disconnector / earthing switches. Under chemically polluted areas, some gases such as
Hydrogen, sulphur oxides, fluorides along with silicate waste are generally present. These
gases decrease the life span of outdoor electrical equipment due to high corona, frequent
flashovers & corrosion effects. Corrosion effects leads to jamming of the contacts and
operating pipes so under such situation disconnector / earthing switches may not follow the
operational command when actually required. As disconnector & earthing switches are
enclosed with SF6 gas in Hybrid switchgear, these are fully insulated from the exposure to
209
5
detrimental pollution & corrosion and this leads to decreased failure in site which means High
operational reliability and require minimum maintenance.
Current transformers in AIS substation are filled with oil so they carry the risk associated with
oil. One has to perform dissolved gas analysis (DGA) to check whether the oil inside is
operationally pure or not. Further tan delta test is performed to assess the conditions of the CT
insulation. The CT of Hybrid switchgear is low voltage ring type which means that primary
conductor is inside the bushings of the switchgear and secondary cores are inside a ring type
tank wrapped around the neck of the bushing. So there is no oil used in Hybrid switchgear and
also no Tan delta test is required at site as the CT is of low voltage type. This type of design
increases the reliability of CT and leads to minimum maintenance at site. (Figure 6)
Figure 6 –Polymer Bushings & Slip ring type Current transformer on Hybrid switchgear
Component
Contribution
MaF
(CompYears)
(Failures /100
Comp-Years)
Type
Voltage Level
Air Insulated
300≤U<500 kV
18381
1.13
SF6 enclosed
300≤U<500 kV
14801
0.32
Air Insulated
300≤U<500 kV
79773
0.36
SF6 enclosed
300≤U<500 kV
33882
0.07
Air Insulated
300≤U<500 kV
103691
0.14
SF6 enclosed
300≤U<500 kV
60425
0.01
Circuit-breaker
Disconnector and
earthing switches
Instrument
Transformers
Figure 7 – CIGRÉ WG A3.06 equipment reliability reports based on survey made during 2004-2007
[6]-[8]
210
6
The figure 7 shows the equipment reliability reports based on global survey made by CIGRE
work group A3.06 during 2004-2007. The survey was performed to report the actual failure
rates observed in air insulated and SF6 insulated substations across the world. One could
observe in the report that SF6 insulation leads to much lower failure rates.
Hybrid switchgear has polymeric type outdoor bushings which has increased pollution
performance due to the hydrophobic surface of these insulators. Such hydrophobic surfaces
allows water (like rain water) to deposit on the surface as “individual droplets” thereby not
creating a continuous water film on the insulator surface. As there is no continuous film,
leakage currents tend to be very minimum under polluted conditions so this leads to strong
inherent pollution performance. (Refer figure 6).
LOW LIFE CYCLE COST
IEC 60300-3-3 defines a method to calculate the life cycle cost of an installation.
Total Life Cycle cost = Investment cost + Operation & Maintenance cost + Disposal cost
Investment cost == Equipment cost + Land cost + Civil works cost + cost of erection &
commissioning
Operation & Maintenance Cost == Operational cost + maintenance cost (planned maintenance
& unplanned maintenance cost)
Disposal Cost == cost of removal of the old installation after the end of life
Figure 8 – CIGRÉ B3-204, 2004 session – Analysis of LCC of AIS / GIS / GIS module
Figure 8 shows a CIGRE paper comparison between life cycle costs of AIS / GIS / GIS
module. GIS module means Hybrid switchgear.
Since Hybrid switchgear encapsulates most of the substation functions inside a gas insulated
module, it requires lesser land to make a Hybrid substation. Such integration also leads to
reduction of civil works related to individual equipment as no separate foundation is to be
211
7
prepared for circuit breaker, disconnector, current transformers etc. Further the erection and
commissioning works at site are reduced heavily since there is only one integrated module to
handle which comes fully tested, including HV tests, from factory and only few functional
tests are performed at site.
The maintenance is defined as planned maintenance and unplanned maintenance. Planned
maintenance is performed based on some regular time interval or after a specific condition is
achieved, whichever is earlier. Since the observed failure rates are lower for SF6 insulated
modules and the reliability is high, planned maintenance are expected to be less in Hybrid
technology. The unplanned maintenance is performed when there is a failure which needs to
be corrected immediately (which cannot possibly be scheduled for planned maintenance
timeline). Again since reliability of Hybrid switchgear is higher as compared to AIS
substation, the occurrence of unplanned maintenance is expected to be quite lower.
Disposal cost for Hybrid switchgear is quite low as only module and its associated single
foundation set is to be handled & removed.
USE IN EXISTING & OLD SUBSTATION AS BUS SECTIONALIZER
Figure 9 – A typical Bus section application of Hybrid switchgear in an AIS Single Busbar
configuration (SBB)
AIS substation with Single bus bar (SBB) configuration generally tends to have low reliability
/ availability because to take out any Bus bar isolator for maintenance, the whole substation
has to be shut down. Under worst conditions, like an unfortunate Bus bar fault, the whole
substation would be shut down again as there is only a single Bus bar to feed to the connected
loads.
To minimize full substation shutdown, one could create a section on the Bus bar so that only a
section of the busbar would be out during a Bus disconnector maintenance or Busbar fault.
212
8
Creating such a Bus section in existing AIS substation could be a challenge as this would
require the conventional space to install circuit breaker, disconnector, earthing switch &
current transformers. All these equipments are required to create an effective and useful Bus
section which could work together with Busbar protection system. Finding such space within
the middle of an existing substation is a challenge however Hybrid switchgear could address
this challenge as all the required switchgear functions are within SF6 module and area
required is quite low so that a hybrid switchgear could be fitted under an existing middle
gantry of busbar. (Refer Figure 9).
So Hybrid switchgear could be used in existing AIS substation to create Bus sectionalizer to
increase the reliability & availability of the substation without making any significant change
/ impact in the existing substation layout and without requiring any special civil works etc.
CONCLUSION
Substation design and planning mostly depends on careful evaluation and assessment of the
single Line diagram (SLD) requirement, physical space required, reliability needs and
available substation technology. The designers should carefully evaluate all available
substation technology options while planning for construction of a new substation, extension
of an existing substation and uprating of an existing lower voltage substation in order to
address cost, time and maintenance needs in an available space.
Based on design, operational performance & experience of the Hybrid switchgears, following
conclusions could be drawn –
 Hybrid switchgear offers a compact and fast, factory tested, AIS substation solution,
for New and existing substation, without requiring HV tests at site.
 Since most of the switching elements are within SF6 gas module, the reliability of
Hybrid switchgear is expected to be higher than AIS solution.
 The life cycle cost of Hybrid switchgear is expected to be low.
 The reliability and availability of old existing substation could be improved by
creating Bus section using Hybrid switchgear.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
IEC 62271-205 for mixed technology switchgear (Hybrid switchgear)
CIGRE working Group B3-204, “Mixed Technology Switchgear & Substations: Optimized
Service strategies “, (session 2004, Paris, page 6)
CIGRE working Group A3-06 TB 510/511/512, “International enquiry on reliability of High
voltage equipment, part 2 & 3 & 4, (Final report 2004 – 2007)
CBIP –CIGRE Conference on advances and innovation in substation, adoption of Hybrid
switchgear for improvement & upgradation of substation, (New Delhi June 2015)
213
9
http : //www.cigre.org
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
Global
trends in the development of Power Transmission and distribution
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
System including smart Grid
http : //www.cigre.org
Global trends in the development of Power Transmission and distribution
System
including smart Grid
SUBSTATIONS
‘GIS AND ITS EXPERIENCE WITH NEW EMERGING TRENDS’
SUBSTATIONS
‘GIS AND ITS EXPERIENCE WITH NEW EMERGING TRENDS’
SUKHBIR KAPOOR
Sukhbir.kapoor@alstom.com
SUKHBIR KAPOOR
Sukhbir.kapoor@alstom.com
SANTOSH ANNADURAI
SANTOSH ANNADURAI
ALSTOM GRID –INDIA
RACHIN AGARWAL
RACHIN AGARWAL
ALSTOM GRID –INDIA
SUMMARY:
SUMMARY:
In recent In
times
design
of substation
recentthe
times
the design
of substationhas
has been
been
evolving
with to
respect
to layout,
configurationand
and level
level
evolving with
respect
layout,
configuration
of automation involved. With the increasing awareness
of automation
involved. With the increasing awareness
and need for smart-grid, it has further necessitated the
and need for
smart-grid,
it has further
necessitated
the
evolution of digitalization
of network.
This paper
elaborates
the key design
aspects associated
with
evolution of
digitalization
of network.
This paper
substation
designassociated
and its online
elaborates EHV/HV
the keyGIS
design
aspects
with
condition monitoring system. It will also focus on
EHV/HV digitalization
GIS substation
design and
its with
online
of GIS substation
in future
the
condition monitoring
It will also
on
implication of system.
digital equipment’s
such asfocus
CT and
CVT.of GIS substation in future with the
digitalization
Multi-Building Layout Design, On-Line
implicationKEYWORDS:
of digital equipment’s
such as CT and
Condition Monitoring System, VFTO, Digital GIS
CVT.
Substation, Non-Conventional Instrument Transformers.
Optical Multi-Building
Current and Voltage
Sensors,
Process
Bus,
KEYWORDS:
Layout
Design,
On-Line
IEC61850
Condition Monitoring System, VFTO, Digital GIS
Substation, INTRODUCTION:
Non-Conventional Instrument Transformers.
Optical Current and Voltage Sensors, Process Bus,
Substations are integral part of a power system &
IEC61850
form important links between the generating stations,
transmission system, distribution system & the load
INTRODUCTION:
points. In India majorly Air insulated substations (AIS)
installations are more as compare to Gas insulated
substations
(GIS). With
growing
& power
Substations
are integral
part
of a populations
power system
&
demands
in orbetween
around the
cities, limited
land
form important
links
theurban
generating
stations,
availability and its high cost are forced to think for a
transmission
system,
distribution
system
& substations
the load
different
solution
such as Gas
insulated
points. In India
(AIS)
whichmajorly
requires Air
one insulated
fourth landsubstations
space approx.
as
to AISassubstations.
nowadays,
it is
installationscompare
are more
compareHence
to Gas
insulated
found that GIS substations are more commonly used
substationsthan
(GIS).
With growing populations & power
AIS under above conditions.
demands in or around the urban cities, limited land
Designing
of cost
Gas are
Insulated
Switchgears
availability and
its high
forced
to think (GIS)
for a
substation such
is quit
as it requires
lot of
different solution
as complex
Gas insulated
substations
interfaces. GIS equipment may have all the major
which requires
oneequipment
fourth such
landas breaker,
space isolator,
approx.earthas
substations
compare toswitch,
AIS buses,
substations.
Hence
nowadays,
it is
CT, PT, surge
arrestor.
Majorly wave
reactor, capacitors,
CVT commonly
are not been part
of
found that trap,
GISICT,
substations
are more
used
GIS now.
These
few equipment form part of AIS
than AIS under
above
conditions.
substation with connecting lines, which needs to be
interfaced with GIS equipment.
Designing of Gas Insulated Switchgears (GIS)
paper
will present
challenges
for
substation isThis
quit
complex
as theit various
requires
lot of
interfacing, designing experiences of one of our
interfaces. GIS
GIS
equipment
may
have
all
the
major
ongoing 400/220KV GIS project. It also covers the new
substationsconcept
equipment
such as
breaker,
isolator,
of digitization
of GIS’s
components
(as a earth
part of
SmartCT,
Grid)PT,
and new
trends
in condition
monitoring
switch, buses,
surge
arrestor.
Majorly
waveto
improve the
reliability/ heath
assets.
trap, ICT, reactor,
capacitors,
CVTindex
are ofnot
been part of
GIS now. These few equipment form part of AIS
substation with connecting lines, which needs to be 214
interfaced with GIS equipment.
This paper will present the various challenges for
DESIGN
CHALLENGES
:
1) 1)
KEYKEY
DESIGN
CHALLENGES
:
a) Layout
optimisation:
designlayout
the overall layout
a) Layout
optimisation:
To design To
the overall
withwith
least least
lengthslengths
of Gas Insulated
Ducts and
lessDucts and less
of Gas Bus
Insulated
Bus
carbon foot prints of GIS building is a biggest
carbon foot prints of GIS building is a biggest
challenge without compromising operational space
challenge
withoutlook.compromising operational space
requirement
and aesthetic
requirement and aesthetic look.
In GIS substations major cost lies in GIS
equipment & it’s GIB (Gas insulated bus duct). GIS
In GISequipment
substations
major
bays & its primary
are fixed
as percost
the lies in GIS
equipment
& it’s
GIBcan(Gas
insulatedbybus duct). GIS
requirement
whereas
its GIB
be optimising
adopting
practices.
bays good
& engineering
its primary
equipment are fixed as per the
requirement whereas its GIB can be optimising by
In our latest experience of 400/220kV GIS
adopting
good
engineering
substation
in India
constituting
400kVpractices.
GIS with one &
half breaker scheme (having 24 Nos. bays, including
two reactor switching
220kV GIS with
In our bays)
latest& experience
of two
400/220kV GIS
main bus scheme (having 14 bays including bus
substation
in
India
constituting
400kV
GIS with one &
coupler bay).
half breaker scheme (having 24 Nos. bays, including
b) Usage
of Multi-layering
andbays)
different
two reactor
switching
& angles
220kVof GIS with two
Bends:
concept
reduces (having
the space requirement
mainThisbus
scheme
14 baysof including bus
outgoing Gas Insulated Bus ducts & helping to reduce
bay).
the coupler
carbon foot
prints.
FIG:
shows 400kV
two bays with and
outdoor
space
b)1Usage
of Multi-layering
different
angles of
requirement of 16 Meters with single layer of outdoor
Bends:
This
concept
reduces
the
space
requirement
of
gas insulated bus ducts arrangement. Generally we do
outgoing
Gas inInsulated
Bus ducts
to reduce
have
limited spaces
GIS substations,
where &
we helping
need
to adopt
some different
approach to accommodate all
the carbon
foot prints.
our substation equipments. FIG 2 shows the same 400kV
two bays outdoor space requirement which is reduced by
shows 400kV
baysmultilayer
with outdoor space
3.8 FIG:
Meters1 approximately
by two
adopting
requirement
16 inMeters
single
layer of outdoor
method,
about 24% of
saving
foot printwith
of outdoor
space
requirement
of bus duct.
gas insulated
bus ducts arrangement. Generally we do
have limited spaces in GIS substations, where we need
to adopt some different approach to accommodate all
our substation equipments. FIG 2 shows the same 400kV
two bays outdoor space requirement which is reduced by
3.8 Meters approximately by adopting multilayer
method, about 24% saving in foot print of outdoor space
requirement of bus duct.
1
further quantity optimisation in gas insulated bus duct
if AIS connections have been considered in place of
GIB connections between buildings for main buses
connections. This multi building concept is very useful
wherever project schedule is very tight & it is required
to compress the duration of GIS erection time by using
more EOT cranes resulting reduce in installation time
by 40%. (approx.).
In this method we can accommodate up to three tiers of
bus ducts in one route.
We may also use GIB bends at different angles to
optimise its length & further it also help to reduce the
space requirements. In this method it may have some
draw backs of complex design with hard maintenance
activity.
c) Multi Building concept: Optimisation in the overall
length of outgoing Gas Insulated Buses duct from
GIS hall by adapting more than one building concept
in one voltage level and it gives better aesthetic look.
TABLE 1: GIS BOQ COMPARISON BETWEEN
SINGLE AND MULTI-BUILDING CONCEPT
i) One building design concept at one voltage
Level: Available plot area was 300x200 sq. meter &
initially we have started with one GIS building each
for both voltage levels. Under one GIS building
concept it was difficult to reduce the GIB lengths of
farer bays & also difficult to accommodate outgoing
GIB in a given confined space. Keeping in view of
space constraints, we have used double layer GIB
technique & rotate our GIB with different angles to
achieve it in optimise way. In this way we found that
still our layout was not simple & optimised (refer fig3).
ii) Two building design concept at one voltage
Level: We have further explore the new way to
simplify & optimised the layout by splitting our
building as per the line orientation & proposed two
building concept. In this design, GIS buildings will be
split in two or more to fulfil the line orientation
requirement reducing GIB length & provides an
aesthetic look with simplicity in layout.
d)
Prefabricated Buildings: Generally covered
civil buildings were prepared to put all these GIS bays
in to it. But now day’s prefabricated steel buildings are
taken place of civil buildings. Prefabricated GIS
building having its own major benefits, major are
‘Quick to install at site, saves lot of time’, better
aesthetic look.
FIG: 5 Pre-Fabricated GIS Hall
e) Very Fast Transient over Voltages (VFTO)
Studies: Focus on the Very fast transient over voltages
due to operation of GIS internal disconnetors switches
(DS) under worst condition and compared with design
data.
VFTO is a result of number of prestrikes and restrikes
occur which leads to travelling waves in the bus bar
duct create complex waveforms depending of DS and
GIS configuration. Damping of VFTO is generally by
integration of damping resistor which is quite proven.
There are some other methods like ferrite or high
Main buses of multiple building shall be connected by
using GIB or AIS bus & provide an extra EOT crane in
other buildings as indicated in figure-4. This design
requires the same space as compare with single
building concept with only minor changes in electrical
& civil quantities as tabulated in below table-1. This
comparison shows that this multi building concept is
overall economical & gives more accessibility for the
maintenance of outdoor bus ducts. There will be
2
215
frequency resonators. These resonators cover a wider
frequency range & dissipate VFTO energy.
f) Open interface for Future Extensions: IEC
62271-203 item 5.107.4 describes the interface for
future extensions of GIS of different manufactures and
avoids future failures. This is limited to bus bar or bus
duct only.
2) LATEST TECHNOLOGY WITH CONDITION
MONITORING TO IMPROVE RELIABILITY:
As per figure-5a, 60 to 70% of the failure could
have been detected by sensitive monitoring system
before & after its occurrence. Major detections can be
noticed by using onsite insulation monitoring tools.
Therefore most of the faults can be detected before it
causes major faults with the help of following advance
GIS condition monitoring & diagnostic techniques:a)
−
−
−
−
−
GIS Condition Monitoring System
Dielectric gas density monitoring
Gas leakage detection
Enclosure internal fault localisation
Circuit-breaker condition monitoring
Self-diagnosis of the complète system
FIG: 5a Detectability of Defects Leading to Dielectric
Failures in 123KV AND 400KV (SOURCE-CIGRE-15-305)
System architecture
A monitoring system has majorly three components:
 Sensing elements,
 Measuring devices,
 Supervision level includes services like remote
access, communication, friendly-user
interfaces, and events data-base.
SF6 Gas Monitoring: - Less than 0.1% leakage rate
can only be achieved by using online monitoring of
SF6 gas. It is also provides a full view of SF6 gas state:
density, pressure and temperature for preventive
actions like early leakage detection techniques, gas
quality, immediate leak repair & state of art of gas
handling.
Travel sensors in the circuit breakers:- to measure
the speed / velocity / acceleration of moving contacts
to ascertain the heath index of circuit breakers.
b) Partial discharge (PD) online monitoring: Using UHV sensors to measure and predict the
possible failures to enable an insight condition of
the apparatus, the incipient state fault detection and
detailed root cause analysis. Condition monitoring
devices embed capabilities of generating alarms, on
settable thresholds, in absolute value and time trend
for preventive maintenance. Advanced Online PD
monitoring system is developed for:
 Mitigating the effect of the external noise on
the measurement,
 Improving the reliability of the components to
verify their normal operation,
 Increasing the robustness of the hardware
regarding the harsh environment,
 Providing the user with a reliable PD detection
scheme and help making-decision tools.
System Evolution:
Earlier the focus was concentrated in the supervision
level.
The measuring devices were passive driven by the
supervision level, acquiring UHF signals without the
capability to apply signal processing and to detect
whether something happens. This functioning way
evolves; intelligence is now deported in UHF
measuring devices which are able to:
 elaborate statistical descriptors,
 detect by themselves that something happens,
 Change their functioning mode in accordance,
leave from the frequency scanning mode to an
event mode.
These deported intelligence features prevent
supervision level and communication network from
overload, and so make the system compliant with very
large substation with huge numbers of sensors.
No drastic evolution has to be noted concerning the
UHF measurement. The spectral analysis is confirmed
because it allows a better noise suppression capability
and a better accuracy. In order to discriminate between
signal and external noise, existing sensing elements
were completed with external sensors (Figure 7).
3
216
The measuring devices of the experimental system
were equipped with 6 UHF inputs, that is to say, two
sensors for each GIS phase. In the new system, they
are equipped with a 7th input for an external noise
sensor (Figure 7).
External noise sensors are applied for increasing the
signal-to-noise ratio; they make it possible to
discriminate between external disturbances which
entered the GIS from the partial discharges signal.
They are made of a fixing part designed for steel
structures, the same antenna and insulator (UHF
sensitive chain) than the internal sensors fitted on the
GIS, in order to have exactly the same frequency
response.
For the purpose of the time domain analysis,
the way of sharing the synchronisation signal between
measuring devices was re-designed. By the way, new
equipment was introduced, called the PD-timer.
The requirements concerning the communication
between the supervision level and the measuring
devices evolved because of the return of experience of
the experimentation. In the experimental system, UHF
measuring devices were connected one to another
through a Modbus RS485 network. This network made
of twisted pair between went from a Central PC
(supervision level) to the different modules in Daisy
chain and ended by a resistor (Figure 6a).
Figure 6a: Old Communication schematic
Figure 7: External noises sensor
Thus, on the new system, the communication is insured
by a self-healing Ethernet ring, made of optical fibber
cables (Figure 6.b). The advantages are numerous:
 High bandwidth: 100 Mb/s
 High EMC withstand due to optical fibber
 Good availability: In case of breakdown of a
link, communication can continue through the
other side of the ring.
 Files download enabled in FTP protocol, very
convenient and efficient solution for
configuration deployment.
The UHF measuring devices of the experimental
system had the capability to self-diagnose:
 Sensor is improved, as now it is compliant
with every sensor protection type (50 Ohm
resistive, as well as lambda/4 short-circuit).
 IED: presence of UHF module, communication
 Synchro: presence of synchronization voltage
The hardware is dedicated to spectrum analysis signal
processing. It has been entirely re-designed mainly for
three reasons:
 Performance and technical obsolescence:
The UHF components of the experimental
system were based on a standard heterodyne tuner,
used in public broadcast equipment. The drawbacks of
this integrated solution were on the one hand, that it
was rather slow; on the other hand, this kind of
components is made in high quantity and redesigned
each year; so its obsolescence cycle is very short. Thus
it is replaced by a dedicated tuner, more accurate and
faster, and made with several discrete components, so
that the obsolescence cycle can be managed.
The digital part is also modified, featuring a
communication outlet in Ethernet (rather than in
Modbus for the former one), and a new central unit
with a faster sampling. These evolutions make it
possible real time acquisitions and data transfers,
which enable the use of this monitoring system during
the GIS HV test.
Figure 6b: New Communication schematic
Measuring devices
The UHF measuring devices are real embedded
spectrum analysers, and are designed to run on two
modes:
 Sweeping spectrum analysis,
 Time domain analysis (equivalent to span
zero).
Versatility:
This module can be either integrated itself in a
stand-alone box (called PD-Box) or in the local control

4
217
cubicle. For operation continuity reason, the 2nd
solution has been chosen, as it avoids GIS bays outage
before intervention inside the local control cubicle.
Figure 9.a: Spectrum without discharges (without PD)
Industrial toughness in harsh environment:
Electronic is protected inside the module metal
clad, so that the box can be opened during operation,
even if there are electromagnetic transients. Peripheral
elements to the module are mainly an Ethernet switch,
and electrical devices as anti-condensation resistor,
power supply, terminal blocks.

Figure 9.b: Spectrum with discharges (during PD)
Signal processing and signal interpretation
Concerning
the
signal
processing
and
interpretation, the methodology relevant:
 Increasing the signal-to-noise ratio,
 Detecting and generating an alarm,
 Getting further in the defect identification,
providing the users with tools to help in
decision-making.
Figure 9.c: Discharges mixed with noises
Signal processing is partly supported by the measuring
devices, in the new system.
External sensors
Enhancing signal-to-noise ratio
This tool did not exist on the experimental
system. It is an evolution of the new system that aims
at discriminating temporary disturbances that cannot be
suppressed by exclusion bands, which are more
adapted for stationary noises.
Signals from internal sensors fitted on the GIS are
compared with those coming from external noises
sensors, in order to determine the better frequency for
analysis (Figure 8).
Several noises discrimination tools are
implemented in the PD monitoring system, in order to
avoid any spurious PD alarm which could be caused by
external UHF disturbances, entering the GIS through
holes on the enclosures (apparent spacer flanges, view
port, bushings,).
Exclusion bands
Before HV tests, the GIS is not yet energized. So, no
UHF signal can propagate inside the GIS, excepted
external noises (disturbances).
A spectrum analysis is performed, and allows
identifying of these noises.
Concerned frequency bands are then masked (Figure
9.a).
After energisation of the GIS, new signals may appear
on non-masked bands. They could be generated by real
PD, so they shall be detected by the system (Figure
9.b).
New signals may also appear on masked bands. At the
contrary, they must be ignored, as they will be mixed
with noise, and will not enable accurate analysis
(Figure 9.c)
Figure: 8: Use of external sensor for reducing noise
disturbances
Close and linked sensors comparison
In case of event, signals from concerned sensor are
compared with those from close sensors (same location,
adjacent phase), those from linked sensors (adjacent
location, same phase) and those from external noise
sensors (Figure 10).
5
218
Figure 10: Close and linked sensors comparison
Detecting and generating an alarm



The algorithms begins with a cyclic step,
which measures signals spectrum, calculate the
statistical descriptors: mean and variance of
the spectrum (Figure 11).
In case where there is enough signals activity,
one of these descriptors reaches a threshold,
and so trigs an event “signal detected”.
In case of event, the algorithm continues with a
spectrum and a time domain measurement, in
order to check if it is a real PD or an external
noise. In case, it’s a real PD, the event is
transformed into an alarm “PD suspected”.
Figure 12b: Trend curves
3)
NEW TRENDS IN GIS:
i) Point-on-wave switching
Switching operations on transformers / reactors,
capacitor banks and overhead lines can produce
transient overvoltages of significant magnitude.
Mitigation of these switching transients in high-voltage
transmission grids is gaining importance as the
generated stresses lead to power quality problems and
accelerated ageing. Conventionally, techniques such as
installing additional protective devices (e.g. surge
arresters), adding pre-insertion resistors to circuit
breakers and over-rating the electrical equipment are
applied to limit the overvoltages. Due to major
improvements in intelligent electronic devices (IEDs)
in the past few decades, controlled switching or pointon-wave switching of circuit breakers has emerged as a
smart and cost-effective alternative to the conventional
solutions.
Point-on-wave switching involves segregation of a
random three-phase switching command into separate
commands for the three phases issued such that each
pole is switched at the optimal point on the respective
reference voltage waveform. The effectiveness of
point-on-wave switching relies mainly on:
- Identification of right target point for
energizing or de-energising of the load
- Reliable estimation of the operating time of the
breaker being controlled
Figure 11: PD identification algorithm
Making-decision tools and friendly-user HMI
The new system has indigenously developed data
analysis tool with embedded Expert systems and userfriendly trending modes to review and analyse the past
events at our convenience.
The optimal point for switching is pre-defined based
on the type of load (capacitive or inductive) and the
kind of switching operation (energisation or deenergisation). However, identification of the right
target point in real time requires a very precise
assessment of reference voltage in advance. Reliable
estimation of the operating time is a challenge due to
its dependency on various factors such as:
- Ambient temperature
- Actual control voltage or stored energy in
drive mechanism
- Time since the circuit breaker was last
operated (idle time)
Figure 12a: Automatic pattern recognition
6
219
-
Long term drifts of operating time
The point-on-wave controller is basically an
advanced microprocessor based synchronizer relay.
The optimal switching sequence is programmed based
on the type of load the breaker is going to switch. In
operation, the relay continuously monitors the key
influencing parameters mentioned above and stores the
information in its integrated memory. Upon receipt of
a command to trip or close the breaker, the relay
processes the command based on the stored
information through specially designed algorithms.
The command is processed separately for each of the
phases and appropriate time delay is added such that
each phase is switched at its respective optimal point.
Figure 13a: Switching Technology Comparison w.r.t overvoltages produced in system
Figure 13b: Overhead transmission line dimensions
reduction after usage of CSD
ii) Digital components in GIS: The Digital Substation
is one of the major components of the Smart Grid
and supported by the application of the IEC61850
within the substation by using digital CT, EVT and
Digitalization of all data Implementation of “realtime” communications
Integration of all measure & protection,
control, and monitoring functions. Future optical
devices based on Faraday effect (current) &
Pockel’s effect (voltage). Such optical devices have
been applied to Eliminate open circuit in CTs and
Eliminate problem of potential Ferro
resonance
on Electromagnetic VTs.
The efficiency of point-on-wave switching
depends not just on the capability of the controller. If
the operating time of the breaker is not consistent the
operating time settings made by the controller based on
the previous operation will not hold good for the
subsequent operation. Hence, particular attention
should be given to the operating time scatter of the
breaker. Besides, characteristic data of the breaker
such as RRDS (Rate of Rise of Dielectric Strength)
and RDDS (Rate of Decay of Dielectric Strength)
should be known in order to correctly estimate arcing
and pre-arcing times. Thus, the point-on-wave
controller should be properly integrated with the
breaker to be controlled to ensure effective controlled
switching.
Figure 14: Architecture of Digital CT/PT System

There will be huge reducing in the overall dimensions
of transmission line when controlled switching is been
considered. Pl refer figure 13b where it is clearly shown
the reduction in tower height & write off land.
GIS condition monitoring
Since mists of time, the monitoring in GIS
consisted of:
− Conventional SF6 gas control uses density
switches
− Gas alarms only carried over the LVCC mimic
Main drawbacks :
− No indication in case of any sensor problem
− The SF6 was slackening in the atmosphere
without indication before the threshold 1
7
220
GIS like compact, safe etc., this will remains first
choice. Remote data monitoring and processing as per
IEC61850 to meet the smartgrid requirements will be
the next goal of all OEMs.
On-line fully digital GIS monitoring system ( refer
figure -15 ) & its Main functions are :
− Dielectric gas density monitoring
− Gas leakage detection
− Enclosure internal fault localisation
− Circuit-breaker condition monitoring
− Self-diagnosis of the complète system
5)
REFERENCES

P. PRIEUR, S. DUBOSCQ, J-F. PENNING, A. SARR, A.
GIRODET, J-L. RAYON “UHF partial discharge
monitoring: return of experience installed in 400 kV GIS”,
CIGRE Session 2014, B3-206.
ALSTOM NOT 200.8560_En Rev. D, “RPH3 Point-onWave Controller – Product description guide”
M. WALDRON, F. AÏT-ABDELMALEK, A. FICHEUX, J-L.
RAYON, “Qualification Process of a GIS 400 kV SF6 High
Voltage Circuit Breaker Controlled Switching Solution”,
CIGRE 2014, A3-204,
F. AÏT ABDELMALEK, J-P. DE SANTIS, A. FANGET, J.
BORDES., “Power transformer controlled switching –
Various strategies to cope with detrimental inrush
currents and enhance power quality”, MATPOST 2015,
Session 5, No. 47,
GIS Monitoring architecture (full Ethernet)




C.NEUMANN, B.KRAMPE, R.FEGER K, FESER, M.
KNAPP, A BREUER, V. REES “PD measurements on GIS
of different design by non-conventional UHF sensors”
CIGRE 15-305,

CJ Jones, W Degen, J S Finn, P L Fletcher, D Kopejtkova, Z
Lefter, E Duggan, C Tschannen “ GIS – State of Art 2008 “
CIGRE WG B3-17
Figure 15: On-line fully digital GIS monitoring system
Latest Technology with Condition Monitoring
Improving Reliability, Availability and Life—
Asset Conditioning
Figure 16: Asset Condition Monitoring architecture
4)
CONCLUSION:
In GIS Design it has been found that the multi-building
design is beneficial with respect to cost. The
developments in the area of digital technology has
paved path for developments such as GIS Gas
monitoring systems, PD monitoting systems and
Controlled switching devices with higher accuracy to
enhance the reliability of GIS in operation. In future
integration of digital electronic and controls will be
part of main primary equipments and Transfer data by
using optical links. Due to inherent advantages of a
8
221
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems
on including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Deploying
Integrated,
Scalable and Manageable
IEC System
61850 Substation
“Global
Trends
in the Development
of Power T&D
includingwith
Smart Grid”
Seamless Redundancy
ELEANOR HUANG
Inc.
Deploying Integrated, Scalable andMoxa
Manageable
IEC 61850 Substation with
Seamless Taiwan
Redundancy
ELEANOR HUANG
Moxa Inc.
Taiwan
SUMMARY
In today’s complex substation automation industry, network and system reliability is
paramount in ensuring onsite safety and consumer quality of service. One solution to ensure
highly-reliable systems communication is to implement network redundancy without a single
point of failure. An optimized IEC 61850 network architecture with seamless redundancy
technology should provide scalable integration for easy modification of system functionality
SUMMARY
and extension of the substation. However, existing end devices in substation automation
systems are complex and perform many different communication characteristics to ensure
In today’s
complex substation automation industry, network and system reliability is
redundant communication. An efficient and high interoperability solution to maximize system
paramount
in ensuring
onsite
safety goal
and for
consumer
quality of service. One solution to ensure
availability
will be
the ultimate
future deployment.
highly-reliable systems communication is to implement network redundancy without a single
point of failure. An optimized IEC 61850 network architecture with seamless redundancy
technology should provide scalable integration for easy modification of system functionality
and extension of the substation. However, existing end devices in substation automation
systems are complex and perform many different communication characteristics to ensure
redundant communication. An efficient and high interoperability solution to maximize system
availability will be the ultimate goal for future deployment.
KEYWORDS
PRP: Parallel Redundancy Protocol
HSR: High-availability Seamless Redundancy
RSTP Transparent
In today’s complex substation automation industry, network and system reliability is
paramount in ensuring onsite safety and consumer quality of service. One solution to ensure
highly-reliable systems communication is to implement network redundancy without a single
point of failure. In the past, proprietary dual LAN network was commonly deployed in order
KEYWORDS
to avoid any error communication because of single point of failure. However, in
PRP: Parallel
Redundancy Protocol
eleanor.huang@moxa.com
HSR: High-availability Seamless Redundancy
RSTP Transparent
In today’s complex substation automation industry, network and system reliability is
222 quality of service. One solution to ensure
paramount in ensuring onsite safety and consumer
highly-reliable systems communication is to implement network redundancy without a single
point of failure. In the past, proprietary dual LAN network was commonly deployed in order
consideration of the difficutly in maintenance and function extension, uncontrollable
performance within large scale network and costly, a standardized protocol to ensure high
interoperability communication is expected. The IEC 62439-3 specifies two redundancy
protocols, PRP (parallel redundancy protocol) and HSR (high-availability seamless
redundancy), designed to provide seamless recovery in case of single failure of an inter-bridge
link or bridge in the network, perfectly for next generation IEC 61850 Substation or critical
control system.
When applying an optimized IEC 61850 network architecture with seamless redundancy
technology, interoperability, scalability and manageability will be three major challenges to
ensure system availability.
The major challenges to Substation Automation System :
1. Moderately Efficient Network Construction
Constructing a PRP or HSR redundant communication network infrastructure will provide
seamless redundancy and error-free operation. However, existing end devices in a
Substation Automation System perform different communication capabilities, which can
include SAN (single attached nodes), DAN (dual attached nodes), DANP (dual attached
nodes for PRP) and DANH (dual attached nodes for HSR). Applying a 3-port PRP/HSR
redundancy box is one way to integrate legacy devices to a PRP/HSR network.
Connecting each end device to a redundancy box with an independent "traffic lane" for
critical system communication will provide higher reliability for Substation automation
system. However, this type of deployment will not only be very costly to implement if
multiple legacy devices eager to upgrade, it will require a considerable increase of
maintenance effort and installation space limitation.
2. Interoperability Performance and Scalability within Operation
While constructing a Substation Automation system communication infrastructure, not
only to consider the integration effort but also need to take flexible deployment for future
upgrade into consideration. However, the device complexity, variety, multiple form
factors and function independent operation requirement to ensure optimal system
availability will impact the system interoperability and scalability. Without a complete
solution that encompasses communication platform and systems management, substation
operators will be left with a network consisting of devices from multiple sources and
hardly to modularize extend new sub-function or new site. This will severely complicate
systems interoperability, maintenance, troubleshooting, and increases the total cost of
ownership.
3. Heterogeneous Device and Network Management Interface
Aggregating information and generating alarms is a well-known functionality in the
domain of substation automation. The Manufacturing Messaging Specification (MMS) is
the main monitoring and messaging protocol used for this purpose and supports
communication in IEC 61850 compliant systems. Any information related to electrical
operational status of a substation is supposed to be managed and transferred via MMS.
However, in contrast to power equipment, the protocol used today for managing IT
equipment is Simple Network Management Protocol (SNMP), which is based on a totally
different logical structure. As PRP/HSR devices use Supervision Frame for device
management, it is difficult to simply integrate these two systems for monitoring and
management.
223
1
With the increasing implementation of IEC 61850 based networking devices like
switches, embedded computers this protocol incompatibility has to be bridged.
Given the fact that most Power SCADA software suites available on today’s market are
compatible only to MMS protocol but not SNMP or Supervision Frame, network
management on a single Power SCADA seems to be impossible. Networking devices are
invisible to the Power SCADA so far.
As a result, today’s IEC 61850 system operators are forced to use separate monitoring
platforms: The Power SCADA and a SNMP-based network managing software brings an
inefficient and error-prone situation challenging substation operation.
Figure 1
Recommended Solutions
1. An optimized way to integrate legacy devices in a highly-reliable communication
backbone.
Most existing end devices have dual access points to the network and are capable of using
the RSTP redundant protocol. Where second-level recovery time is tolerated, operators
will prefer a cost-effective method to integrate these DANs to a more reliable backbone
network to enhance system availability. Integrating existing ring networks with a
PRP/HSR architecture using RSTP-transparent technology is an ideal method to achieve
this objective.
Figure 2
2. A wide range of product options for a scalable and highly interoperable deployment.
Deploying redundancy has a direct impact on system complexity and cost, which will
depend on system requirements and application criticality. With a limited budget
allocation, engineers must meet substation requirements while optimizing system
224
2
availability. Existing device/ring networks must integrate easily into the PRP/HSR
network, and the system architecture must be scalable according to system needs. While
there are many different types of PRP/HSR network designs, flexibility, modularity, and
integrity will be the key factors to optimize the PRP/HSR architecture.
A 3-port Redundancy box is an ideal device for the needs of critical communication,
function isolation, and integrating many RSTP-supported DANs. High-port density
PRP/HSR switches with hot-swappable communication module design minimizes the
mean time to repair and provide higher installation flexibility. PRP/HSR embedded
modules enable legacy devices to natively support PRP/HSR protocols without the impact
of having a single point of failure between the connection of the Redundancy box and the
end device. PRP/HSR embedded computers will provide a management platform to
enable visually-represented PRP/HSR network management.
Figure 3
3. Control devices and redundant networks can be monitored on a single Power
SCADA platform
The solution can be derived learning from other markets’ SCADA applications. Proposing
to translate SNMP-based network information to MMS, the network nodes like switches,
redundancy boxes, device servers, gateways and even embedded computers should run a
MMS server with data synchronized to the device’s SNMP status. The Power SCADA’s
MMS interface can query and communicate now in the same way with network nodes as
if they were protection relays or other intelligent electrical devices. The result is a unified
Power and Network SCADA.
4. Management Middleware will aggregate and bridge
Considering dozens of status parameters, to deploy dedicated PRP/HSR management
middleware on substation computers running the Power SCADA will provide an efficient
way on management. The middleware collects and analyzes the raw data from various
distributed devices. For versatility and compatibility reasons, the PRP/HSR management
middleware should be able to support both SNMP and MMS interfaces, allowing the
connection of various substation devices that run different communication protocols.
225
3
Figure 4
Communicating via MMS the PPR/HSR management server can enable the Power SCADA to
fully monitor the current redundant network status with little efforts.
Single-point failures can be immediately discovered and real-time troubleshooting becomes a
simple task. Even system administrators with little knowledge of PRP/HSR technology can
easily manage, monitor, and troubleshoot the PRP/HSR network on a single Power SCADA
platform. Substation operators will find it easy to manage all devices on the PRP/HSR system
via the Power SCADA visual tools. In addition, troubleshooting can be easy as any single
failure point can be shown on the Power SCADA, making the Substation Automation System
more reliable and stable.
Conclusion
There are many methods to integrate existing and new bays with IEC 61850-compliant
devices specifically calibrated for PRP and HSR redundancy, seamless control and
monitoring can be achieved using an optimized hybrid network topology to meet highly
integrated, scalable and manageable Substation automation system.
226
4
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGREAORCin
Technical
Meeting 2016 – of
International
Conference
on Global
Trends in
the Development
“Global
Trends
the Development
Power T&D
System
including
Smart
Grid”
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends
in the Development
of in
Power
System including Smart Grid”
Electro-Magnetic
Field Study
UHV T&D
Substations
D. MAHESWARAN, K.K. JEMBU KAILAS, R. MALARVIZHI, MANIVANNAN.C
Electro-Magnetic
StudyLIMITED
in UHV Substations
LARSEN Field
& TOUBRO
INDIA
D. MAHESWARAN, K.K. JEMBU KAILAS, R. MALARVIZHI, MANIVANNAN.C
LARSEN & TOUBRO LIMITED
INDIA
SUMMARY
Rapid increase in expansion of Electrical energy utilisation and ascending demand has led to
increase in the transmission capacity, thereby necessity to upgrade the system to EHV &
UHV levels. While operating switchyards/Transmission at Extra High voltage levels are being
adopted by most utilities across globe, there is considerable impact on ecological system
SUMMARY
because of higher ionisation & radiation due to the higher voltage levels putting living beings’
survival
at stake.
Rapid
increase
in expansion of Electrical energy utilisation and ascending demand has led to
increase in the transmission capacity, thereby necessity to upgrade the system to EHV &
It is more evident that there is an essential need to mitigate the effects of electromagnetic field
UHV
levels. While operating switchyards/Transmission at Extra High voltage levels are being
interference in the switchyards for human, livestock & plants. Enough studies are made and
adopted
by most utilities across globe, there is considerable impact on ecological system
validated results are available for voltage levels up to 500kV indicating value of fields within
because
of higher
ionisation
radiation
due to theHence,
higherit voltage
levels
putting living
beings’
tolerable
limits, research
for&765kV
is underway.
has become
mandatory
that, the
survival
at
stake.
geometry of switchyard has to be decided considering the Electro-magnetic field and to
restrict the values within limits. This technical paper deals on the electric and magnetic field
It iseffects
more for
evident
thatswitchyard
there is anand
essential
need toofmitigate
the ineffects
of electromagnetic
765kV
interpretation
EM field
analytical
and real time field
measurement.
A case
study wasfor
conducted
a 765kV &
Switchyard
to examine
the values
of and
interference
in the
switchyards
human,atlivestock
plants. Enough
studies
are made
EM field
using are
COMSOL
software,
where levels
using finite
exact
fieldofvalues
validated
results
available
for voltage
up toelement
500kV analysis,
indicating
value
fieldsatwithin
specified
heightresearch
can be calculated
and is
theunderway.
results are compared
tolerable
limits,
for 765kV
Hence, itwith
has real-time
become measurement.
mandatory that, the
geometry of switchyard has to be decided considering the Electro-magnetic field and to
restrict the values within limits. This technical paper deals on the electric and magnetic field
effects for 765kV switchyard and interpretation of EM field in analytical and real time
measurement.
A case study was conducted at a 765kV Switchyard to examine the values of
KEYWORDS
EM field using COMSOL software, where using finite element analysis, exact field values at
UHV ACheight
– Electric
– Magnetic field
FEM
- Realare
timecompared
measurement.
specified
canfield
be calculated
and –the
results
with real-time measurement.
KEYWORDS
dmaheswaran@lntecc.com
UHV
AC – Electric field – Magnetic field – FEM - Real time measurement.
227
1.0 INTRODUCTION:
Till several decades ago, human exposure to Electric & Magnetic fields (EMF) were limited
to those generated naturally. With technology growing at rapid pace, there are too much of
Electromagnetic Fields around us predominantly due to Electric Power Generation,
Transmission & Distribution where Electro-magnetic fields are with greater magnitudes. EHV
& UHV transmission lines, which pass through human, livestock occupied locations and/or
plantation areas, could be prime source of EMFs. Biological effects of EMF on the human
body, animals and plants have been a subject of specific interest and public concern for their
risk on the living organisms.
Electric power system frequencies (50 Hz) are at the lower end of the range of frequencies of
electromagnetic radiation and are sometimes referred to as extremely low frequencies (ELFs).
Although considering the electric and magnetic forces together and collectively calling them
electromagnetic fields are common, in the ELF’ range, even though the forces are two
separate entities, both have unique interactions with living beings & plants. For power lines,
electric fields are created whenever a voltage is applied to the conductor; whereas magnetic
fields are created when current flows through the conductor.
The electric field created near a charged conductor is a vector, quantified by the electric field
strength, E. This vector is the force exerted by an electric field on a unit charge and is
measured in volts per metre (V/m). This vector either oscillates along a fixed axis when there
is a single phase source or rotates in a plane when there is a three-phase source. The magnetic
field, is also a vector, whose vector properties are similar to Electric field. Magnetic Field
strength, H, is the axial vector whose rotation equals the current density vector, including the
displacement current, and is expressed in amperes per metre (A/m).
This paper throws limelight on simulation of Electric & Magnetic fields in a UHV substation
using COMSOL software and validating the results using real time measurement using ELF
survey Meter and further ensuring the values are within safer limits. Towers, Equipment &
Conductors were modelled considering for a 765kV Substation in India and EMF results are
measured at a height of 1.8m from ground at various locations of switchyard. Interpretation of
measured and simulated fields are used to verify the substation model and figure out the
locations where field values are expected/likely to be experienced higher and layouts could be
designed considering this phenomenon so that it doesn’t cause any harmful effects to human
movement.
In this paper, following aspects are discussed:
a) Analytical methods for calculation of field effects
b) Interferences / impacts and recommendations of ICNIRP guide lines[1]
c) Analysis of Electro-magnetic field using FEM approach
d) Actual field measurements made in a UHV AC station
e) Interpretation of results
2.0 ANALYTICAL METHODS FOR CALCULATION OF FIELDS:
Electric field is a vector field of Electric-field strength defined by its space components along
three orthogonal axes. For steady-state sinusoidal fields, each component is a phasor that may
be expressed by a rms value (V/m) and a phase as follows.
228
1
E = ex (t) ux + ey (t) uy + ez (t) uz
…Eqn.(1)
where ux, uy & uz are unit vectors along the direction x, y & z axes and e x (t) ux, ey (t) uy, ez (t)
are phasors function of time as shown below;
ex (t) = Excos(ωt + ϕx) = Ex,r cos (ωt) + Ex,i sin (ωt)
…Eqn.(2)
where Ex is the magnitude and ϕx is the phase angle (0 to 360°) of ex (t) and r & i represents
the real & imaginary parts. E expressed in Eqn.(1) is a vector moving in space which rotates
in a plane and describes an ellipse where the maximum field strength occurs along the major
axis of ellipse and the length of semi-axis represents the field strength.
Fig (1) Electric field ellipse at a point space
Magnetic flux density (B) is used to describe the Magnetic field generated by currents in the
conductors of substation/transmission lines and thus defined as a vector field of magnetic flux
density. The vector properties of magnetic field is also similar to Electric field and the
magnitudes of their space components are expressed by their rms values. B-field are denoted
by Tesla (T) or commonly by, Gauss (G) which is 10-4 Tesla.
3.0 CALCULATION OF ELECTRIC & MAGNETIC FIELDS:
Electric fields in proximity to AC transmission lines or substations are calculated assuming
that there is no free charge in space. The earth is assumed to be of perfect conductor which
quickly redistributes the charges under the action of applied field as time taken is extremely
small when compared to power frequency.
Field Gradient (kV/m)
10
8
6
4
2
0
0
10
20
30
40
50
Distance from centre of line (m)
60
Fig (2) Electric field measured at 765kV
Switchyard – flat conductor configuration
Fig (3) Electric field measured at 525kV TL
(delta configuration) & 1050kV switchyard
(flat configuration)
229
2
In case of regular bundled conductors, for calculation of Electric fields away from the
conductor surface, it is better to consider equivalent single conductor. D.W.Deno &
L.E.Zaffanelia [2] in their study have made the empirical methods for calculating the Electric
& Magnetic fields in case of Transmission lines and substations.
Magnetic field in substations can be calculated by a two dimensional analysis assuming
parallel conductors carrying current above an even ground surface. Consider a line parallel to
Z-axis with a current flowing along z-direction, the magnetic field strength H at a point x i,yi at
a distance rij from the conductor carrying current, will have an amplitude of, Hj,i = Ii / (2πri,j)
and in vector notation, Hi,j = Ii * ϕi.j / (2πri,j) where ϕi.j is the unit vector in the direction of
product of the vector current & vector segment ri,j.
The total magnetic field is the sum of all the contributions from line currents as follows. This
equation is sufficient to calculate the magnetic field in vicinity of lines up to 100m.
Hi, j = Ʃ Ii * ϕi.j / (2πri,j)
…Eqn.(3)
Y
(Hi,j)
ri
(Xj,Yj)
j
(Xi,Yi)
X
Z
Fig (4) Magnetic field around current carrying conductor
4.0 INTERFERENCES / IMPACTS AND RECOMMENDATIONS:
Many studies from different part of the world are being conducted towards assessing the risk,
the operating personnel are put into while operating in UHV switchyards. Though, the data
available based on researches made on EM fields of low frequency till now are inconclusive
and inconsistent to narrow down on the biological effects, there are more probabilities that
these fields may lead to Neurodegenerative disorders & chronic effects. International
Commission of Non-Ionizing Radiation Protection [1] have established guidelines for limiting
exposure to electric and magnetic fields (EMF) that will provide protection against all
established adverse health effects. ICNIRP have conducted the studies assessing both direct
and indirect effects of EMF: direct effects result from direct interactions of fields with the
body; indirect effects involve interactions with a conducting object where the electric
potential of the object is different from that of the body.
Occupation Exposure –
Public Exposure
-
Electric field can be up to 10 kVrms/m &
Magnetic field up to 500 µT or 5000 mG
Electric field can be up to 5 kVrms/m
Magnetic field up to 100 µT or 1000 mG
Human and animal bodies significantly perturb the spatial distribution of a low frequency
electric field. At low frequencies, the body is a good conductor, and the perturbed field lines
external to the body are nearly perpendicular to the body surface. Oscillating charges are
230
3
induced on the surface of the exposed body and these produce currents inside the body. For
magnetic fields, the permeability of tissue is same as that of air, so the field in tissue is the
same as the external field. Magnetic field due to low frequency doesn’t significantly perturb
Human and animal bodies. The main interaction of magnetic fields is the Faraday induction of
electric fields and associated currents in the tissues.
Studies reveal that exposure to induced fields beyond threshold values can affect brain
functions like visual processing & motor co-ordination.
5.0 ELECTROMAGNETIC FIELD – FINITE ELEMENT APPROACH:
Due to the complexity of the geometry of the switchyard, a FEM approach using COMSOL is
adopted to analyse Electromagnetic (EM) field. In this approach, the nonlinear EM field is
solved by dividing the enclosing volume of the switchyard into millions of tiny tetrahedral
elements and assuming that the element is so small with respect to the geometry of the
switchyard that the EM field can be assumed to be practically uniform inside the volume of
the tetrahedron. Under this assumption, EM field is solved (along with variables like voltage,
current density, etc.) in each of the tiny tetrahedral element. Assuming a linear relationship
among the variables involved within a limited region, a linear equation of the form is
constructed as
Ax= b
…Eqn.(4)
where ‘x’ corresponds to the vector of field variables to be solved for at each of the tetrahedral
elemental domain, ‘A’ is a matrix which shows dependencies of the field variables in terms of
other local field variables (within a limited region) and is a sparse matrix in form and ‘b’
corresponds to the applied potential or current constituting the boundary conditions of the
Maxwell’s equation. Equation (4) can be expressed as,
x = A-1b
…Eqn.(5)
Since the dimension of x and A is in order of several millions, only a numerical iterative
solution of (5) is possible. The solution sought is of the form
x – A-1b < Tolerable limit (shall be less than tolerable/acceptable values)
…Eqn.(6)
6.0 GEOMETRICAL MODEL OF SWITCHYARD:
For analysis, two typical 765kV diameter (consisting of 4 feeders with 2 Tie bays in one &
half scheme) of switchyard are developed with conductors at different plane.
Strung Bus (Quad Bull with 450mm sub-conductor spacing) at 39 m height, Main bus (Quad
Bull) at 27 m and Equipment bus (4.5” Al. Tube) at 14 m height from ground with all jumper
arrangements and interconnections, Insulating medium as air and switchyard is perfectly
earthed. The quad conductors are modelled as equivalent conductors and tower structures are
modelled as metallic blocks at ground potential and equipment like Circuit Breakers,
Isolators, CT, CVT and LA are modelled as metallic objects at ground potential. Fig. 5 shows
the modelled switchyard. With the switchyard modelled as a finite element space, simulation
is made by injecting a voltage or current.
231
4
Fig (5) Switchyard as modelled
Fig (6) Switchyard configuration- meshed
7.0 SIMULATION - RESULTS:
The results displayed corresponds to the field distribution along the horizontal cross- section
of the switchyard at a height of about 1.8 m above ground (corresponding to the typical height
of a human operator). The electric field is measured in terms of kV/m. The magnetic field is
expressed in terms of mG (milli Gauss). The different colors represent the gradient of field
distributed across the switchyard.
ELECTRIC FIELD:
Fig (7) shows the electric field values at a plane parallel to the ground plane and at a height of
1.8 m above ground. It is seen that the electric field at some locations exceed the prescribed
limit of 10 kV/m as per regulations.
232
5
Fig.(7) Electric Field (kV/m) distribution at 1.8m from ground level
As a solution to curb the electric field within limits, a shield wire is run in plane parallel to
conductors (approximately 8m from ground) and the electric field were below the limiting
value of 10kV/m at all the locations where the field exceeded the limit originally. Refer Fig
(8).
Fig.(8) Electric Field (kV/m) distribution at 1.8m level with shield wire
It can be noted that, the Electric field limits are reduced (please refer there is a difference in
scale’ ‘) after stringing shield wire.
MAGNETIC FIELD:
Fig (9) shows the magnetic field distribution at a plane parallel to the ground and at a height
of 1.8 m above ground level. It is inferred that the value of the magnetic field along the plane
under consideration is much less than 10 mG whereas the regulatory limit prescribes for far
above this value at 5000 mG. So, more aptly, the current levels provided no risk is perceived
through magnetic field.
233
6
Fig.(9) Magnetic Field (mG) distribution at 1.8m from ground level
8.0 ACTUAL FIELD MEASUREMENTS MADE IN A UHV AC STATION:
In order to assess the real time scenario, actual field measurements were carried out in a UHV
(765kV) AC station in India using Electromagnetic field survey meter. Typical tower profile
inside the substation is indicated in Fig (10). All measurements are done at approximately
1.8m height above ground. Conductor used here is Quad bundle of 38.25mm diameter, with
450mm sub-conductor spacing, Shield wires are of 7/3.66mm galvanised steel strands as
illustrated in Fig (10).
As per generally acceptable guidelines, for an average human adult, the tolerable electric field
gradient would be 10kV/m & magnetic field of 500 µT (5000mG). Hence, the field effects
were found to be within the permissible limits.
Location
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Electric field (kV/m)
Measured Calculated % Variance
7.8
6.2
-25.8%
6.3
7.3
13.7%
8.4
8.1
-3.7%
6.7
8.7
23.0%
6.3
8.3
24.1%
6.3
7.5
16.0%
7.4
7.2
-2.8%
5.9
6.9
14.5%
6.5
5.6
-16.1%
6.3
6.1
-3.3%
4.2
3.4
-23.5%
4.3
3.6
-19.4%
6
5.8
-3.4%
6.3
5.6
-12.5%
7.7
6.7
-14.9%
Magnetic field (mG)
Measured Calculated % Variance
3.7
4.8
22.9%
3.8
4.2
9.5%
2.8
3.8
26.3%
2.5
3.2
21.9%
2.7
3.6
25.0%
3.8
4.2
9.5%
4.1
4.8
14.6%
4.2
5.1
17.6%
0.7
0.9
22.2%
0.5
0.7
28.6%
1.6
2.2
27.3%
1.8
2.4
25.0%
0.5
0.8
37.5%
0.3
0.7
57.1%
0.9
0.8
-12.5%
Table (1) Comparison of Real-time EM field measurements and calculated values (from 1.8m
from ground) in a 765kV substation (with shield wire).
234
7
Fig (10). Location of real-time measurements made at 765kV Switchyard
9.0
INTERPRETATION OF RESULTS:
Based on simulation results of Electric field inside the 765kV substation, see Fig (7) the
values appear to be closer or slightly more than the acceptable regulatory limits. In contrast,
the real-time measurements indicate values less than the acceptable levels. Though there is
variance/difference between the analytical values and real-time measurements, the reason
could be based on number of parameters like, atmospheric conditions that may affect
humidity, sag in conductors, the number of bays considered in simulation vis-à-vis the actual
bays present in the switchyard where measurements were made. Further it can be noted that
the values of magnetic fields made using simulation as well as real time measurement are far
less than tolerable limits.
10.0 CONCLUSION:
The Electromagnetic simulation results were compared with the real time measurements made
at selected points and it is generally found that the measurements supports and portrays a
similar range of field values perceived through simulation. However, there are few points
where a slight increase is observed and as a solution, shield wires (or ground wires) are strung
at 8m on the structures of Equipment which reduces the values.
Hence, it is suggested to measure the values of Electro-magnetic field at energised Switchyard
for validation. In case if the values are exceeding the prescribed limits, a shield wire may be
strung in the grounded structures in a plane parallel to conductors, as explained in Fig (8).
11.0 BIBLIOGRAPHY:
[1] Guidelines by International commission for Non-Ionising Radiation protection published
in Health Physics 99(6):818-836; 2010.
[2] Transmission line reference book-effect of Electric & Magnetic fields by D.W.Deno &
L.E.Zaffanelia for Electrical Power Research Institute, California.
[3] Electromagnetic Fields by The Connecticuit Light & Power Company
[4] Proceedings of the International Conference on Non-Ionizing Radiation at UNITEN
(ICNIR 2003) Electromagnetic Fields and Our Health, 20th–22nd October 2003.
235
8
CIGRE- AORC Technical Meeting 2016 and International Conference on
CIGRE-“Global
AORC
Technical
Meeting 2016
and T&D
International
Conference
on
Trends
in the Development
of Power
System including
Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Implementation Techniques of Substation Control System of Switching-unit
Substations for Increasing Reliabilities of Customer Substations
Implementation TechniquesUnder
of Substation
Control
System of Switching-unit
MEA’s SCADA
Constraints
Substations for Increasing Reliabilities of Customer Substations
Under MEA’s
SCADA
Constraints
PICHIT
JINTAGOSONWIT
METROPOLITAN ELECTRICITY AUTHORITY (MEA)
THAILAND
PICHIT JINTAGOSONWIT
PICHIT.J@MEA.OR.TH
METROPOLITAN ELECTRICITY AUTHORITY (MEA)
THAILAND
PICHIT.J@MEA.OR.TH
SUMMARY
In MEA’s distribution system, customer substations typically have one incoming-line
which is tapped on an open-loop transmission line according to normal conditions at that
SUMMARYtime. Nowadays, an environment of MEA’s distribution area has changed such as severe
traffic jam, a high number of high constructions, and a high number of high advertising
boards resulting in higher chance of overhead-transmission-line faults than before. For
In MEA’s
distribution system, customer substations typically have one incoming-line
switching operations, MEA also has installed three remote-controlled switches at any tap
which is tapped
on
an open-loop
according
normal
conditions
at athat
point for quickly
switchingtransmission
in some urgentline
situations
such astoa faulty
preferred
line has
time. Nowadays,
an environment
of MEA’s
area has
changedload
such
as severe
location-known
fault. So MEA
is able distribution
to remotely transfer
customer’s
to another
emergency
line
within
a
short
time
by
a
dispatching
center.
However,
some
faults
happen
traffic jam, a high number of high constructions, and a high number of high advertising
with aninindistinct
has to take time to find and clearfaults
them before
switching For
chanceMEA
of overhead-transmission-line
than before.
boards resulting
higher location,
causing long outage duration especially during severe traffic jam. A lot of solutions to detect a
switching operations,
MEA also has installed three remote-controlled switches at any tap
fault’s location from a line-tap point of view are tried out but they are not long-term solutions
point for quickly
switching
in some
situations
such
as a faulty
has a
due to several
constraints
such urgent
as FCI (Faulted
Circuit
Indicator)
often is preferred
malfunctionline
in high
location-known
fault.
So
MEA
is
able
to
remotely
transfer
customer’s
load
to
another
temperature or long-sight CCTVs are not able to detect some faults locations.
Consequently,
Authority
has to some
create afaults
projecthappen
to
emergency line within
a short Metropolitan
time by a Electricity
dispatching
center.(MEA)
However,
build
a
switching-unit
substation
for
any
large
customer
who
has
a
substation
with
one
with an indistinct location, MEA has to take time to find and clear them before switching
incoming line from MEA for increasing customer’s reliability and also MEA’s reliability. The
causing longlarge
outage
duration especially during severe traffic jam. A lot of solutions to detect a
customers need electric reliability due to their lifeline depends on their productions
fault’s location
fromare
a line-tap
point
are large
triedcustomers
out but they
arethe
notproject
long-term
solutions
whether
on schedule
or of
not.view
Several
joining
also support
due to several
constraints
such
FCI (Faulted
Circuit
Indicator)substation
often is due
malfunction
in high
building
area and
someasbudget
for building
a switching-unit
to them realize
benefits
of a switching-unit
switching-unit
substation
actually is a smalltemperature or
long-sight
CCTVs are substation.
not able toThe
detect
some faults
locations.
unmanned switching
substation
which hasAuthority
two incoming
lines and
Consequently,
Metropolitan
Electricity
(MEA)
has one/two/three
to create aoutgoing
project to
lines for customer substations. For faster switching operation, the switching-unit substation
build a switching-unit
substation
anyandlarge
customer
who
hasallowing
a substation
with one
have to has proper
protectivefor
relays
a substation
control
system
MEA’s SCADA
incoming line
from
MEA
for
increasing
customer’s
reliability
and
also
MEA’s
reliability.
is able to control and monitor especially in an urgent situation. However, number ofThe
switching-unit
substations
is originally
on a design
of depends
MEA’s SCADA
resulting
in a
large customers
need electric
reliability
due not
to their
lifeline
on their
productions
number
of
spared
SCADA
channels
is
not
enough
for
all
switching-unit
substations
today.
whether are on schedule or not. Several large customers joining the project also support
solution has been created and will be described
building areaThus,
anda some
budget for building a switching-unit substation due to them realize
The paper will present useful techniques to implement a composite substations control
benefits of asystem
switching-unit
substation.
The switching-unit
substation
is a smallamong substations
with IEC61850
over WAN for
controllingactually
the switching-unit
unmanned switching
which
hasThetwo
incoming
andhow
one/two/three
outgoing
substations substation
during a fault
occurs.
paper
will alsolines
describe
to apply IEC61850
lines for customer
substations.
For faster
operation,
switching-unit
substation
messaging
to create a high-speed
lineswitching
transfer function
betweenthe
substations
for automatic
load
PICHIT.J@MEA.OR.TH
transfer protective
function resulting
higher
availability. control system allowing MEA’s SCADA
have to has proper
relaysin and
a substation
is able to control and monitor especially in an urgent situation. However, number of
KEYWORDS
switching-unit substations is originally not on a design of MEA’s SCADA resulting in a
number of spared
SCADA
channels
is notSubstation,
enough for
all switching-unit
substations
Customer
Substation,
Switching-unit
Reliability,
Number of Spared
SCADA today.
Channels,
Composite
Substations
System, IEC61850
Thus, a solution
has been
created
and willControl
be described
The paper will present useful techniques to implement a composite substations control
system among substations with IEC61850 over WAN for controlling the switching-unit
236
substations during a fault occurs. The paper will
also describe how to apply IEC61850
PICHIT.J@MEA.OR.TH
1. MEA’s Distribution System
Metropolitan Electricity Authority (MEA) is a power distribution utility in Thailand
responsible for distribution of electric power to the customers in Bangkok and two
neighboring provinces (Nonthaburi and Samutprakarn). MEA receives power from Electricity
Generating Authority of Thailand (EGAT) at 230 kV, 115 kV, and 69 kV buses of 17 terminal
stations. The voltages are reduced to 24 kV or 12 kV at distribution substations and
distributed to medium-voltage customers and distribution transformers. The low-voltage
customers receive power from distribution transformers at 400/230 v. In 2014, the electric
energy of 50,060.23 GWh was supplied by 150 distribution substations through 1,749.73
circuit-kilometers high-voltage sub-transmission lines and 17,854.01 circuit-kilometers
medium-voltage feeders.
2. Customer Substations
In MEA’s distribution system, high voltage customer’s substation typically has one
incoming-line which is tapped on an open-loop transmission line according to normal
condition as shownin Figure 1.
Figure 1. Typical Customer Substation on MEA’s Distribution System
But the increasing of high rise building and others infrastructure also increase the risk
of overhead-transmission-line faults, for example Figure 2 shows the interruption due to
billboard canvas fell on high voltage line. For switching operations, MEA installs three
remote-controlled switches at tap point for quickly switching in some urgent situations such
as fault on preferred line. So MEA is able to remotely transfer customer’s load to another
emergency line within a short time from dispatching center. However, some faults occurred
with an indistinct location, MEA has to take time to find and clear them before switching
causing long outage duration especially during severe traffic jam. A lot of solutions to detect a
fault’s location from a line-tap point of view are tried out but they are not long-term solutions
due to several constraints such as FCI (Faulted Circuit Indicator) or long-sight CCTVs are not
able to detect some faults locations.
237
2
Figure 2. An Advertising Board Causing a Fault on a Sub-transmission Line
3. Switching-unit Substation
Metropolitan Electricity Authority (MEA) has redesign transmission line for customer
tapped point by installing a switching-unit substation to increasing customer’s reliability and
also MEA’s reliability. For high voltage customers, which is mostly industrial on business
complex, reliability of supply is crucial to their daily operation. Some of these customer
participate in the project by providing land / space for switching unit substation installation.
Moreover, MEA also lays underground cable to customer substations for maximizing
reliability of an outgoing line of the switching-unit substation.
Figure 3. Connections of Switching-unit Substation and Customer Substations
238
3
The switching-unit substation actually is a small-unmanned switching substation
which has two incoming lines and one/two/three outgoing line for customer substations
shown in Figure 3. For faster switching operation, the switching-unit substation have to has
proper protective relays and a substation control system allowing MEA’s SCADA to control
and monitor especially in an abnormal situation. In addition, each transmission line between
terminal substation will have maximum 8 substations (switching-unit substation and typical
substation) based on load calculation for limiting functional complexity.
4. Substation Control System for Switching-unit Substations
Number of switching-unit substations is originally not included during the design of
MEA’s SCADA system, consequently causing inadequate communication channel for all
switching unit substation. Moreover, cost of a SCADA channels is quite high (about 1M
Baht), so MEA has to design SCS (Substation Control System) for Switching-unit Substation
to meet the best cost efficiency. MEA will use a dedicated SCADA channel for a customer
substation which belongs to the government. For private customer substations will use a
shared SCADA channel with a nearby MEA’s substation for saving cost, but control functions
of the switching-unit substation and other sharing substations cannot be performed at a same
time increasing chance of switching delay. Due to Switching-unit substations may have
several design caused by customer budget and level of importance. For fulfilling all possible
requirements, the SCS has to support an IEC61850-MMS-client function for connecting to
IEC61850 protective relays for retrieving data (measurements and alarms) inside protective
relays. However, for non-IEC61850 protective relays, the SCS will use hard-wires for
connecting to the protective relays for getting protection alarms making use of Modbus
meters for measurements. The SCS also monitors and controls switching equipments via
hard-wiring. Significantly, the SCS has to have an IEC61850-MMS server function with
enough reports to meet number of IEC61850 clients at nearby substation which acts as a
gateway to SCADA shown in Figure 4.
Figure 4. System Configuration of SCS for a Switching-unit Substation
239
4
One of the example is a switching-unit substation in Ladkrabang Industrial Estate,
This switching substation send data to CCUs (Central Control Unit) of Ladkrabang
Substation. So HMI of the Ladkrabang substation can monitor and control the switching-unit
substation along with Dispatching Center shown as Figure 5.
Figure 5. Switching-unit Screen on nearby-substation’s HMI by IEC61850 MMS
Due to our SCADA uses two single-point indication representing status of switching
devices, but IEC61850 HMI normally use double-points indication. For various requirements,
the SCS has to have a mapping function to share physical I/O for different IEC61850 logicalnode (LN) objects shown as Figure 6.
Figure 6. Several LNs use same physical I/Os
5. Intersubstation Line Transfer Function
An intersubstation line transfer function (ILTF) is one of automatic line transfer
function that designed for increasing reliability of inline substations including switching-unit
240
5
substations. The ILTF works on data from several concerned substations so a data
communication system is needed for implementing.
Figure 7. Configuration of the ILTF by IEC61850
Substation automation using IEC61850 (IEC61850 SA) now is more widely
implemented in many power utilities around the world. Currently, communication architecture
of IEC61850 SA is based on Ethernet and TCP/IP technology. Thus, the IEC61850 SA can
communicate to other substation to perform the ILTF function. Due to an ILTF requirement
of fast response time, a GOOSE (Generic Object Oriented Substation Event) messaging is
needed. The GOOSE messaging works in a data-link level so it needs to make a large local
network of several substations by F/O to Ethernet modems for supporting the GOOSE
messaging shown as Figure 7. However, the large local network has weak points from several
network effects such as a traffic flooding and security issues, so a network administrator has
to configure managed switches to reduce the effects as less as possible. Furthermore, the ILTF
by IEC61850 SA also needs an IED that has a big logic-gate capacity. Thus, the ILTF by
IEC61850 has to be designed carefully.
Figure 8. Line Transfer for Open-loop Substation and Faulty Line of the Terminal Station 1
For an example of ILTF operation shown as Figure 8, once an undervoltage relay
detects undervoltage occurring on the terminal-substation of the inline substation for 0.2
241
6
seconds and no pickup of any distance relay that ensures there is fault between the terminal
station 1 and the inline substation. After that the ILTF will open the faulty incoming-line CB
that receives an electric power from the terminal station 1 then the ILTF will close the bus
coupler CB of the open-loop substation for delivering a electric power from the terminal
station 2 to the inline substation.
6. Conclusion
Business-oriented management of a distribution process has been greatly enhanced.
Reliability based network is essentially required for customer satisfaction. Proposed
techniques and application of the switching-unit substation can increase reliability of power
distribution system and ultimately prevent outage due to fault in transmission line which will
affect a large number of customer. The project also can get rid of a weak point of line-tapping
customer substations. This paper presents the ILTF to increase reliability of switching-unit
substations. The ILTF also is able to decrease a wide area outage of load of whole switchingunit substations from 5-10 minutes to 0.2-0.3 seconds
BIBLIOGRAPHY
Pichit Jintagosonwit received the B.S. and M.S. degrees in computer engineering in 1982 and 1984
from Prince of Songkla University and King Mongkut’s University of Technology respectively. From
1984 to 1994, he worked for Mitsubishi Motor Corporation, and his last position was a System
Engineer. Since 1994, he has been working as a Senior System Engineer at Metropolitan Electricity
Authority. His research interests include automation system and reliability set applications to power
system control and security.
242
7
Overhead Lines
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGREAORCAORC
TechnicalTechnical
Meeting 2016 –Meeting
International
Conference
Global Trends in the
Development
on
CIGRE2016
andonInternational
Conference
of
Power
Transmission
&
Distribution
Systems
including
Smart
Grid,
24-26
Feb.
2016,
New
Delhi, India
“Global Trends in the Development of Power T&DSystem including Smart Grid”
on
“Global Trends in the Development of Power T&DSystem including Smart Grid”
STUDY OF PERFORMANCE OF COMPOSITE INSULATORS REMOVED FROM
DIFFERENT CONTAMINATED SITES
STUDY OF PERFORMANCE OF COMPOSITE INSULATORS REMOVED FROM
DIFFERENT CONTAMINATED SITES
B.Sravanthi*, B.Yashodhara**, K.A.Aravind**, Pradeep M Nirgude**,
V.Kamaraju***, A.V.R.S.Sarma*
*
**
**
Dept of*EEE,
OsmaniaUniversity,
Central **
Power
Research
Institute,**,
,
B.Yashodhara
,
K.A.Aravind
, Pradeep
M Nirgude
B.Sravanthi
***
Mahaveer Institute of
INDIA
***Science and Technology,
*
*
V.Kamaraju , A.V.R.S.Sarma
Dept of EEE, OsmaniaUniversity, **Central Power Research Institute,
***
Mahaveer Institute of Science and Technology, INDIA
SUMMARY
Insulator pollution is the major cause of several interruptions in the electrical network.
Various contaminants affect the behaviour of the composite insulators. This paper presents
investigations on the performance of 25kV composite insulatorsafter 4-5 years of field
SUMMARY
exposure. For this study insulators are collected from different contaminated areas of the
south central
railway lines
These samples
include the
composite
insulators
Insulator
pollution
is the(Indian
majorRailways).
cause of several
interruptions
in the
electrical
network.
exposed to contaminants of cement, marine and coal pollution. The effects of these polluted
Various contaminants affect the behaviour of the composite insulators. This paper presents
deposits on the surface of field aged composite insulators were studied.The pollution severity
investigations
of 25kV
composite
insulatorsafter
years tests
of field
of these on
sitesthe
wereperformance
observed by ESDD
and NSDD
methods.
Electrical and 4-5
mechanical
exposure.
For
this
study
insulators
are
collected
from
different
contaminated
areas
of the
were carried out to assess the behaviour of contaminated samples. Results of the study
south central
lines degradation
(Indian Railways).
These
samples include
the
. composite insulators
indicaterailway
that no major
observed on
the contaminated
samples
exposed to contaminants of cement, marine and coal pollution. The effects of these polluted
deposits on the surface of field aged composite insulators were studied.The pollution severity
of these sites were observed by ESDD and NSDD methods. Electrical and mechanical tests
were carried out to assess the behaviour of contaminated samples. Results of the study
indicate that no major degradation observed on the contaminated samples.
KEYWORDS
Composite Insulators, Electrical test, Mechanical tests, Pollution,ESDD,NSDD,
Contaminants, degradation.
KEYWORDS
Composite
Insulators, Electrical test, Mechanical tests, Pollution,ESDD,NSDD,
sravanthi.boinala@gmail.com
Contaminants, degradation.
245
1. INTRODUCTION:
Contamination flashover of insulator is the one of the major problems for power
transmission and affects the reliability of energy transportation. The use of composite
insulators has increased significantly over the years because of their superior performance due
to hydrophobic property under contaminated conditions. The other advantages of composite
insulators include lower weight, higher mechanical strength, reduced maintenance and high
resistance to vandalism.
Indian Railways has replaced most of the porcelain insulators with the composite
insulators.Nearly 28% of the Indian Railway lines reported the failure of porcelain insulators
subjected to heavy pollution and vandalism. Since the population of composite insulators
have increased in recent years, a performance check is necessary for further improvement in
design characteristics to meet the future pollution scenario [1].
The continuous service and ageing of insulator may lead to significant deterioration in
their pollution withstand characteristics and may result in flashover of insulators. The
properties of composite insulators tend to change with time because of long time exposure to
environmental stresses, mechanical loads and electrical discharges in the form of arcing or
corona [2]. Such a reduction in the electrical and mechanical properties is termed as ageing.
The composite insulators tend to lose one of their most important properties of
hydrophobicity when they are continuously subjected to extreme levels of contamination
along with other stresses. Hence periodic assessment of these insulators may need to be
performed in order to check their withstand capability.
This paper is mainly focused on study of performance of composite insulators removed
from service. The 25 kV composite insulators under service are selected from South Central
Railway (SCR) region of India. The insulators are selected from critical points of SCR region
which are affected by contaminants like coal, cement, marine etc. The insulators being tested
are removed from the SCR lines as a representative of aged insulator family of a particular
line. The lines chosen for study are Manugur-Badrachalam railway line with coal deposited
insulators, Thandur railway line with cement deposited insulators and Samarlakota railway
line with marine polluted insulators etc., and the samples are of 4 to 6 years aged in service.
The pollution severity level of these sites is calculated through Equivalent Salt Deposit
Density (ESDD) and Non-Soluble Deposit Density (NSDD) and the severity levels of the
sites are classified into medium for coal deposited insulators, high and very high for cement
deposited insulators and high for marine polluted insulators. A procedure for performance
study is adopted in such a way that the composite insulator is tested both electrically and
mechanically to meet railway requirements. The electrical tests performed on these aged
composite insulators are visual inspection, state of hydrophobicity, lightning impulse voltage
withstand, lightning impulse voltage flashover, dry power frequency withstand, wet power
frequency withstand and clean fog test observed with leakage current variation. The insulators
are subjected to specified mechanical load (SML) test. A relative performance of similar
composite insulators having same arcing distance and creepage distance when subjected to
various contaminants in site are studied and compared with the virgin sample. The results of
the performance study are presented in this paper.
2. VISUAL OBSERVATION:
The visual appearance of the insulator is assessed, and the characteristics of samples are
given in Table 1. This inspection reveals that there were no signs of tracking and erosion on
the surface housing of the insulators. Traces of electrical activities were observed on the
insulators. Contaminants were deposited on the top and bottom surface and end fittings of the
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samples. When compared with virgin sample, the colour of the aged contaminated sample is
changed.Figure 1 shows the picture of insulatorsafter 4-5 years in service.
Table 1Characteristics of the test insulators
S2-Coal
S3S5-Vigin
Cement
Sample
Voltage (KV)
25
25
25
ArcingDistance(mm)
380
385
380
CreepageDistance(mm)
1180
1093
1224
Sample
(a) S2
S6Marine
25
375
1150
(b) S3
(c) S5
(d) S6
Figure 1-Visual observation of samplesafter5-6 years in service
3. DETERMINATION OF POLLUTION SEVERITY
The surface contaminants on insulators are composed of both water soluble and nonsoluble materials. The soluble component consists of various types of salinity expressed as
equivalent salt deposit density (ESDD) and non-soluble part of the pollutant expressed as
non-soluble deposit density (NSDD). The ESDD and NSDD were measured according to
IEC60507 and the range of pollution is classified as light, medium, high & very high as per
IEC 60815 [3, 4].
3.1.ESDD:
ESDD is the quantity of NaCl in water which would give same volume conductivity as
that of actual deposit dissolved in the same quantity of water. Table2 shows the result of
ESDD measurement [3, 4, 5] –
ESDD = (SA*V)/A mg/cm2
Where SA = (5.7*σ20)1.03
σ20=Volume Conductivity of Polluted water at 20°C
V =volume of distilled water
A = area of washed surface of insulator
SampleID
S2
S3
S6
Table 2 ESDD Measurement
Contamination
ESDD(mg/cm2)
ESDD(mg/cm2)
Larger Shed
Smaller Shed
Coal
0.045
0.557
Cement
0.205
0.217
Marine
0.069
0.102
Pollution Range
Medium
High
High
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2
3.2.NSDD:
This method is the developed form of ESDD method, in which non-soluble pollution
content in available samples is measured. Table3 shows the result of NSDD
Measurement.The Non-Soluble Deposit Density is measured by the following procedure
[3,4]:
NSDD = Wf – Wi/A mg/ cm2
Where
Wfis the weight of pollutant with filter paper under dry conditions in milligrams
Wiis the weight of filter paper under dry condition in milligrams
A is the surface area of the insulator in cm2
SampleID
S2
S3
S6
Table 3 NSDD Measurement
Contamination
NSDD(mg/cm2)
NSDD(mg/cm2)
Larger Shed
Smaller Shed
Coal
0.000303
0.005686
Cement
0.002685
0.005036
Marine
0.00276
0.00575
Pollution Range
Light
Light
Light
4. HYDROPHOBICITY MEASUREMENT
The degree of hydrophobicity, for the different contaminated insulator surfaces is
measured in accordance with the STRI guide[6]. This guide classifies the hydrophobicity of
surfaces to seven categories, HC1 to HC7. The HC1 refers to the highest surface
hydrophobicity while HC7 represents the lowest hydrophobicity[6].
Distilled water was sprayed several times on the surface of the insulator. Figure2 shows
picture of contaminated silicone rubber insulator samples. Comparing the figures with STRI
guide figures for hydrophobicity, concludes that the hydrophobicity of the samples after
removal from service is ranging between HC1 to HC4 shown in Table 4.It was observed that
the polluted areas showed better hydrophobicity even after six years of service. It indicates
excellent hydrophobicity transfer to the pollution layer which is a positive affect that can
reduce the leakage characteristics of the contaminated sample [7, 8].
(a). S2-HC3
(b).S3-HC4
(c). S6-HC3
Figure 2 Hydrophobicity picture of in service samples
Table 4 Hydrophobicity Class of in service samples
Sample
Hydrophobicity Class
S2-Coal
HC3
S3-Cement
HC4
S6-Marine
HC3
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5. MECHANICAL TEST
This test is carried out on all the contaminated samples of 3 regions. The load shall be
applied to the insulators in line with its axis as per Indian Railway Technical Specifications
[9, 10] for 25kV composite insulators. 70 KN of the load is applied to these samples. It shall
be maintained at this value for one minute and no separation or breakage of metal fittings or
total insulator should occur. Figure 3 represents the mechanical test of the samples and all the
three aged contaminated samples have withstood the test.
Figure 3 Mechanical Test
6. ELECTRICAL TESTS
Electrical tests are performed in order to assess the capability of external electrical
insulation to withstand the contamination. Tests are carried out according to IEC61109
[10].The different tests include:
6.1.Dry and Wet power frequency withstand voltage test:
The specified power frequency voltage of 100 kVrms [9] is applied to all the
contaminated samples for minute. All the samples with stood this short duration voltage both
in dry and wet conditions.
6.2.50% Lightning Impulse Flashover Voltage Test:
The test is performed with sample mounted in normal suspension mode. For this test the
up-down method is followed as specified in IEC 60060-1 standard [11]. Table 6 gives the
50% LI impulse flashover values.The 50% ligthning impulse flashover voltage for marine
contaminated sample is found to be less comparatively for positive polarity while that for
cement contaminated sample is found to be less comparatively for negative polarity.
Table 5 50% Dry Lightning Impulse Flashover values
50% Dry LI Impulse Flashover
Voltage kVp
Sample ID
Positive
Negative
S2-Coal
247
291
S3-Cement
238
287
S5-Virgin
266
322
S6-Marine
229
306
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6.3.CleanFog Test
The test is performed as per the standard IEC 60507 in an artificial test chamber and the
leakage current is continuously recorded. The recorded leakage current shows the level of
contamination severity and test results are compared [8].
6.3.1Experimental test setup and test procedure:
The experimental test set up with test sample is shown in figure 4. Insulator is suspended
vertically inside the chamber. A plastic tent, surrounding the test object is used to limit the
volume of the test chamber. The test voltage applied is 25 kVrms. The leakage current was
measured through a digital ammeter. The continuous steam of de-ionized water is used to
generatefog in chamber. The samples are exposed to steam generation and leakage current
values are recorded. The magnitude of leakage current through the test samples is
continuously monitored and the value is recorded for a total period of 90minutes [12].
Figure 4 Test setup for clean fog test
6.3.2. Clean FogResults:
Three regions were chosen to observe the different contaminated site conditions along the
25kV railway lines of south central region, India.
A. Region 1(Coal Pollution): The figure 5 gives the leakage current level of 6 years
aged coal contaminated sample. The maximum leakage current measured for this
sample is 60 µA.
Figure 5 Leakage current in insulator of coal
deposit
Figure 6 Leakage current in insulator of
cement deposit
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5
B. Region 2(Cement Pollution): The figure 6 represents the leakage current level of 4
years aged cement contaminated sample.The maximum leakage current measured for
this sample is 66 µA.
C. Region 3(Marine Pollution): The figure 7 represents the leakage current level of 4
years aged marine contaminated sample. The maximum leakage current measured for
this sample is 1.3 mA.
Figure 7 Leakage current in insulatorwith marine deposits
Figure 8 represents the leakage current of all samples. The leakage current of
contaminated samples is compared with virgin sample. It is observed that the insulator
exposed to marine pollution has more leakage current.
7. CONCLUSION:
Figure8 Leakage Current of all Samples
Comparing the performance and behaviour of 4-6 years aged composite insulators under
the different contaminated regions, the observations are –



The electrical tests performed on the all contaminated samples are found to be
satisfactory as per railway specifications.
Mechanical tensile performance of all the aged samples is also found to be
satisfactory as per specifications.
The testing experience along with the measurement of hydrophobicity and
pollution severity proves that pollution performance of silicone rubber insulators is
adequate. The results obtained demonstrate that the hydrophobicity of composite
insulator was found to decrease with service which is a sign of ageing.
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6


The leakage current during clean fog test of coal and cement polluted insulators
does not show much change in comparison to the virgin sample, but the leakage
current of marine sample is high.
The composite insulators are affected by marine pollution under tropical Indian
conditions. Further research is to be focused on marine contamination to reduce its
effect on composite insulators.
8. ACKNOWLEDGEMENT:
The authors wish to thank staff & technicians of UHVRL for help in conducting the
experimental work and CPRI management for permitting to publish this paper.
9. BIBLIOGRAPHY:
[1] Report of the Committee of experts to review the insulation requirement of the EHV
transmission lines of various voltages,CEA,ministry of power,( GOI,Nov 2008)
[2] Niroo Research Institute,Majid Rezaei, Iman Ahmadi –Joneidi, Evaluation of Actual field
ageing on Silicone Rubber Insulator under Coastal Environment,( Life Science Journal
2013;10(5s) , pages 200-201)
[3] “Artificial Pollution Tests on High – Voltage Insulators to be used on AC systems”,(IEC
60507, 3rdED 2013).
[4] “Guide for the selection and dimensioning of high-voltage insulators for polluted conditions”,
(IEC 60815, 3rd ED 2001).
[5] M.A.Abouelsaad, M.A.Abouelatta, Environmental Pollution effects on Insulators of Northern
Egypt HV Transmission Lines, (Annual Report Conference on Electrical Insulation and
Dielectric Phenomena, 2013).
[6] Composite Insulator Status program: Field inspection of Composite Line Insulator, STRI
Guide 3 , 2005
[7] Working Group 2.21,481 CIGRE, Assessment of Composite Insulators after removal from
service.
[8] A.Sheik Sidthik ,Evaluation and Prediction of Contamination level in Insulators based on the
Leakage Current Characteristics using Neural Network,( 2015).
[9] “Technical specifications of Indian Railways for Silicone Composite Insulators for 25 kV AC
50 Hz single phase overhead traction lines”, (No. TI/SPC/OHE/INSCOM/, page 21).
[10] “Composite insulators for AC overhead lines with a nominal voltage greater than 1 000 V –
Definitions, test methods and acceptance criteria”, (IEC 61109, 2008).
[11] “High Voltage test techniques – Part 1: General definitions and Test requirements “, (IEC
60060-1, 3rd ED 2010).
[12] Majid Rezei, Evaluation of Actual Field Ageing on Silicone Rubber Insulator under Coastal
Environment, (Life Science Journal 2013)
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1
1
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power
Transmission
Systems
including
Smartand
Grid, International
24-26 Feb. 2016, New
Delhi, India
CIGREAORC& Distribution
Technical
Meeting
2016
Conference
CIGRE- AORC Technical Meeting 2016 and International Conference
on
on
“Global
Trends
in
the
Development
Power
T&D
System
including
Smart
“Global Trends in the Development ofofPower
T&D
System
including
Smart
Grid” Grid”
EGAT
TransmissionEquipment
Equipment Performance
Assessment
System
EGAT
Transmission
Performance
Assessment
System
MR.TANACHAI
TANACHAI LIMPASUWAN
MR.
LIMPASUWAN
“Global
Trends
in
theAuthority
Development
of
T&D
System
including
Smart
Grid” Grid”
Electricity
Generating
of Thailand,
System
Control
and
Operation
Division
“Global
Trends
in
the
Development
of Power
Power
T&D
System
including
Smart
Electricity Generating Authority of
Thailand,
System
Control
and
Operation
Division
THAILAND
THAILAND
SUMMARY
SUMMARY
This paper describes the implementation and the structure of Transmission Equipment
Performance
anddescribes
Availability
which was and
developed
by EGATof(Electricity
Generating
This paper
theSystem,
implementation
the structure
Transmission
Equipment
Authority
of
Thailand)
in-house
programmers.
The
presentation
illustrates
how
the
system
Performance and Availability System, which was developed by EGAT (Electricity Generating
works starting from the operator input to the retrieval of information. Finally, this paper
Authority
of Thailand) in-house programmers. The presentation illustrates how the system
shows the how EGAT utilizes the Transmission Equipment Performance and Availability
works
starting from the operator input to the retrieval of information. Finally, this paper
System to improve power system reliability.
shows the how EGAT utilizes the Transmission Equipment Performance and Availability
System
to improve power system reliability.
KEYWORDS
System performance indices, SAIFI, SAIDI, SISI, Outage cause
KEYWORDS
System performance indices, SAIFI, SAIDI, SISI, Outage cause
Email : tanachai.l@egat.co.th
253
Email : tanachai.l@egat.co.th
2
I.
Introduction
Unquestionably, one of the main concerns of power or transmission utilities is the
reliability of the system. In order to measure the reliability of bulk power system, System
Performance Indices (SPI), such as System Average Interruption Frequency Index (SAIFI),
System Average Interruption Duration Index (SAIDI), System Interruption Severity Index
(SISI), System Average Restoration Index, and Energy not Served (ENS), are widely
employed in many utilities around the world.
Nevertheless, it is obvious that these indices provide just only final results of the
performance. As a result, supplementary information concerning the performance of the
system equipment is needed in order to determine what cause those indices to go up or down.
In other words, a good record keeping system of how transmission assets perform is required
as the performance record of the equipment is very essential for improving the final results or
the mentioned indices. Hence, EGAT Transmission Equipment Performance and Availability
System, or TEPA System, was implemented to record the performance of EGAT’s
transmission equipment in order to improve overall system reliability; also this system can
automatically calculate SPI whenever the equipment performance is updated.
This paper describes how EGAT measures the main transmission grid’s performance
and how EGAT maximized the benefits by utilizing TEPA System. TEPA System is an inhouse-developed web-based software that records transmission equipment outage event
details and generates graphical results of transmission system performance indices, or SPI,
based on the equipment outage records. In addition, the equipment outage details can be used
to analyze system weakness in order to improve system reliability.
II.
A Brief Detail of EGAT Transmission System and Market Structure
EGAT main operating voltages are 500, 230, and 115 kV. In addition, EGAT has a
300 kV voltage HVDC interconnection with Malaysia. The line length and the transformer
capacity of each voltage level are shown Table1. (The data are approximated as of 2015.)
Voltage Level
(kV)
500
230
115
300 HVDC
Transformer Cap
(MVA)
23,200
56,000
14,600
388
Circuit-Km
5,000
14,100
13,800
23
Table 1. Transformer Capacity and Transmission Line Length
Concerning power system control and operation, there are four regional control
centers (see Figure 1); which are central, northern eastern, southern, northern, and
metropolitan control center. These regional control centers operate and control in harmony
with the National Control Center (NCC). Generation dispatching and frequency control are
under NCC responsibility. For the voltage control, NCC dispatches MVar from synchronized
generators where as the regional control centers employ compensation devices such capacitor
banks. For switching operations, NCC is responsible for 500kV system. On the other hand,
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254
3
the regional control centers are responsible for switching in the system below 500 kV within
their responsible areas.
Figure 1. Regional and National Control Centers’ Locations
Electricity market structure in Thailand is Enhanced Single Buyer or ESB (see Figure
2). Under this framework; All generators are required to sell their electricity to EGAT only.
However, there are SPPs or small power producers that are allowed to sell electricity directly
to customers, especially in industrial estates. EGAT sells electricity to the two distribution
companies, and some direct customers. The two main distribution companies are MEA
(Metropolitan Electricity Authority) and PEA (Provincial Electricity Authority). MEA
distributes electricity to customers who reside in Bangkok (the capital city) and its vicinity,
whereas PEA supplies electricity to the rest of Thailand.
Figure 2. Enhanced Single Buyer Market Structure
III.
EGAT Transmission System Reliability Measurement
Basically, EGAT measures the power system performance using some SPIs which are
SAIFI (System Average Interruption Frequency Index), SAIDI (System Average Interruption
Duration Index), SARI (System Average Reforestation Index), SISI (System Interruption
Severity Index), UER (Unsupplied Energy Ratio), and ENS (Energy Not Served).
Nevertheless, EGAT has selected SAIFI, SAIDI, and ENS as the main KPI (Key Performance
Index). For the purpose of KPI, only unplanned outages, which beyond one minute duration,
are counted for the calculation of the indices. The outages’ causes are also recorded for
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255
4
further analysis, the outage causes for transmission lines and substations can be briefly
classified as the followings:
 Adverse environment (such as fire, flood, pollution and contamination);
 Abnormal system condition (such as power swing, overload, and over voltage);
 Defective equipment (such as transmission line or substation equipment itself,
protection equipment, communication equipment, and power control
equipment);
 Human error (such as non-EGAT personnel and EGAT personnel); and
 Animal (such as birds, snakes, insects, monkeys and others);
The weather condition is also included in an outage cause report as for supplementary
information, but it will not be considered as a cause.
In order to improve the performance, good record keeping is required as the basic
needs for further analysis which is to identify the weakness in the system or the priority of
system improvement. EGAT employs TEPA System, which is an in-house-developed webbased software that records transmission equipment outages, for record keeping and reporting
tools that the record and the report can be used as information for outage analysis.
IV.
TEPA System
Before TEPA System was implemented, outages details of transmission equipment
such as transmission lines, transformers, and breakers are kept in form of database using
conventional commercially-available database, namely Microsoft Access. The program had
to be installed on the computers for all regional control divisions, therefore it had to be reinstalled at all regional sites when it was changes or upgraded. In other words, the system
was localized and users could customize, or alter, the formulas and the procedures before
sending the data to centralized database. As a result, the regional data were inconsistent.
Moreover, there were limited options for producing report by Microsoft Access.
In order to improve the data consistency and the versatility in reporting including the
accessibility of the historical outage records, TEPA System was implemented to eliminate the
mentioned drawbacks. TEPA System employs Oracle database system as the main
centralized database. All procedures for indices calculation are performed within Oracle
itself. Hence, the programs are centrally developed and installed. The regional users input
only raw data in according to specified format. Any changes can be made up on mutual
agreement of all regional representatives, then, the procedures can be modified centrally by
specified programmers.
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256
5
Figure 3. Local Data with Centralized Computation and Programming
TEPA System uses Oracle database to keep outage records and to calculate all indices
required. For reporting, Crystal Report as the main third party application because of the
variety of reporting formats. Due to the consistency of data and the variety of reports,
performance indices and outage causes can be analyzed with high confidence. Outage causes
can point out the weakness in the system and pin point which equipment need to be kept in
close attention. The analysis of the outage cause can provide working priority and awareness
of what to be improvement in order to enhance the all overall system performance indices.
EGAT has established Working Groups (WG), such as WG for Reducing Human Error, WG
for Preventing Animal-Caused Outage, and WG for Benchmarking Reliability, which used
data from TEPA System for analyzing and calculating results. The basic outage data are input
to TEPA System by selected regional operators thru TEPA System website. All performance
indices are updated whenever new data arrive or updated. Both monthly and yearly reports
are automatically generated by the system. Other special requested outage reports can be
generated in according to users’ requirements, and the output of the reports are in Exel
format.
Figure 5 shows the form in which to be filled in order to report the outage of
equipment. The requested data for equipment outage are: equipment name; begin outage
time; end of outage time; is there a power outage; duration of the power outage, planned or
unplanned outage; weather condition; outage cause category; and outage cause details.
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Figure 5. Local Outage Data Reporting Form
Figure 6 shows one of the SPI results, in the picture is SISI. Users can select the study
periods, the graphical result is display with PA (Performance Agreement) score so that we can
see how we are performing in according with the annual performance agreement. Other
indices, such as SAIFI, SAIDI and ENS are also presented in this format.
Figure 6. SISI Report
Equipment outage records can be retrieved and reported in Exel format as shown in Figure 7.
258
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7
Figure 7. Outage Report in Excel Format
TEPA System also calculates outage indices for both transmission lines and transformers,
those outage indices are:
 Outage Rate (OR);
 Mean Time Between Outage (MTBO); and
 Mean Outage Duration (MOD).
V.
Conclusion
EGAT has employed TEPA System since 2010 as a replacement for a legacy SPI
database built on Microsoft Access. Since then, the outage data become more stable as the
database system has been improved. Moreover, as the outage data and indices calculation
have been centralized, the data and all calculations have become very consistent and accurate
for all regions. Since TEPA System is accessible on the company intranet, the outage data
become widely available to all divisions. As a result, information in TEPA System has been
used as a reference for many projects concerning the improvement of power system
reliability. The further improvement of TEPA System is to employ the outage data of all
regions to benchmark the transmission equipment maintenance efficiency among the five
operating regions.
VI.
Appendix
This section provides some of the EGAT system performance index definitions.
System Average Interruption Frequency Index (SAIFI)
(𝑇𝑜𝑡𝑎𝑙 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 𝑝𝑜𝑖𝑛𝑡𝑠 𝑖𝑛𝑡𝑒𝑟𝑟𝑢𝑝𝑡𝑒𝑑)
𝑆𝐴𝐼𝐹𝐼 =
(𝑇𝑜𝑡𝑎𝑙 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 𝑝𝑜𝑖𝑛𝑡𝑠)
System Average Interruption Duration Index (SAIDI)
(𝑇𝑜𝑡𝑎𝑙 𝐼𝑛𝑡𝑒𝑟𝑟𝑢𝑝𝑡𝑖𝑜𝑛 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛)
𝑆𝐴𝐼𝐷𝐼 =
(𝑇𝑜𝑡𝑎𝑙 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦 𝑝𝑜𝑖𝑛𝑡𝑠)
System Average Restoration Index (SARI)
(𝑇𝑜𝑡𝑎𝑙 𝐼𝑛𝑡𝑒𝑟𝑟𝑢𝑝𝑡𝑖𝑜𝑛 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛)
𝑆𝐴𝐼𝐷𝐼 =
(𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑡𝑒𝑟𝑟𝑢𝑝𝑡𝑖𝑜𝑛)
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8
System Interruption Severity Index (SISI)
(𝑇𝑜𝑡𝑎𝑙 𝑈𝑛𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑑 𝐸𝑛𝑒𝑟𝑔𝑦 (𝑀𝑊 − min))
𝑆𝐼𝑆𝐼 =
(𝑆𝑦𝑠𝑡𝑒𝑚 𝑃𝑒𝑎𝑘 𝐿𝑜𝑎𝑑 (𝑀𝑊))
Unsupplied Energy Ratio (UER)
(𝑆𝑢𝑚 𝑜𝑓 𝑢𝑛𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑑 𝑒𝑛𝑒𝑟𝑔𝑦)
× 100%
𝑈𝐸𝑅 =
(𝑆𝑎𝑙𝑒𝑠 𝑒𝑛𝑒𝑟𝑔𝑦 + 𝑠𝑢𝑚 𝑜𝑓 𝑢𝑛𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑑 𝑒𝑛𝑒𝑟𝑔𝑦)
Outage rate of transmission line
𝑂𝑅 =
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑖𝑠𝑜𝑛 𝑙𝑖𝑛𝑒 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
(𝐶𝑖𝑟𝑐𝑢𝑖𝑡 𝑙𝑒𝑛𝑔𝑡ℎ)
Mean time between outage of transmission line
𝑀𝑇𝐵𝑂 =
(𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑖𝑛 − 𝑠𝑒𝑟𝑣𝑖𝑐𝑒𝑑 𝑝𝑒𝑟𝑖𝑜𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑐𝑖𝑟𝑐𝑢𝑖𝑡 𝑙𝑒𝑛𝑔𝑡ℎ)
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑠𝑛𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑙𝑖𝑛𝑒 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
Mean outage duration of transmission line
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑙𝑖𝑛𝑒 𝑜𝑢𝑡𝑎𝑔𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛)
𝑀𝑂𝐷 =
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑠𝑛𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑙𝑖𝑛𝑒 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
Outage rate of transformer
𝑂𝑅 =
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
(𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟)
Mean time between outage of transformer
𝑀𝑇𝐵𝑂 =
(𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑖𝑛 − 𝑠𝑒𝑟𝑣𝑖𝑐𝑒𝑑 𝑝𝑒𝑟𝑖𝑜𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟)
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
Mean outage duration of transformer
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 𝑜𝑢𝑡𝑎𝑔𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛)
𝑀𝑂𝐷 =
(𝑇𝑜𝑡𝑎𝑙 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 𝑜𝑢𝑡𝑎𝑔𝑒𝑠)
Email : tanachai.l@egat.co.th
260
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 and International Conference
on
on
“Global Trends
the Development ofof
Power
T&D T&D
SystemSystem
including Smart
Grid” Smart Grid
“Global Trends
in thein Development
Power
including
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
EMERGING SOLUTIONS FOR LINE COMPACTION
EMERGING SOLUTIONS FOR LINE COMPACTION
D. Prasad*, R. Kumaran, G. Agarwal, P.K. Reddy, Md. I. Khan
Supreme & Co. Pvt. Ltd.
(India)
D. Prasad*, R. Kumaran, G. Agarwal, P.K. Reddy, Md. I. Khan
Supreme & Co. Pvt. Ltd.
(India)
SUMMARY
This paper presents various solutions for line compaction. The paper presents four
emerging technologies that support increased power transmission capacity for a given right of
way (RoW) and clearance level. Use of high temperature low sag (HTLS) conductor, which has
relatively low sag at high operating temperatures, is suggested to reduce the height of the tower.
Sag-tension calculations were made at different temperature levels and comparison was made
SUMMARYto indicate how the usage of HTLS can have an impact on line compaction. Insulated crossarms
can restrict the inward and outward swinging of the insulator. Since the insulators are directly
attached to the tower, a metallic crossarm is not required and thereby, the load on tower is
This reduced.
paper Monopole
presentsstructures,
variouswhich
solutions
for small
line footprint
compaction.
The instead
paperof presents four
have a very
are suggested
broader lattice tower.
Monopolesincreased
are more flexible
andtransmission
have improved stability
against
emerging technologies
that support
power
capacity
forwind
a given right of
loads. Testing of monopole structure at different load conditions is also presented. Interphase
way (RoW) and
clearance level. Use of high temperature low sag (HTLS) conductor, which has
spacers are presented as an optional feature to prevent conductor galloping on EHV lines.
relatively low
sag attypes
highof operating
temperatures,
to reduce
the isheight
Different
interphase spacers
are discussed is
in suggested
brief. At the end,
a comparison
made of the tower.
between
conventional
towers
with
a
monopole
type
structure
with
insulated
crossarm.
Sag-tension calculations were made at different temperature levels and comparison was made
to indicate how
the usage of HTLS can have an impact on line compaction. Insulated crossarms
KEYWORDS
can restrict the inward and outward swinging of the insulator. Since the insulators are directly
RoW; Compact; HTLS; Monopole; Insulated crossarm; Interphase spacer.
attached to the
tower, a metallic crossarm is not required and thereby, the load on tower is
reduced. Monopole
structures, which have a very small footprint are suggested instead of
1. Introduction
broader lattice tower.
moreinflexible
and have
improved
stability against wind
There Monopoles
is a continuousare
increase
electric power
demand
due to technological
advancement
and risingstructure
living standards.
This increase
in power
demand has
in an over
loads. Testing
of monopole
at different
load
conditions
isresulted
also presented.
Interphase
utilization of the transmission system. Growth in industrialization, increasing per- capita
spacers are income
presented
as an optional feature to prevent conductor galloping on EHV lines.
and rapid urbanization has led to a ~50% growth in the installed power generation
Different types
of interphase
spacers
are discussed
in brief.
theonly
end,
a comparison is made
capacity
over the last 5 years.
However,
transmission capacity
has At
grown
by ~30%.
between conventional towers with a monopole type structure with insulated crossarm.
* engineeringteam@supreme.in, dharmbirprasad@yahoo.com
KEYWORDS
RoW; Compact; HTLS; Monopole; Insulated crossarm; Interphase spacer.
1. Introduction
261
There is a continuous increase in electric power demand due to technological
advancement and rising living standards. This increase in power demand has resulted in an over
New generating stations using conventional fuels such as coal, gas etc. and large scale
renewable plants are being developed to meet the power demand. To accommodate the growing
demand and generation, it is imperative to either upgrade their existing transmission
infrastructure or provide new corridors for power transmission. To develop such networks
several aspects like RoW, environmental issues, cost of development must be taken into
account. Of all the issues, the most important impediment is securing RoW. High land prices
and difficulties in getting permission from landowners have enforced the power sector to
explore an alternative solution to improve the power transmission capacity. These constraints
can be overcome with the new and innovative design concepts which led to the compact of
transmission line (CTL) formation.
2. Description of CTL and its’ components
The basic concept of power transmission using CTL is same as that of a conventional
transmission line i.e., to transmit power at higher voltage level to reduce losses during
transmission. The most important hurdle in transmitting power at higher voltage is providing
the required electrical clearance along the line. This is because as the transmission line voltage
increases, the required clearance level also increases [1]. This increase results in a larger RoW
requirement which can be minimized with the help of compact transmission line.
Line compaction is the reduction of tower dimension such that it leads to the reduction
of RoW requirement compared to a conventional tower of same voltage level. The design of
structure, conductor materials and hardware accessories has evolved in CTL to reduce RoW
requirement [2]. It uses basic components that are designed with the goal of line compaction. It
may include certain concepts like usage of composite post insulators as crossarm to restrict the
conductor swinging, interphase spacers to avoid conductor galloping, use of high performance
conductor and monopoles with less footprint [3]. The most important aspect of compact
transmission line is to design a structure which is compact, at an acceptable cost without
compromising reliability and safety standards. Four components which contributes for line
compaction is discussed in the following sections.
2.1. HTLS conductor
HTLS conductors are gaining more attention in
the field of transmission over the past few years. It
allows the thermal rating of the line has to be increased
[4]. Many of the HTLS conductors are made of strands
that are non-cylindrical (i.e., trapezoidal) as portrayed in
Fig. 1, which enables them to incorporate more
Aluminium thereby allowing the conductor to carry
more amount of current. HTLS conductor, not only carry
a large amount of current, they carry it at a sag very less
when compared with a conventional conductor. Another
unique feature of HTLS is that their core is made of glass
Fig. 1 Cross sectional view of
fibre composite material rather than steel as in
ACSR and HTLS conductor.
conventional conductor. Steel in ACSR conductors has
high coefficient of linear expansion which makes them to sag more at higher temperature. But
the composite core of HTLS does not expand easily and hence offers a less amount of sag when
compared with an equivalent ACSR conductor.
262
1
2.1.1. Sag performance of ACSR and HTLS
Sag calculation will be the primary asset that need to be determined while designing a
transmission line. It is one of the most important factor which determines the height of the
tower. The catenary of a transmission line is usually considered to be a parabola and the sag
with respect to particular tensioning of the conductor is determined using Eq. (1).
S = WL2/8T
(1)
where
𝑆 : Sag of the conductor,
𝑊 : Weight of the total conductor load,
𝐿 : Span of the conductor and
𝑇 : Working tension in the conductor.
Sag of the conductor depends upon the coefficient of linear expansion of the conductor
and modulus of elasticity [5]. These two parameters determine the conductor expansion and
allowable tension. Usually, worst case scenario (i.e., the maximum operating temperature) of
the conductor under no wind condition is considered for determining the height of the
conductor. It is under this condition the conductor tends to have maximum sag.
Sag (m)
To verify the sag performance of ACSR and HTLS conductor, sag was calculated for
various operating temperature. For this purpose, an ACSR ‘Moose’ which is traditionally used
in 400 kV line is compared with a HTLS of same diameter. Calculation is made for a span of
400 m with an average wind speed of 45 m/sec and terrain category of 2. ACSR ‘Moose’ has a
maximum operating temperature of 850C whereas HTLS can be operated even about 2000C.
15
13
11
9
20
HTLS
70
120
ACSR
170
Temperature ( 0 C)
Fig. 2 Comparison of sag between ACSR and HTLS.
When ACSR is subjected to its maximum temperature, the conductor sags are calculated
to be 13.6 m. At the same temperature, HTLS sags only about 10.8 m and thereby give us
reduction of tower height by almost 2.8 m (as presented in Fig. 2). Replacement of ACSR by
HTLS gives us a reduction of almost 20 % of the overall height of the tower.
2.2. Insulated crossarm
The freedom of movement provided to the insulator string determines the clearance that
should be provided for the line. Clearance should be given to both inward and outward
movement of the insulator. Instead of attaching the insulator from metallic crossarm, if we
attach them directly to the tower, it is possible to restrict the insulator swinging and thereby the
required electrical clearance. This concept is known as insulated crossarm which was started
way back from 1960s [6]. Another factor that must be considered while designing a
263
2
transmission tower is the length of the insulator string. As the voltage rating increase, the
insulator chain length also increases. But in the case of insulated crossarm, the insulators are
strung in horizontal manner which greatly reduces the height of the tower. But for attaching
insulators horizontally, they must have high bending strength and high ultimate strain [7].
Composite insulators made of silicone rubber are employed for this purpose. Insulated crossarm
consists of a brace made of long rod composite insulator which works under tension and a post
insulator that mostly works under compression caused by the horizontal load such as wind [8].
The vertical load such as the conductor (and ice load if present) are taken up by the brace.
Precaution must be taken so that the brace of the insulated crossarm is never been subjected to
a compression which will result in the contact of metallic fittings and thereby leading to radio
interference voltage (RIV) disturbances.
Fig. 3 Insulated crossarm configurations.
The way in which insulated crossarms are connected to the tower is of great importance.
In case of rigid connection (as shown in Fig. 3), the insulator must withstand the forces that
occurs in the line direction. But in the case of pivoted connection, the insulators are free to
rotate which enables them withstand the unequal tensile forces occurring in the adjacent span.
During the early stage of development, it was not possible for the manufacturers to develop
core of larger diameter. Hence hollow core composite insulators were used which were made
of glass fibre and reinforced by epoxy tubes. With advancement in manufacturing process of
composite insulators, post insulators with larger diameter and compression load are developed.
Now-a-days, insulated crossarm with non-cylindrical shapes are also developed so that the post
is capable of withstanding the very high compression load.
2.3. Monopole type structure
Pole type structures are most widely used in the distribution system because of their less
footprint in the congested urban areas. But now-a-days, pole type structures are also
implemented in transmission system to reduce the RoW requirement. Monopoles are tubular
structures with uniform taper throughout the length. Usually monopoles consist of 3 to 4
sections which are joined using slip or flange joints [9]. Due to its low aerodynamic coefficient,
the wind loads are lesser when compared with a lattice tower. Monopoles are made of High
tensile steel confirming to IS 2062. Monopoles are more flexible when compared with a
traditional lattice tower which enables them to permit larger deflections. Thus in case of broken
wire condition, the uneven tension in the adjacent span is easily reduced by the deflection of
the pole. The type of foundation used for monopoles depends upon the overturning moment in
the base. For small moment, shallow foundation is considered whereas if the overturning
moment is high, pile foundation tends to be economical. Fig. 4 depicts a comparison between
264
3
a conventional 132 kV lattice tower and a monopole structure with insulated crossarm. ACSR
is considered for the lattice tower whereas HTLS is taken for the monopole structure.
Monopoles reduces the RoW requirement whereas both HTLS and insulated crossarm reduces
the height of the pole.
Fig. 4 Comparison between Lattice Tower and Monopole structure.
Type of structure
Lattice tower
Monopole
Design span
335 m
160 m
Description
"S" type
"M" type
Overall height
28 m
16 m
Base width
9.8 m
1.97 m
Table 1 Design features of lattice tower and monopole structure.
265
4
2.4. Interphase spacer
Conductor galloping is a serious issue in case of EHV lines especially in winter season
[10]. EHV lines are of larger spans, which is the main cause for the conductor galloping. In
order to reduce the effect of conductor galloping, it is necessary to use the interphase spacers.
At the early stage of development, interphase spacers are made of porcelain insulators, which
were heavy and were increasing the tension on the conductor. These porcelain insulators were
then replaced by lightweight composite insulator [11]. Another desirable feature of interphase
spacer is that it maintains the phase to
phase clearance all along the line.
Interphase spacers are mostly
subjected to compressive load which
sometimes leads to the breakage of
spacers [12]. This was overcome with
the development of integrated
flexible interphase spacer. Interphase
spacers are proposed here as an
optional component for transmission
line. It may not have influence in line
compaction but it has a great impact
in increasing the reliability of the line
Fig. 5 Schematic view of interphase spacer.
especially in the case of EHV lines
installed in cold climatic regions with high wind speed Fig. 5.
3. Analysis and observations
Line compaction requires careful and proper analysis of the line’s mechanical and
electrical properties. Transmission lines are installed with a minimum reliable period of 50
years. There are several factors which are to be considered before designing a compact
transmission line. After proper designing, it is essential to validate those results by conducting
an actual field test. Considering this, we made several numbers of tests to evaluate the
performance of the above mentioned components. Two of those tests and their results are
discussed in the following sections.
3.1. HTLS conductor
HTLS conductors are known for their high operating temperature. HTLS conductors
may operate at a temperature of about 2000C whereas the conventional ACSR conductors use
to operate only around 900C. The high operating temperature may have certain negative impacts
on the hardware fittings associated with it. Hence, hardware fittings were specially designed to
withstand the high operating temperature of the HTLS conductor. In order to evaluate their
performance, they were attached to the HTLS conductor similar to their working situation. The
test arrangements are shown in Fig. 6. Transducers were attached on both the fittings and
conductor to measure the temperature variations. Current injector was used to supply the current
necessary for increasing the temperature on the conductor. It was noted that even when the
conductor was reaching its thermal limit, the hardware fittings were only under 400C. This is
possible because the resistance of the fitting assembly is less when compared with the
conductor. Further due to its larger size, it is able to dissipate the heat easily. The temperature
of hardware fittings corresponding to the conductor temperature is showed in the Fig. 7 & Fig.
8.
266
5
Fig. 6 Testing arrangement.
Fig. 7 Variation in temperature at fittings with respect to time.
Temperature (o C)
150
108.5
100
117
127.7
149.2
158.1
158.6
158.9
159.2
34.9
35.6
36.4
36.9
85.2
50
26.3
0
135.5
142.7
0
Joint
30
28.8
10
31.4
32.3
20
Conductor
34
33.2
30
40
50
Time (hours)
Fig. 8 Variation in temperature at joints with respect to change in conductor temperature.
3.2. Monopole type structure
When designing any structure, it is necessary to compute the loadings on the structure.
The vertical, horizontal and transverse load are computed for a 132 kV monopole structure. The
vertical load corresponds to the load offered by the conductor. Transverse loads are due to the
267
6
effect of wind and longitudinal loads are the unbalanced loads that occur during broken wire
condition. Based on the load, the monopole was designed and series of test were made to verify
its performance (Fig. 9). The line parameters of 132 kV double circuit transmission line is
provided in Table 2.
Voltage rating
132 kV
No. of circuits
2
Wind pressure
182 kg/m2
Conductor
ACSR ‘Panther’
Earth wire
(stranding)
7/3.15 (mm2)
Table 2 Line parameters of 132 kV
double circuit transmission line.
Fig. 9 Testing of monopole.
Test was carried on as per IS 802 part III. The monopole was loaded in all three
directions (vertical, longitudinal and transverse). During the entire testing process, the full
transverse load was applied to the monopole.
Primarily, Bolt Reliability test was carried out and it was followed by Safety and
Security tests. In Bolt Reliability test, the vertical load considered during the design process is
applied for 120 seconds to estimate the amount of permanent deformation that incur on the
monopole. Safety Tests were carried out under both normal and broken wire condition. For
normal condition, longitudinal loads were not applied. The vertical load is increased in steps to
its full designed load. Except at full load condition which is maintained for 300 seconds, all the
other loads are maintained for 120 seconds. Under broken wire condition, both vertical and
longitudinal loads are increased simultaneously. For security test only broken wire condition is
considered. The full vertical load is applied on monopole and Longitudinal load is increased in
steps. These tests are again followed by Bolt reliability test to confirm the monopole design.
During Safety test under normal condition, when the load was increased to 90% during safety
test under normal condition, a small crack was noticed on the welding near the top crossarm. A
fresh welding was provided and the test was continued. After this little modification, no crack
or failure was noticed during the entire testing process. The loadings are showed in Fig.10, Fig.
11 & Fig.12.
Condition
Reliability
Safety
Security
Load (%)
Normal
Vertical Longitudinal Transverse
100
100
Normal
50-100
-
100
Broken Wire
50-100
50-100
100
Broken Wire
100
50-100
100
Table 3 Test procedure and loading condition.
268
7
120
100
100
50
60
200
Transverse
400
600
Vertical
800
1000
20
0
200
Vertical
Time (Sec)
100
50
40
0
0
100 100 100 100
90 95
75
80
Load (%)
100 100 100 100
90 95
75
Load (%)
120
100
80
60
40
20
0
400
Transverse
600
800
Longitudinal
1000
Time (Sec)
Fig. 10 Safety test under normal condition. Fig. 11 Safety test under broken wire condition.
120
Load (%)
100
100
80
60
40
100
75
100
90
100
95
100
50
20
0
0
200
Longitudinal
400
600
800
1000
Transverse
Vertical Time (Sec)
Fig. 12 Security test under broken wire condition.
4. Conclusion
Compact transmission line and its need in today’s scenario are discussed in brief.
Features of HTLS and their performance is compared with conventional conductor. Tests were
performed to validate that HTLS conductor are feasible to work on hardware and fitting
accessories that are meant for conventional conductor. Use of monopole is suggested to reduce
the footprint of the transmission line and thereby decrease the RoW requirement. Comparison
is made between a normal lattice tower and a monopole type structure to explain how monopole
is used in compact transmission line. Testing is made to verify the mechanical performance of
the monopole structure. Concept of insulated crossarm, different configuration and its impact
on line compaction is also explained. Further, use of interphase spacers is suggested to prevent
conductor galloping in EHV lines especially installed in cold climatic regions.
BIBLIOGRAPHY
[1] A.D.Singh “Power transmission: The real bottleneck”, FICCI, September, 2013.
[2] S. Maruvada, V. Chartier “Compact line experience”, EPRI transmission line reference
book: 115-345 kV compact line design, 2008.
[3] M.L. Sachdeva, V.K. Kanjlia, P.P. Wahi “Manual on transmission lines”, Research
report/ Publication No. 323. CBIP, 2014.
[4] CTC Cable Corporation “High capacity/low sag conductor for power industry”,
Aluminium Conductor Composite Core (ACCC), March, 2011.
[5] K. Kopsidas, S.M. Rowland, M.N.R. Bahrom, I. Cotton “Power transfer capacity
improvement of existing overhead line systems”, The University of Manchester, United
Kingdom.
[6] C. Zachariades, S.M. Rowland, I. Cotton, P.R. Green, C.A. Veerappan, D. Chambers
“A trial installation of high voltage composite cross-arms” XVII International
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269
[7] M. Ammann, P. Dalleves, K.O. Papailiou, M. Leva, S. Villa “A new 400 kV line with
compact towers and composite insulated crossarms”, Session 1998, 22/33/36-06, Cigre,
Paris.
[8] M. Hinteregger, T. Judendorfer, M. Muhr, S. Berlijn, A. Olsen “Voltage withstand tests
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[9] S. Prema, V. Mohan “Damage detection of steel monopole using correlation approach”
International Journal of Research and Innovations in Science and Technology
[10] G. Fu, L. Wang, Z. Guan, L. Hou, X. Meng, M. MacAlpine “Simulations of the
controlling effect of interphase spacers on conductor galloping” IEEE Transactions on
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[11] L. Hou, L. Wang, D. Yan, M. Lu, Z. Guan “Mechanical parameter optimization of
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[12] F. Zi, H. Shuying, Z. Kuntano, Z. Qichang “Effect of interphase composite spacer on
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270
9
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
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
CIGRE- AORC Technical Meeting 2016
– International Conference on Global Trends in the Development

of Power
Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India

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
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Wissarut Yuttachai
Electricity Generating Authority of Thailand (EGAT)
Thailand
Wissarut Yuttachai
Yuttachai 
Wissarut
Electricity Generating Authority of Thailand (EGAT)
Electricity Generating Authority
of Thailand (EGAT)
Thailand
Thailand
SUMMARY
The optical networks have been deployed by several power utilities to support the control and
operation of power system. Particularly in Electricity Generating Authority of Thailand (EGAT), we
have utilized the Synchronous Digital Hierarchy (SDH), based on time division multiplexing (TDM)
technology and it has been proven of its reliability, availability and survivability for almost two
The designed SDH network can offer recovery of communication link within sub-50
SUMMARYdecades.
milliseconds which has been satisfied for power utility backbone communication infrastructure.
Although the trend of communications technology is moving toward to utilize packet network, some
operation application
such adeployed
teleprotection
stills power
dependingutilities
on TDM to
technology
to the
The optical networks
have been
bysystem
several
supportduethe
control and
requirement on the high dependability, security and short transmission time of teleprotection signals.
operation of power system. Particularly in Electricity Generating Authority of Thailand (EGAT), we
MMARY
have utilized The
the typical
Synchronous
Digital
Hierarchy
(SDH),
based on
time
division
multiplexing
(TDM)
SDH network
consists
of data plane
and management
plane
separately.
In the
data plane
SDHittransmits
payload
data andof
in the
the separatedand
network
management system
technology and
has been
proven
its management
reliability,plane,
availability
survivability
for almost two
(NMS)
provides
network
and
network-element
provisioning
and
performance
management.
optical
networks
have been
several
power
utilities to link
support
control
decades.
The designed
SDH deployed
network canby
offer
recovery
of communication
within the
sub-50
Improvement to the mentioned technique, SDH equipment can be enhanced with the use of control
which
has
been
for
power
utility
backbone
communication
infrastructure.
ation milliseconds
of power system.
Particularly
infrom
Electricity
Generating
of optical
Thailand
(EGAT),
plane
as described
in thesatisfied
standard
ITU-T
Recommendation
G.8080;Authority
automatic
switched
network
(ASON).
This enhancement
can add the advantage
on implementing
an
opticalpacket
mesh network
Although
the
trend
of
communications
technology
is
moving
toward
to
utilize
network,
some
utilized the Synchronous
Digital
Hierarchy
(SDH),
based
on time
division
multiplexing (TD
that can improve
availability over a system
typical ring
network.
Several SDH
networks
have beendue to the
operation application
such the
a teleprotection
stills
depending
on ring
TDM
technology
deployed
in EGAT
utilizingof
Composite
overhead ground availability
wire with optical fiber
(OPGW).
nologyrequirement
and it has
been
proven
its
reliability,
and
survivabilitysignals.
for almost t
on the
high dependability,
security
and short transmission time
of teleprotection
des. The designed
SDH network can offer recovery of communication link within sub
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the data plane
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has
been
satisfied
for plane
power
utility
backbone
infrastructu
areas has been increased and it is good opportunity for us to integrate the control plane technology for
SDH
transmits
payload
data
and
in
the
management
plane,
the
separated
network
management
system
SDH network within our technology
procurement and later
will be implemented
in those
mentioned packet
areas.
ough the trend ofnewcommunications
is moving
toward
to utilize
network, so
(NMS) provides
network
and
network-element
provisioning
performance
management.
Our proposed
planning
involves
a building of mesh networks
for given and
nodes (substations)
and given
ation Improvement
applicationavailable
a teleprotection
system
stills
depending
on TDM
technology
of fibers
inside OPGW.
At the
first
stage of
this plan,
the network
design the
is created
tosuch
the number
mentioned
technique,
SDH
equipment
can
be enhanced
with
use of controldue to
by using
(a linear
programming)
obtain the
best solution
forof
a full
mesh
irement
onasthe
high
dependability,
security
and
shorttotransmission
time
teleprotection
plane
described
inthe
theoptimization
standard tool
from
ITU-T
Recommendation
G.8080;
automatic
switched
optical signals
network that all nodes are connected by one another with the objective of a least use of optical fibers.
network (ASON).
This
enhancement
can
the advantage
on implementing
optical
mesh
However,
to be
realistic, in case
thatadd
the budget
may be limited,
the constraint on an
limited
number
of network
links isthe
added
for the second
stageaoftypical
the design
and network.
finding out the
solutions.
thatSDH
can improve
availability
ring
Several
SDH ring
networks have
beendata pl
typical
network
consists
ofover
data
plane
and
management
plane
separately.
In the
deployed in EGAT utilizing Composite overhead ground wire with optical fiber (OPGW).
transmits payload data and in the management plane, the separated network management syst
wissarut.y@egat.co.th
S) provides
network
and network-element provisioning and performance manageme
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opportunity
for us to integrate G.8080;
the control automatic
plane technology
for
280
e as described
in the
standard
Recommendation
switched
opt
new SDH network within our procurement and later will be implemented in those mentioned areas.
ork (ASON).
Thisplanning
enhancement
add of
themesh
advantage
implementing
an optical
mesh netw
Our proposed
involves acan
building
networks on
for given
nodes (substations)
and given
can improve
the availability
overOPGW.
a typical
ring
networks
available number
of fibers inside
At thering
first network.
stage of thisSeveral
plan, the SDH
network
design
is createdhave b
The result from both ideal and more realistic solutions are compared in this study which will be very
useful information for network planners in their further design and procurement process. Although, the
acquisition of equipment may differ from the optimized solutions, the information on how far the
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Moreover, the mesh network planning can be useful for the enhancement of optical networks
supporting the power distribution network where there are more substations and fiber-optic
connections among them than the transmission network.
KEYWORDS
SDH ASON ± OPGW ± Mesh Network ± Optimization
1. Introduction
The communication system is needed to provide the low figure of unavailability in power utility.
Toward this requirement, for instance, synchronous digital hierarchy (SDH) equipment has been
designed with the redundancy for power supply modules, control units, processing units,
communication/management functions, optical interfaces, and cross-connection matrix. For the
network protection, SDH can provide the recovery time within 50 milliseconds for the event of a fiber
cut or link failure. For mission-critical applications such as teleprotection for power utility, SDH
equipment has still been used even though the trend is to migrate to IP networks or toward new
technologies such as ITU-7¶VRSWLFDOWUDQVSRUWQHWZRUN 271 >@
In this paper, the overview of equipment in EGAT main telecommunication network will be illustrated
including composite overhead ground wire with optical fiber (OPGW) and SDH. Since the availability
of SDH network can be enhanced further by implementing a control plane with SDH equipment, the
detail of SDH with control plane is discussed. Then, the design of mesh network utilizing OPGW and
SDH will be shown.
2. EGAT Main Telecommunications Network
2.1
Composite Overhead Ground Wire with Optical Fiber (OPGW)
Composite overhead ground wire with optical fiber (OPGW) cable, which is the overhead ground wire
that contains optical fibers in the tube within the cable, becomes the highly reliable medium as can be
experienced by EGAT. For two decades, the records have shown that OPGW was severely broken
only a few times. The incidents mostly occurred because of lightning strikes and gunfire. Therefore, in
power transmission network, it is very advantageous to use optical fibers which are installed at the
topmost of towers for high voltage transmission. OPGW has been increasingly installed and replaced
instead of regular overhead ground wire in EGAT transmission system.
OPGW has been proved to be a very reliable physical layer together with the installation of SDH
equipment in substations as backbone ring networks. The record of incident on OPGW affecting the
telecommunications network from 1993 to 2011 is shown in Table 1. However, rarely has OPGW
hanged on high voltage transmission towers been totally broken. To be more reliable, the design of
OPGW topology connecting substations shall be at least (if applicable) a ring type.
Table 1. Records of EGAT OPGW incidents
Incidents
Lightning strike
Bullet shot
Others
Number of occurrence
16
18
58
The requirements on specifications of OPGW that needed to be considered are as follows.
i. Optical Fiber Characteristics: the parameters consist of
ƒ Type of fiber,
ƒ Number of optical fiber,
281
1
ƒ
ƒ
ƒ
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Profile of optical fiber,
Splicing loss,
Mode field diameter,
Cladding diameter,
CD coefficient,
PMD coefficient,
Operating and maximum temperature,
Maximum loss due to temperature changes.
OPGW characteristics: the parameter consists of
Ultimate Tensile Strength,
Overall outside diameter,
Nominal cross sectional area of conductor,
Number of strands,
Outer layer direction,
Nominal weight,
D.C. Resistance @ 20°C,
Length per reel,
Nominal modulus of elasticity,
Nominal Coefficient of linear expansion,
Capacity fault current.
Most optical fibers inside OPGW of EGAT are in compliance with ITU-T Recommendation G.652c
[2] which characterizes a low water peak single mode fiber. Besides the OPGW cable itself,
accessories are also needed for the transmission line construction. OPGW accessories requirements for
EGAT, for instance, are as follows:
ƒ Suspension Clamps
ƒ Dead End/Tension Clamps
ƒ Grounding Clamp, parallel groove clamp
ƒ Vibration dampers
ƒ Armor Rods
ƒ Joint Boxes
The OPGW cable and these accessories will need to be assured in both quantity and performance,
which needed to be inspected by the utilities before the installation to avoid the construction delay.
2.2
Synchronous Digital Hierarchy (SDH)
SDH has been used in EGAT for more than 15 years. The core bandwidth is STM-16 with a bit rate of
2,248.32 Mbit/s. SDH equipment is designed with multiple rings in which the single cut of fiber optic
will not interrupt the service, and is procured from several vendors through e-Auction procurement.
One network protection mechanism utilized with SDH networks is sub-network connection protection
(SNCP) that the receivers will select the signal to receive from the direction that has the best quality as
shown in figure 1. Moreover, the connections between ring networks are designed with dual node
interconnection (DNI) to increase the reliability as shown in figure 2.
Working path
Protection path
(a) Normal working condition.
(b) Protection after fiber cut.
Figure 1. Example of SDH network protection
282
2
Figure 2. Dual node interconnection
3 SDH with Control Plane
The control plane has been implemented by several telecommunication vendors. Its functions are in
according to automatically switched optical network (ASON) international standards which are
actively maintained by organizations such as International Telecommunication Union ±
Telecommunications sector (ITU-T), Internet Engineering Task Force (IETF), and Optical
Internetworking Forum (OIF). ASON has two aspects which are a framework and a technology [3].
ASON is a framework that describes control and management architecture, and also a technology that
has routing and signaling functions.
OCC
UNI
PI
Client equipment
(IP router, ATM switch, ...)
NNI
OCC
Control Plane
OCC
CCI
Management
Plane
EM/NM
Optical
switch
Optical
switch
PI
Optical
switch
Transport Plane
CCI:
NMI-A:
NMI-T:
NNI:
OCC:Optical ConnectionController
Connection Control Interface
Network Management Interface for the ASON Control PlanePI:Physical Interface
Network Management Interface for the Transport Network UNI:User to Network Interface
Network to Network Interface
Figure 3. ASON logical architecture
ASON architecture consists of transport plane, control plane, and management plane as shown in
figure 3.
‡ The transport plane provides the optical channels with the ability of cross-connecting optical
signals using SDH or optical transport network (OTN) for client of ASON.
‡ The control plane provides the ability to establish the end-to-end connections including
signaling and routing of client signals that are specified by clients themselves in setup process.
‡ The management plane provides management functionality that is related to both control plane
and transport plane.
‡
‡
Implemented with the control plane, SDH can provide the benefits as follows.
Fast service provisioning
In this aspect, network operators need the switching flexibility of networks. With the advance
of management and control functions, the configuration and re-configuration of networks can
be fast. The optical channel can be routed via ASON signaling and routing functions.
Network topology discovery
A new network element can be automatically discovered. As well as neighbor discovery,
topology of networks can also be automatically constructed. Each control plane unit of
network elements has knowledge of overall topology.
283
3
‡
‡
‡
‡
‡
‡
‡
Network resiliency
The optical channel can be recovered after failures with several classes of service. For
instance, the protection from multiple fiber cuts can be achieved. This provides higher
resiliency and flexibility of services to network clients.
ITU-T focuses on the architecture issuing specifications as follows.
Requirements and Architecture ± G.8080: ASON Architecture,
Auto-Discovery ± G.7714: General process and model, G.7714.1: Discovery for SDH/SONET
and OTN
Signaling ± G.7713: Distributed connection management model, G.7713.1, G.7713.2,
G.7713.3: signaling protocols
Routing ± G.7715: Routing architecture and requirements, G.7715.1: Link state routing
protocols requirements, G.7715.1: Remote route query requirements
DCN/SCN ± G.7712: Data communication network architecture
Management ± G.7718: Framework for ASON management, G.7718.1: Protocol neutral
information model for ASON management
‡
‡
IETF focuses on the building blocks issuing specifications as follows.
Architecture ± RFC.3495, GMPLS Architecture, GMPLS extension for SDH Control
Link Management ± Link management protocol
Signaling ± RFC 3471: GMPLS Signaling Functional Spec, RFC 3473: GMPLS-RSVP-TE,
RFC 3472: GMPLS-CR-LDP, RFC 3474, RFC 3946
Routing ± RFC 4202, GMPLS extensions for OSPF-TE
Management ± GMPLS MIB RFCs
‡
‡
OIF focuses on the applications and interoperability issuing specifications as follows.
Signaling ± E-NNI 1.0, E-NNI 2.0, UNI 1.0, UNI 2.0
Routing ± E-NNI OSPF 1.0
‡
‡
‡
The telecommunication vendors that manufacture SDH with ASON features are such as Huawei
Technologies (China), Tejas Networks (India), ECI Telecom (Israel) and ZTE Corporation (China).
4 Mesh Network Design
SDH with ASON features can improve the availability of optical networks with the tolerance of
multiple failures in mesh networks whose network elements may connect to their neighbors with more
than two directions. The improvement is that, for instance, in the event of a main link or a main optical
interface fails, the pre-assigned protection route will be used for the traffic instead while the network
management signaling through the control plane automatically searches for a new protection route and
assigning it, if available, for the protection of the next failure.
As mentioned earlier the OPGW has been proven to be very reliable that rarely it has been totally
broken interrupting the service of optical networks. This fact will be considered as an assumption of
this paper. That means the optical interfaces or boards are likely to fail more than the cut of fiber
optics inside OPGW. In the results from the design, some source-destination pairs can utilize the same
OPGW but with different fiber cores. Consequently, the design of mesh network will mainly aim to
provide the protection over the failures of optical interfaces.
4.1
Formulations
Two integer linear programming problems are formulated to design the links of network elements for
a mesh network with the minimum use of fiber cores. While the first one will try to solve for a full
mesh solution, the other contains a constraint on the budget such that the establishment of links
connecting network elements is limited. The given information is the existing 16 substations and 19
OPGW cables which contain 36 fiber cores in each cable as exemplified in figure 4.
284
4
36c
SNO
RS
CHW
36c
36c
LLA
36c
36c
36c
NB
36c
NCO
36c
LPR
36c
RPS
BN
36c
36c
STB
BK
36c
36c
36c
36c
ON
SB
36c
TPR
BPK
36c
36c
36c
BPL
Figure 4. Substations in metropolitan area
The details of formulations are as follows.
Given Information
: Set of network element pairs
: Set of directional links
: Set of bi-directional links
: Set of directional links into node
: Set of directional links out from node
: Set of number of optical fibers available for link
: Available budget
Decision Variables
: equal to 1 if and only if the network element pair has link on its connection path
: equal to 1 if and only if the connection path is established between the network
element pair
FORMULATION 1
««««««««««««««««««««««« (eq.1)
««««««««««««««««««««««« (eq.2)
««««««««««««««««««««««« (eq.3)
............... (eq.4)
The objective (eq.1) is to minimize the total number of fiber optics used for every connection of
network elements. The constraints are that each OPGW contains a limit number of fiber optics (eq.2)
that can be utilized, and all substations are needed to interconnect (eq.3). The last constraint (eq.4)
makes sure that the fiber cores are connected continuously from a source node to a destination node.
285
5
FORMULATION 2
««««««««««««««««««««............ (eq.5)
«««««««««««««««««««««««.(eq.6)
................ (eq.7)
««««««««««««««««««««««««(eq.8)
«««««««««««««««««««««««.(eq.9)
The objective (eq.5) is to maximize as many connections of network element pairs as possible. The
limitation on number of useable fiber cores (eq.6) and the flow connectivity of a source to a
destination (eq.7) are retained. The additional constraints on the required assignment of links for any
established connections (eq.8) and the upper bound on an available budget (eq.9) are included.
The formulations can be run using an open-source program such as PuLP which is an linear
programming (LP) modeler written in python [4].
4.2
Results
To construct a full mesh connection of a network with a total of 120 source-destination pairs shown in
figure 4, from the formulation 1, the number of connections for overall network is 358, and 23
connections are the maximum requirement on the link as shown in figure 5. Thus, for bidirectional
links, the 46 fiber cores are mostly needed. As the additional cost required to construct a mesh
network includes optical interfaces and fiber links between them, the formulation 2 is used to construct
the partial mesh network such that the cost does not exceed the available budget which is represented
in a term of maximum number of connections for overall network. The number of source-destination
pairs that can be established for a given number of connections allowed for the whole network is
shown in figure 6.
SNO
RS
13
CHW
14
22
LLA
15
23
16
NB
22
NCO
19
LPR
20
RPS
BN
20
23
STB
BK
21
23
22
11
SB
ON
23
TPR
BPK
21
22
8
BPL
Figure 5. Required connections in each OPGW
286
6
Number of source-destination pair established
Number of allowed connections for the whole network
Figure 6. Results from formulation 2
SNO
RS
1
CHW
2
2
LLA
2
2
1
NB
2
NCO
2
LPR
1
RPS
BN
2
1
BK
STB
1
2
2
2
ON
SB
2
TPR
BPK
2
2
1
BPL
Figure 7a. Design A: Required connections on each physical link for the implementation on
the improvement of availability of optical network
SNO
RS
1
CHW
2
2
LLA
2
2
1
NB
1
NCO
1
LPR
2
RPS
BN
1
2
STB
BK
1
1
1
2
SB
ON
1
TPR
BPK
1
1
1
BPL
Figure 7b. Design B: Required connections on each physical link for the implementation on
the improvement of availability of optical network
In the real implementation, the setup may depend on several issues such as the traffic or the important
role on that node as a control center. Figures 7a and 7b show the network that will be implemented
7
287
Number of source-destination pair established
using SDH ASON in which the connections between NB- BPK and NB- STB nodes are added. The
total of 32 and 26 connections for 21 source-destination pairs is designed as label on each link in
figures 7a and 7b, respectively. For the optimized network, the higher number of source-destination
pairs can be established with the same number of connections as illustrated in Figure 8.
21
Design B
26
Design A
32
Number of allowed connections for the whole network
Figure 8. Comparison between an optimized setup and the implementation of a network in
figures 7a and 7b.
5 Conclusions
The plan of using available fiber cores of OPGW can enhance the availability of communication
system. With ASON standard, the mesh network can be constructed with the protections to survive on
multiple failures.
Constructing an optical meshed network could impose a high implementation cost. The optimization
tools can provide the insight of a design for network planners. The comparisons between the
implementing networks and the optimized solution with given parameters can be made to show the
cost-effective design.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
R. Leal, V. Meneguim, M. Mehrdad, J. Jesus. Paper D2-01_02: ³Building a Resilient Optical
Transport Network (OTN) Transporting Critical Applications´, SCD2 Colloquium, Peru, 2015.
Characteristics of a single-mode optical fibre and cable, ITU-T Recommendation G.652, 2009
L. Ong, Optical Control Plane Standardization - OIF / IETF / ITU [Online]. Available:
http://www.oiforum.com/public/downloads/Ong.ppt
Python, https://www.python.org/
288
8
UG Cables
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
“Global
Trends
in
the
Development
of Power
System
Smart
of Power Transmission & Distribution Systems
including T&D
Smart Grid,
24-26including
Feb. 2016, New
Delhi,Grid”
India
CIGRE- AORC Technical Meeting 2016 and International Conference
DEMANDS OF DIELECTRIC TESTING
OF HVAC AND HVDC
on
POWER
CABLES
WITH EXTRUDED
INSULATION
“Global Trends
in the
Development
of Power
T&D System including Smart Grid”
Dipl.-Wirt.-Ing. Andreas Sebastian Horeth
HIGHVOLT Prüftechnik Dresden GmbH
Germany
DEMANDS OF DIELECTRIC TESTING OF HVAC AND HVDC
POWER CABLES WITH EXTRUDED INSULATION
Dipl.-Wirt.-Ing. Andreas Sebastian Horeth
HIGHVOLT Prüftechnik Dresden GmbH
Germany
SUMMARY
Dielectric testing of extruded HVAC and HVDC cables in the factory or on-site is a challenge when it
comes to longer lengths or special applications. Such verification of insulation coordination requires
high voltages for quality assurance tests to represent stresses in service like wave shape, partial
discharge behavior and dielectric field stress in the insulation medium. Hence, different technical
solutions are available to provide the required testing voltage like AC voltage (50/60 Hz or 20...300
Hz), very low frequency voltage (0.01...0.1 Hz) or DC voltage.
Nevertheless, not each test voltage is applicable for all dielectric test requirements due to physical,
SUMMARY
technical and economical constraints. With regard to the above mentioned facts this contribution will
discuss important aspects concerning economical, physical and technical challenges of dielectric
testing of extruded HVAC and HVDC cables.
Dielectric testing of extruded HVAC and HVDC cables in the factory or on-site is a challenge when it
comes to longer lengths or special applications. Such verification of insulation coordination requires
high voltages
for quality assurance tests to represent stresses in service like wave shape, partial
KEYWORDS
discharge behavior and dielectric field stress in the insulation medium. Hence, different technical
cables; extruded
cables; test
testing
solutionsHVDC
are available
to provide
thestandards;
requireddielectric
testingtesting;
voltage
liketechnology;
AC voltage (50/60 Hz or 20...300
Hz), very low frequency voltage (0.01...0.1 Hz) or DC voltage.
Nevertheless, not each test voltage is applicable for all dielectric test requirements due to physical,
technical and economical constraints. With regard to the above mentioned facts this contribution will
discuss important aspects concerning economical, physical and technical challenges of dielectric
testing of extruded HVAC and HVDC cables.
KEYWORDS
HVDC cables; extruded cables; test standards; dielectric testing; testing technology;
horeth@highvolt.de
291
INTRODUCTION
Quality assurance in terms of dielectric testing of extruded cables is the indemnification of the full
performance of the cable in the test field at manufactures site as well as after the transportation, laying
and installation process like setting the joints (splices) and terminations. Said applicable tests are well
defined in various IEC, IEEE standards or CIGRE recommendations and mainly consist of a withstand
voltage test in combination with complementary partial discharge measurement. Special tests like
impulse voltage and heating cycle tests for prequalification or type tests are also applicable. The
intention is to accelerate possible failure mechanisms caused by example given voids and impurities in
the insulation material respectively transport defects or assembly defects after laying procedure.
Additionally, it is possible to start condition assessment of laid cables systems regarding the estimated
remaining life time.
For selection of the appropriate test procedure it has to be distinguished between the testing
requirements for extruded HVAC and HVDC cables and common testing requirements in general.
This topic will be discussed in the following paper with focus on routine and on-site tests.
DIFFERENCES BETWEEN EXTRUDED AC AND DC CABLES
Basically the principle design of extruded AC and DC cables is similar. The conductor is covered with
a semi-conductive layer followed by the polymeric insulation, a semi-conductive outer layer finishes
the main insulation of the cable. However, major differences between AC and DC cables are the
following:
Table 1: Major differences between extruded AC and DC cables
Headword
Losses
Electric
field
Aging
Charging /
Relaxation
Extruded AC cable
Losses in conductor, screen
sheath and armor
Determined by permittivity
which is linear and isotropic
Higher grade of aging due to
possible partial discharge
activity / intensity
No conduction current, only
polarization of the dielectric at
operating frequency
Extruded DC cable
Losses only in conductor
(long lengths)
Determined by conductivity
which is non-linear and
anisotropic; local field
enhancement under transient
over voltages with opposite
polarity possible due to space
charge built-up;
Lower grade of aging due to
low partial discharge activity /
intensity
Small amount of charge
carriers; space charge build-up;
several hours or even weeks
needed for ready-state
condition;
Based on the above mentioned facts the requirements for testing are divergent for AC and DC
technology because a significant influence due to different electric field distribution or charging /
relaxation procedure is given. [1]
REQUIREMENTS FOR TESTING
As shown before, cables are inherently insulation systems which will be subject to failures if the
insulation contains a defect or weak spot, even though most of the cable shall be still in good
condition. Therefore testing at manufacturing site respectively laying site has to ensure that newly
produced cables are free from weak spots in the insulation like voids, impurities or metal particles.
292
Weak spots resulting in failure during operation and will lead to local field enhancements which can
trigger partial discharge activities and treeing processes. For newly installed cable systems assembly
defects in joints (splices) and terminations during laying procedure (approx. 60% of all defects) shall
be detected and avoided. [2]
With regard to diagnostic testing of service aged cables the detection of other failure mechanisms is
important. Possible failures are mentioned below:





Water trees, especially in MV XLPE cables
Aged insulation material
Defects caused by high temperatures of the conductor or thermal cycling
or maybe current overload.
Influence of water, chemicals, weather, etc.
Defects caused by overvoltage resulting from lightning strikes or
switching maneuvers, or mechanical damages resulting from short circuit current forces
If such tests shall be considered as usable, the test method for AC or DC has to fulfill certain
requirements as follows:
Table 2: Summary of requirements for test methods based on [3]
Parameter
Test effectiveness
Representation of
stresses in service
Danger for healthy
insulation
Comparability,
repeatability
Test procedure
well-defined
Relevant experience
Quality acceptance test
Required for all types
of defect
Required by applicable
standards
Diagnostic
maintenance test
Required for types of
defect searched for
Desirable for
comparability
To be avoided
Required
Required, very exact
Very high requirement,
standardized
Necessary, but not as
strict
Necessary, but not as
strict
Required for types of
defect searched for
As per [3] the following requirements have to be considered:
Effectiveness of a test
As the withstand voltage test is a statistical process [4], there is no test procedure available detecting
all dangerous defects without causing damage to parts of insulation that contain no or only minor
defects. So, the probabilities for a wrong or right result of a test depend among others on the voltage
wave shape, test voltage value and the duration. The given example by reducing test duration or test
voltage value the probability of damage of healthy insulation is reduced at the cost of also reducing the
capability of proving a defective cable to be faulty.
Representation of stresses in service
Test voltages shall “produce the same dielectric effect in the insulation as overvoltages in service” [5].
That means for AC cables which face mostly AC stresses in operation an AC test voltage (same order
and magnitude) is suitable and vice versa a DC test voltage for DC cables. This ensures that the same
stress type as the operating stress is present as well as the same electric field distribution in the
insulation like in service conditions.
Different to the requirements for quality assurance tests are requirements for diagnostic maintenance
tests which are more free in their choice of methods, since the outcome is not an acceptance criterion.
293
2
Test duration
As the life expectancy of XLPE, or the necessary time to fail a new cable with defects depends on the
applied test voltage, a life time exponent k ≥ 9 is given by [6], see also exemplary figure 1 [7].
Fig.1: Relative life expectancy vs. dielectric field stress
The higher the percentaged share of applied test voltage the higher the possibility that failure
mechanisms are accelerated, so that defects can be found in a relatively short time. Nevertheless the
increase of test voltage is limited by the requirement not to start failure mechanisms in parts of the
insulation that are healthy or contain negligible defects.
Field experience in terms of detectable partial discharges and reported later service failures after onsite test for AC cables shows that up to a test voltage of 1.5 x U0 service failures were reported and up
to 30 % of detectable partial discharges were found. For test voltages up to 1.7 x U 0 or higher no
service failures reports are available and up to 70 % or more detectable partial discharges were found.
A more detailed evaluation as well as a tutorial is currently prepared by CIGRE working group B1.28.
Danger for healthy insulation
Tests might create the preconditions for later breakdown. Especially space charge build-up, which can
occur during applied DC stress, will significantly influence the electric field distribution in a layered
AC cable. When the AC cable later is operated with AC voltage, these space charges will likely still be
present due to the extraordinarily low conductivity of XLPE in the region of 10 -14 S/m up to 10-16 S/m.
Such space charges might lead to local field enhancement under opposite polarity reversals. [8]
Therefore, a suitable test procedure prevents the formation of space charges in the cable under test.
Comparability and repeatability of tests
Due to the fact that cables are tested several times during their lifetime the test results of quality
acceptance tests shall be comparable with each other. So the conditions of the test like test voltage,
wave shape, test voltage and test duration must be similar.
Additionally, if a comparison of test results of different cables in terms of diagnostic testing shall be
enabled, the above mentioned condition must also apply. Thus, tests should be repeatable with
different test sets that use the same testing principle to ensure comparability in case the original test
system should become unavailable.
Definition of test procedure
As the withstand voltage test is a statistical process [4], the chosen test procedure for detecting failures
has to be well defined. Therefore, it needs to be considered which voltage amplitude, wave form and
test duration is more suitable for a test on an insulation system. Furthermore, the amount of stress for
the cable system depends on keeping these values in a defined range. This is especially important for
quality acceptance tests, but helpful for diagnostic maintenance tests as well.
294
3
Experience
The difference between using or understanding a certain test method is becoming important. The fact
is that elaborated data about effectiveness of various test techniques and published faithful analysis of
failure statistics are still missing. Besides that the difference in the operating field strength of extruded
cables must be considered. In a MV voltage cable the field strength is typically in the range of
3 to 5 kV/mm and in HV / EHC cables within 13 to 20 kV/mm.
Hence, acceptance test methods shall be standardized as the result of research and evaluation.
TEST METHODS
In the following a principle overview about different dielectric test methods with focus on routine,
partial discharge and on on-site installation tests will be given (see table 3 on next page). Possibilities
and limits of the technologies will be discussed.
As extruded cables undergo stringent requirements for quality assurance purpose, dielectric test in
terms of withstand voltage testing along with complementary partial discharge measurement apply.
Buried cables (see column A and B of table 3) which are operated with AC power frequency voltage
the testing requirements are defined in various standards. [10; 11; 12]. Routine testing carried out at
manufacturing site includes testing with mains frequency of comparatively short lengths along with
conventional partial discharge measurement. Normally the partial discharge measurement is carried
out in shielded rooms with high measuring sensitivity to test the quality of the whole cable length. At
the time of installation, the separate cable elements are connected together by use of joints and
terminations to reach the required system length. Before commissioning the cable system a quality
check by AC voltage in combination with a partial discharge measurement test is done directly at the
joints. As an alternative a VLF test may also apply, but only for medium voltage cables. In the latter
test scenario it might be considered that:



field distribution can be different from service
lower number of polarity changes compared to mains frequency compensated by higher test
voltage level (factor ~ 1.5) which enhances the field stress at the conductor significantly
compared to AC
partial discharge behavior might differ as well as signal to noise ratio
295
4
296
Table 3: Principle overview of cable manufacturing and testing technique for extruded MV, HV and EHV cables based on [9]
In comparison to buried cables there exists no specific standard for submarine cables besides CIGRE
recommendations and brochures. [13, 14]. Planned and conducted dielectrical tests as per table 3,
column C and D may follow beside the recommended testing procedure proposed by CIGRE also
manufacturer’s data or requirements of the customer. Due to the long length of extruded submarine
AC and DC cables of 10 km factory length to 100 km of total delivery length the requirements for
testing are getting more defined by the physical testing plausibility combined with trade-offs in terms
of possibilities for testing.
Nevertheless, AC-submarine cables (see column C, Table 3) are being tested by withstand voltage
tests by using high AC-voltage. During this process the cables are tested on basis of on-site testing of
buried cables corresponding to IEC 60060-3 [15] where a testing frequency smaller than the powerline frequency is used in order to limit the required testing current. As an analogy to the above
mentioned factory length, DC-submarine cables are being logically tested using high DC-voltage
(column D, Table 3).
Regarding to the partial discharge measurement applied to extruded submarine cables, it has to be
mentioned that the possibilities for detection are limited. The reason is the high attenuation of the
partial discharge impulses caused by wave propagation inside the cables achieving damping factors up
to 100 p.u. after 10 kilometers. Nevertheless, the cables are singly tested on cable-pieces (beginning
and end of cable). After connecting the factory lengths the partial discharge measurements are being
taken directly at the splices. In order to gain a reliable partial discharge diagnosis the tests are done
using AC-voltage, no matter if the submarine cable is intended for AC- or DC-voltage transmission.
As submarine cables are difficult to access after installation, partial discharge measurements at the
splices are excluded of the commissioning tests. Therefore a withstand voltage test is recommended
after installation. According to the service conditions there are physically reasonable tests of the AC
cables with HV AC-voltage and of the DC cables with HV DC-voltage.
TEST EQUIPMENT FOR DIELECTRIC TESTING
This chapter will discuss HV testing technology considering the state of the art technology compared
with an overview of suitability for different field applications. [16; 17]
HVDC testing equipment
HVDC voltage generation circuits can be mainly distinguished between two rectifying circuits. The
Greinacher circuit represents the conventional design for asymmetrical voltage duplication which
allows a system design having heavy duty operation at continuous duty. Moreover, a cascading
connection of single Greinacher circuits is possible but leads to big size applications. The test system
can be designed for indoor as well as full outdoor application even under unfavorable condition by
having one or two poles. Such systems are mainly used for factory testing of extruded DC cables.
Fig. 2: Outdoor HVDC test system type FGP 200/1200 (200 mA, 1200 kV); Manufactured by HIGHVOLT
Contrary to that the Delon circuit based on symmetrical voltage duplication has a small size and can
be used for medium duty operation. It is possible to cascade single stackable modules for higher
6
297
voltage applications. Furthermore, all necessary components of the test system (transformer, capacitor,
and rectifier) can be built in one insulated vessel to achieve a reliable and transportable system with
short mounting time. This test system meets the increasing trend for a mobile (outdoor) test system
which needs less space for installation.
Fig. 3: Modular DC test system type GPM 30/800 (30 mA, 800 kV); continuous operation;
Manufactured by HIGHVOLT
In addition to the different test technologies for generating high DC voltages, the build-up and stored
energy WCable in the DC cable has to be considered during testing [18]. It can reach very high values
up to several MJ and influences the charging / discharging time. Depending on the capacitance of the
cable CCable and the test voltage UTest, the stored energy can be calculated as follows:
For safety reasons and to reduce stresses on the cable a moderately discharge of the cable is necessary
and can be realized within one or two hours by example given discharging resistors or water resistors.
Without using such designated discharging units potential discharging times of up to 12 h or more for
cables having a length of more than 100 km are possible.
HV AC testing equipment
Resonance Test System with variable Inductance (50 Hz / 60 Hz)
Resonant test systems are applied to the generation of high-voltage AC of power frequency for
routine, type and development testing of (highly) capacitive test objects. There are two types: steel
tank type and modular insulating case type. The test system itself consists of the exciter transformer, a
reactor with variable inductance and a voltage divider / coupling capacitor. Together with the
capacitive load of the test object it forms a resonant circuit.
The main advantage of the resonant test systems is the low power demand described by the quality
factor q (in the range 40 to 80) as only the losses in the test circuit must be covered by the power
supply. This aspect is especially a major issue for on-site testing of cables, because the feeding power
S to be supplied is a criterion for the feasibility of a test. The kilometric capacitance C` is constant, so
the total cable capacitance Ccable increases linear with length lcable, the needed test power S quadratic
with the applied test voltage UTest. For AC test systems S can be calculated according to:
As discussed before an important aspect for such AC test system is the fact, that they can be designed
as resonance test systems. Thus, only the active power has to be fed in the test circuit which reduces
the feeding power down to 1% of the required testing power or even less. The required feeding power
P can be calculated by implementing the quality factor q (ratio between test power and feeding power)
298
7
as well as the efficiency of the power supply feeding of the test system
calculation above:
in the
This type of test system is mostly suitable for indoor operation. In order to test very high capacitive
loads several reactors of such a system can be connected together via a virtual electric shaft to extend
the capacitive load range for testing. [9] This shaft guarantees the synchronous operation of the
mechanically divided motor drives and therefore core positions (= variation of inductance). However,
due to maneuverable parts, frequent transportation can lead to mechanical damages and the weight to
power ratio of 3 ... 10 kg/kVA is moderate. Therefore, an on-site application of this technology is not
used for field cable testing.
AC Test System with variable frequency
Due to the need for even more compact (weight to power ratio of 2 ... 4 kg/kVA) and robust test systems
with higher quality factors (q >> 100), which are especially used on-site, resonant test systems with
variable frequency were engineered and represent the state of the art solution for this purpose as well
as on-site testing of long AC and DC cables. The difference of the AC test system with variable
frequency compared to the system with variable inductance is the static frequency converter and
control system located in front of the exciter transformer and the fixed inductance LH, s. figure 4.
Fig. 4: Circuit diagram of an AC resonant test system with variable frequency
The great benefit of this test system is the possibility to provide very high test power for on-site testing
of very long cables by using a test frequency as low as 10...20 Hz or by parallel connection of several
systems. Hence, with this proven technology and test system a wider range of capacitive loads can be
tested compared to resonance test systems with variable inductance. With regard to equation (2)
assuming that the same test parameters but differing in test frequency of f test = 20 Hz and a quality
factor q = 160 it is possible to test a (extruded) AC cable ten times longer with the same feeding power
by the use of a test system based on variable frequency.
An additional example given in [19] demonstrates the use of this technology as test on cables with
lcable = 52 km in total. Moreover, with this AC resonant test system routine tests of extruded DC cables
were also successfully performed [19]. Furthermore, during testing of such very long HVDC cables
the test systems were connected at both ends of the cable in order to minimize the screen losses up to
25 per cent compared to single end feeding to avoid overheating of the screen [20]
299
8
CONCLUSION AND SUMMARY
Different types of test methods and their requirements were presented and discussed. Focused was
their suitability to perform factory as well as after installation tests on extruded DC and AC cables. It
was mentioned, that depending on the design of the extruded cable different dielectric tests may apply
due to different physical and electrical behavior. Moreover, information was provided that partial
discharge measurement depends on several factors like length of the cable, test frequency and test
amplitude. Also different testing technologies were presented with regard to their suitability for
factory and on-site testing. The following points can be concluded:
There is no universal test method available which can perform all test and diagnostic tasks. Suitable
test technology and testing procedure for AC and DC cables depends strongly on material, cable
design and applied test voltage to detect possible defects
Resonant test systems with variable frequency are the most efficient and most powerful test systems
for on-site testing of AC cables and DC cables shall be tested with DC on-site.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
R. Pietsch: After installation tests of extruded AC and DC cables – Test procedures and their
physical background -; CIGRE SCD1 Colloquium; Rio de Janeiro; Brazil; 13-18 September
2015
B. van Maanen et al.: Failures in underground power cables – return of experience; 9th
Internation Conference on Insulated Power Cables; JICABLE 2015; Paper D9.2
S. Fuchs, S. Hensel: Suitability of test voltages applied to high and extra-high voltage extruded
cables and cable systems for quality assurance during commissioning and for condition
assessment during operation; JICABLE 2015; Paper C5.5
D.H. Damon, 1992, “Breakdown statistics for XLPE containing the volatile by-products of the
cross-linking reaction”, Proceedings of the 4th International Conference on Conduction and
Breakdown in Solid Dielectrics, 1992, pages 513-517
IEC 60071-1:2006+AMD1:2010 CSV: “Insulation co-ordination – Part 1: Definition, principles
and rules”
A. Küchler, 2009: Hochspannungstechnik: Grundlagen - Technologie - Anwendungen 3., neu
bearb. und erw. Aufl.. Springer
Björn Dellby et al: Hochspannungs- XLPEPERFORMANCE kabeltechnik; HV Cable
Technology; page 35 – 44; ABB Technik 4/2000
K.H. Krefter (ed.), 1991, “Prüfungen zur Beurteilung von Kabelanlagen in
Mittelspannungsnetzen”, Tagungsband VDE-Fachtagung Bochum
S.Schierig et al: Alternatives for HV-AC testing of long HV cables in the factory and on-site;
JICABLE 2011; Paper A8.5
IEC 60502-2: 2004-04: Power cables with extruded insulation and their accessories for rated
voltages from 1 kV (Um = 1.2 kV) up to 30 kV (Um = 36 kV) - Part 2: Cables for rated voltages
from 6 kV (Um = 7.2 kV) up to 30 kV (Um = 36 kV)
IEC 62067 (ed. 1.1-2006-03): “Power cables with extruded insulation and their accessories for
rated voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV) - Test methods and
requirements”
IEC 60840 (ed. 3.0-2004-04): “Power cables with extruded insulation and their accessories for
rated voltages above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV) - Test methods and
requirements”
CIGRE Technical Brochure, Working Group 21.01, no. 219, 02/2003 (replaced by CIGRE
Brochure 496, April 2012)
CIGRE Working Group B1.32: Recommendations for Testing DC Extruded Cable Systems for
Power Transmission at a rated voltage up to 500 kV, CIGRE Brochure 496, April 2012
IEC 60060-3:2006-02; ed. 1.0: Definitions and requirements for on-site testing
300
9
[16] A. Horeth: Review of dielectric testing of HVDC converter transformers; ICHVET 2015;
Hyderabad; India
[17] A. Horeth: Review of on-site testing of extruded HV AC cables; CABLETECH 2013;
Bangalore; India
[18] A. Horeth; R. Pietsch: On-site testing of Extruded AC and DC Cables above 36 kV and up to
500 kV; ICPADM 2012; ISSN: 2160-9225
[19] Karlstrand, J., Henning, G., Schierig, S., Coors. P.: Factory testing of long submarine XPLE
cables using frequency-tuned resonant systems. CIRED 2005, Turin 6-9 June 2005
[20] P. Coors; R. Pietsch: Application of AC test voltage during factory testing of super long HVDC
cables; ICHVET 2015; Bangalore; India
301
10
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
on including Smart Grid, 24-26 Feb. 2016, New Delhi, India
of Power Transmission & Distribution Systems
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
on
Trends in the
Power T&Dfor
System
including
Smart Grid”
BHEL“Global
experience
inDevelopment
the EHVofCables
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Raj Kumar
D.K.Mandal
Rakesh
Gautam Chaklader
BHEL experience
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forSingh
Power Transmission
Dy. Manager
DGM (Engineering)
AGM(Engineering) GM (Const.,Engg. & Quality)
Suratgarh Site
TBG , Noida
TBG , Noida
TBG , Noida
Raj Kumar
D.K.Mandal
Rakesh Singh
Gautam Chaklader
Dy. Manager
DGM (Engineering)
AGM(Engineering) GM (Const.,Engg. & Quality)
Suratgarh Site
, Noida
TBG , Noida with metallic
TBG , screen
Noida (corrugated and seamless
Summary:
BHEL has TBG
executed
the following EPC
contracts for EHV cable in various locations of India to
fulfil the requirement of various needs of utilities
Summary: BHEL has executed the following EPC
for EHV
locationsdouble
of Indiacircuit
to
contracts
Diversion
of cable
the 2in various
Nos. 400kV
fulfil
the
requirement
of
various
needs
of
utilities
transmission lines through 400kV XLPE Cable of
core of
(two
at Bamnauli
/Delhicircuit
to create
 single
Diversion
theruns)
2 Nos.
400kV double
space
for
750MW
Pragati-III
CCPP
(Combined
transmission lines through 400kV XLPE Cable of
Cycle
Plant).
has installed
single Power
core (two
runs)BHEL
at Bamnauli
/Delhi toaround
create 20
Kms,
400
kV
EHV
cable
through
outdoor
cable
space for 750MW Pragati-III CCPP (Combined
Cycle Power Plant). BHEL has installed around 20
trench.
Kms, 400 kV EHV cable through outdoor cable
The
power evacuation from 400kV GIS at Pārbatitrench.
III HEP to 2 nos. overhead Transmission line has
 The power evacuation from 400kV GIS at Pārbatibeen done through 400kV XLPE cable of 3.5 Kms.
III HEP to 2 nos. overhead Transmission line has
The EHV cable has been installed in underground
been done through 400kV XLPE cable of 3.5 Kms.
tunnel
having
gradient
of installed
up to 32 in
degree.
The EHV
cable
has been
underground

tunnel having gradient of up to 32 degree.
Due to space constraints in Power Plant area , 1200
mm
, 400 kV
EHV cables
(1.5Plant
Kms)area
and
220 kV
 sq.
Due
to space
constraints
in Power
, 1200
sq. Km)
mm , 400
kV EHV
Kms) outdoor
and 220 kV
(1
cables
has cables
used (1.5
through
cable
(1
Km)
cables
has
used
through
outdoor
cable
trenches to evacuate power from power house
trenches outgoing
to evacuate
from power
house
through
linespower
in GSECL
(Gujarat
State
through
outgoing
lines
in
GSECL
(Gujarat
State
Electricity Corporation Limited) , Ukai substation.

Electricity Corporation Limited) , Ukai substation.
Keywords:
Keywords:
EHV
cables, jointing, termination, support structure,
EHV cables, jointing, termination, support structure,
installations,
testingand
andcommissioning,
commissioning,
Etc.
installations, testing
Etc.
1.1. Design
ConstructionofofXLPE
XLPE
Cable
Design &
& Construction
Cable
: :
The
XLPE Cable
Cable has
hasthetheconstruction
construction
The XLPE
of aof a
conductor (copper
insulated
withwith
conductor
(copperororaluminum)
aluminum)
insulated
the cross-linked
cross-linked polyethylene
andand
then
shielded
the
polyethylene
then
shielded
aluminum or wire shield), to be covered by PVC
or polyethylene for anticorrosion.
with metallic screen (corrugated and seamless
aluminum
or wire shield),
to be covered
by PVC
a) Conductor:
The conductor
consists
of annealed
or polyethylene
for
anticorrosion.
copper or hard aluminum stranded wires and
classified
into three
(3) ofmajor
a) Conductor:
The conductor
consists
annealedtypes of
concentric,
compacted
circular
andand
segmental
copper or hard aluminum stranded wires
compacted
concentric
classified
into circular.
three (3)The
major
types isofthe wires
wounded
up concentrically,
the compacted
concentric,
compacted
circular and segmental
compacted
circular.
The concentric
is the of
wiressegments
circular
conductor
consists
wounded
up concentrically,
the compacted
wounded
up and then compacted.
circular
conductorScreen:
consistsThe
of conductor
segments screen
b) Conductor
wounded
up
and
then
compacted.
consists of an extruded semi-conducting
b) Conductor
Screen:
The conductor
screen
polyethylene
to minimize
electrical
stresses due
consists of an extruded semi-conducting
to the stranded configuration of the conductor.
polyethylene to minimize electrical stresses due
The semi-conducting material used for
to the stranded configuration of the conductor.
conductor
screen hasmaterial
no deleterious
The semi-conducting
used effect
for on the
conductor.
Semi-conducting
tape
is
sometimes
conductor screen has no deleterious effect on the
applied
as
a
separator.
conductor. Semi-conducting tape is sometimes
c) Insulation
Screen: The insulation screen is
applied
as a separator.
c) Insulation
Screen:
insulation screen
is
provided over The
the insulation
by extruding
the
provided
over
the
insulation
by
extruding
the
semi-conducting compound concentrically and
semi-conducting
concentrically
and
circularly compound
to minimize
the possibility
of
circularly
to
minimize
the
possibility
of
ionization on the outer surface of the dielectric.
ionization on the outer surface of the dielectric.
d) Insulation: The insulation material is extruded
d) Insulation: The insulation material is extruded
cross-linked
polyethylene.
The conductor
cross-linked
polyethylene.
The conductor
screen,
the
insulation
and
the
insulation
screen, the insulation and the insulation screen screen
mentioned
are extruded
simultaneously
in
mentioned
above above
are extruded
simultaneously
in
process
to ensure
the and
screen and
one one
process
to ensure
that thethat
screen
insulation
are intimately
and
insulation
are intimately
bonded bonded
together together
and
free free
from from
all possibilities
of voidsof between
all possibilities
voids between
Page | 1
302
Page | 1
layers. The extrusion process is carried out under
strictly controlled atmospheric conditions.
e) Metallic Screen: The metallic screen consists of
the wire shield, the corrugated aluminum sheath
or the lead sheath. The corrugated aluminum
sheath and the lead sheath is also adopted where
the surface of duct is poor and where moisture is
high.
f) Outer Sheath: To protect the metallic sheath
from electrical or chemical corrosion, it is
covered by PE or PVC.
The detailed Technical Specification of the EHV cables installed by BHEL as EPC contract
Sr.
No.
Particulars
Unit
400kV XLPE
cable at Bamnauli
1
2
Rated System Voltage
System earthing
kV
400
Solidly Grounded
3
kA
6
7
8
Rated Normal Current
at nominal system
voltage (400KV)
System fault current
for one second
Nominal Cross
section area of
conductor (Double
Run)
Type of conductor
Insulation
Metallic sheath
9
Outer Sheath
10
Creepage distance for
termination
Sheath voltage under
full load condition to
ground
Laying method
4
5
11
12
400kV XLPE
cable at Ukai
220kV XLPE
cable at Ukai
400
Solidly
Grounded
953
220
Solidly Grounded
3150
400kV XLPE
cable at ParbatiIII
400
Solidly
Grounded
2400
kA
40
40
40
40
sq.
mm
2500
2500
1200
330
Copper
XLPE
Corrugated/Lamin
ated Aluminium
Copper
XLPE
Corrugated
Aluminium
Sheath/Corrugat
ed Copper
Sheath/Welded
Aluminium
Sheath
PE with HFFR
layer
Copper
XLPE
Corrugated/Lami
nated
Aluminium
Copper
XLPE
Corrugated/Lamin
ated Aluminium
HDFE with outer
conductive layer
Black HPDE
mm/
kV
V
182
25
25
HDFE with
outer conductive
layer
31
90 (Max)
90 (Max)
90 (Max)
65 (Max)
Flat Formation
Laying in outdoor
Cable trench
Flat Formation
Laying in Tunnel
having in
gradient max 30
degree
Trefoil
formation
Laying in
outdoor cable
trench
Trefoil formation
Laying in outdoor
cable trench
31
Page | 2
303
2. Selection of type of cable jointing system:
3. Selection of the type of cable termination to be
used:
Basically, a joint connects two end sections of cable
using a connector for the conductor as well as an
insulating body to maintain the system’s insulation level.
The other major components are the connection device
for the cable screen and the outer protection against
moisture and mechanical damage. However, the most
complex and also the most important element of the joint
remains it’s insulating body.
Section of joint bay is based on the sizes of cables and
sizes of joints and the width of joint portion is higher than
the width of the normal trench.
It is always advisable that there should be no joint in
EHV cable, as there is always probability of failure of
EHV cable at joints if jointing work not done properly.
However it is not possible to avoid the joints if the length
of the transmission line is more than 1 km in general and
have higher power rating.
The selection of the type of cable termination
depends upon its end connection i.e. AIS (Air
Insulated Substation) , GIS (Gas Insulated
Substation) and Oil. In case of XLPE to AIS outdoor
termination suitable for XLPE to air insulation,
XLPE to GIS indoor termination suitable for XLPE
to SF6 gas and XLPE to HV Bushing indoor
termination suitable for XLPE to oil immersed shall
be used.
Type of jointing system shall be selected from available
products (i.e. conventional joining, cold shrinkable
jointing etc.), and shall have to decide the no of joints
with consideration that it shall have minimum joints and
shall not face any problem in transportation/execution.
The EHV cable at Parbati-III has been installed without
any jointing though the project is in deep Himalaya but
in Bamnauli and Ukai joints were used.
The XLPE to SF6 & XLPE to Air termination has
been done at Parbati-III project, XLPE to air
terminations has been at both the ends of EHV cable
at Bamnauli and XLPE to air & XLPE to Oil/HV
bushing termination has been done at Ukai.
Photograph of outdoor termination under execution at
Bamnauli job:
Photograph of complete joint enclosed in coffin box:
Page | 3
304
4. Selection of type of support structure
This is another field which require lot of attention and
BHEL play major role in the design of the supporting
structure. It has always been put on priority that the
design should be as simple as possible in addition to
required mechanical strength. BHEL faced lot of
problem while installation at site particularly at ParbatiIII site where the supporting structure has been installed
in the tunnel having slope up to 32 degree. The
supporting structure shall be designed on basis that it
shall have minimum interface during the civil work of
wall of cable trench/tunnel, shall be easy for installation
at site as well as shall have minimum fabrication at site
5. Selection of earthing
In order to reduce circulating current and electric
potential difference between the sheathings of single
core three-phase cables, the sheathing is grounded and
bonded at one or both ends of the cables.
The earthing system shall always in line with the
technical specification of the contract, and there is not
too much scope for the alteration.
At present solidly grounded earthing is preferred by end
user utility to reduce the sheath voltage below 90 V
(Earthing through copper bonding cable)
6. Installation , Testing and Commissioning of EHV
cable at site:
The installation of the EHV cable can broadly be
divided in the following categories:
a) Embedment of the supporting structure:
This part is very crucial and shall always be
advisable that supporting structure of EHV cable
shall have minimum interface with the civil
work. However in certain circumstances where
the EHV cable has huge loading due to gradient
in case of tunnel especially in Hilly area and in
addition to that the walls of the tunnels shall
have been casted with lean concrete, in that
particular case we cannot achieve the required
mechanical strength with the anchor faster. We
have to use long length embedment bolts and
that shall have been fixed during the concreting
stage to achieve the required mechanical
strength.
b) Transportation of the EHV cable from works
to site:
To minimise the joints it shall be preferred that
EHV cable shall be packed and transport in the
length of 1000 mtrs. but there is always
difficulty in handling the same as the weight/size
of the EHV cable drum will be very large.
Further the 1000 mtrs. Length EHV cable
packing is not possible if the power rating of the
EHV cable shall be large side. In addition to that
geographical condition of the project area also
plays major role in deciding the packing length
of the EHV cable, as transportation of the heavy
and saggy drum is not possible in hilly area.
c) Storage of the material in the store:
The material of termination kit and jointing kit shall
have to be stored in covered store, and the EHV
cable shall have to be stored in fashion that there
shall be no issue while reloading of the material for
further dispatch to works site. In addition to that it
shall also be cared that the termination/jointing kit
material shall not reach at site too before its use, as
the lot items has selves’ life.
d) Installation of the Supporting structure for the EHV
cable.
e) Shifting of the material to works site:
BHEL faced lot of problem for shifting of material
to work site and even deciding the place for unrolling of the EHV cable due to geographical
conditions at Parbati-III site. So it is advisable to
decide the works place for unrolling of EHV cable
and it shifting up to that works place especially in
case of hilly area to avoid any ambiguity in future.
f) Installation of the EHV cable:
The un-rolling of the EHV cable shall have been
done on the hydraulic jacks, the pulling of the EHV
cable shall have been done with the hauling machine
Page | 4
305
having common breaking system, and the direction
of the EHV cable shall be guided by rollers. The
nos. of hauling machine are decided on the basis of
length, weight and slope of the surface. The
communication system have to be installed before
starting the installation of the EHV for on line
communication throughout the EHV cable route.
i)
Site testing of the EHV cable:
The after completion of installation work including
jointing/termination the sheath healthiness and soak
test at rated voltage for 24 hours shall be performed.
After the successful completion of the soak test
system can be put on rated load.
The installation of the EHV cable can be done
directly on the supporting structure if the slope of
the route is in the range of 2-3degree i.e. Bamnauli
and Ukai. The laying of the EHV cable was done on
ground at Parbati-III and the same was lifted to
supporting structure after the completion of laying
operation as the slope was up to 32degree.
Photographs of installed cable at Bamnauli site.
Bibliography:
1) Various catalogue of LS cable , Korea
2) Various catalogue of Viscas Cable ,Japan
g) Clamping and fixing of the EHV cable on the
supporting structure shall have been done with the
non-magnetic material. The clamping require lot of
attention if the EHV cable route have high gradient.
h) Termination/Jointing: The termination and jointing
operation is most sensitive operation for the EHV
cable to be done at site. The same operation is
always done in controlled environment conditions.
Page | 5
306
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
“Global Trends in the Development of Power T&D System including Smart Grid”
of Power
Transmission
Systems
including
Smart and
Grid, 24-26
Feb. 2016, New
Delhi, India
CIGREAORC& Distribution
Technical
Meeting
2016
International
Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
Socio-Technical Initiatives for UG Cable Asset Management
Mr NILESH KANE, Mr RAJEEV KUMAR, Mr SANDIP PAL, Mr ANUJ KUMAR
TATA
Power Delhi
Distribution
Socio-Technical
Initiatives
for
UG CableLimited
Asset Management
India
Mr NILESH KANE, Mr RAJEEV KUMAR, Mr SANDIP PAL, Mr ANUJ KUMAR
TATA Power Delhi Distribution Limited
India
SUMMARY
Power Delhi Distribution Limited is a joint-venture of Tata Power Company & Govt.
Tataof NCT
of Delhi. It is one of the Distribution Companies which operates in an area of 510
Sq Km in North & North-West part of Delhi serving around 1.6 million consumers. TPDDL
caters peak demand of around 1750 MW with its vast UG cable network to the tune of 10,000
SUMMARY
Circuit KM installed capacity.
Power Delhi Distribution Limited is a joint-venture of Tata Power Company & Govt.
Tataof NCT
of Delhi. It is one of the Distribution Companies which operates in an area of 510
The Power distribution utilities all across glove are striving for reliable and un-interrupted
power to ensure customer satisfaction. UG cables have played a major role by undergrounding
Sq Km in North & North-West part of Delhi serving around 1.6 million consumers. TPDDL
the overhead distribution network. It provides higher safety, reliability and ultimate system
caters
peak demand
of around
1750and
MW
with its vast
UGTPDDL
cable network
to the tuneurban
of 10,000
economy
by reducing
operation
maintenance
cost.
with predominant
Circuit
KM
installed
capacity.
geography has vast UG cable network which delivers reliable and quality supply to its
valuable customers. Frequent external damage of this critical power delivery asset results in
dissatisfactionutilities
viz. lossall
of across
revenue glove
due to are
unserved
energy
expenditure
incurred
The customer
Power distribution
striving
forand
reliable
and un-interrupted
on to
repair
and customer
maintenance
to the tune UG
of approx.
Croreplayed
in FY 2014-15.
Based
the cable
power
ensure
satisfaction.
cables2have
a major role
byonundergrounding
fault data, distribution
it has been observed
thatIt there
was ahigher
rising and
alarming
trend in
failure
of UGsystem
the overhead
network.
provides
safety,
reliability
and
ultimate
cables
in
recent
years.
Reason
of
rising
trend
in
UG
cable
is
mainly
due
to
External
damages
economy by reducing operation and maintenance cost. TPDDL with predominant urban
as multiple utilities are working in Delhi to improve the infrastructure facility all across Delhi.
geography
has vast UG cable network which delivers reliable and quality supply to its
Our analysis reveals that the key reasons for External damage are no separate trench for
valuable
customers.
external
damage ofbetween
this critical
power
delivery
asset results
in
different
utilities, Frequent
lack of proper
communication
different
utilities,
assignment
of
customer
dissatisfaction
viz.
loss
of
revenue
due
to
unserved
energy
and
expenditure
incurred
work to contractors to subcontractors, unskilled digging manpower, inconsistency in cable
on repair
maintenance
to the tune of approx. 2 Crore in FY 2014-15. Based on the cable
depth and
profile
etc.
fault data, it has been observed that there was a rising and alarming trend in failure of UG
There
is no clear
cut Reason
technicalofsolution
challenges
duedamages
to
cables
in recent
years.
rising available
trend in to
UGcope-up
cable the
is mainly
dueassociated
to External
cable
damaged
by
external
agencies.
We,
TPDDL
had
taken
Socio-Technical
initiatives
where
as multiple utilities are working in Delhi to improve the infrastructure facility all across Delhi.
involved
public that
to reduce
the reasons
external damages.
In initial
stageare
all no
the separate
damage prone
Our we
analysis
reveals
the key
for External
damage
trench for
location were identified and Physical route markers were installed at all the locations.
different
utilities, lack of proper communication between different utilities, assignment of
Physical route markers were installed at all the fault prone/critical locations, but there was not
worksignificant
to contractors
to insubcontractors,
unskilled
manpower,
reduction
the cable damage
cases. Todigging
find out the
root causeinconsistency
of the problem,ina cable
depthfield
profile
etc.
survey has been conducted on JCB/HDD machines operators/Labor people. After
nilesh.kane@tatapower-ddl.com
There
is no clear cut technical solution available to cope-up the challenges associated due to
cable damaged by external agencies. We, TPDDL had taken Socio-Technical initiatives where
we involved public to reduce the external damages. In initial stage all the damage prone
location were identified and Physical route markers were installed at all the locations.
Physical route markers were installed at all the307fault prone/critical locations, but there was not
significant reduction in the cable damage cases. To find out the root cause of the problem, a
field survey has been conducted on JCB/HDD machines operators/Labor people. After
analysis of collected data, very surprising result were observed. The phone number
mentioned on the route markers was not toll free, most of the people either do not have
balance in phone or they are not willing to spend a single penny to inform the TPDDL
officials regarding the digging because most of the time, labor persons present at site during
excavation.
Thereafter, A Toll free number was introduced to eliminate the above problem. The same toll
free number is mentioned on the route markers. Awareness sessions for Operators of
JCB/HDD also conducted. Stickers of Toll free number also pasted on JCB/HDD machines to
eliminating the risk of forgetting the number by JCB/HDD machine operators.
This initiative became a mile stone for our efforts. Frequent calling started on the Toll Free no
from General Public, Operators of JCB/HDD, Civic agencies and significant no of cables has
been saved successfully with the joint effort of FLC/Zone/OMS. Approx. 35% reduction was
observed in external damage cases in FY 2015-16 as compared to FY 2014-15.
KEYWORDS
HDD (Horizontal Directional Drilling), OMS (Outage Management System), FLC (Fault
Location Cell), NCT (National Capital Territory), TPDDL (Tata Power Delhi Distribution
Limited), ED (External Damage), UG (Underground)
PROBLEM DEFINITION
Power cables are like the vein in the human body, which carries the life blood of power
distribution sector. Any External Damage of Power cables lead to high operation &
maintenance cost, Revenue loss, Reduced Reliability, unexpected power cut and consumer
dissatisfaction etc.
Some of the possible identified reasons of External Damages are as follows: Due to lack of road cutting permission from the civic agencies, the best suitable
method of cable installation is HDD (Horizontal Directional Drilling) technique. This
technique is time efficient as well as cost effective. So, all the utilities are using this
technique for their UG infrastructure installation. Other side, it has some disadvantage
too. Installation by HDD technique is very much prone to damage of other utilities. It
may lead to damage of other utilities many times, which creates the hurdles for other
utilities. Whenever other utilities tries to repair the same, it leads to damage to some
other utilities. This is like a chain reaction many times, which repeated again and
again.
 Lack of Communication: - Lack of communication between utilities operating in an
area is also a major reason of external damage. There is no proper channel of
communication between utilities.
 Unskilled manpower is also a major reason of external damages. Most of the project
work is carried out by the contractors who depute the unskilled manpower at site to
make the project cost effective.
nilesh.kane@tatapower-ddl.com
308
 Unknown route and depth profile of UG assets: - Many utilities do not map their UG
assets. Even, depth profile mapping is a toughest task in case of UG cable installation
by HDD machine due to variable depth at various points.
 Govt. Regulations: - There is no clear cut govt. regulation regarding the UG
infrastructure installation of various utilities. Moreover, there is no provision of
separate trenches for UG infrastructure installation by various utilities.
To avoid the premature failures due to external damages by other utilities is a very
challenging task now-a-days. All the above factors are leading to rise in damage of power
cable.
MEASUREMENT
UG power cable damage is a pain area for distribution companies since long which are
operating in urban areas but from last 2-3 years, urban areas are developing with high pace.
This is leading the road excavation, road widening, new UG asset installation by all the
utilities to cope up the future demand. Moreover, telecom sector is growing very rapidly.
Most of the telecom companies are upgrading their existing network to make it compatible for
4G internets to reap the benefit of first mover of the industry.
In TPDDL, cables damages by other
utilities contribute a significant share
of total UG cable failures.
The given figure-1 shows the UG
cables faults trends due to external
damage in TPDDL. From the figure,
it can be very easily stated that there
is alarming rising trend of UG cable
faults due to external damage year of
year.
[Fig-1: YoY fault trend of UG cables due to ED]
The trend is rising in spite of using sophisticated technologies for the monitoring the
performance of power cables like optimization of loading, Route cause analysis of failures,
Joint failure analysis, cable jointing kit specification revision, design enhancement of UG
cables etc. The sole reason of this rising trend is exponential rise in external damages Year of
Year.
PROPOSED SOLUTION
nilesh.kane@tatapower-ddl.com
309
Joint failure analysis, cable jointing kit specification revision, design enhancement of UG
cables etc. The sole reason of this rising trend is exponential rise in external damages Year of
Year.
PROPOSED SOLUTION
There is no clear cut technical solution available to cope-up with the challenges associated
due to cable damaged by external agencies. This is the era of science. The technology has
nilesh.kane@tatapower-ddl.com
been updated manifold from the last decade. We are also looking forward for the wireless
technology for power distribution but it the thought of future. Demand of power is rising
exponentially year by year. New infrastructure is required to cope up the future demand of
electricity as well as replacement of old infrastructure is also necessary to provide reliable and
cost effective power.
This paper is a result of several
years of experience of challenges
faced & solutions made in the
TPDDL. We have taken several
Socio-Technical initiatives in phase
wise manner (fig-2) to reduce the
external damage of UG cables by
other utilities.
A detail of activities of each
phase is given in the concerned
figure.
[Fig-2: Initiatives for ED Reduction]
Phase-1:- Since the UG cable infrastructure in Delhi is very old. Electrification was started
here in the early stage of 19th century as well UG cable infrastructure was installed in the
middle of 19th century. At the time of DESU (Delhi State Electricity Utility), there was no
drawing/mapping of UG cables. Knowledge of the UG cable route was only limited to the
people working in that particular area. There was no data base for UG cables route. People
were only dependent on the memory of old people working in that particular area. At the time
of privatization in year 2002, people were shuffled from one company to other according to
their convenience. So, exact route of the existing UG cables was not known to anyone.
TPDDL have very huge UG cable infrastructure, Route tracing of all the old cables and
updation in GIS was a great challenge.
Phase-2:- In second phase, Fault prone locations were identified and physical cable route
markers were installed at all such locations. Approx. 3000 Nos Physical markers were
installed at all such identified locations.
Phase-3:- Physical route markers were installed at all the fault prone/critical locations, but
there was not significant reduction in the cable damage cases. To find out the root cause of the
problem, a field survey has been conducted on JCB/HDD machines operators/Labor people.
After analysis of data collected, very surprising result were observed. The phone number
mentioned on the route markers was not toll free, most of the people either do not have
balance in phone or they were not willing to spend a single penny for informing the TPDDL
officials regarding the digging. Even, we can’t hope for spending some penny to inform
TPDDL officials form labor people.
nilesh.kane@tatapower-ddl.com
310
Phase-4:- A Toll free no (fig-3)
introduced to eliminate the above
problem. The same number was
mentioned on the physical markers as
well as stickers pasted on the
JCB/HDD Machines to eliminating
the risk of forgetting the number by
JCB/HDD machine operators. This
initiative became a mile stone for our
efforts. Frequent calling started on the
Toll Free no and significant no of
cables has been saved successfully in
FY 2014-15 & FY 2015-16 with the
joint effort of FLC/Zone/OMS.
[Fig-3: Toll Free No. Sticker]
OBSERVATION
After taking above initiatives, the
failure rate of the UG cables by
external damage was tracked. It is
found that there was significant
reduction in the UG cables Faults by
external damage.
From the given figure-4, it can be
clearly stated that there is approx.
35% reduction in external damage
cases in FY 2014-15 in comparison of
FY 2013-14
[Fig-4: YoY reduction in external damage cases]
The figure-5 represents the month of
month (MoM) comparison of external
damage cases in FY 2014-15 and FY
2015-16. From the same figure, it can
be clearly stated that there is
significant reduction in external
damage cases month of month.
There is total 33.86% reduction in
external damage cases in FY 2015-16
as compared to FY 2014-15 till
August.
[Fig-5: MoM reduction in External Damage Cases]
nilesh.kane@tatapower-ddl.com
311
CONCLUSION
External damage of UG cables in TPDDL was taken as a research problem. The subject
initiatives are based upon the root cause analysis coupled with public survey, counselling of
JCB/HDD operators, and introduction of Toll free number and installation of Physical cable
route markers on damage prone locations which results in radical downfall in UG cable fault
due to external damage by other agencies.
BIBLIOGRAPHY
[1] http://www.ieee.org/index.html
[2] http://www.wikipedia.com
[3] http://www.tatapower-ddl.com
[4] http://www.tdworld.com
[5] IEEE Standard power cable ampacity table, IEEE Std. 835-1994.
[6] Transmission and Distribution World (2003), “Underground cables need a proper burial”
[7] Lawrance J. Kelly Carl C. Landinger “Electrical Power cable engineering”
[8] Transmission and Distribution World (2003), “Underground cables need a proper burial”
[9] Lawrance J. Kelly Carl C. Landinger “Electrical Power cable engineering”
[10] Power cable catalogue- Cable Corporation of India Ltd.
[11] Power cable catalogue- KEI Industries Ltd.
nilesh.kane@tatapower-ddl.com
312
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
The deployment of mature DC cable technology
MJP Jeroense1, N Mahimkar2, Santhosh BVMP3, J Svahn4, M Moritz1
The deployment of mature DC cable technology
MJP Jeroense1, N Mahimkar2, Santhosh BVMP3, J Svahn4, M Moritz1
1 – ABB High Voltage Cables, PO Box 546, 37123 Karlskrona, Sweden,
2 – ABB HVDC, Ludvika, Sweden / Faridabad, India
3 – ABB GISPL,
Mount
Road
600089,
Chennai,
Tamil
Nadu, Chennai,
1 – ABB
HighPoonamalle
Voltage Cables,
PO Box
546, 37123
Karlskrona,
Sweden,
India
2 – ABB HVDC, Ludvika,
Sweden / Faridabad, India
3 4– ABB
GISPL,
Mount
Poonamalle
Road
600089,
Chennai,
Tamil Nadu,
Chennai,
– ABB Kabeldon, Sävelundsgatan
2, 441
38, Alingsås,
Sweden
India
4 – ABB Kabeldon, Sävelundsgatan 2, 441 38, Alingsås, Sweden
SUMMARY
SUMMARY
Global energy demand is increasing year by year. In order to meet this in a sustainable way renewable
Globalare
energy
demand isin
increasing
by year. In
orderSolar
to meetenergy,
this in a onshore
sustainableand
wayoffshore
renewablewind
energy sources
introduced
an everyear
increasing
pace.
energy sources are introduced in an ever increasing pace. Solar energy, onshore and offshore wind
parks and hydro
energy
examples
of energy
generation
typesthat
that
a bright
parks and
hydro are
energy
are examples
of energy
generation types
willwill
see asee
bright
future. future.
Another Another
significantsignificant
trend thattrend
is seen
in
Asian
countries
is
the
move
of
people
from
rural
area’s
to the cities
that is seen in Asian countries is the move of people from rural area’s to the cities
with a resulting
of energy
consumptionininthese
these urban
TheThe
location
of generation
is
with a resulting
increaseincrease
of energy
consumption
urbanareas.
areas.
location
of generation
is
often from
far away
the growing
urban
areas
wherethe
the energy
energy isis
consumed.
Energy
is mostisefficiently
often far away
thefrom
growing
urban
areas
where
consumed.
Energy
most efficiently
in the form of electricity at high voltage which has the added advantage of lower energy
transmittedtransmitted
in the form
of electricity at high voltage which has the added advantage of lower energy
losses. Overhead lines are and will also be in the future a proper means to transmit large amounts of
losses. Overhead
lines areinand
also
be areas,
in thewhere
future
a proper
means
to transmit
large amounts of
power. However,
and will
around
urban
space
is limited,
the small
foot-print of
power. However,
in and
around
urban
areas,
space
is limited,
the small
underground
cables
is a good
and often
the where
only viable
solution.
Underground
cablesfoot-print
can transmitof
power
through
environment
visually
or by using valuable
and transmit
underground
cables
is aurban
goodareas
andwithout
often disturbing
the only the
viable
solution.
Underground
cables can
limited
space.
They
can
also
be
installed
in
existing
infra-structures
as
ducts
and
tunnels.
power through urban areas without disturbing the environment visually or by using valuable and
limited space.
They can
alsoover
besmall
installed
in existing
infra-structures
as ductscurrent
and tunnels.
Transmitting
power
distances
is normally
done by using alternating
(AC) solutions,
whereas direct current (DC) solutions are in favour when transmitting large amounts of power over
large
distances.
Two
DC cable
technologies
are mostdone
popular,
extruded
cables and
mass- (AC) solutions,
Transmitting
power
over
small
distances
is normally
by i.e.,
using
alternating
current
impregnated
(MI)
cables.
Whereas
MI
technology
has
a
longer
commercial
history,
extruded
whereas direct current (DC) solutions are in favour when transmitting large amounts ofcable
power over
have picked up in installed base significantly since their introduction in the late nineties. The
large distances.
Two
DC
cable
technologies
are
most
popular,
i.e.,
extruded
cables
and
massdevelopment of extruded cables has been gradual, from 80 kV to the now world-record level of 525
impregnated
cables.development
Whereas MI
has a longer
commercial
extruded cable
kV.(MI)
This gradual
has technology
secured the understanding
of the
cable systemhistory,
and has safeguarded
their
by proven
operational experience.
The extruded
cable system
a particular
have picked
upavailability
in installed
base significantly
since their
introduction
in thehas
late
nineties. The
advantage
over thecables
MI alternative
for land
applications
power
density
significantly higher.
It isof 525
development
of extruded
has been
gradual,
from as
80itskV
to the
nowis world-record
level
expected that for sub-sea applications the extruded and MI cable technologies will co-exist for several
kV. This gradual
development has secured the understanding of the cable system and has safeguarded
years in the future.
their availability by proven operational experience. The extruded cable system has a particular
advantage Both
overcable
the MI
alternative
land applications
as accepted
its power
density
is significantly
higher. It is
systems
have beenfor
qualified
according to well
CIGRÉ
recommendations
such as
Electra
189
for
the
MI
cables
and
TB
496
for
extruded
cable
systems.
Extruded
cable
systems
have
expected that for sub-sea applications the extruded and MI cable technologies will co-exist for several
type tested and long term tested (pre-qualified), according to these recommendations. Preyears in thebeen
future.
fabricated joints mainly for land applications, factory joints mainly for sea applications and a novel
termination were part of the test program. The novelty of the termination is that it contains no fluid. It
Both cableissystems
have
been qualified
toofwell
accepted
CIGRÉ
a gas filled
composite
termination.according
The principle
electric
field control
of therecommendations
pre-fabricated joint such as
is making
of the
developed
andsystems.
are in service
since itscable
inception,
i.e. have
Electra 189and
fortermination
the MI cables
anduseTB
496technology
for extruded
cable
Extruded
systems
been type tested and long term tested (pre-qualified), according to these recommendations. Prefabricated marc.jeroense@se.abb.com
joints mainly for land applications, factory joints mainly for sea applications and a 1novel
313 of the termination is that it contains no fluid. It
termination were part of the test program. The novelty
is a gas filled composite termination. The principle of electric field control of the pre-fabricated joint
and termination is making use of the technology developed and are in service since its inception, i.e.
non-linear field control. It guarantees robustness against variations in material parameters due to
varying temperature and field stress.
The installation of extruded cable systems on land is efficient. The cable is robust which allows
different methods of installation for direct burial, duct and tunnel installation as well as crossing rivers
or obstructions by directional drilling. Jointing of a pair of cables is performed in a special
transportable container guaranteeing a clean environment necessary for a successful mounting.
KEYWORDS
XLPE, HVDC, Cables, Accessories
INTRODUCTION
For power transmission, the two basic alternatives are alternating current (AC) and direct current
(DC). Nowadays, in many applications, especially for transmission of power over long distances and
with low power losses, DC is preferred over AC technology. The market for High Voltage DC
(HVDC) cable connections has increased dramatically during the last decade, driven mainly by
interconnectors for land and sea, off-shore wind farms and power supply to oil-and-gas fields. The two
main types of cable system technologies are the MI cable technology and the later introduced extruded
DC cable technology. In the early 90´s intensive research and development efforts have been put into
extruded DC cables, resulting in the first commercial project with a transmission voltage of 80 kV and
a moderate power level. Innovation in DC insulation materials and manufacturing techniques then led
to the commercial deployment of extruded high voltage direct current (HVDC) cable systems, and
after about 15 years of commercial experience, extruded HVDC cables have become a major player in
the portfolio of HV cable products. For a while, the highest voltage on the market for extruded DC
cable systems was limited to 320 kV until recently when the 500 kV range has entered the market.
TECHNOLOGY
The HVDC cable system generally includes two cables, one for positive and one for negative voltages
and accessories. The accessories included are terminations and joints. Depending on the cable
technology joints could be factory joints or prefabricated joints. The classification of cable system can
be done based on several factors, few of main factors are mentioned below.
(i)
AC/DC
(ii)
Insulation system
(iii)
Sea cables or Land cables
AC/DC
An AC cable system differs significantly from a DC cable system in many ways – transmission length,
cable design, field distribution etc. The maximum transmission length for a HVAC cable is decided by
the capacitive charging current while DC cables can be of unlimited lengths as leakage current through
the insulation is negligible, see Table 1.
The principal cable designs differ mainly in the properties of the insulation system and the conductor
configuration. Consideration of skin effect is essential for AC systems and hence the conductor is
segmented. Since there is no skin effect in DC, conductors are mostly compacted or profiled, see
Figure 1.
314
marc.jeroense@se.abb.com
2
(a)
(b)
(c)
Figure 1 Different types of conductor used for HV transmission (a) Segmented (b) Compact (c) Profiled
In AC cables the electrical stress is only a function of insulation geometry and the maximum electrical
stress always occurs at the conductor screen. However, for a DC cable the resistivity of the insulation
decides the electrical stress. Since resistivity is temperature dependent, the electrical stress is also
influenced by the temperature conditions in the cable [1, 3]. During stationary DC conditions the
electrical stress is a function of the ohmic conductivity of the insulation, which in turn is a function of
electrical stress and the temperature according to the formula
𝜎 = 𝜎� 𝑒 (𝛼𝜃��|𝐸|)
where
𝜎� = electrical conductivity of insulation at ambient temperature (1/*m)
𝜃 = temperature at radius r above ambient temperature (˚C)
𝐸 = electric stress at radius 𝑟 (kV/mm)
𝛼 = temperature coefficient for insulation (˚C-1)
𝐾 = stress coefficient for insulation (mm/kV)
The electrical stress in the insulation will therefore vary both with radius and temperature gradient in
the insulation. At no load the maximum electrical stress will occur at the conductor screen, similar to
the AC – conditions. However, when the temperature at the conductor increases, the stress at the
conductor will decrease and the electrical stress at the outer surface of the insulation will increase.
Consequently the electrical stress in the insulation will be a function of the load.
INSULATION SYSTEM
Many insulation materials have been in use from the beginning of cable technology. The first cable
that was developed is a telegraph wire in 1845, manufactured in United Kingdom using tree latex
called “Gutta-Percha”. Some of the major insulation systems used today for AC and DC are listed
below.
 Extruded (mostly XLPE) insulated cables for AC and DC
 Mass impregnated cables for DC
 Oil filled paper insulated cables for AC and DC
Among these technologies the first two cable technologies are predominant in HVDC, shown in
Figure 3. The XLPE cable has an insulation of cross-linked polyethylene where the semiconducting
layers and insulation layer are extruded in one step, whereas the mass impregnated cable has kraft
paper lapped around the conductor including semiconducting layers and is afterwards impregnated
with very high viscosity oil [2]. These cable technologies have been in use for several decades and are
now available up to 525 kV.
As shown in Figure 3, a power cable comprises of three major components - conductor, insulation and
outer jacket. The conductor determines the current carrying capacity and the thickness of insulation
determines the operating voltage. Power density, a measure to relate the power to the size of cable,
depends on the voltage and conductor material. Power densities of aluminium and copper are
compared for HVAC and HVDC cables in Figure 2. From the figure it is evident that the power
density is higher at higher operating voltages in case of HVAC cables. A close observation reveals two
marc.jeroense@se.abb.com
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3
important points. One, that copper and aluminium have power densities close to each other; two, for
HVDC, extruded cables have higher power density than MI cables.
Power density [MVA/kg] - 3-ph
HVAC sea
Power Density [MW/kg] - HVDC
525 kV
6
60
5
50
40
4
30
3
20
2
10
1
0
Land
0
72.5 kV
145 kV
245 kV
Copper
Aluminium
420 kV
Sea
Land
Extruded
Copper
Sea
MI
Aluminium
Figure 2 Power densities per meter cable for some typcial HVAC and HVDC cable designs
The maximum voltage, transmission capacity and maximum transmission length for different
technologies is compared in the Table 1. It should be pointed out that the information in this table is
generalized and the values might vary depending on the specific details, like conductor size and
ambient conditions.
Table 1 Maximum transmission length using different cable technologies
Type of cable
XLPE Cables AC
XLPE Cables – DC
Mass impregnated cables – DC*
Max Voltage
550 kV/420 kV
525 kV
525 kV
Power rating
1200 MVA
>2000 MW
>2000 MW
Length
60 – 150 km**
Unlimited
Unlimited
*PPLP cables are also available for voltages higher than 525 kV.
**The limits are approximate. The lower limit is true for large powers and high voltages, whereas the upper limit is
valid for lower powers and voltages.
Figure 3 Different kind of cables – From left to right, Extruded DC, MI and HVAC.
SEA OR LAND
Another classification is a sea cable or a land cable. Typical configurations of extruded sea and land
cables are shown in Figure4. The main difference lies in the mechanical aspects. The sea cables need
to qualify mechanical stresses when being installed and protected. Hence sea cables have armouring as
an additional layer to take care of the forces during cable laying and protection. The number of
armouring layers depends on the depth of installation and the thickness of the steel. Generally, for
shallow waters single layer armour is used and for deep sea applications double layer is used.
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4
1. Conductor
1
2
3
4
5
6
7
8
8
9
1
2
2. Conductor Screen
3. Insulation
4. Insulation Screen
3
4
5
10
5. Water Barrier
6. Lead Sheath
7. Inner Sheath
8. Armouring
11
12
9. Outer Cover
10. Metallic Screen
11. Metallic Sheath
12. Outer Sheath
(a)
(b)
Figure4 Extruded cable models for (a) deep sea applications (b) land applications.
EXTRUDED DC
CABLE
Extruded cables have advantages over the paper lapped cables such as higher power density, simpler
production process, lower weight, easier joint installation, etc. An ideal DC extruded insulation
material needs to have proper DC conduction behaviour apart from having the properties like high
electrical withstand, chemical stability and good ageing properties [3]. Different options are available
for the insulation of a HVDC extruded cable like Cross linked polythene, thermoplastics and there are
also few concepts with fillers in insulation [2].
Since its introduction, XLPE has been a preferred insulation material for extruded DC. Currently
cables from 80 kV to 320 kV are produced and being installed. A recent breakthrough in extruded DC
cable systems is the voltage level of 525 kV. After more than a decade of commercial experience and
an installed base of about 2500 km from Sweden, extruded HVDC cables have become a major player
in the portfolio of HV cable products.
ACCESSORIES
In addition to the cable, the accessories are essential components in extruded cable systems to enabling
jointing and connecting cable ends. Joints are used for connecting two cable ends and can simplified
be categorized into sea (factory) type joints or land (prefabricated) type joints. Terminations are used
for connecting cable ends into indoor or outdoor switchgears.
In the case of underground installations short cable sections are transported to the site using drums and
consequently require several land joints to link the sections. When installing sea cables a cable laying
vessel is used allowing transportation of cables in one or few lengths. The manufacturing lengths are
jointed by factory joints to form a delivery length. For very long cables requiring more than one laying
campaign, field joints are made on sea.
While the factory joint has welded conductor connector and moulded layers using the same materials
as in the cable insulation system, the land joint is a rubber one-piece prefabricated design. The
prefabricated joint can be installed within only one or two days.
Most robust is the use of patented non-linear resistive stress grading technology in combination with a
geometrical stress grading for the prefabricated HVDC joint. The combination of the continuous layer
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5
of stress grading material and geometrical stress control ensures a robust design even when
temperatures vary in the cable system during load cycling and dynamic loads. The essential property
of the non-linear resistive material is that its electrical conductivity is strongly electrical stress
dependent; the material is adjusting its conductivity if the electrical field increases and thereby
controls the stress level. The stress distribution in the adjacent insulating layers of the cable and the
joint are dominated by the field distribution in the non-linear material layer. This makes a very robust
system under load changes [2]. Fast transients such as impulse wave shapes can be effectively graded
by controlling the onset values as well as the time scale on which the material should act by the proper
choice of the conductivity´s electrical field and temperature dependence. The unique combination of
non-linear parameters and geometrical stress control gives the robust design for extruded HVDC
accessories even up to 525 kV.
The termination design is based on existing HVDC bushing technology and has the same type of
robust stress control as the joint, polymeric composite insulator filled with insulating dielectric gas
(SF6) and a non-linear resistive stress grading layer inside along the cable combined with a stress
cone. This ensures the same combined non-linear material and geometrical stress control as for the
joint.
TESTING
Testing of a cable system and its components is an integral part of development and supply of cable
systems. In order to gain from international common knowledge and coherence in testing strategies,
standards and recommendations have always been at the core of the technology business. Several
categories of testing are commonly used, that is, development testing, long term testing – sometimes
referred to as pre-qualification testing, type testing, routine testing, sample testing, factory acceptance
testing and after-installation testing. The relevant test documents for MI cables are Electra 189 titled
“Recommendations for tests of power transmission DC cables for a rated voltage up to 800 kV”
published by CIGRÉ. For extruded DC cables the relevant CIGRÉ document is TB496 titled
“Recommendations for Testing DC Extruded Cable Systems for Power Transmission at a Rated
Voltage up to 500 kV” [4]. These two documents state the procedures of electrical testing of cable
systems. Especially submarine cable systems have to be tested for the mechanical forces that may
occur during installation, repair and recovery. To this end one should use – for both MI and Extruded
DC cables – the CIGRÉ recommendation TB623 titled “Recommendations for mechanical testing of
submarine cables” [5] which replaces the Electra 171 document. The remainder of this section will
deal with the tests of extruded cable systems.
The type and number of developments tests is not regulated nor advised by the recommendations. It is
up to the manufacturer as part of their extensive development program to perform the relevant and
necessary tests. For the extruded cable system it can truly be stated that leakage current measurements
are of high importance, especially for the development of the highest voltages as 320 and 525 kV.
A prequalification test or long-term test, two names for the same test, has to be performed to qualify
the technology. Such a test is typically performed only once and is not delivery project specific. Later
on we will see that the type test is the right tool for this purpose. The long-term test is to be performed
on a test circuit with at least 100 meters of cable and including all the relevant accessories. The test
consists out of two parts; a cycling part with a 1 year duration followed by a sequence of
superimposed surge tests. During the 1 year test a number of current loading schemes have to be
followed (see left hand side of Figure 5). The voltage that has to be applied continuously should be
1.45 U0. The purpose of the surges is just to check the integrity of the system after the 1 year
stressing. The world’s first 525 kV extruded cable system with accessories has been long-term tested
and type tested.
marc.jeroense@se.abb.com
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6
Figure 5. Left: long term test scheme. Right: 525 kV cable system type test set-up.
A Type test is performed when a specific design or solution has to be qualified. This is often related to
a commercial delivery. The test duration is much shorter as compared to the long-term test and is 30
days of cycling followed by a number of superimposed surge tests. The surges should be of the
switching type (obligatory), they are superimposed on the DC voltage at U0. Both surges of the same
polarity as well as the opposite voltage as the underlying DC voltage shall be applied; 10 of each type,
resulting in 40 surges. If the cable system shall be exposed to lightning, for instance mixed overheadcable systems, also a set of superimposed lightning surges shall be applied.
Routine tests are performed to check the integrity of every manufacturing length or accessory piece
under delivery. This is done by applying a DC voltage and for the cables also an AC voltage. AC
voltages have been shown to be a good way to detect and burn out possible manufacturing defects.
Factory acceptance tests are performed on a complete delivery length, typically for sea cables, where
several manufacturing lengths are connected together to delivery lengths. Also in this case a DC
voltage is used, but also an AC test voltage is recommended. The possibility of applying AC voltages
here might be limited by the cable length and the capacity of the test equipment. It is important to
realise that a routine test never can replace a supreme quality system; it should merely be seen as a
proof of such system.
Finally an after-laying test is performed to verify that the transport and installation has not led to any
significant problems.
INSTALLATION
Cable systems, land as well as sea, are installed such that a limited visual impact remains. The
following section describes some general aspects of sea and land cable installations.
SEA
Single armoured cables can be coiled on a smaller vessel or barge. Double armoured (counter
helically) cables intended to be installed at larger depths (typically more than 1-200 meters) cannot be
coiled and shall be installed with a lager vessel with a rotating turn table. Special cable installation
vessels exist with one or two turn tables with together up to or exceeding 10,000 metric tonnes of
cable weight. In the case the vessel is equipped with two turn tables, both a plus and minus DC pole
can be laid simultaneously. When leaving the vessel they are bundled together with a wire. The
advantage of laying two cables simultaneously is the lower cost as one only has to pass the route once.
Both MI and XLPE cables are suitable for laying at all depths from shallow to deep – the deepest
installed up to now being 1640 meters. Extruded DC cables are a robust solution that more and more
are used as interconnectors and have a good track record in Offshore Wind and Oil & Gas
applications. Depending on the level of risk of damage due to for instance anchor dropping, the cable
can be trenched into the soil or rock. Rock dumping can also be used for local protection. Pre-rock
dumping techniques might be used to level out the seabed in order to avoid free-spans. The CIGRE
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Recommendation TB 623 Recommendations for mechanical testing of submarine cables should be
used in order to qualify the cable system for the intended application.
LAND
The installation of land cables can be performed in different ways. In a rural, non-urban area, the cable
installation is often performed in three steps: excavation, pull-in and back fill. The step of excavation
means creating the cable bed, the pull-in operation is the step where the cable is installed. And finally
the back-fill operation means filling the cable trench with either the previously excavated soil or a
mixture of that with cable sand with specific thermal properties. Examples can be seen in Figure 6.
Figure 6. Example of land cable installation : excavation, pulling, back-filling.
In case the trajectory is very long with no obstacles special laying techniques can be used that combine
the excavation, laying and back-fill operation in one sequence. River crossing can be made by
Horizontal Direct Drilling (HDD) methods for lengths up to at least 1500 m. Open trench methods are
used for urban areas.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
Anders Gustafsson, Marc Jeroense, Hossein Ghorbani, Tobias Quist, Markus Saltzer, Andreas
Farkas, “Qualification of an extruded HVDC cable system at 525 kV”, JICABLE 2015 Paper
A1-7.
Marc Jeroense, Markus Saltzer, Hossein Ghorbani, “Technical challenges linked to HVDC
cable development“, JICABLE 2013, HVDC Seminar Perpignan 18-20 November 2013, also
published in REE N0 4 / 2015, pages 3-10
V. Eriksson, J. Andersson, V. Englund, P.-O. Hagstrand, A. Kontro, U.H. Nilsson, E.
Silfverberg, A. Smedberg, ”Long term performance of XLPE insulation materials for HVDC”,
JICABLE 15, June 2015, Paper B6.2.
CIGRE Technical Brochure 496, “Recommendations for testing DC extruded cable systems for
power transmission at a rated voltage up to 500 kV”, April 2012.
CIGRE Technical Brochure 623, “Recommendations for Mechanical Testing of Submarine
Cable Systems”, June 2015.
marc.jeroense@se.abb.com
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on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
CIGREAORC
Technical
Meeting
2016Grid,
and
International
Conference
of
Power
Transmission
& Distribution
Systems
including
Smart
24-26
Feb. 2016, New Delhi,
India
Riser
Cable
Installation
for
7MW
Floating
Wind
Turbine
In Fukushima Floating Offshore on
Wind Farm Demonstration Project
“Global Trends in the Development of Power T&D System including Smart Grid”
H. SAKAKIBARA, T. KAGOURA
S. FUJII
Furukawa Electric Co., Ltd
Y. TATENO, K. YAGIHASHI
H. TANAKA*
VISCAS Corporation
Riser Cable Installation for
7MW Floating Wind Turbine
Japan
In Fukushima Floating Offshore Wind Farm Demonstration Project
H. SAKAKIBARA, T. KAGOURA
S. FUJII
Furukawa Electric Co., Ltd
Japan
Y. TATENO, K. YAGIHASHI
H. TANAKA*
VISCAS Corporation
SUMMARY
The research and development for the renewable power energy to utilize marine energy, such as an
offshore wind power generation and an ocean thermal energy conversion, are promoted with IndustryGovernment-Academia collaboration.
Furukawa Electric Company (FEC) and VISCAS Corporation have proceeded with a Fukushima
floating offshore wind farm demonstration project (Fukushima FORWARD Project) as a partner of the
commissioned project under the Ministry of Economy, Trade and Industry and are responsible for a
transmission system (including a power and an optical transmission lines) for the whole project.
SUMMARY
The authors have reported those details of development of the dynamic cable system applied in the 1st
The stage
research
andThis
development
forthe
thedevelopment
renewable ofpower
energyjoint
to utilize
energy,
such
[1], [2].
paper reports
a submarine
and themarine
technique
of cable
andas an
joint wind
installation
the sea applied
2nd stage.
offshore
powerin generation
andinantheocean
thermal energy conversion, are promoted with IndustryThe submarine jointcollaboration.
has been developed to connect cables having different designs since the
Government-Academia
transmission
system
was composed
of VISCAS
combinations
of riser cable
submarine
The
Furukawa
Electric
Company
(FEC) and
Corporation
have and
proceeded
withcable.
a Fukushima
performance
of
submarine
joint
such
as
mechanical
strength
and
water
pressure
resistance
were
floating offshore wind farm demonstration project (Fukushima FORWARD Project) as a partner of the
checked to comply with the criteria.
commissioned
project under the Ministry of Economy, Trade and Industry and are responsible for a
During cable installation it had been carried out with a great care so that the riser cable shape and
transmission
system
a power
and an optical
positions could
be(including
checked to meet
the designed
values.transmission lines) for the whole project.
The The
authors
have
reported
those
details
of
development
of the dynamic
system
in the 1st
cable installation and connection to the offshore substation
and windcable
turbines
wereapplied
successfully
stagecompleted,
[1], [2]. This
reports
the development
of a submarine joint and the technique of cable and
and itpaper
is under
operation
now.
joint installation in the sea applied in the 2nd stage.
The submarine joint has been developed to connect cables having different designs since the
KEYWORDS
transmission
system was composed of combinations of riser cable and submarine cable. The
Renewableofenergy
- Floating
windsuch
turbine
High voltage strength
- Dynamicand
cable
- Riserpressure
cable - Submarine
performance
submarine
joint
as -mechanical
water
resistance were
joint to
- Water
protection
checked
comply
with the criteria.
During cable installation it had been carried out with a great care so that the riser cable shape and
positions could be checked to meet the designed values.
The cable installation and connection to the offshore substation and wind turbines were successfully
completed, and it is under operation now.
KEYWORDS
Renewable
energy - Floating wind turbine - High voltage - Dynamic cable - Riser cable - Submarine
h-tanaka@viscas.com
joint - Water protection
321
1. INTRODUCTION
An offshore floating wind turbine is a promising power generation method in Japan, because Japan has
the 6th largest exclusive economic zone (EEZ) in the world and has few suitable shallow shores for
the implantation of the offshore type wind power generations. Offshore floating wind power
generations are very few in the world. The construction of a wind farm which consists of floating wind
turbine and an offshore floating substation was the first experience in the world.
The authors have developed the dynamic cable systems for power transmission from offshore wind
turbine generators to the shore system grid, and completed the cable installation in Fukushima
FORWARD Project [2], [3]. This paper reports the high voltage dynamic cable, submarine joint and
installation method which have been developed for offshore floating system.
2. OVER VIEW OF THE FUKUSHIMA FORWARD PROJECT
2.1 Project Overview
Fukushima FORWARD Project consists of a 1st stage (2011-2013) and a 2nd stage (2014-2015). In
the 1st stage, a 2 MW down-wind type offshore floating wind turbine generator and a 25 MVA
offshore floating substation, for the first time in the world, were constructed and the riser cables
connected those facilities as dynamic power cables. Fig. 1 shows the project overview [4]. The authors
have reported those details of development of the dynamic cable system applied in the 1st stage [1],
[2].
Fig. 1 Project overview
322
1
2.2 Transmission and Substation System
The wind power generation capacities are 2 MW and 7 MW, and a 22 kV cable (inter-array cable) was
selected for the transmission line from the generators to the offshore substation.
The route distance from the proposed shore position to a wind turbine installing position was approx.
25 km long and those were connected with a submarine cable.
An offshore substation was constructed to raise the cable (export cable) voltage to 66 kV for power
transmission from the substation to the shore port because a 22 kV cable had higher transmission loss.
For grid connection, the export cable on shore was connected with an existing 66 kV overhead
transmission line which had been operated by a power utility. Fig.2 illustrates the transmission and
substation system [4]. Only a 7 MW wind turbine is illustrated in Fig. 2 as a representative, however
three sets of wind turbine will be connected to the floating substation eventually.
In the 1st stage the 22 kV inter-array cable was a riser cable with no joint, but the inter-array circuits
in the 2nd stage were configured as a combination of "Riser cables - Submarine cable - Riser cable"
with submarine joints due to some reason in installation schedule.
Fig. 2 Transmission and substation system
3. DESIGNING OF RISER CABLE SYSTEM
3.1 Designing of Riser Cable
Fukushima FORWARD Project is designed with a submarine riser cable consisting of optical fibers to
control a wind turbine, a floating body and also to transmit measured data at site.
The riser cable connected to an offshore floating body shows quite complicated movements due to
shakes of floating body (irregular motion on 6 degrees of freedom) and fluid forces. To design the
riser system, therefore, the riser shape and accessories such as a bend stiffener, distributed buoyancy
modules (DBM) and protection tubes have been designed by analytic simulation of underwater cable
behavior [5]. A riser shape should be selected at first, and then, a static behavior analysis, a dynamic
behavior analysis and a fatigue analysis are in turn conducted with combinations of the various
parameters in accordance with the riser cable design flow illustrated in Fig. 3. Based on those analytic
simulations, the 22 kV riser cable structure is defined as shown in Fig. 4 and Table 1.
323
2
Fig. 3 Design flow of riser cable
Fig. 4 Structure of 22 kV riser cables
Table 1 Structure of 22 kV riser cables
Nominal voltage
22 kV
Conductor
3 x 150 mm2
Insulation thickness
6 mm
Armor
Double layers of galvanized steel wires (6.0 mm)
Outer diameter
147 mm
Weight
43 kg/m in air
324
3
3.2. Designing of Submarine Joint
Since the inter-array circuit in the 2nd stage was configured as a combination of "Riser cables Submarine cable - Riser cable" with submarine joints, the authors developed the submarine joints to
connect cables having different designs (a riser cable and a submarine cable). Based on JEC-3408,
CIGRE TB 490 and CIGRE Electra No.171, the required characteristics of the submarine joint are
shown in Table 2.
Table 2 Required characteristics of submarine joints
Item
Requirements
Nominal voltage
22 kV
Connection
It enables to connect a submarine cable and a riser cable.
- AC: 57kV x 3 hours (at R.T.)
Withstand Voltage
- Lightning Impulse: -230kV x 3 times (at R.T.)
130m of maximum depth
Bearing Water Pressure
Water permeability ” 1×10-7 [g·(cm/cm2)·day·mmHg]
Bearing Tensile Strength
93.1kN approx. of immersing tension
Assembling
It can be assembled on the vessel.
The submarine joint involves three splices of power cable connection and one set of optical cable
splice box inside the 4m protection tube. It is designed that the protective tube is for external damage
resistant to be buried and the structure of cable joint box should have a waterproof function. It is also
designed to have proper strength to withstand mechanical stresses during both installation methods of
horizontal hanging style and catenary shape style. A taped joint have been selected for power cable
connection and water-tight structures have been provided in a protective copper tube. Bend restrictors
have been attached on both edges of the submarine joint to avoid excessive cable bending. It was
ensured that the prototype submarine joint could pass a water permeability test under 1.3 MPa water
pressure. The assembled submarine joint is shown in Fig. 5.
Fig. 5 Assembled submarine joint
325
4
4. CABLE AND JOINT INSTALLATION
4.1. Installation Procedure
The vessel equipped with a turntable was used for cable installation and operated with a function of
Dynamic Positioning System (DPS). The cable laying vessel "KAIYO" is shown in Fig. 6.
Fig. 6 Cable laying vessel (KAIYO)
In the 1st stage the 22 kV inter-array cable was manufactured and installed as a long continuous riser
cable with no joint. But the inter-array circuits in the 2nd stage were configured as a combination of
"Riser cables - Submarine cable - Riser cable" with submarine joints due to the following reasons.
In 2014 (a first year in 2nd stage) the both wind turbines were under construction and hadn't been
installed yet. On the other hand it was considered to complete the cable installation and connection
with two sets of wind turbine in only 2015 (a second year) was quite hard. Therefore, it was decided
that the cable installation work was divided two portions. The cable installation procedure in 2nd stage
is illustrated in Fig.7.
4.2. Installation Work in 2014
The first part which was done in 2014 was installation of a riser cable, a submarine joint and a
submarine cable from the offshore substation to the point at which 7 MW wind turbine would be set
up. At that time, the 7 MW floating wind turbine was under construction in the factory.
It started with pulling up the first riser cable to the floating substation, and DBM and other accessories
were fixed on the cable with unreeling. The riser cable was installed to the expected position with a
care of the touch down point, and the first submarine joint was assembled on the vessel. That joint was
installed in catenary shape style as shown in Fig.8. While the joint was touching on seabed, the
installation process was monitored through Remotely operated vehicle (ROV) with great attention to
cable status and that curvature. Fig.9 shows the joint touch down monitored by ROV.
After the cable installation work, insulation resistance measurement to the power cables and OTDR
measurement to the optical cable were carried out from the offshore substation terminal point.
4.3. Installation Work in 2015
The second part, which was done after installation of the 7MW floating wind turbine, was installation
of a riser cable and a submarine joint in 2015. The submarine joint connected the riser cable and the
submarine cable which had been installed in 2014. At this time, the submarine joint was laid down in
horizontal hanging style as shown in Fig.10. The joint was hung on a horizontal bar and suspended
from a crane and sunk into the sea with a winch. After the installation of transmission system, DC
voltage withstand test (57.5 kV/10 minutes) to the power cables and an OTDR measurement to the
optical cable were done to check the soundness. It was confirmed by ROV monitoring that the riser
326
5
cable shapes and positions were meeting the designed values. Fig. 11 shows cable linear shape
monitored by ROV.
Fig. 7 Installation procedure of 22 kV riser cables and submarine cable
327
6
Fig. 8 Installation of 1st submarine joint
Fig. 9 Joint touch down monitored by ROV
Fig. 10 Installation of 2nd submarine joint
Fig. 11 Cable linear shape monitored by ROV
7. CONCLUSION
The cable installation and connection to the world's largest floating 7 MW offshore wind turbine in the
2nd stage were successfully completed, and it is already under operation.
There is, so far, not enough experience in riser cable transmission system which is required for the
floating power generation system. With the facts found throughout the Fukushima FORWARD Project,
the best transmission system design and the maintenance method will be established.
ACKNOWLEDGMENTS
This research has been carried out as a part of Fukushima floating offshore wind farm demonstration
project funded by the Ministry of Economy, Trade and Industry. The authors wish to express their
deepest gratitude to the concerned parties for their assistance during this study.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
S. Fujii, Y. Tateno, K. Tomikuda, Y. Tominaga, N. Horiguchi, H. Nakano, H. Kon, T. Kagoura, T.
Yamaguchi, H. Sakakibara, "Development of Power Transmission System for Fukushima FORWARD
Project", (Furukawa Review, No.43 pp.28-33, 2013)
Y. Tominaga , H. Nakano, K. Tomikuda, M. Toyoda, S. Torii, K. Yagihashi, M. Minamide, Y. Tateno,
"Dynamic Cable Installation for Fukushima Floating Offshore Wind Farm Demonstration Project", (B11090, AORC CIGRE 2014)
K. Yagihashi, Y. Tateno, H. Sakakibara, H. Manabe, "Dynamic Cable Installation for Fukushima Floating
Offshore Wind Farm Demonstration Project", (B4.3, Jicable 2015)
Fukushima Offshore Wind Farm Consortium
K. Kagoura, "Ocean Power Transmission System", (The Japan Society of Naval Architects and Ocean
Engineers: KANRIN, No.62, 2015) in Japanese
328
7
Protection
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Update from CIGRE India NSC B5
“Power System Protection and
Automation”
By Sanjay Patki
Chairman NSC –B5 CIGRE India
update from NSC B5 : S G Patki
1
CIGRE India
National Study Committee B5
The national study committee on Protection and Automation comprises of 15
Members from Utilities and OEMs
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Sanjay G Patki , Chairman : former Vice President , Tata Power
Mr Rajiv Krishnan, ABB
Mr Abhay kumar , Power Grid
Mr B B Mukherjee, Power grid
Mr Subhash Thakur, NTPC
Ms Saroj Chelluri , NTPC
Mr Ray Mohopatra, CEA
Mr H B Mukund , Essun Reyrolle
Mr M V Kini, Tata Power
Mr Uday Trivedi, Adani Power
Mr Kamin Dave, Ashida
Mr Deepak Saxsena, welspun group
Mr Ritesh Bharat, Alstom
Mr kuldeep Tickoo, Siemens
Mr G K Papneja, Omicron
update from NSC B5 : S G Patki
331
2
Protection Coordination
Uniformity in philosophy and guidelines for Settings :
- Present Protection Manuals published by CBIP act as guide for
Protection Engineers in India. The first publication No 274 , “
Manual on Protection of Generators, Generator Transformers
,220KV & 400KV networks “ was released in November 1999. This
was followed by publication number 296 ,”Manual on reliable Fault
clearance and Back up protection of EHV and UHV Transmission
Networks”, in Sept 2005
- The manuals have been revised to update with the current practices
and new technologies. New Manual was released by CBIP in Dec
2015.
- Apart from revising some of the philosophies (specially from the
perspective of Grid Stability), the Manual has additional chapters to
cover HVDC, FACTs, Renewable Energy Integration, Special
Protection schemes, Application of IEC 61850 standard etc.
update from NSC B5 : S G Patki
Protection Audits and refurbishments
of Protection systems
3
• Consequent to Grid collapse in North and NE
India in 2012, comprehensive audit of protection
schemes was mandated .
• A sub committee on Protection prepared
comprehensive checklist to facilitate Protection
Audits by utilities
• Comprehensive refurbishment and
modernization of Protection systems by
numerical technology has been undertaken by
utilities.
update from NSC B5 : S G Patki
332
4
Special Protection schemes
• The revised planning and operational requirements and security
standards brought out in the Transmission Planning Criteria issued
by Central Electricity Authority in Jan 2013. It stipulates –”To ensure
security of the grid, the extreme/rare but credible contingencies
should be identified from time to time and suitable defense
mechanism such as Load shedding, Generation rescheduling,
Islanding, special Protection schemes (SPS) etc may be worked out
to mitigate adverse impact”
• Number of SPS have since been conceived and commissioned
for Generating stations and transmission systems. Islanding
schemes are also being designed and commissioned for major
urban load centres. Performance of such schemes is being
monitored and further fine tuning will be necessary for
effectiveness.
update from NSC B5 : S G Patki
5
Large scale penetration of renewable
generating resources in the grid
• Large scale solar and wind generations are getting
connected to grid at HV/EHV Level. Further Ultra
mega solar power stations are planned.
Transmission corridors are also planned for
evacuation of renewable power. This will have
new challenges in terms of protection and control
of networks and mitigations measures at points
of connection.
• NSC is studying the protection and control
aspects and will come out with guidelines on the
same.
update from NSC B5 : S G Patki
333
6
New Technology applications in
Protection and Automation
• Application of protection schemes based on
IEC61850 standard
• Pilot projects with Non conventional CT/PTs
• Deployment of PMUs is taking place for wide
area monitoring applications. Further synchro
phasor applications for wide area protection
and control by SPS is planned.
• Digital substations and Smart Grid applications
at Transmission as well as distribution level.
update from NSC B5 : S G Patki
Conclusion
7
• As the Power System is growing with
increasing complexity, new applications will be
emerging while consolidating the applications
of available technologies to make them
effective.
• National Guidelines, standardization, new
tools , engineering /Testing facilities , training
of Protection Engineers will be key for
successful adoption.
update from NSC B5 : S G Patki
334
8
CIGREAORC
Technical
Meeting
2016
and
International
Conference
CIGRE- CIGREAORC
Technical
Meeting
2016
– International
Conference
on International
Global
Trends
in the
Development
AORC
Technical
Meeting
2016 and
Conference
of Power Transmission & Distribution Systems including
Smart
Grid,
24-26
Feb.
2016,
New
Delhi,
India
on
on
“Global
Trendsininthethe
Development
of Power
T&D System
Smart Grid”
“Global Trends
Development
of Power
T&D System
includingincluding
Smart Grid”
The Ground Fault Neutralizer – Smart Bushfire Protection for Australia
The Ground Fault Neutralizer – Smart Bushfire Protection for Australia
Klaus Winter
SwedishWinter
Neutral AB
Klaus
Stockholm,
SwedenAB
Swedish Neutral
Stockholm, Sweden
Ken Barber
Istana Park
Ltd.
KenPty.
Barber
Melbourne,
Australia
Istana Park Pty. Ltd.
Melbourne, Australia
SUMMARY
Bushfires are a common occurrence in many parts of Australia and can start from a number of
SUMMARY
causes. On days of very severe climatic conditions the clashing of bare conductors or broken
power lines can result in bushfire ignition and it is a well-known fact that such ignition can
Bushfires
are a common occurrence in many parts of Australia and can start from a number of
occur with very low currents and quite low voltages.
causes. On days of very severe climatic conditions the clashing of bare conductors or broken
power
linesthe
candisastrous
result inbushfires
bushfire
ignition
it is aonwell-known
such
Following
in the
State ofand
Victoria
February 7th, fact
2009that
where
moreignition can
than with
170 people
lost their
lives on
to bushfires, the Victorian government and
occur
very low
currents
anda single
quite day
lowdue
voltages.
Victorian Utilities undertook an extensive testing program to better understand conditions for
electrical the
arcsdisastrous
to start a fire
and at in
thethe
same
time
protection
Following
bushfires
State
of evaluate
Victoriathe
on best
February
7th, systems
2009 where more
currently available world-wide.
than 170 people lost their lives on a single day due to bushfires, the Victorian government and
Victorian
extensive
testingGovernment
program tois better
understand
conditions for
The nett Utilities
result of undertook
this work isanthat
the Victorian
proposing
to introduce
electrical
to start
a all
fire
anddistributors
at the same
best or
protection
systems
legislationarcs
that will
require
power
to usetime
Rapidevaluate
Earth Faultthe
Limiters
replace
bare wires
with appropriate
insulated cable systems.
currently
available
world-wide.
Thisnett
paper
addresses
the possible
and explains
that the alternative
solution to
is introduce
The
result
of this
work iscable
thatoptions
the Victorian
Government
is proposing
clearly to adopt the Ground Fault Neutralizer (GFN) system which is used extensively in
legislation
that will require all power distributors to use Rapid Earth Fault Limiters or replace
Europe for providing not only public safety but also security of supply.
bare wires with appropriate insulated cable systems.
This paper addresses the possible cable options and explains that the alternative solution is
1. BACKROUND
clearly
to adopt the Ground Fault Neutralizer (GFN) system which is used extensively in
Europe for providing not only public safety but also security of supply.
After the bush fires in 1983 steps were taken so that from 1986, progressively in most states
in Australia, virtually all low voltage (LV) distribution lines were either put under-ground or
provided as insulated Aerial Bundled Conductors (ABC). The solution for medium voltage
(MV) or high voltage (HV), distribution was however far more difficult to solve. This was
because with the very low population density in many rural areas, providing
1. mainly
BACKROUND
underground cabling or using HV ABC was considered cost prohibitive.
After the bush fires in 1983 steps were taken so that from 1986, progressively in most states
in klaus.winter@swedishneutral.se
Australia, virtually all low voltage (LV) distribution lines were either put under-ground or
provided as insulated Aerial Bundled Conductors (ABC). The solution for medium voltage
(MV) or high voltage (HV), distribution was however far more difficult to solve. This was
335
mainly because with the very low population
density in many rural areas,1 providing
underground cabling or using HV ABC was considered cost prohibitive.
It was well known from the past and recent bush fires, that in the event of a phase to ground
fault, bushfire ignition is clearly unavoidable with the protection systems that are in the
existing distribution network. What we did not know was the degree of sensitivity that the
protection systems needed to achieve in order to completely, or very significantly avoid
bushfires being started. Some of the reports of this very extensive testing have already been
made available to the public by the Victorian Government and others are soon to be released.
Basically it has been established that where a bare line comes in contact with the ground or
earthed object, (tree branch etc.), to avoid a fire starting, the fault protection needs to operate
in less than 85 msec and the voltage injection into the fault site must be limited to less than
250V within two seconds. Most of overhead line faults are mid-span where ground contact is
generally poor. To detect these high impedance faults, detection sensitivity must be at least
25kOhm. The current injection during subsequent fault tracing also needs to be limited to less
0.5A in order not to start a fire.
Clearly one solution is to replace bare conductors with some form of fully or partially
insulated cable system. The other is to introduce a modern protection system which will meet
the above criteria. It is therefore proposed to discuss the merits and limitations of both of
these options.
2. TESTING NEW TECHNOLOGY FOR BUSHFIRE PROTECTION
As a result of the 2009 bushfires in Victoria - many of them started by power lines - the
Victorian Bushfire Royal Commission initiated the Powerline Bushfire Safety Taskforce in
2011. The PBST’s primary purpose was to look into different options to reduce the harm to
people and property from bushfires started by electrical assets.
Working closely with industry, regulators and the research community the PBST soon
focused on exploring new protection technology which promised a most cost efficient and fast
way to minimize the risk for bushfires started by power lines. A Rapid Earth Fault Current
Limiter, based on fast detection algorithm and power electronics can eliminate fault currents
in a very short time. No fire will start, even in worst case scenarios like broken conductors
falling on dry grass or tree branches coming into contact with power lines. The technology,
originally developed in Sweden for safe power supply in critical industry grids, is also known
under the brand name GFN Ground Fault Neutralizer.
The GFN was intensively tested in 2014 and 2015 with several thousand primary faults in
different test sites. The outcome was presented in a final test report (6) also establishing the
basic performance standard which now is incorporated in the new Victoria bushfire safety
regulations. In a first roll out forty-five GFN systems will be installed in the most fire prone
areas of Victoria.
3. DIFFERENT OPTIONS – DIFFERENT SOLUTIONS
3.1 Solution 1 - REPLACEMENT of BARE CONDUCTOR SYSTEMS
In residential areas and in rural areas in many densely populated countries underground
cabling is the solution. However, despite the significant cost reductions in insulated cables,
the costs for installation in remote or lightly populated areas is such that, the total cost is still
many times the cost of the bare wire systems and hence impractical for sparsely populated or
economical poor regions.
336
2
In some countries, particularly rural European areas, or in places where bush fires are not a
likely to occur, an option to avoid the problems with clashing of conductors is to adopt
Covered Conductors in an open wire system which is similar to the bare conductor system.
Providing a covering on the conductor does not add
significant costs, but the added weight often means extra
poles or newer poles are required increasing the overall
costs.
The improvement in quality of supply by avoiding circuits tripping with clashing of
conductors or contact with vegetation often warrants this cost increase. However, in the case
where a live Covered Conductor falls to the ground it acts no differently to that of a bare
conductor so these Covered Conductor systems are just not suitable for areas where bush fire
mitigation policies are required.
The obvious choice is to adopt a fully insulated Aerial Bundled Cable design (HV ABC)
which can be installed on poles and avoid the cost of underground installation. There are
several design options, and thus whilst these cables are similar in cost to underground cable
the overall installed cost is lower than the underground solution despite the need to more
poles than the conventional bare wire system.
Metallic Screened HV ABC in Malaysia
Non Metallic Screened HV ABC
in Australia
There is now an alternative which we will call the SPACER CABLE system where the
Conductors are partial insulated and additional insulation is provided by the specially
moulded polymer hangers which are connected to the Steel messenger which provides support
for the conductors. In the past these systems where considered very unsightly and so not
selected but with the use of modern UV and track resistant materials they can be made to
blend into the environment as can be seen below.
3
337
Spacer cable in rural Victoria Australia
The SPACER
Spacer cable system in treed area
Because the Spacer cable system has its
own earthed messenger it can be considered
as being similar to the HV ABC system in
terms of electrical performance.
So it can be seen where there are a few
feeders in a region. Where there is a bush
fire risk then there are practical cable
solutions
3.2 Solution 2 – RAPID EARTH FAULT CURRENT LIMITER
Protection is about safety and minimizing risks to people and property. The risk with an
electrical fault is generally described as proportional to the energy injected into the fault site.
Therefore, the IEC standard defines the risk to be proportional to fault current and
interception time – the well-known I2 t criteria.
Everybody understands - protection must be fast – however fault current levels are even more
important to minimize consequential damages. The good news is - both fault current and
interception time can be influenced through the neutral.
Benchmarking for different types of system grounding and neutral treatment with respect to
fault current levels and interception time clearly proves the superiority of the Ground Fault
Neutralizer. Even better - almost all existing grids can be converted to GFN grounding.
This conversion offers one of the most cost efficient investments in grid performance,
improved SAIDI/SAIFI figures and last but not least safety.
338
4
Figure 1
Benchmark for neutral treatment and earth fault protection
4. THE GFN GROUND FAULT NEUTRALIZER
The Ground Fault Neutralizer is normally connected to the neutral of the supplying power
transformer (Y-winding) or a separate grounding transformer (Z-winding). A complete GFNsystem is composed of a modern solid core arc suppression coil (ASC), see Figure 4, a cabinet
with power electronics for voltage/current injection (RCC - Residual Current Compensator)
and the GFN control cabinet.
Figure 3 GFN control cabinet (courtesy Sarawak Energy
Figure 2 Modern solid core dry-type arc suppression coil
339
5
Beside the controls for the RCC voltage/current injection the GFN also provides automatic
retuning for the arc suppression coil and a new twin-scheme fault locator with superior
detection capabilities. Distance-to-fault information can be obtained by feeder looping.
The arc suppression coil forms a parallel resonant circuit with the phase-to-ground capacitive
leakage (Co) of the network. By this resonant circuit the source impedance for single phaseto-ground faults increases in the order of ten to twenty times, sufficient to quench singlephase flashover faults on overhead lines. But it is still necessary to trip the faulty feeder, in
order to minimize the risk for fire and personal hazards due to the remaining active current.
The GFN Ground Fault Neutralizer now provides fast and complete compensation of all
remaining earth fault currents – both fundamental and harmonics – by injecting a 180 degree
opposite current into the neutral. This is beneficial especially in industry- and urban cable
grids where almost all faults start single phase-to-ground (cable screen). If not properly
compensated, a re-striking cable fault quickly develops into a multi-phase or cross-country
fault with subsequent long term outages.
In utilizing the inherent - but so far unused – zero sequence properties of the 3-phase system,
the GFN Ground Fault Neutralizer elevates grid protection to new levels of performance and
takes all the benchmarks of good protection – namely speed, selectivity and last but not least
detection sensitivity.
Figure 1 GFN basic approach to earth fault protection
Figure 3 GFN adaptive zero sequence admittance scheme
Moreover, the GFN action is smart in the way that voltage injection and fault current can be
cancelled out completely without interrupting the power supply – a truly smart grid solution.
Instead of feeder tripping “fault surgery” with lots of outages, the GFN now offers “smart
medication”. The “antidote” – a current equal but opposite to the fault current - is simply
injected into the neutral. No immediate interruption of any power supply is required.
5. The GFN - a paradigm shift in protection by smart neutral treatment
The GFN protects all parts of an interconnected grid – from the power transformer over the bus bar
and the outgoing feeders down to the last corner of the grid – a truly overall protection scheme. This
overall action is accomplished in a very cost efficient way from one point – the neutral.
340
6
Also with respect to personal safety and fire prevention the GFN offers premium protection [3]. A
fault interception in less than three cycles in praxis can never be reached by traditional protection
schemes working on breakers.
6. CONCLUSIONS
There are clearly two solutions to avoiding bush fire ignition the first is the use of fully are partly
insulated cable systems the second is by means of Rapid fault protection. Unless there are very few
bush fire risk areas the cable solution is not economic so that the GFN is the obvious choice
Upgrading the traditional arc suppression coil to a full scheme Ground Fault Neutralizer means that
Waldemar Petersen’s superior protection concept of resonance grounding will survive the ongoing
cabling in many MV grids. (1) (2) (3) The Ground Fault Neutralizer also provides for the first time
truly fire and personal safe operation of sustained faults. As many injury files and bush fire
investigations indicate, speed is still the most essential aspect of protection. With a total response time
of less than 3 cycles – independent of the actual fault location the Ground Fault Neutralizer is
substantially faster than traditional protection schemes (4) (6).
Finally, the possibility to improve already existing PD online detection methods into true “Early
Warning Systems” adds another strong argument for GFN resonance grounding as the superior
grounding concept (5) (7). When you consider all these advantages it is expected that the best solution
for the Victorian distribution network will be to retain the bare wire system and adopt the GFN
solution.
KEYWORDS
Rapid Earth Fault Current limiter, REFCL, Ground Fault Neutralizer, GFN, Neutral Treatment,
Neutral Earthing Resistor, NER, Bush Fire Ignition, Aerial Bundle Cable, HVABC, Spacer Cable
BIBLIOGRAPHY
[1] Wilheim R. and Waters M. “Neutral Grounding in High Voltage Transmission Networks”, Elsevier
Publishing, New York 1956
[2] Winter K. “Swedish Distribution networks – A new method for Earth-fault Protection in
Cable- and Overhead Systems” 5th International Conference in Power System Protection, IEE conference
publication No 368, York/UK 1993
[3] Koetzold B., Gauger V. and Winter K. “ Erdschluss-Vollschutzsystem mit Reststrom-kompensation – ein
Weg zur höheren Versorgungsqualität in erdschlusskompensierten Verteilungsnetzen” ETG Fachbericht Nr 66,
ETG/PSE Summer Meeting, Berlin/Germany 1997
[4] Winter K. “The RCC Ground Fault Neutralizer – a Novel Scheme for Fast Earth Fault Protection,
Proceedings of the 18th Internat. Conference on Electricity Distribution, CIRED, Turin/Italy 2005
[5] Winter K. et al “The RCC Ground Fault Neutralizer – a Novel Scheme for Pre- and Post-Fault Protection”,
Key note address at the Australasian Power Engineering Conference AUPEC, Melbourne/Victoria 2006
[6] Powerline Bushfire Safety Program, REFCL Technologies - Final Test Report, Department of Economic
Development, Jobs, Transport and Resources, Melbourne/Victoria December 2015
[7] M. Seltzer-Grant, K. Winter et al “On-line Partial Discharge Detection on MV cable networks with Ground
Fault Neutralizer” CIRED Stockholm 2013
341
7
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 –on
International Conference on Global Trends in the Development
of Power
Transmission
Distribution Systems
24-26 including
Feb. 2016, New
Delhi,Grid”
India
“Global
Trends
in the& Development
of including
Power Smart
T&D Grid,
System
Smart
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
Addressing Topics of Interoperability and Performance in an IEC 61850 Series
based Power Utility Automation System
THOMAS
RUDOLPH
Addressing Topics of Interoperability
and
Performance in an IEC 61850 Series
Schneider
GmbH System
based Power
UtilityElectric
Automation
Germany
THOMAS RUDOLPH
MAYANK
SHARMA
Schneider
Electric
GmbH
Schneider Electric
Protection
and Control
Germany
France
MAYANK SHARMA
Schneider Electric Protection and Control
France
SUMMARY
IEC 61850 series of standard is more than just a communication protocol – it provides principles and
tools to specify and design a system using a set of information models, services and mapping of these
models and services over a communication protocol. Further, the standard also specifies file format to
SUMMARY
enable information exchange between different equipments during engineering process. The goal of
IEC 61850 series is to reach interoperability between functions to be performed by power utility
IEC automation
61850 series
standard is more
than justFurther,
a communication
protocol –requirements
it provides principles
in of
a multi-vendor
environment.
verifying performance
of such and
toolsfunctions
to specify
and design
a system
using a setrequirements
of information
and mapping of these
against
the standard
or contractual
is yetmodels,
anotherservices
area of investigation.
models and services over a communication protocol. Further, the standard also specifies file format to
Allinformation
of the above exchange
principles between
can be realized
through
present generation
of vendor agnostic
enable
different
equipments
during engineering
process. engineering
The goal of
tools
which
are
capable
of
addressing
requirements
of
a
power
utility
automation
system
along
its
IEC 61850 series is to reach interoperability between functions to be performed by power utility
system
life
cycle.
Further,
adding
a
layer
of
analytics
on
top
of
the
engineering
process
has
additional
automation in a multi-vendor environment. Further, verifying performance requirements of such
benefits
in terms
increasing
system specification
efficiency,
phase of project and
functions
against
theofstandard
or contractual
requirements
is yetimprove
anothertendering
area of investigation.
identify and then mitigate risks such as detecting non-interoperable behaviour and failure to meet
function
performance
requirements
duringthrough
early phase
of project
life cycle.
All of
the above
principles
can be realized
present
generation
of vendor agnostic engineering
tools which are capable of addressing requirements of a power utility automation system along its
In this paper, 2 enhancements in context of a power utility automation system life cycle are proposed.
system
Further,
adding
layer of analyticsbehaviour
on top ofand
the estimate
engineering
process
has additional
Thelife
usecycle.
of analytics
could
detecta non-interoperable
function(s)
performance
of
benefits
in
terms
of
increasing
system
specification
efficiency,
improve
tendering
phase
of project and
a power utility automation system, thereby reducing project risk in a multi-vendor environment.
identify
andathen
risks such
as detectingoffers
non-interoperable
behaviour
and failure
to meet
Further
cloudmitigate
based approach
to engineering
data consistency
and collaborative
framework
function
requirements
during early phase of project life cycle.
over performance
entire system life
cycle.
In this
paper, 2 enhancements in context of a power utility automation system life cycle are proposed.
KEYWORDS
The use of analytics could detect non-interoperable behaviour and estimate function(s) performance of
a power
system,
thereby reducing
project risk
in a multi-vendor
environment.
IEC,utility
61850,automation
smart grid, utility
automation
system, substation
automation
system, interoperability,
Further
a cloud based
approach to engineering offers data consistency and collaborative framework
performance,
SGAM.
over entire system life cycle.
KEYWORDS
thomas.rudolph@schneider-electric.com
IEC, 61850, smart grid, utility automation system, substation automation system, interoperability,
performance, SGAM.
342
THE GROWING PERVASIVENESS OF IEC 61850 AND ISSUES AT HANDS
IEC 61850 series of standard [1] has become a standard of choice for designing substation automation
systems (SAS). Since the publication of its first edition in 2003 comprising of 10 parts, the standard
has become a popular choice to build SAS with number of delivered projects going to some thousands.
The main value of IEC 61850 is not just the mapping to a communication stack; it is the detailed
support of business- related semantic models which allows modelling of power system equipment,
associated “smart” functions, and related global information exchange. Furthermore, it provides
enough flexibility to address new demands as demonstrated by the recent evolution towards the Smart
Grid, as depicted in the Smart Grid Architectural Model (SGAM), adopted by IEC 62559 and IEC
62913-1 [2, 3]. The SGAM clearly specifies the outreach of the IEC 61850 to all domains concerning
power and energy sector and all the way upto the control centre zone. The interfacing with zones
covering operational, enterprise and market dynamics is modelled by the IEC 61968 and IEC 61970
[4, 5].
Figure 1 – The SGAM model.
The central goal of the IEC 61850 series of standard is to provide interoperability between all devices
in power utility automation systems. However, utilities who have been an early adopter of the IEC
61850 series for their SAS have presented case studies listing out elements that could improve
interoperability aspect in a multi-vendor SAS. Lessons learned during project design and
commissioning have been documented and published. Some of these publications [6] advocate
developing a higher level of interoperable functions and propose standard test cases to assure a
minimum level of interoperability.
In addition to interoperability, another important subject is performance estimation of a given
application function within an automation system. IEC 61850-5 provides automation system
performance requirements for different message types. Performance estimation of a given automation
system function during the design phase has a direct impact on the contractual requirements.
Therefore, it is prudent to have some kind of performance estimation capability early on during the
project design phase.
HOW RULES BASED SYSTEM SPECIFICATION IMPACTS INTEROPERABILITY
From a system engineering perspective, the IEC 61850 standard provides a high degree of flexibility
in terms of data model implementation hosted within an intelligent electronic device (IED). This
means that each IED has a different information support and service model in terms of implementing
optional fields/features within the IEC 61850 standard. Thus, a subset of IEC 61850 can reside in
different products and solutions, which potentially could lead to an interoperability issues when using
multi-vendor IEDs.
The pyramid of Figure 2 depicts the different levels at which interoperability is addressed.
343
0
At level 1 rests the IEC standardization body responsible for interoperability issues. IEC has
developed processes to ensure the issuance of a high level of quality within its standards. For example
technical committee 57 (TC57) has put into place a dedicated process called TISSUES (technical
issues) to address interoperability issues. The edition 1 of part 10 the IEC 61850 series covers
compliance testing of IEDs which has been extended - in its edition 2 - to cover IEC 61850 compliant
clients as well as the engineering tools. Several clients and tool suites exist as well that serve as base
for compliance testing of certification bodies. Guidelines such as draft technical report IEC 61850-7500 [7] provide information about recommended implementations of application functions based on
the core standards of IEC 61850. Ongoing work by TC57 WG10 (working group 10) involves
development of Basic Application Profiles (BAPs) [8] which make mandatory the use of service
models and data objects in order to model different application functions. Such profiles which could
be region, country or customer specific would impose a common level of implementation within all
IEDs, clients, and tools which support them. When published, this could be another level to address
interoperability.
Level 2 represents the independent and authorized certification labs which establish IED conformance
to certain parts of the IEC 61850 standard and issue conformance certificates.
Level 3 represents a rule-based system specification and automation system engineering. These rules
act as a supplement to all of the existing levels and provide an additional knowledge base to address
interoperability issues.
Level 4 involves the Utility Communication Architectures International User Group (UCAIug) which
hosts interoperability tests meetings (IOP) in order to address IED and system engineering tools and
IED interoperability.
Level 5 involves real world projects and automation system testing at factory or customer sites with an
emphasis on interoperability issues and the direct impact on project time and costs.
Cutomer project execution - Acceptance Tests
(FAT and SAT)
UCAIug - Interoperability tests (IOP)
Rules driven system specification and automation
system engineering
Independent certification parties - device and
tool conformance
Standard bodies IEC - Technical standard and
reports, application modeling guidelines,
BAPs*, and TISSUES
Figure 2 – Different levels of interoperability.
Rules driven system specification
A system specification begins with a description of the system. This consists of an electrical one
line diagram, and allocation of functional elements – described as logical nodes - to the parts and
equipment associated to the one line. Then, the IEDs provide a defined set of logical nodes that are
bound to a specific process function and primary equipment. Finally, service models are selected to
344
1
address the information sharing functions and are mapped to a communication protocol. Now the
elements are in place to build an automation system.
System configuration description language (SCL) plays an important role during system specification.
The creation of a set of rule definitions that supplements SCL file exchanges provides an additional
way to leverage IED capabilities during system specification. Rules will incorporate aspects on device
capabilities, manipulations during device interactions and formalized past project knowledge during
system integration activities. Thus, specification is more robust because a knowledge base of IEC
standard compliant capabilities is accessed as is previous project and systems integration experience.
Such a definition methodology allows system integrators to create rules in a specific project
context and store them for exploitation during the project design phase. This helps during the
tendering system design phase for greenfield or retrofit solutions. A system integrator role for
solution engineering could be a vendor, a user or a 3rd party engineering company. Location
independence is possible as the rules are stored in a cloud environment. Thus access across
different vendor sites is possible or the public cloud can be used by utilities or external system
integrators. In cases where the system integrator role is executed by a user or a 3rd party
engineering company, the rule editing context can be easily shared and applied to an agreed-upon
business model. Dynamic rules specific to a given project may also be created and pushed into the
rules repository in real time thus allowing for greater flexibility during project design activities.
Figure 3 – Architectural context for rule manipulations during engineering.
Listed below are few examples of various levels of complexity that could be modeled via rules:
1.
A rule based upon the constraints on an IED “A” with respect to the string length of a
subscribed GOOSE control block name published from an IED “B”. If the string length
exceeds or is under a certain threshold, IED “A” can’t subscribe to a GOOSE message from
IED “B”. This results in non-interoperable behavior.
2.
The configuration of 1 of the 4 types of control models (services) in an IED to operate
switchgear needs to be supported in an equal manner by the related clients.
3.
An IED compliant with an Edition 2.0 needs to provide an Edition 1.0 compatibility mode to
allow easy integration into an existing Edition 1 system.
4.
If an IED doesn’t support the data quality “test” it cannot be used in test mode which could
impact the entire test strategy.
In conclusion, when linked to a given project life cycle, it can be said that rule based intelligence
(and a consistent upgrade to such rules) could be an effective approach to reducing interoperability
risk in IEC 61850-based systems.
345
2
PERFORMANCE ESTIMATION IN AN IEC 61850 BASED SYSTEM
Performance requirements have a direct impact on the architecture chosen for a SAS solution. For
example, consider a fast load shedding system that must react in less than 100 milliseconds. In this
example we see that the performance of a given application function is always related to a
specification. A “rough estimate” of the collaborative performance of the IED(s) early in the design
phase helps to assess risk and will provide commercial benefits later on upon project completion.
Further, a formal way of studying response time performance of an IED must be established. Most
modern microprocessor based IEDs are multitasking computers that execute multiple functions
simultaneously based upon a priority list. For example, tasks such as RMS value computation and
disturbance file storage are low priority tasks. There is as well cyclic scanning of analog and binary
data. High priority tasks include event driven actions – protection and control functions – leading
to detection and execution of trips and event recording.
The interaction of low and high priority tasks introduces a random delay in response to an input
trigger which causes variance in timing of outputs exposed to the IED. This variance can be studied
using application of statistics as it allows users to measure and benchmark any deviations in IED
response time against the requirements of a project or those coming from the standard itself. Such
variations in response time may be small, but in the case of distributed functions they may lead to
deviation in expected performance requirement (see Figure 6).
Performance measurement, recorded on a test bench running well defined test procedures, allows
system integration engineers to foresee possible impacts in the preliminary design phase of
engineering. Figure 4 illustrates the architectural context under which the statistical data coming
from a test bench is stored in a database. It is then acted upon by a set of web services to generate
IED performance reports and system performance studies. This information can be requested by
connected clients (on the left of figure) via their laptops, tablet PCs, or smart phones.
Figure 4 – Transforming test bench data into knowledge base for service creation.
IED and system design performance reporting management
All of this knowledge can be formalized and delivered as a part of service contract to outside users
(e.g., customized reporting service). It can be thought of as part of a service offering that provides
performance information regarding a given IED or that can be used to perform comparative analysis
between IEDs (see Figure 5).
Since the performance of an IEC 61850 system depends on the performance of its constituent
IEDs, the same modeling approach can be extended to estimate response time performance of an
application. A given system application function can be broken down into one or several sub346
3
functions (represented by logical nodes) which may be housed in a single IED or several IEDs
interacting over a given communication link.
Suitable enhancements to an engineering tool can be envisioned that allow a system integrator to
have estimation capability on the performance of the designed application scheme. Such
enhancements can allow:
1. User selection of a given arrangement of IED(s) to realize an application function, e.g.
breaker failure, protection, or a fast load shedding automation function.
2. Selection of IEDs for an application function.
3. Definition of IEC 61850 configuration on each of the participating IEDs.
4. Generation of a system report with response time estimates for the selected application
function.
An example to consider would be that of a breaker failure scheme. The breaker on the incomer
must trip within a given time duration upon receiving a breaker failure status from an outgoing
IEDs in order to protect a part of the power system. Such a mission critical application function
could be studied for its response time performance using the methodology described above.
Figure 5 – IED performance reports repository.
CONCLUSION
IEC 61850 based SAS represent one of the earliest manifestations of the efficacy of IEC 61850 series
of standards for substations. However, the aspects of interoperability and performance of different
SAS functions in a multi-vendor environment continue to pose as topics to be addressed. Ensuring the
necessary functionality over the lifecycle of a given SAS or any utility automation system still remains
a challenge. The value of engineering data is increasing a lot and the upcoming use of data analytics
will allow risk control in project planning and execution as demonstrated in this paper.
An effective application of data analytics is requesting new architectures of tools providing the
benefits to stakeholders. Cloud based tools are enabling up-to-date information sharing as well as
continuous increase of domain specific knowledge to interpret the data. The applications discussed in
this paper are just the starting point. Other tools like profile managers and testing environments are on
the horizon.
347
4
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
IEC61850, ‘Communication networks and systems for power utility automation – ALL
PARTS,’ IEC 61850:2015 SER, 2015.
IEC 62559, ‘Use case methodology – ALL PARTS,’ IEC 62559:2015 SER, 2015.
IEC 62913-1, ‘Generic smart grid requirements - Specific application of the use case
methodology for defining generic smart grid requirements according to the IEC system
approach,’ IEC 62913-1:2013.
IEC61968, ‘Application integration at electric utilities – System interfaces for distribution
management – ALL PARTS,’ IEC 61968:2015.
[7] IEC 61970, Energy management system application program interface (EMS-API) – ALL
PARTS,’ IEC 61970:2015.
J. Holbach, J. Rodriguez, C. Wester, D. Baigent, L. Frisk, S. Kunsman, L. Hossenlopp, "Status
on the First IEC61850 Based Protection and Control, Multi-Vendor Project in the United
States," (Protective Relay Engineers, 2007. 60th Annual Conference vol., no., pp.283-306, 2729 March 2007.)
IEC61850-7-500, ‘Use of logical nodes for modeling applications and related concepts and
guidelines for substations,” IEC DTR 61850-7-500:201, 2013.
L. Guise, G. Huon, P. Lhuiller, M. Haecker, C. Brunner, “IEC 61850 interoperability at
information level. A challenge for all market players” (CIGRE 2014 session, Paris, Aug.
2014.)
348
5
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
“Global
Trends
in
the
Development
of Power
including
Grid”
of Power Transmission & Distribution Systems
includingT&D
SmartSystem
Grid, 24-26
Feb. 2016,Smart
New Delhi,
India
CIGRE- AORC Technical Meeting 2016 and International Conference
on
IP Party
Line,
The Revolution
of voice communication
in Power Utility
“Global
Trends
in the Development
of Power T&DPlatform
System including
Smart Grid”
W. WICHAI, S. YONGYUT, T. CHATREE, C. PATCHARA, S. TAWAN
Electricity Generating Authority of Thailand, Communication System Division
THAILAND
IP Party Line, The Revolution of voice
communication Platform in Power Utility
W. WICHAI, S. YONGYUT, T. CHATREE, C. PATCHARA, S. TAWAN
Electricity Generating Authority of Thailand, Communication System Division
THAILAND
SUMMARY
With the emergence of Internet Protocol that effect to the development platform of
communication equipment, most of communication system in power utility have change their
platform to be IP base due to more flexibility maintainability and cost effectively. In
marketing term, there always use the term IOT (Internet of Things) to present the influence of
SUMMARY
the internet technology in many application area. Telemeter reading and sensor are the good
example
IOT
applicationofinInternet
power utility.
Meanwhile,
theretohave
application of
IOT in of
With ofthe
emergence
Protocol
that effect
thethe
development
platform
other industry such as health care, agriculture that apply IOT to improve their productivity.
communication equipment, most of communication system in power utility have change their
By the same direction, this internet technology trends impact to the change of traditional party
platform
to be IP base due to more flexibility maintainability and cost effectively. In
line development platform that is a system using for communication between substation. In
marketing
term,wethere
always
use the term
IOT (Internet
Things)
towhich
present
thedevelop
influence
this article,
address
the platform
development
of partyofline
system
was
on of
the internet
technology
in
many
application
area.
Telemeter
reading
and
sensor
are
the
good
circuit switch to be internet protocol basis. Our design prototype system compose of
example
of IOT
application
in and
power
utility.
Meanwhile,
therebehave
application
of IOT
embedded
controller
system
software
module
which shall
usedthe
in the
actual system
in in
otherelectricity
industryoperation
such as health
care,
agriculture
that
apply
IOT
to
improve
their
productivity.
and maintenance. Because of this IP basis, we shall use only single IP
centric
for this
all communication
in substation
that reduce
cost of
By the
samenetwork
direction,
internet technology
trends impact
to thethe
change
of operation
traditionaland
party
management
of view,using
all management
message in between
MIB format
shall be In
line maintenance.
developmentInplatform
that point
is a system
for communication
substation.
andwe
integrated
present
the performance
andof
status
of line
thosesystem
IP Partywhich
Line system.
this send
article,
addresstothe
platform
development
party
was develop on
In summary,
the mainprotocol
advantages
of our Our
proposed
IP party
line are
more flexibility
circuit switch
to be internet
basis.
design
prototype
system
compose of
portability
manageability
and
cost
effectively
than
previous
traditional
party
line
system.
This in
embedded controller system and software module which shall be used in the actual system
IP Party Line development project is now during consideration for EGAT R&D funding.
electricity operation and maintenance. Because of this IP basis, we shall use only single IP
centric network for all communication in substation that reduce the cost of operation and
maintenance. In management point of view, all management message in MIB format shall be
send and integrated to present the performance and status of those IP Party Line system.
In summary, the main advantages of our proposed IP party line are more flexibility
KEYWORDS
portability
manageability and cost effectively than previous traditional party line system. This
IP Party Line development project is now during consideration for EGAT R&D funding.
Party Line System, Voice Communication, Internet Protocol
Wichai.wa@egat.co.th
KEYWORDS
Party Line System, Voice Communication, Internet Protocol
349
1. Introduction
Due to the responsibility of EGAT (Electricity Generating Authority of Thailand)
which are about electricity generation and transmission around Thailand, electricity/power
stability or power quality are the key performance indicators. Therefore, the electricity
dispatching and control of electricity flow are very important for power stability. EGAT has
introduced lot of technology to support power dispatching and control system. Party Line is
one of the voice communication technology which was introduced to support dispatching and
control system as well as communication between substation. In the past, Party Line system,
traditional Party Line, was developed base on circuit switch principle and normally couple
with multiplexing system. Hence, it is not flexible and manageable due to the nature of analog
base system.
With the emergence of Internet Protocol that effect to the development platform of
communication equipment, most of communication system in power utility have change their
platform to be IP base due to more flexibility maintainability and cost effectively. In
marketing term, there always use the term IOT (Internet of Things) to present the influence of
the internet technology in many application area. Telemeter reading and sensor are the good
example of IOT application in power utility. Meanwhile, there have the application of IOT in
other industry such as health care, agriculture that apply IOT to improve their productivity.
By the same direction, this internet technology trends impact to the change of traditional party
line development platform that is a system using for communication between substation. In
this article, we address the platform development of party line system which was develop on
circuit switch to be internet protocol basis. Our design prototype system compose of
embedded controller system and software module which shall be used in the actual system in
electricity operation and maintenance. Because of this IP basis, we shall use only single IP
centric network for all communication in substation that reduce the cost of operation and
maintenance
This paper address the revolution of voice communication which was normally use for
dispatching and control system by introducing IP Party Line. The organization of paper are as
follows. The design and system architecture of our propose IP Party Line are introduced in
section 2. In section 3, we present the key feature and system application of IP Party Line.
The last section is paper summary.
2. IP Party Line System Architecture
To present the system architecture of IP Party Line, the whole picture that demonstrate
our design module are shown in Figure 1.
Figure 1. IP Party Line System Architecture
350
1
The architecture of IP Party Line composes of difference module. The fonction of each
module are summarized as follows.
x
x
x
x
x
Controller module: The function of this module is about hardware and software control
system.
Sound Module: The function of this module is about analog to digital transformation.
Interface module: This is about any hardware interface
Display Module: This is about the presentation and graphical demonstration of network
performance
Networking module: This is about networking connection.
3. Application of IP base party line system in power utility
To demonstrate the application of IP Party Line in the actual communication network,
the diagram that depict the IP Party Line application is presented in Figure 2-3 respectively.
Figure ŚThe application of IP base party line system in power utility
As shown in Figure 2, the application of IP Party Line system is introduced to support
Voice Communication between control center substation and power plant. This system is
normally working as a support system for dispatching and control.
351
2
Figure 3. The application of IP Party Line
As shown in Figure 3, IP party Line will be used at EGAT National Control
Center(NCC) for dispatching and control of power around country. This voice
communication system use EGAT data network as a media to set up a communication
between control center, Power Plant and substation. The system converter is introduced as a
gateway to connect between IP base system and native analog Party Line system.
4. Key Feature comparison
To shown the key feature of IP Party Line which has been develop to be a core system
for voice communication. The investigation of system key feature are introduced in Table 1.
The results are presented as a comparison in each key feature between IP base and traditional
system
Table 1. Key feature comparison
Party Line System
IP base Party Line
Traditional Party
Perspective
System
Line System
1. scalability
3
Remark
More scalable and
expandable
2. flexibility
more flexible and easy
3
to installation
3. multimedia support
Extended feature to
3
support multimedia
4. managibility
Standard NMS support
3
5. security
3
352
Cyber security issue
3
Party Line System
Perspective
6. capital investment
IP base Party Line
Traditional Party
System
Line System
Remark
Cheaper in initial cost of
3
investment
7. operational investment
3
cheaper O/M
8. technology trend
3
Follow technology
Direct ion
AS summarized in Table 1, the advantages of IP base party line system are system
scalability, flexibility, performance managibility as well as total cost of ownership. However,
cyber security is still being an issue which need to has future investigation.
5. Conclusion
This paper presents the IP base Party Line system which is a revolution platform of
voice communication using in power utility. System architecture as well as application are
demonstrated in detail. The key feature of our proposed system are presented as a comparison
between IP base system and traditional Party Line system. Obviously, IP base Party Line
system has many advantages such as more scalability flexibility managibility over traditional
Party Line system. However, there still has an issue in system security which need further
investigation.
353
4
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global
Trends
the Development
Power T&D
including
Smart
Grid”
CIGREAORCin
Technical
Meeting
2016 – of
International
Conference
on International
Global
Trends in
theConference
Development
CIGREAORC
Technical
Meeting
2016System
and
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
on
“Global Trends in the Development of Power T&D System including Smart Grid”
Planning EGAT’s IP/MPLS Network as IP Communication Infrastructure for
Power Grid and Smart Grid
1 IP Communication
Planning EGAT’s IP/MPLS
Network as
Infrastructure for
E. DHAVARUDHA
, T. SRIJANTHUB1
1
Power
Grid
and
Smart
Grid
Electricity Generating Authority of Thailand, Communication System Division
THAILAND
E. DHAVARUDHA1, T. SRIJANTHUB1
1
Electricity Generating Authority of Thailand, Communication System Division
THAILAND
SUMMARY
The concept of substation automation has been adopted to Electricity Generating Authority of
Thailand (EGAT)’s power grid for several years. The Internet protocol/multi-protocol label switch
SUMMARY
(IP/MPLS) plays the role as IP communication infrastructure to support all of our operation and
administration applications which serve several intelligent devices in EGAT’s power grid functioning
The concept of substation automation has been adopted to Electricity Generating Authority of
as protecting, controlling and monitoring the equipment in automation substations and power plants.
Thailand (EGAT)’s power grid for several years. The Internet protocol/multi-protocol label switch
These operational technologies (OT) and applications are included IEC60870-101/104 IP remote
(IP/MPLS) plays the role as IP communication infrastructure to support all of our operation and
terminal unit (IP RTU), phasor measurement unit (PMU), automatic meter reading (AMR), fault
administration
applications which serve several intelligent devices in EGAT’s power grid functioning
recording system (FRS), and IP closed circuit television (IP CCTV) are included meanwhile EGAT
as protecting,
controlling
monitoring
the equipment
in automation
powerforplants.
also provides
Voice overand
IP (VoIP)
including
all world wide
web (WWW)substations
and intranetand
services
These
operationaltasks.
technologies
and applications
are very
included
administration
Since the(OT)
mentioned
applications are
curtailIEC60870-101/104
to run our business,IPtheremote
implementation
of reliable
and secured
IP/MPLS
network
to provide
quality
of service
upon fault
terminal
unit (IP RTU),
phasor
measurement
unit
(PMU),
automatic
meter
reading(QoS)
(AMR),
their service
level
agreement
(SLA)
has been
provided.
recording
system
(FRS),
and IP
closed
circuit
television (IP CCTV) are included meanwhile EGAT
also provides Voice over IP (VoIP) including all world wide web (WWW) and intranet services for
In our network, SLAs are categorized into four levels as a real time application service, a critical
administration
tasks. Since
theoperational
mentioned
applications
very
curtail
to run
our
operational service,
a normal
service,
and a bestare
effort
service.
In this
paper,
thebusiness,
reliable the
implementation
of reliable
and secured
IP/MPLS
network
provide
quality
of service
(QoS)
IP/MPLS topology
and physical
installation
together
with atobrief
IP/MPLS
technology
review
are upon
theirdiscussed
service level
agreement
has been
and then
the QoS(SLA)
requirements
of provided.
our IP applications are provided. Later, our designed
mechanisms to provide such a secure and reliable network such as routing protocol, QoS mechanism,
In our
SLAs are
into fourthe
levels
asofa our
realdesigned
time application
service,
a critical
and network,
traffic engineering
are categorized
explained. Moreover,
details
parameters for
IP/MPLS
operational
normal
operational
and a The
bestparameters
effort service.
In thisIP/MPLS
paper, the
reliable
network service,
to ensureaeach
application’s
SLAservice,
are proposed.
are included
VPN
IP/MPLS
topology
and physical
installation
together
withand
a brief
IP/MPLS technology review are
configuration,
bandwidth
assignment,
IP address
assignment,
QoS configuration.
discussed and then the QoS requirements of our IP applications are provided. Later, our designed
Ekularn.d@egat.co.th
mechanisms to provide such a secure and reliable network such as routing protocol, QoS mechanism,
and traffic engineering are explained. Moreover, the details of our designed parameters for IP/MPLS
network to ensure each application’s SLA are proposed. The parameters are included IP/MPLS VPN
354
configuration, bandwidth assignment, IP address assignment, and QoS configuration.
In addition to our IP/MPLS implementation for power grids as mentioned,
we know that global
electric power industries including EGAT are now facing a new era of transformation to smart grids as
the driving force of global warming and shortage of the fossil and gas fuel resource problems. High
performance IP communication infrastructures are major key success role in smart grid as they are
utilized for advance communications, automated control, and information technology. Smart grid
communications infrastructures are needed to integrate huge amount of power grid and customer
devices such as advanced meter device (AMI), storage facilities, demand response management
(DSM) information, and enormous data of information technology (IT). Thus, the communication
networks need to support high performance data delivery which enable reliable remote control systems
and also carry the real time and fast real time monitoring & controlling of condition and performance
of electric systems. In addition, two-way communications for smart grid operation and administration
tasks including data, voice, and video applications are more demanded.
In this paper, we also give the discussion about how EGAT plan our IP/MPLS network for the
upcoming smart grid applications. The discussion is included our planning to upgrade our IP/MLS
network elements to ensure reliability & availability with great amount of bandwidth for EGAT’s new
IEC 61850 substations of which they are planed to be included the new operation applications as IEC
61850 IP RTU, IEC 61850 FRS, micro energy management system (µ-EMS) and so on. The result of
our plan can efficiently support the near future intelligent services for smart grids; however, there are
some important topics shall be focused such as how to integrate OT and IT network. Thus, this issue is
discussed in the last topic.
KEYWORDS
IP/MPLS network, Smart substation, Smart grid, Quality of service, Service level agreement, IP
Application, IEC 61850
1. Introduction
EGAT’s existing protocol/multi-protocol label switch (IP/MPLS) network is a backbone network
severing both operation and administration IP applications. The main purposes of operation
technologies (OT) are providing IP communication for monitoring & controlling, managing,
protecting, and executing the equipment of electric networks (power generation, transmission systems,
substations, and distribution networks) in real time or near real time operation. The voice and video for
operational communication are also categorized in the operation applications. For administration tasks,
they provide information technologies (IT) which are mostly software applications for commercial
decision making, planning, business, processes management and resource allocation for power
utilities. The IP/MPLS technology can reserve network resources with differentiated service (Diffserv)
model by providing traffic differentiation based on per-hop quality of service (QoS) and specifying
basic mechanisms on the way to treat packets. In addition, Difserv is defined into two services which
are absolute service differentiation and relative service differentiation. The first one provides a worstcase service to guarantee the application in each class whereas the second one relatively defines QoS
355
1
based on other classes. In our case, the IP/MPLS can provide QoS in the first sense and we classify
the IP services into four classes as follows:
- Class 1: Best effort. All the Internet, IT and World Wide Web (WWW) applications including the
closed circuit television (CCTV) running on the same virtual network as the IT application are best
effort. No committed SLA and QoS is assigned. Therefore, when the network is congested the traffic
in this category will be dropped first. However, this class consumes majority bandwidth (average of 60
percent) in the network.
- Class 2: Critical. This class is mainly for the monitoring, metering, and tele-control applications
which consume low bandwidth per one session. This class is included phasor measurement unit
(PMU) conforming IEEE C37.118 standard, wide area monitoring (WAM), fault recording systems
(FRS), and lightning location system (LLS) which are monitoring service. For the automatic meter
reading (AMR), it is a periodic service requiring low network resource per one session. Lastly the
management IP ports which can be classified as tele-control function of the line fault location (LFL)
and tele-protection network management (TPNM) are in this class. All applications in this class are
treated as not so serious operational tasks as they can tolerate packet loss and delay; therefore, when
the network is congested they will be dropped right after the class 1.
- Class 3: Mission Critical. The Internet Protocol remote terminal unit (IP-RTU) and the dam remote
control are very important for power utilities because they control and acquire most operational data
for supervisory control and data acquisition from power grids and power generators. Although they
consume less bandwidth and can tolerate to packet loss and delay; we cannot take risk. This class is set
its QoS with the second best from class 4.
- Class 4: Real time. Voice over IP (VoIP) and video conference are defined in this class. They require
real time network. Although, their one way end-to-end delays can be bounded in 150 ms [1], for
practical implementation with marginal extra network delay compensation, their delays for high grade
of services should be less than 100 ms.
The class category of each application utilized in EGAT existing IP/MPLS network and its service
level agreement (SLA) together with the quality of service (QoS) are summarized in Table 1. It is
noted that the advanced metering infrastructure (AMI) in class 4 and the teleprotection over IP
network and PMU (Class a) of the class 5 category have not been yet implemented. They are future
plan for smart grid services.
2. Network Designing and Engineering
The conceptual designs of our IP/MPLS network topology are as follows:
- Hierarchical design: The network is designed into 3 levels as core, distributed, and access levels.
This model allows building a reliable, scalable and focusing on the three functional areas.
A core layer is considered as a backbone of the network and the core routers must be highspeed equipment because they aggregate all traffic from the distributed layers. No packet
manipulation is done by devices in this layer. Rather, this layer is concerned with speed and ensures
reliable delivery of packets. EGAT Backbone capacities are 2.5 Gbps and multiple of 155 Mbps
respectively. To ensure high reliable and high available of the backbones, the core routers are designed
with full redundancies (equipment and CPU & power supply redundancies). Fig. 1 a illustrate core
router redundancies.
Distribution layer: This layer ensures routing between access layers to the core layers and
routing crossing between the different regional areas. The link bandwidth of the distributed routers are
155 Mbps and multiple of E1 channels. Because this layer is less traffic aggregation than the core
layer, the distributed routers are redundant only power supply parts. Fig. 1 b shows distributed router
implementation.
356
2
Table 1 Class category, SLA, and QoS policy for EGAT’s IP Applications.
SLA
Class
Category
Application
Blocking
QoS Policy
Delay (ms)
Probability
1
Best Effort
Internet, IT , and WWW
Best Effort
Best Effort
Guaranteed
Drop
Bandwidth
Packets
-
Dropped
First
2
Critical
AMR
FRS /WAM/PMU
AMR is a periodic
meter
reading.
Once an hour or
lower reading; it
can restart reading
when
communication
lost detected.
Non-real time
applications
consuming low
bandwidth.
No specified
requirement.

PMU
IEEE
C37.118 is real
time
application
consuming
low
bandwidth.
LLS/LFL/TPNM
3
Mission
IP-RTU
Critical
Real Time
Non-real time
applications
consuming low
bandwidth.
See Table 2
Dropped
Second

PMU = 500 ms
[1]
No specified
requirement.
IP-RTU is a
master/slave soft
real–time
Communication
and can restart
pooling when
communication
lost detected.
< 1 s [1]
See Table 2
No specified
Control
Non real time
application; no
specified
requirement.
VoIP, Video Conference
0.01 [2]
150 ms [2]
DAM Remote
4
AMR  1 s [1]
Dropped
Third
requirement.
128 bps
Dropped
Last
AMI
0.02
[2]
(Equivalent
to
200 ms [1]
video quality by
Future Plan for Smart Grid
assuming AMI can
transmit
triple
plays.)
5
Fast Real
Teleprotection/PMU
Time
(Class a)
0.001 [3]
10 ms/
16 ms [1]
Future Plan for Smart Grid
Access layer: This layer focuses on connecting to distributed layer and to the client nodes,
such as local area network (LAN) switches and workstations. This layer ensures that packets are
delivered to the distributed areas and end user application services. No redundancy is assigned and the
357
3
link capacities are only multiple E1 offered. Fig. 1 c shows access router configuration and Fig. 2
illustrates EGAT’s IP/MPLS hierarchical network topology. We have more than 200 nodes of
IP/MPLS routers and within the year 2016-2021 we are planning to replace the existing routers
approximately by 100 nodes. The plan is included upgrading the core and distributed routers with 10
Gbps and multiple of 1 Gbps up link capacities respectively. For the access routers, we consider
upgrading their power supply to be redundant design and we will increase their down link and up link
streams due to tremendous bandwidth requirement for both IT and OT applications in the near future.
Table 2. Illustration of IP/MPLS Parameter Setting for Each Class.
IP/MPLS
RD
IP/MPLS
Class
VLAN:A
VLAN:B
VLAN:C
VLAN:D
VLAN:E
VLAN:F
VLAN:G
VLAN:H
4
4
3
3
2
2
2
2
128
1
128
512
128
128
128
128
kbps
Mbps
kbps
kbps
kbps
kbps
kbps
kbps
LFL, TPNM
VLAN:I
2
128, 64
kbps
IT CCTV
IT
VLAN:J
VLAN:K
1
1
Best Effort
Best Effort
-
Application/VRF
VLAN
VoIP
Video Conference
IP-RTU
Any Integer
DAM Remote Control
WAM
FRS/PMU
AMR
LLS
Guaranteed Bandwidth
Note: A-K is any integer.
Host
Begin
Host
End
Table 3. Illustration of IP Address Assignment for EGAT’s IP Applications.
Host
Qty.
Application
2
254
255
IP-RTU
254
255
VoIP
49
62
15
WAM
Private IP Address
34
62
29
FRS/PMU
Private IP Address
66
94
29
AMR
255.255.255.224
Private IP Address
194
222
29
Video Conference
255.255.255.224
Private IP Address
2
30
29
DAM Remote Control
255.255.255.240
Private IP Address
33
46
14
LLS
255.255.255.192
Private IP Address
2
61
60
TPNM
255.255.255.192
Private IP Address
194
254
61
IT CCTV
IP Address
Block
Subnet Mask
Assigned IP
Block 1
255.255.255.0
Private IP Address
Block 2
255.255.255.0
Private IP Address
2
255.255.255.224
Private IP Address
255.255.255.224
255.255.255.224
Block 3
Block 4
Block 5
In addition to the topology design, all the following parameters for the IP/MPLS network must
be well planed as they are:
- Class of services, bandwidth assignment, virtual local area network (VLAN), virtual private
and network (VPN) assignment according to SLA and QoS: The details have been discussed in section
1 and Table 2 illustrates the mandatory parameters setting for each class in EGAT’s IP/MPLS network
which are virtual private network routing and forwarding instance (VRF), VLAN and route
distinguisher (RD) accordingly.
- IP addresses planning: We must predefine address assignment for each application
according to the maximum number of their host and server nodes per one station and the number of
network location per VPN. Although we have our well designed IP addresses planning, due to the fact
358
4
that more IP applications and more IP end terminals need IP connection to our network, we are facing
risk in lacking of IPv4 available spacing for the smart grid applications such as AMI. Therefore, we
have initiated a strategic plan for migration our IPv4 to IPv6 addressing (under study). Table 3 shows
illustration of IPv4 private address assignment for our applications.
a. Core Routers.
b. Distributed Router.
c. Access Routers.
Figure 1 Illustration of Equipment Design.
Figure 2 Illustration EGAT’s IP/ MPLS network topology.
- Routing protocol and security: The intermediate system-to-intermediate system (IS-IS)
routing protocol is deployed over IP/MPLS network. This protocol allows large scale and flexible of
network implementation and it also provides traffic engineering function on MPLS network. For the
security issue, as we implement the pure MPLS VPN environments without Internet access for our
operational VPN, where the network is used to connect different sites, the core network and network
address space is concealed hundred percent. This means that no information is revealed to third parties
359
5
or to the Internet. However, some operational applications such as AMR, DFR and IP-RTU have some
connections to the small power producers (SPP) and independent power producers (IPP); the access
control list (ACL) policies and static routing are deployed at the WAN connection to the external
network for security.
3. EGAT’s Communication System for Smart Grid
From the year 2015 to 2019, EGAT has initiated strategic plans to research and develop the new
model of IEC 61850 substations of which they are planed to be included the new smart grid
applications as IEC 61850 IP-RTU, IEC 61850 FRS and micro energy management system (µ-EMS).
The Communication system division is a supporting team responsible for preparing our IP/MPLS and
telecommunication networks for them. As in section 2 we have discussed that we have more than 200
IP/MPLS nodes to server EGAT’s IT and OT services and they can give IP coverage throughout all
EGAT’s office, power plants and substations. In addition, we are planning to replace the old routers
with higher performance specifications which will be able to offer the huge demand of IT and OT
applications for upcoming smart grid pilot plans. However, there are some issues of smart grid that we
have to study in order to prepare ourselves to support the full implementation of smart grid in long
term future. The study is included interoperability standard and information and communication
technology (ICT) integration for smart grid. In addition to that, as we have separated virtual network
among each application for security; thus our IT and OT are also separated. Both the administration
and operation groups will face significant challenges in terms of infrastructure, communications,
business processes and coordination when trying to deal with this issue outlined of smart grid because
smart grid seriously requires merging the two infrastructures to improve the reliability of power
distribution, promote the mass introduction of renewable energy and optimize energy use by
consumers. Hence, an effective integration of these two groups not only will solve the problems but
more importantly, will transform power utility industry like never before.
4. Conclusion
In this paper we share our experience in EGAT’s IP/MPLS network designing and engineering to
serve our OT and IT applications by giving clear illustration of our network parameters and plans. In
addition, the plan of preparing EGAT’s Communication system for smart grid is discussed in section 3
and we concluded that EGAT shall study interoperability standard and ICT integration for smart grid.
Last, addition to the first study, EGAT shall prepare efficient integration plan of OT and IT
infrastructures in order to serve smart grid in full functions.
BIBLIOGRPHY
Ekularn Dhavarudha received the B.S.E. degree in Electrical Engineering from Kasetsart University,
Thailand in 1992, and the M.S.E. in Electrical Engineering from Fairleigh Dickinson University, USA
in 1994. In 2014, she received her Ph.D. (Engineering) from Sirindhorn International Institute of
Technology, Thammasat University. Also, she is now with Electricity Generating Authority of
Thailand (EGAT) as engineer level 9 (Senior Engineer of Communication and Planning Engineering
Department.) whose expertise in planning and designing of voice network and IP/MPLS network.
[1]
[2]
[3]
KC. Budka, JG. Deshpande, TL. Doumi, M. Madden, T. Mew (2010) “Communication network
architecture and design principles for smart grids” (Bell Labs Technical Journal 2010 volume 15
issue 2 pages 205-227)
J. H. James, B. Chen, and L. Garrison (2004) “Implementation VoIP A Voice Transmission Performance
Progress Report” (IEEE Communications Magazine July 2004 pages 36-41)
GW. Scheer, DA. Woodward (2001) “Speed and reliability of Ethernet networks for teleportation and
control” (Paper #8 Western Power Delivery Automation Conference Spokane WA April 2001)
360
6
Asset Management
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“GlobalCIGRETrends
in the
Development
Power T&DSystem
including
Smart
AORC
Technical
Meeting 2016of
– International
Conference on
Global Trends
in theGrid”
Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE- AORC Technical Meeting 2016 and International Conference
on
ERP Integrated Maintenance Management
& Best Practices for T&D Asset
“Global Trends in the DevelopmentManagement
of Power T&DSystem including Smart Grid”
KuldeepKumar Jain, Raj Kumar Sharma, Yogesh Gupta, Zia Al Nasir Khan
TATA Power
Delhi Distribution
Limited
ERP Integrated Maintenance
Management
& Best
Practices for T&D Asset
INDIA
Management
KuldeepKumar Jain, Raj Kumar Sharma, Yogesh Gupta, Zia Al Nasir Khan
TATA Power Delhi Distribution Limited
INDIA
SUMMARY
TPDDL operates in an area of 510 sq. km. with fleet of nearly 120,000 maintainable electrical assets
and an installed capacity of nearly 3900MVA. A majorof the O&M effort is currently under way to
maintain the required asset availability but it is already clear that the average age of the asset cannot be
maintained at its current leveldue to several constraints like financial and human resource availability
limitations as also regulatory constraints. TPDDL is taking the following approaches to maintain the
SUMMARY
required electrical asset availability inthe coming years: - Gradually renewing the ageing fleet of assets in line with regulatory guidelines, starting with those
TPDDLwhose
operates
in an is
area
of 510
sq. km. and
withamong
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and optimizedmaintenance.
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at its current leveldue to several constraints like financial and human resource availability
Key challenges
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real time and
planning the
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as also regulatory
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TPDDL
is taking
the followinginapproaches
to maintain
efficient
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Given
thesechallenges,
TPDDL
is
taking
the
following
approaches
to
required electrical asset availability inthe coming years: extract the most potential from agingassets while ensuring reliability and optimizing costs.
- Gradually renewing the ageing fleet of assets in line with regulatory guidelines, starting with those
- Current Approach
: Preventive and Condition Based Maintenance
whose - condition
cause forconcern
and among
them,Based
thoseMaintenance
which are most critical to the
FuturisticisApproach
: Condition
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maintenance
of
reliable
supply
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With a view to bring in a turnaround in commercial, operational and financial performances TPDDL
- Reduction
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number
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also of impact
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the useachieve
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based andrespond
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risk and
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inabilityontoERP
monitor
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enhancement
and
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extract the most potential from agingassets while ensuring reliability and optimizing costs.
SAP (System Application and Products in Data Processing) is the ERP implemented at TATA Power- Current Approach
: Preventive and Condition Based Maintenance
DDL. The Plant Maintenance Module of SAP (SAP-PM)caters to the needs for its T&D maintenance
- Futuristic
Approach
: Condition
and enterprise
asset management
purposes. and Reliability Based Maintenance
With a view to bring in a turnaround in commercial, operational and financial performances TPDDL
wentahead with implementation of Enterprise Resource Planning (ERP)to achieve excellence in
Operational activities.
KEYWORDS
This paper
will elaborate on ERP based maintenance framework and algorithm for risk indexing,
condition based maintenance technique deployed for reliability enhancement vis-à-vis life
ERP, SAP,
Condition Based Maintenance, Risk Based Maintenance,Risk
enhancement
andPreventive
utilizationMaintenance,
of critical assets.
Index,
Notification,
Measuring
Point,
Measuring
Document, is
SAP-PM,
Customer
Exit IMRC0001.
SAP (System Application and Products in
Data Processing)
the ERP
implemented
at TATA PowerDDL. The Plant Maintenance Module of SAP (SAP-PM)caters to the needs for its T&D maintenance
and enterprise asset management purposes.
ziaalnasir.khan@tatapower-ddl.com
KEYWORDS
363
ERP, SAP, Preventive Maintenance, Condition Based Maintenance, Risk Based Maintenance,Risk
Index, Notification, Measuring Point, Measuring Document, SAP-PM, Customer Exit IMRC0001.
1. INTRODUCTION
ERP are software packages composed of several modules, such as operations and maintenance, human
resources, sales, finance and production, providing cross-organization integration of data through
imbedded business processes. These software packages can be customized to answer the specific
needs of each organization. ERP systems integrate (or attempt to integrate) all data and processes of an
organization into a unified system. SAP PM Module encompasses the Maintenance Management and
the Enterprise Asset Management functions.
1.1
Maintenance Strategies in Transmission and Distribution Networks
The maintenance framework and philosophy are based on two primary factors of the object i.e. its
condition and the importance.
Based on this the maintenance strategies are primary of four types
(i)
Failure Based Maintenance (FBM)
Failure Based Maintenance is maintenance performed once breakdown occurs and the equipment is
out of service. It is based on a breakdown maintenance trigger. It may be either planned or it can be
unplanned. Breakdown maintenance can be costlier than preventative maintenance.
(ii)
Preventive Maintenance (PM)
Preventive maintenance is maintenance that is regularly performed on a piece of equipment to lessen
the likelihood of it failing. Preventative maintenance is performed while the equipment is still
working, so that it does not break down unexpectedly. Preventive maintenance can be time based (i.e.
calendar based) and number of operations based (i.e. counter based)
.
(iii)
Condition Based Maintenance (CBM)
CBM is a maintenance strategy that monitors the actual condition of the asset to decide what and when
maintenance needs to be done. CBM dictates that maintenance should only be performed when certain
indicators show signs of decreasing performance or upcoming failure.
The goal of condition based maintenance is to spot upcoming equipment failure so maintenance can be
proactively scheduled when it is needed – and not before and also not after.
(iv)
Risk Based Maintenance (RBM)
RBM aims to implement a specific maintenance strategy for each of the assets of the company. RBM
identifies the functions and in turn equipment of the company that are most critical and then seeks to
optimize their maintenance strategies to minimize system failures thereby leading to an increase in
equipment reliability and availability. Assets likely to fail often or have large consequences of failure
are the most critical ones. RCM aims to identify the possible failure modes and their consequences;
taking into account both the condition and importance of the asset. Cost-effective maintenance
techniques that minimize the possibility of failure can then be determined. The most effective
techniques are then adopted to improve the reliability of the facility as a whole.
2. PRESENT APPROACH: PREVENTIVE AND CONDITION BASED MAINTENANCE
In “As-Is” scenario Condition Based & Preventive Maintenance philosophy and associated scheduling
is undertaken at TPDDL.
2.1
Preventive maintenance
PM refers to all the measures for determining the actual condition (inspection) and for maintaining the
target condition (maintenance) of assets.Every technical asset has a certain service life. If the service
364
life is exhausted, then maintenance measures must be taken to renew it. As a rule, these measures are
carried out periodically. PMhas fixed timeframe of maintenance schedules irrespective of asset health
parameters, ageing, loading, fault stress and criticality of equipment.
In time-based preventive maintenance, the maintenance tasks are planned and performed depending on
the time-dependent intervals determined.Further it involves shutdown of asset at periodic interval
which may result in over or under maintenance of asset.
In counter-based preventive maintenance, the tasks are planned and performed based on the service
characteristics of the technical assets. (e.g. number of operations of a breaker, number of operations of
an OLTC).
Daily
Daily
Six month
Annual
Two years
Four Years
Six month
Annual
Two Years
Daily
Six month
Current
And Potential
Transformers
Contact resistance, IR value, Relay maintenance
Dynamic contact resistance
Physical condition, Oil level, Oil leakage, Silica
W/O shutdown
Gel, Abnormal sound
W/O shutdown Ultrasound, Infrared inspection
Outdoor
Indoor
Bus
Shutdown
Shutdown
Daily
Daily
Daily
Daily
W/O shutdown
Monthly
Half yearly
W/O shutdown
W/O shutdown
Half Yearly
Condition Monitoring Parameters
Physical condition, Oil level, Oil leakage, Silica
W/O shutdown Gel, Abnormal sound, Oil level in capacitor
bushing, Fan operation, NIDS healthiness
Ultrasound, Infrared inspection, Oil BDV,
W/O shutdown
Moisture, DGA
W/O shutdown Oil Analysis (Resistivity, Tan Delta etc.)
IR value, PI , DC logic for PTR & NIDS, Relay
Shutdown
maintenance
Shutdown
Complete testing.
Physical condition, Oil level, Oil leakage, Silica
W/O shutdown
Gel, Abnormal sound, OLTC operation
W/O shutdown Infrared inspection, Oil BDV
Shutdown
OLTC maintenance based on operation count
Winding resistance (only when contacts /
Shutdown
mechanism are attended / replaced)
Physical condition, Abnormal sound, Visible hot
W/O shutdown
spot
W/O shutdown Ultrasonic, Infrared inspection
Capacitor
Bank
Two years
Four years
Type
Battery
Charger
Circuit
Breakers
Power Transformer
Timelines
On Load Tap
Changer
Equipment
Two years
Shutdown
IR value, PI
Four years
Shutdown
Tan delta
Physical condition, Visible hot spot, Abnormal
sound, bird nest
Ultrasonic, Infrared inspection
IR value
Physical condition, Oil level, Oil leakage,
Abnormal sound, Unbalance current
Ultrasound, Infrared inspection
Capacitance of individual unit, complete bank, IR
value, IR value of reactor
Physical condition, Abnormal sound, Float voltage
& current, leakage current
Checking important parameters
Remote signal
W/O shutdown
Six month
Four years
W/O shutdown
Shutdown
W/O shutdown
Half Yearly
W/O shutdown
Two Years
Shutdown
365
Battery
Bank
Daily
W/O shutdown
Monthly
Annual
W/O shutdown
Shutdown
Isolator
Daily
W/O shutdown
Six month
Four years
W/O shutdown
Shutdown
Lightening
Arrestors
Daily
W/O shutdown
Six month
Two years
Four years
W/O shutdown
W/O shutdown
Shutdown
Physical condition, Electrolyte level, pilot cell
checking
Specific gravity, Cell voltage
Capacity testing, Impedance testing
Physical condition, Visible hot spot, Abnormal
sound, bird nest
Ultrasonic, Infrared inspection
IR value
Physical condition, Visible hot spot, Abnormal
sound
Ultrasonic, Infrared inspection
Leakage Current Measurement
IR values
Table 1: Preventive & Condition Based Maintenance Strategy of TPDDL.
2.2
Condition Monitoring Parameters
A prerequisite of condition-based maintenance is that the critical asset conditions that make certain
maintenance necessary are known. There must also be a connection between asset condition and the
maintenance tasks to be performed.The assets’ conditions must be monitored automatically or
manually and entered or copied to the ERP system.TPDDL uses three main condition monitoring
techniques: (a) Infrared Scanning (I/R)
(b) Dissolved Gas Analysis (DGA)
(c) Ultrasonic Scanning (U/S)
The inputs from the above three monitoring techniques are fed into the SAP system. The data entry is
subject to the definition and assignment of counters or measuring points to technical assets. One or
more counters or measuring points can be assigned to an asset.
Measuring points in the ERP system describe the physical and/or logical locations at which a
condition is described. Measurement readings are taken at measuring points in particular measurement
units at particular intervals. Table 2, shows a set of sample measuring points for a power transformer.
Lower Limit
Upper Limit
Measuring Point
Unit of Measure
1 TAN DELTA MAIN TANK
Unit less
50 MOISTURE CONTENT
Ppm
2500 CARBON DI-OXIDE CONTENT
Ppm
350 CARBON MONO-OXIDE CONTENT Ppm
35 ACETYLENE CONTENT
Ppm
50 ETHYLENE CONTENT
Ppm
65 ETHANE CONTENT
Ppm
120 METHANE CONTENT
Ppm
100 HYDROGEN CONTENT
Ppm
40
OLTC OIL BDV
kV
40
MAIN TANK OIL BDV
kV
500
IR VALUE LV TO HV
MOhm
300
IR VALUE LV TO EARTH
MOhm
500
IR VALUE HV TO EARTH
MOhm
Table 2: Sample of Power Transformer Measuring Points with their limits
366
In many cases, there may be an optimum value or range of values for a particular measuring point to
which the device concerned is calibrated. You can specify this measurement reading as a target value
for the measuring point, in case of optimum value, or define limits (lower/upper) in case of operational
range.
The data transferred to the system after a measurement has been taken at a measuring point or a
counter is described in the SAP system as a measurement document. This transfer can be performed
automatically or manually. The measurement document is therefore the result of a measurement or
counter reading being entered in the system.In a standard SAP system measurement document creation
is a one to one job i.e. one measurement document for each measuring point. To facilitate the
Maintenance Engineer a customized program (Z-development in SAP ABAP)has been developed in
SAP-PM for bulk uploading of Measurement Values. The data for measurement documents against
measuring points is directly uploaded from Excel format as listed below.
Measuring Date
Point
&
Time
321 20.08.2015
11:00:00
322 21.09.2015
10:00:00
Reading
Valuation
Code
65 0010
52 0020
Document Reading Done By
Text
SAMPLE
TEXT
SAMPLE
TEXT
MAINTENANCE
ENGINEER
MAINTENANCE
ENGINEER
Measuring
Point
Description
OIL FLASH
POINT
OIL FLASH
POINT
Table 3: Measuring Document Bulk Creation Format
The above excel format saves the data entry time of a Maintenance Engineer in SAP.Thereafter, the
standard Plant Measurement Information System is used for analysis of created measurement
documents.
Figure 1:Sample Measurement Documents for Oil Flash Point
367
SAP UserExit IMRC0001 is used to :1. Define particular field contents in measuring points, counters and measurement documents
2. Define and trigger automated business processes
3. Update customer-specific tables
You have the following options for automating business processes with the customer exit IMRC0001:
a) Condition-Based Maintenance (via Notifications/Orders)
b) Scheduling Maintenance Plans
In Customizing for Measuring Points, Counters and Measurement Documents, you can configure the
settings so that the system issues a warning or an error message in the event of the measurement
exceeding the measurement range.
TPDDL has configured the customizing so that a preventivemaintenance notification is triggered when
measurement readings exceed a particular threshold value. In addition to the measurement reading,the
valuation code which is a standardized code for evaluating the measurement reading is also specified.
For example, measurement point for Bushing Temperature of a Transformer is 60degrees Celsius with
valuation code 0010 (which means Temperature OK)while a measurement reading 80 degrees Celsius
with the valuation code 0020 (which means) “Hotspot-HT Bushing” or 0030 symbolizing “HotspotLT Bushing” . In certain cases, it is sufficient to specify a valuation code (for example inputs from
Ultrasonic Inspection it is recorded as follows, 0010“Corona Suspected”, 0020 “Tracking Suspected”,
0030 “Arching Suspected” and 0040 “Ultrasonic Scan OK”. In the case of certain predefined valuation
codes, the system automatically triggers a preventivemaintenance notification that contains the text of
the valuation code as theproblemdescription.
Figure 2: Sample Measuring Point for Ultrasonic Scan
The coding code is used to provide the linkage for condition based maintenancenotifications triggered
from the creation of maintenance documents against measuring points. The Maintenance Engineer can
further adopt these notifications to plan, schedule and execute maintenance tasks to enhance the life of
the electrical asset and bring it to the desired target state. Figure-2 shows the structure of a sample
notification created against a measuring point violation.
368
Figure 3: Predictive Maintenance Notification for CBM
3. FURTURISTIC APPROACH:RISK BASED MAINTENANCE
Maintenance Philosophy and planning is critical component of utility asset management and has direct
impact on Reliability, Operational Expenditures, Inventory Planning vis-à-vis a replacement plan for
ageing asset. Risk Based Maintenance Plan for Sub-Transmission& Distributionasset involves risk
segmentation of critical asset based on failure probability and impact of failure. In simplistic terms,
high risk assets will have shorter timeframe between two maintenance cycles while low risk asset will
have longer timeframe between two maintenance cycles. Overall Risk Based Maintenance plan and
schedules will balance out Over & Under maintenance issue and result in optimized maintenance
framework.
3.1
Potential Benefits
Following are potential benefits associated with Risk Based Maintenance: 1.
2.
3.
4.
5.
6.
3.2
Reduction in Planned Shutdown and associated loss of un-served energy.
Reduction in Operational Expense from optimized manpower cost and lesser equipment failures.
Improvement in system reliability.
Material requirement for maintenance activities.
CAPEX planning.
Scheduling of Condition Monitoring like DGA, Ultrasonic, Thermal Imaging, and Physical
Inspection cycle can be customized and scheduled based on risk categorization of assets (Power
Transformer, Switchgear, and Sub-Transmission Lines).
Trigger
Following are key triggers which corroborates need to adopt Risk based Maintenance framework at
TPDDL.
1. Fixed Preventive Maintenance Schedule: In as-is framework, maintenance schedule of Power
Transformer, Line Bays, 66/33/11kV Switchgear is 2 years irrespective of asset health
369
2.
3.
4.
5.
6.
parameters like DGA result, Inter Facial Tension, Furan, Degree of Polymerization, Tan Delta
etc. and doesn’t take into account result of Ultrasonic, Thermal, fault interruptions, loading
and ageing factors.
Fleet of Ageing Assets
Regulatory Environment.
Global Operational Experiences
Manpower Optimization
Data Analysis and Outcomes
Above 30
29
16
25-30
18
13
20-25
FY 2020
18
0
5
10
15
20
30
25
30
20-25
25-30
Above 30
FY 2020
30
18
29
FY 2015
18
13
16
35
Figure 4: Power Transformer Age Analysis
3.3
Risk Index for Power Transformer
TPDDLhas 175power transformers, ranging from 10MVA to 50MVA in service supplying more than
1.4 million customers.The Power Transformer being the most crucial and capital intensive asset for a
T&D Utility, has been selected for a pilot deployment of Risk Based Maintenance Strategy.The
following section depicts the parameterization of the Risk Index for Power Transformers.
Risk is a function of probability of failure and the impact of the failure.
Inputs for determining the “Probability of Failure” are: (1) Oil Parameters
a. DGA (presence of gases e.g.CH4, C2H6, C2H2, C2H4, CO, CO2)
b. BDV (Breakdown strength of Oil in Transformer Main Tank& OLTC)
c. Acidity
d. Water Content
e. Inter Facial Tension
(2) Paper Parameters
a. Furan Analysis
b. Degree of Polymerization (DP)
(3) Electrical Parameters
a. Tan Delta (Bushing)
b. Tan Delta (Transformer Main Tank)
c. Loading of the Transformer
(4) Condition Based Inputs
a. Infrared Scanning
b. Ultrasonic Scanning
(5) General Parameters
a. Age
Inputs for determining the “Impact of Failure” are: (1) Energy Loss (MUs, loss resulting from subsequent Breakdowns, Load Shedding, Emergency
Shutdowns)
(2) Revenue Loss(₹, resulting from consumer supply disruption)
370
As a prerequisitefor allocation of weightages to all the above mentioned parameters under Probability
of Failure the linkage of the critical asset conditions to the internal health of the asset must be known,
so as to triggercertain necessary maintenance tasks to improve the asset condition.
For allocation of weightages involving Impact of Failure, which depends on the MUs and revenue
lost, past historical data for Breakdowns, Load Shedding, Emergency Shutdowns & Planned
Shutdown has to be referred. Table 4, depicts the Risk Index categorization matrix for the
implementing RBM for power transformers in a Transmission and Distribution Utility.
Risk Category
Maintenance Schedule as
per RBM
1 Year
2 Year
3 Year
4 Year
Category A
Category B
Category C
Category D
Risk Index = Probability of Failure X
Impact of Failure
Risk Index ϵ [10,8)
Risk Index ϵ [8,6)
Risk Index ϵ [6,4)
Risk Index ϵ [4,0)
Table 4: Sample Risk Index Categorization Matrix for Power Transformers
The Risk Categorization will now be driving the SAP maintenance plans and not time based
scheduling. The Risk index can be reviewed on a regular basis say quarterly or annually depending on
one’s specific requirements. The maintenance plansare prioritized based on the Risk Index calculated
above. The maintenance plan priority is used to reflect the Risk Indexcategorizationwhich will further
drive the maintenance scheduling of the asset to be maintained, thus achieving ERP integrated
Reliability Based Maintenance Planning.
4. CONCLUSION
The RBM strategy drawn out for power transformers from the Risk Index calculation and its
subsequent categorization will result in
-
-
Lesser number of time based scheduled maintenance outages, lesser supply interruptions for the
customer and lesser MUs lost – Right Maintenance at the Right Time
Focused maintenance leading to reduction in equipment failure, saving in OPEX and manpower
optimization.
Better inventory planning for spares and CAPEX planning for asset replacement
The RBM strategy is being further planned for all the T&D assetsin the network i.e. Overhead Lines,
Underground Cables, Switchgears, Isolator, Current Transformers, Potential Transformers,
Distribution Transformers, Ring Main Units, Lightening Arrestors, and Capacitor Banks.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
TPDDL-o-Pedia - IMS Documents - Maintenance Planning Group
(a) MPG-P-01_Maintenance Management
(b) MPG-P-04_Power Transformer Management
Plant Maintenance with ERP: PracticalGuide3/E2014, SAP Press, Karl Liebstückel.
PLM310Preventive Maintenance and Service, Version 2005.
Configuring ERPPlant Maintenance 1/E 2014, SAP Press, Karl Liebstückel.
371
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
“Global
Trends in the Development of Power T&D System including Smart Grid”
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE- AORC Technical Meeting 2016 and International Conference
on
GHG
Emission
ControlProactive Electrical
Asset
management
throughSmart Grid”
“Global
Trends
in theADevelopment
of Power
T&D
System including
Ultrasound technology
Mr NILESH KANE, Mr SANJEEV ATRI, Mr SANDIP PAL, Mr PANKAJ PATEL
GHG Emission ControlProactive
ElectricalLimited
Asset management through
TATAAPower
Delhi Distribution
Ultrasound
technology
India
Mr NILESH KANE, Mr SANJEEV ATRI, Mr SANDIP PAL, Mr PANKAJ PATEL
TATA Power Delhi Distribution Limited
India
SUMMARY
The distribution utilities are thriving for reliability. So, the need of the hour was to introduce
GIS Substation in 11kV network in the way of Ring main Unit (RMU) to provide N-1 for
improving reliability as well as to install substation in congested areas like metropolitan cities
where the land cost is very high. As of current scenario GIS technology is very successful in
SUMMARY
MV and EHV network as the frequency of operation is very low whereas in 11kV Network it
is not so as the frequency of operation is very high. One of the major concerns from
Theenvironment
distributionpoint
utilities
So, the
of switchgears
the hour was
to the
introduce
of are
viewthriving
is SF6 for
gasreliability.
emission from
theneed
failed
into
GISenvironment
Substationwhich
in 11kV
network
in thebyway
of Ringas main
(RMU)
is almost
overlooked
the utilities
well asUnit
OEMs
too. to provide N-1 for
improving reliability as well as to install substation in congested areas like metropolitan cities
We at TPDDL have around 5000 Nos. of 11KV RMUs & faced around 250 Nos. of RMU
where
the land cost is very high. As of current scenario GIS technology is very successful in
in FY13
whichasresulted
in Gas leakages
which isisequivalent
0.0179250MMTCDE.
MVfailures
and EHV
network
the frequency
of operation
very low to
whereas
in 11kV Network it
Though
the
distribution
utilities
are
sticking
up
to
best
maintenance
practices
available
but the from
is not so as the frequency of operation is very high. One of the major concerns
switch
gears
continue
to
fail
leading
to
losses
in
terms
of
revenue
and
un-served
energy.
environment point of view is SF6 gas emission from the failed switchgears As
into the
the RMU iswhich
completely
enclosed
and maintenance
free, identifying
theOEMs
fault attoo.
infant stage is
environment
is almost
overlooked
by the utilities
as well as
very difficult. The focus of this paper centers on identifying criticality in the RMUs by new
Wetechnology
at TPDDLwhich
havehelps
around
of 11KV the
RMUs
& faced
around
250 Nos. the
of RMU
the 5000
utilityNos.
in maintaining
reliability
as well
as preventing
environment
from
harmful
gas emission.
failures
in FY13
which
resulted
in Gas leakages which is equivalent to 0.0179250MMTCDE.
Though
the distribution utilities are sticking up to best maintenance practices available but the
We use Ultrasound Technology to identify the abnormalities in the equipment by detecting
switch
gears of
continue
leading
losses
in terms
of revenue
and un-served
energy.
As
the source
failure attoanfail
early
stage. to
Any
abnormality
occurring
in electrical
switch gears
is
through electrical
discharge
which is commonly
referred as
Thesestage is
the dispersed
RMU is completely
enclosed
and maintenance
free, identifying
theIonization.
fault at infant
discharges
produce
high
frequency
sound
which
is
beyond
the
human
audible
range.
Usually
very difficult. The focus of this paper centers on identifying criticality in the RMUs by new
these high frequencies lie in the ultra sound region. Thus for their detection Ultra sound
technology
utilityallin areas
maintaining
reliability
preventing
the
scanning which
tool is helps
useful the
in almost
of powerthe
system
due to as
its well
uniqueasfeature
of
detection offrom
abnormality
a distance. Thus by analyzing the sound pattern based on an
environment
harmfulfrom
gas emission.
algorithm we check for the type of abnormality and thus the health of the equipment is
that whether
it is deteriorating
or not.the
In addition,
TPDDLinhas
an android
Wedetected
use Ultrasound
Technology
to identify
abnormalities
thedeveloped
equipment
by detecting
App
to
record
all
the
details
at
site
through
a
smart
phone
&
the
same
is
synchronized
with
the source of failure at an early stage. Any abnormality occurring in electrical switchthegears is
nilesh.kane@tatapower-ddl.com
dispersed
through electrical discharge which is commonly referred as Ionization. These
discharges produce high frequency sound which is beyond the human audible range. Usually
these high frequencies lie in the ultra sound region. Thus for their detection Ultra sound
scanning tool is useful in almost all areas of power system due to its unique feature of
372 by analyzing the sound pattern based on an
detection of abnormality from a distance. Thus
algorithm we check for the type of abnormality and thus the health of the equipment is
detected that whether it is deteriorating or not. In addition, TPDDL has developed an android
server so that all data is readily accessible for further planning & needful action. By
ultrasound technology we prevented around 435 no’s of RMU failure in FY 14 &FY15 which
in turn saved the environment from SF6 gas Emission to the tune of 0.0311895 MMTCDE.
This paper presents the proactive and predictive maintenance practices adopted by TPDDL so
as to prevent untimely failure of switch gears in turn SF6 emission mitigation & also to ensure
efficient working of the power delivery asset i.e. switch gears.
KEYWORDS
R&M (Repair & Maintenance), EHV(Extra High Voltage), HV (High Voltage), LV (Low
Voltage), OEM (Original Equipment Manufacturer), AIS (Air Insulated System), GIS (Gas
insulated System), TPDDL (Tata Power Delhi Distribution Limited),MMTCDE(Million
Metric Tons of Carbon dioxide equivalent)
INTRODUCTION
The power system network in India has evenly doubled in the last two decades and expected
to rise by 250% to the tune of 900 GW by 2032. The transmission and distribution losses
(AT&C losses) are still very high to the tune of average 26% in the Indian power system and
its reduction is a top priority. Increasing complexity of power networks, growing demand,
requirement of greater grid reliability, security & efficiency, energy sustainability and the
environmental concerns continue to highlight the need for a quantum leap in energy efficient
technologies in power sector.
Tata power Delhi Distribution Limited is one of the best distribution utilities in India. It has
pioneered in curtailing its losses through large technological improvements in its operation
and maintenance practices in the field of power sector. TPDDL has a consumer base of
around 1.4 Million with a peak load of 1704MW. It has got an operational span of 510 sq. km.
network with 10,700 circuit Km installed capacity. It has an installed capacity of 8820 MVA
14000 nos. of switchgears. In TPDDL, the AT&C losses have been reduced form a paining
53% in 2002 to 9.87% in 2015. But still this utility is lagging behind countries in UK and
USA which have the loss level of about 4%. So there is a lot of margin to work upon and
bring the loss level down. However, the metering, billing and collection efficiencies have
been greater than 97%, still the technical losses are still a matter of concern. Over the years
with improved technical interventions of maintenance, the efficiencies of the power apparatus
have also been improved. But still there persisted a pain area in terms of the failure of the
power delivery assets and switch gears despite regular maintenance which also led to
environmental degradation in one or the other way.
The most affected switch gears and power delivery assets were transformers and RMUs. The
RMUs use SF6 gas, which is a Greenhouse Gas, as a quenching medium. Thus when the
RMUs failed, they resulted in power shut down leading to customer dissatisfaction and
revenue losses and SF6 gas emission as well. The increasing demand for quality and reliable
power and clean environment necessitated to zero tolerance to any kind of defects. In order to
achieve maximum reliability of the critical equipment like power transformers, circuit
breakers and healthy environment they are required to be monitored and maintained at regular
intervals.
So, to offset the failure rate of RMUs, condition based maintenance with ultrasound scanning
had been launched. Based on which it was decided to run, repair and replace the equipment
and if feasible, use innovative methods to fix the gas leaks. By adopting this method, failure
rate of equipment accessories have come down thus we have been able to save a lot on all
373
1
fronts. The ultrasound scanning acting like the human ears efficiently diagnosis the
abnormalities in the switch gears and prevent their failure and ultimately prevents the SF6 gas
from escaping into the environment emissions which if not taken care of may enhance global
warming.
SF6 GAS AS QUENCHING MEDIA
Sulphur Hexafluoride Gas (SF6) is employed as an insulating gas in all parts of its installation,
and in the circuit-breakers as an arc-quenching media. SF6 is an electronegative gas. It has a
dielectric strength of approximately three times that of air at atmospheric pressure.
It is an incombustible, non-toxic, odorless, chemically inert gas. Its arc-quenching properties
are 3 to 4 times better than air at the same pressure.
SF6 being electronegative has high affinity of absorbing free electron. Whenever a free
electron collides with the SF6 gas molecule, it is absorbed by that gas molecule and forms a
negative ion.
SF6 + e- = SFˉ6
SF6 + e- =SFˉ5 + F
In our utility SF6 gas finds its application in the breaker section of the switch gears in which
the making and breaking of the contacts take place. In order to extinguish the arc between the
fixed and moving contacts of the breaker, SF6 gas, as an arc quenching medium is required
and its functions as per the reaction shown above. The quenching medium used otherwise can
either be air or vacuum based on the voltage levels. Our distribution takes place at 11kV level
where SF6 proves to be the best arc quenching medium. So all the RMUs used in our utility
are SF6 based.
GLOBAL WARMING POTENTIAL OF SF6 GAS
SF6 gas, with its contribution to the greenhouse effect below 0.1% worldwide, the proportion
of SF6 is low compared to that of the better known greenhouse gases (carbon dioxide,
methane, nitrous oxide etc.).
In our utility, each RMU has approximately 3 Kg of SF6 gas in its breaker chamber. SF6 being
a Greenhouse gas, has a lot of Global Warming potential. The global warming potential of
SF6 gas is 23900, so in case of failure of one RMU, it will lead to the escaping of 3Kg of SF6
gas into the atmosphere which will be equivalent to (23900*10-9 *3=) 0.0000717 Million
Metric Tons of Carbon-di-Oxide Equivalent (MMTCDE). This will not look to be a big
concern in case of failure of a single RMU. But when the failure is to the tune of hundreds
then it becomes a matter of concern. For the financial year 2012-2013, around 60 numbers of
RMUs failed due to flash over or leakage in gas chambers or other reasons thus their gas
escaped into the environment. When quantified it will result into (0.0000717*250=)
0.017925MMTCDE. Thus this amount of SF6 escaped in the environment adding to Global
Warming in the year 2012-2013.
This worked as a trigger for us to look to new and innovative methods to save the RMUs from
failure and prevent the gas leakages by fixing them.
PROACTIVE ULTRASOUND SCANNING TO PREVENT SF6 GAS LEAKAGE
When the Global Warming Potential of the SF6 gas was taken into account, we found that if
the RMUs can be prevented from failure, then we can stop the gas from escaping into the
environment. So we decided to switch to Proactive strategy, to diagnose the switch gears for
374
2
abnormality. Proactive Ultrasound Scanning is based on the philosophy of early identification
and rectification of abnormality in the RMUs. We started with this approach because despite
regular maintenance, the switch gears present in the power systems failed. Since every human
before getting affected by any serious illness starts showing some symptoms when the
problem is in infant stage, so thinking on the same lines, these RMUs also show some kind of
abnormality before falling out of service due to failure. Any abnormality which is occurring in
electrical switch gears is generally electrical discharge which is commonly referred as
Ionization. There are three types of discharges in power system Corona, Tracking and Arcing.
All these discharges are different in their nature and have different way of producing the
interruptions.
These discharges produce high frequency
sound which is beyond the human audible
range. Usually these high frequencies lie in
the ultra sound region. Thus for their
detection Ultra sound scanning tool is
useful in almost all areas of power system
due to its unique feature of detection of
abnormality from a distance. This tool
converts the Ultrasound into audible sound.
There is a signature audio or we can say a
pattern, which is unique, for every kind of
discharge taking place in the power system.
Higher the peak and time, higher is the
discharge and thus the severity of
discharge.
Fig.1 Scanning of 11Kv Switch Gear using Ultrasound Scanner
Thus by analyzing the sound pattern based on a certain algorithm we can check for the type of
abnormality and thus the health of the equipment is detected that whether it is deteriorating or
not. The equipment used is an Ultrasound Scanner (fig.1).
The existing maintenance practices were not robust and user friendly. Even if there was some
audible sound coming out of the switch gear, the also nothing could be confirmed regarding
the abnormality and its stage of impact.
Thus an idea was incorporated by studying the sound patterns of various abnormalities. Based
on the study of multiple experimental data an algorithm was developed. According to the
algorithm the line frequency and its harmonics were been used to point out the problems that
whether the problem is corona arcing or tracking.
The observations with their
detection technique are as follows:
CORONA: In the pattern obtained
for corona there are uniform peaks
at equal intervals of time and
components of only line frequency
along with its harmonics were
present(fig.2).
Fig.2 Corona
375
3
TRACKING: Here in its pattern
only a few line frequency
harmonics are present. In
tracking there is less uniformity
in the pattern (fig.3).
Fig.3 Tracking
ARCING: It is quick and abrupt.
It starts and stops abruptly. In its
pattern there is usually a period of
silence then a big discharge, may
be two sets of silence and then
again heavy discharge and no
components of line frequency.
Abnormality identification based
on this algorithm served the
purpose and helped to diagnose
the switch gears on site. It has
proven to be the best method for
proactive maintenance of the
equipment (fig.4).
Fig.4 Arcing
FIELD IMPLEMENTATION AND RESULTS:
The ultrasound scanning has been used effectively to scan the RMUs. The efficiency in
detecting the abnormalities has also improved over the years.
The parameters for identification of abnormality using Ultrasound are as follows:
Abnormality Frequency(Hz)
50, 100,150,200,250,300,350…all harmonics
Corona
Tracking
50,100,150,200.
Arcing
No component of Line Frequency
Intensity
Between -8.0 dBμV to -5
dBμV
Between -5.0 dBμV to -2.0
dBμV
Greater than -2.0 dBμV
Based on the above mentioned parameters, the abnormalities in the RMUs were tracked. Due
to the huge loss of asset, revenue and threat to environment observed in the year 2012-13, we
began to use the ultrasound scanning of the RMUs. Thus we captured the abnormalities and
based on their type, the required maintenance was carried out. Most of the cases were found in
the tracking stage due loose cable termination contacts, improper clearing and work practices
and improper insulation due to geographical constraints. Thus when the abnormality began to
be addressed within time, it started to prove as a major gain in terms of asset savings, repair,
and healthy environment.
376
4
As it can be seen from the graph below the RMU flash over has also been minimized to single
digit in 2015-2016. Thus we have been able to prevent a large amount of SF6 gas from
escaping into the environment.
Fig.5 RMU Abnormality Trend
From the table shown below, it can be seen that with the inception of new technology to
detect the infant abnormalities in RMUs, we have been able to prevent a considerable amount
of SF6 gas getting added to the environment which in turn have resulted in curtailing Global
Warming to some extent. From the year 2013-14 to 2015-16, it can be seen that 0.0505485
MMTCDE of SF6 gas has been barred from escaping into the environment.
2012-2013
2013-2014
2014-2015
2015-2016
No. of RMUs
Scanned
1845
2200
2565
3200
Abnormal
RMUs
NA*
270
274
279
RMUs
Failed
240
62
38
18
SF6 Escaped/Prevented(MMTCDE)
0.0172080
0.0149136
0.0169212
0.0187137
SF6 Gas Escaped Into Atmosphere
SF6 Gas Prevented From Escaping Into Atmosphere
Na* : Ultrasound Scanning was not Started in 2012-2013
The abnormality detection and maintenance have also resulted in saving of the switch gears
and improved reliability. This predictive as well as proactive maintenance practice has
enabled TPDDL to become a pioneer in the distribution sector among other distribution
utilities in taking care of the environment.
Moreover when the switch gears are inspected proactively then it also results in curtailing the
number of visits to the switch gears because when they fail lots of commuting takes place
employing motor vehicles which further add to the carbon emissions as well. Thus this
proactive maintenance approach is also useful in the long run also.
377
5
OTHER MITIGATION STRATEGIES TO CURTAIL SF6 GAS EMISSION
The proactive maintenance strategy using Ultrasound Scanning Technology has helped a lot;
still some other mitigation strategies are also there which we have taken up further to maintain
the balance of the environment.
Unique Compound: For those RMUs wherein the gas leakage started on its own due to
design defects, we started using a unique compound which is capable of fixing gas leakages
even to the size of micrometer. This unique compound consists of poly vinyl chloride, some
metal making it to have enormous strength to prevent the gas leakage.
Ultrasound Android App: In order to record the on-site data of the Ultrasound activity, a
large amount of paper was used. But now we have a developed a unique android app which
has enabled us to record the data on site in digital form and upload the data on a central server
accessible to all. In this way we have also reduced over paper usage and indirectly help to
avoid the cutting of trees for paper. The other mitigation strategy can be reducing the size of
the switchgear, compared to conventional designs so that lesser amount of SF6 gas is used.
The second mitigation strategy is to perform the residual life analysis of the switch gears so
that the asset retiree process may be carried out within the stipulated time. The third strategy
is to specify the norms and act strictly according to it while scrapping the switch gears so that
its SF6 gas bottle may be disposed of properly preventing the escape of the gas into the
environment. These gas bottles can be recycled and may be brought in service by the
manufacturers.
CONCLUSION
Proactive Ultrasound Scanning is successfully implemented in TPDDL for effective & precise
identification of issues for all switch gears well in advance & thus future failure is prevented
to a great extent with proactive measures thus saving the environment as well. The technology
further added new dimensions of thinking and changed our outlook towards all the high value
assets in electrical distribution system and the environment. Now these assets are not seen just
an equipment but an entity which makes noise & reflects thermal signature when its health
deteriorates which can further add to Global Warming and it has only become possible when
the identification of the abnormality present in them could be identified accurately through the
initiative.
6
378
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
“Predictive Maintenance through Ultrasound and Infrared Thermography: A Success Story of
Tata Power Delhi Distribution”,-GRIDTECH 2015, Conference 1, Nilesh Narayan Kane, Sandip
Pal, Sanjeev Atri, Pankaj Patel, Tata Power Delhi Distribution Limited, India
James Hall, “Ultra-Sound Technologies”, Atlanta , GA Area
UE Systems, “Ultrasound scanning of switch gears”.
Environment Sustainabilty Approach Capiel-HV Part-D-Switchgear and SF6 Gas
CIGRE, "SF6 Recycling Guide", TF B3-02-01, Rev 2003
”Application of ultrasound to the inspection of insulation”-Div. of Electr. Eng., Univ. of
Manchester Inst. of Sci. & Technol., UK
Intergovernmental Panel on Climate Change 2007. IPCC Fourth Assessment Report, Working
Group II, "Sinthesis Report", November, 2007
Ludwig Reider, "The SF6 Academy, CIGRE Indonesia Workshop, Jakarta, 2012
Ward, Assessment of Optimum SF6-Air, SF6-N2, and SF6-C02 According to Particle
Contamination Sensitivity. Cairo University, 1999 Conference on Electrical Insulation and
Dielectric Phenomena, IEEE
H. Dieneman , "Material Function of Sulfur Hexafluoride" , J. Phys. D: Appl. Phys., 1983
M. G. Danikas , "The notion of the early stage of ageing indoor and outdoor insulation regarding
surface discharges: A short review" , J. Electr. Eng. , vol. 53 , no. 56 , , 2002
J. Baskin , "Methods to Mitigate Contamination and Moisture Ingress in Switchgear" , IEEE
11th International Conference on Transmission & Distribution Construction, Operation and
Live-Line Maintenance ESMO 2006
Dale C. Rossman Inc.- “High Volatge Switch Gear and Miantenance”, Mullberry Fl, 33860
379
7
CIGREAORCTechnical
Technical Meeting
2016 2016
and International
Conference Conference
CIGREAORC
Meeting
and
International
CIGRE- AORC Technical Meeting 2016
–
International
Conference
on
Global
Trends
in the Development
on
of Power Transmission & Distribution Systems
including Smart Grid, 24-26 Feb. 2016, New Delhi, India
on
“Global Trends in the Development of Power T&D System including Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
PEA-AMR Operation and Maintenance System for Strong Grid
PINTO
PEA-AMR Operation andPAISIT
Maintenance
System for Strong Grid
Deputy Manager, Engineering and Planning Division
Provincial Electricity Authority Area 1 (Central)
PAISIT PINTO
46 M.6 Asia Rd. Huntra Phranakorn
Sri Ayutthaya 13000 Thailand
+668-1832-8767,
paisitpinto@yahoo.com
Deputy Manager, Engineering and Planning Division
Provincial Electricity Authority Area 1 (Central)
46 M.6 Asia Rd. Huntra Phranakorn Sri Ayutthaya 13000 Thailand
+668-1832-8767, paisitpinto@yahoo.com
SUMMARY
All elements in the world are beginning and disappear no matter what the living thing,
all non-living things of the life cycle. In the same time, we might use a smart technology, but it
becomes damaged to the New Normal as the AMR Meter System will have low efficiency and
will become ineffective. This research and development of software is applied for the operation
and maintenance the AMR System. The AMR Maintenance System can monitor the event of
alarm in the energy consumption of customer and we can check the interval data every 15
SUMMARY
minutes. This system can analyze the alarm has strong effects to PEA’s distribution system
consists of 5 types; Any Phase Current = 0, Any Phase Voltage Unbalance, Asymmetric Power
, Over
Current
and Voltage
Tolerance Error
Failure Occurred
). This what
article the living thing,
All Occurred
elements
in the
world
are beginning
and(VT
disappear
no matter
focuses on Over Current because the alarm exceeds the AMR meter, Current Transformer (CT)
all non-living
things of the life cycle. In the same time, we might use a smart technology, but it
Voltage Transformer (VT) damage and also effect to Distribution Transformer, Electrical
becomes damaged
the New
Normal
as the AMR
System
have low efficiency and
Equipment,to
Protection
System,
and Distribution
SystemMeter
too. It will
happen will
with another
customer
in
the
same
feeder
and
substation.
The
reason,
“why
we
focus
on
Over
Current
of the
will become ineffective. This research and development of software is applied
for the operation
warning alarm of the transformer with LV.CT. because of the main effect to Strong Grid”.
and maintenanceProvincial
the AMR
System.
The (PEA)
AMRhasMaintenance
System
can monitor
the event of
Electricity
Authority
been implementing
the Automatic
Meter
alarm in theReading
energy
consumption
and we and
canCommunication
check the interval
data every 15
(AMR)
Project, whichof
cancustomer
integrate Information
Technology
(ICT)
for
the
collection
of
meter
reading
data.
Feedbacks
from
customers
were
positive
because
minutes. This system can analyze the alarm has strong effects to PEA’s distribution system
PEA’s core business is the development of reliability and transparency. Therefore, customers
consists of can
5 types;
Phase
Current
0, Any Phase
Voltage
Asymmetric Power
monitorAny
behaviour
of power
energy=consumption.
The AMR
ProjectUnbalance,
is controlled by selfand riskand
management.
has prepared
a plan(VT
for maintenance
after the AMR
Occurred , assessment
Over Current
VoltagePEA
Tolerance
Error
Failure Occurred
). This article
Project
has
been
completed.
focuses on Over Current because the alarm exceeds the AMR meter, Current Transformer (CT)
Provincial Electricity Authority (PEA) had initially implemented the Automatic Meter
Voltage Transformer
(VT)
damage
and
also
effect
to Distribution
Transformer,
Reading (AMR)
system
in Thailand
in the
year
2007, and
budgeted to invest
889 million baht.Electrical
scope involves
getting information
required to System
start a project,
features
the product
Equipment,The
Protection
System,
and Distribution
too.andItthe
will
happen
with another
would have that would meet its stakeholders requirements are; building renovation, server
customer ininstallation,
the samenetwork,
feederAMR
anddata
substation.
The reason, “why we focus on Over Current of the
center and AMR meter replacement. The AMR meter project
warning alarm
transformer
with35,940
LV.CT.
(Phaseof
1) the
for big
customers is about
sets asbecause
of 2012. of the main effect to Strong Grid”.
Provincial Electricity Authority (PEA) has been implementing the Automatic Meter
Reading (AMR)
Project, which can integrate Information and Communication Technology
paisitpinto@yahoo.com
(ICT) for the collection of meter reading data. Feedbacks from customers were positive because
PEA’s core business is the development of reliability and transparency. Therefore, customers
can monitor behaviour of power energy consumption.
The AMR Project is controlled by self380
assessment and risk management. PEA has prepared a plan for maintenance after the AMR
Project has been completed.
The objectives
1.The technical support teams are suitable for project timeline.
2.The database is controllable to the AMR project in real time. The project
manager has communication channels for decision, everywhere.
3.To build an integrated team for analysis effect of business process and change
management.
4.The preventive maintenance for the purpose of maintaining AMR accuracy
and the maintenance teams are distributed to customer responsibility.
5.To design new business process and job description of AMR’s monitoring.
Customer benefits
1.Customer can monitor load profile at all times and compare data at the same time.
2.Demand-side management (DSM) activity is to produce a load profile, the art
of successful implementation and the ultimate success of the program rests within the balancing
of utility and customer needs. [1]
PEA benefits
1.Reduce the cost of meter reading
2.Can find and fix a variety of problems by PEA-AMR Maintenance System.
3.Detect meter tempering and move quickly to a warning; such as over current
asymmetric power and any phase voltage unbalance etc.
4.The Automatic Meter Reading (AMR) is the best practice in meter reading
process, and the direct experience is applied to control risk of PEA’s Advance Metering
Infrastructure (AMI) project.
Meanwhile, PEA was rolling the AMR project (Phase 1), the pilot project of System
Application Products in Data Processing (SAP) started. The customer service process was
affected by them. In the past, the crew goes out to read meters, which are electromechanical
meters, with a portable computer. Every day after finishing the reading, the crew has to upload
the reading data to PEA server. Nowadays, AMR meter is a remote collection of consumption
data from customers, and process the data to generate the invoice in billing - SAP system. [2]
The consumption data is verified by Service Detail Recording (SDR)
One of the successes of PEA’s projects is AMR Project (Phase 1). The customer
experience exceeds expectations that you want to lead to positive attitude. These will bring
further enhancements to other business services that will occur in the future. [3] PEA was
expansion AMR meter project (Phase 2) for big customer about 50,000 sets in 2011, completed
in 2014.
KEYWORDS
“Automatic Meter Reading (AMR)”
“Alarm”
“Over Current”
“Transformer load”
“Strong Grid”
381
1
1. Introdution
Customer criteria
1. The first priority is big customers in industrial estate.
2. The big customers are out of industrial estate with electricity demand > 30 kW. Or
Transformer > 100 kVA.
The characteristics of AMR system
1. The consumption data were read by Meter Interface Units (MIU), using GPRS/
GSM mobile phone network as a media. The interval data were kept in a server at head office
every 15 minutes. At the end of every month, after finishing the automatic reading, AMR
software has to process the reading data to IS-U SAP server. All the reading data is stored in
AMR data center for further use and reference. When PEA processed invoice to customers,
the consumptions data had already been verified.
2. The AMR Data Center sends an alarm to the operator automatically. The crews will
check the AMR meter on site, such as meter dilapidated, tampering and door opened etc.
3. The conceptual back-up design for the GPRS/GSM mobile phone network-based
automatic meter reading system for the PEA.
4. The AMR system can display load profiles (15 minutes) every day, every month,
and every year and compare the data at the same times. [4]
Figure 1 PEA-AMR Infrastructure System
Operation
PEA has developed 2 web application systems for monitoring and control.
1. The benefits gained from the AMR Monitoring System (URL : http://www.service.
pea. co.th) can be divided into two parts, which are benefits for error alarm and benefits for
warning alarms.
2. The AMR Power Plus system (URL : http://www.amr.pea.co.th) is used for load
profile monitoring. The operators check the alarm in AMR Monitoring System, before they
monitor the AMR Power Plus system. The benefits gained from the AMR Power Plus system
can be displayed into five parts of statistic data which are beneficial for operators in
monitoring currents, voltages, electrical powers, reactive powers, meter reading units, power
factors and phasor diagrams.
382
2
The AMR Maintenace System has been delveloped for momitoring the Automatic
Meter Reading (AMR). This application can reply to customer all the times.
Figure 2 Web Application
Figure 3 The work order list
Figure 4 Customer Profile
Figure 5 Over Current Profile
The figures 2 - 5 are showing the web page of the AMR Maintenance System. The
operator can monitor daily work order in this application. When the technicians have to check
the AMR meter on site, the work order has already been analysed. In this application is
focusing on the customer install transformer 100 kVA. with low voltage current transformer
(LV.CT.) 150/5A. The warning alarm shows Over Current. The current profiles are over the
current limit than the AMR meter. If the customer uses electricity continuously, then the
electrical equipment might breakdown for example; Current Transformer (CT), Voltage
Transformer (VT), AMR meter, Distribution Transformer and Protection Equipment etc.
When the electrical equipment was faulty in the PEA’s distribution system, the SMART
GRID will be weaker.
PEA-AMR Maintenance System (URL : http://service.amr.pea.co.th) has been
developed from AMR Monitoring System. The work orders are generated from PEA-AMR
Maintenance System, before they are sent to PEA’s branch offices.
Then, the operator of PEA’s branch offices must monitor, record, and close work
orders. Load profile are linked to AMR Power Plus automatically. This is the convenient
option to add efficient speed for monitoring and maintenance.
The alarm is consisting of 2 types.
1. The error alarm is occurring at the meter. The mostly have to change the meter.
2. The warning alarm is occurring from another factor. The operator need to consider
in situation with disorder.[5]
383
3
ERROR ALARM
WARNING ALARM
Clock Failure
Asymmetric Power
Data Flash Failure
Door Open
VT Failure
Reverse Power
Analog Reference Failure
Any phase current=0
Calibration Data Lost
Over Current
Program Flash Failure
Voltage Tolerance Error
RAM or LCD Error
Modem Failure
Battery Failure
Terminal Cover Open
Figure 6 Alarm Type
Any Phase Voltage Unbalance
Error Alarm ( Average 1 moth)
In 2015, the error alarm
of the event average data
per month are consist of
- VT Failure (616)
- Analog Reference
Failure (35)
- Clock Failure (4)
- RAM or LCD Error &
Program Flash Failure &
Data Flash Failure &
Calibration Data Lost (0)
Graph – 1 Average Data of Error Alarm in 2015
Warning Alarm ( Average1 month)
moth)
Graph – 2 Average Data of Warning Alarm in 2015
In 2015, the warning
alarm of the event
average data per month
are consist of
- Any phase current=0
(198)
- Any Phase Voltage
Unbalance (30)
- Asymmetric Power
(291)
- Over Current (9)
- Voltage Tolerance
Error (11)
- Door Open (35)
- Reverse Power &Modem Failure (0), - Battery Failure (5), - Terminal Cover Open (4)
384
4
This paper focuses on the warning
alarm in 5 types. The graph - 3 is
showing the important alarms. There
are the effect of stability, reliability and
efficiency of distribution system. The
Any Phase Current = 0 the most of
warning alarm. In this case the over
current are occur 71 times/year (2% of
alarm 5 types)
Graph – 3 Total Warning Alarm in 2015
Graph – 4 LV.CT. Warning Alarm in 2015
Graph – 5 LV.CT. Warning Alarm in 2015
In 2015, the warning alarm of the transformer with Low Voltage Current Transformer
(LV.CT) are consist of Any Phase Current = 0 (81%), Any Phase Voltage Unbalance (11%),
Asymmetric Power Occurred (1%), Over Current (3%) and Voltage Tolerance Error (VT
Failure Occurred ) (4%) in Graph – 4.
In 2015, the warning alarm of the transformer with High Voltage Current Transformer
(HV.CT) are consist of Any Phase Current = 0 (1%), Any Phase Voltage Unbalance (1%),
Asymmetric Power Occurred (98%), Over Current (0%) and Voltage Tolerance Error (VT
Failure Occurred ) (0%) in Graph – 5.
Maintenance
In 2013, PEA concerned about AMR continuity management (ACM) because it is
sensitive to core business. AMR Continuity Management (ACM) is defined as the capability
of AMR to continue the delivery of services at acceptable predefined levels following a
disruptive incident. [6] The strategy is a commitment to the continuous delivery of critical
services that helps prevent immediate severe disruption to an organization. The ACM
includes both risk evaluation, management and control and effective plans, measures and
arrangements for business continuity.
The maintenance planning is as follows:
1. The maintenance by outsources for the purpose of maintaining server, network
software, and system at PEA’s AMR Data Center, is the following:
1.1 Preventive Maintenance (PM) is performed twice per year.
1.2 Corrective Maintenance (CM) is available 24 hours a day.
2. The maintenance by outsources for the purpose of maintaining AMR system and
equipment is as follows:
2.1 Preventive Maintenance (PM) is performed once per year.
2.2 Corrective Maintenance (CM) is available 24 hours a day. The contractor
shall respond to troubles, outages and repair, in accordance with Service Level
Agreement (SLA).
385
5
3. Full-time staff consultants provide assistance with helpdesk and other
administrative application issues.
4. The technical team support data network in sustainable.
AMR process relates to coordinating and synergizing the activities of different units
for realizing the superordinate cross-functional goals and policy deployment. PEA is
concerned with building a better system for achieving such cross-functional goals as
innovation, quality, cost, and delivery. [7]
2. Methods
The operator can prove the initial hypothesis by the interval data of current every 15
minutes. The engineering model calculates the percentage of transformer load as following.
Calculation of kVA capacity for a Three Phase Transformer, based on Winding
Voltage and Amperage information.[8]
To do this you must have at least two pieces of
information:
1. The load line-to-line voltage (V)
2. The maximum load phase current (I)
Calculation of Maximum load from Current are recorded in AMR Meter.
Note: Error of Imax(AMR) depend on the saturation of electric field intensity coils of
Current Transformer (CT), in the same time the transformer load does not exceed 120%.
Calculation of Transformer Load Percentage.
3. Results
Capacity of Transformer vary to CT ratio and KkVA(TR) Calculation.
Every 15 minutes, the interval data of current is instead of the % Transformer load
formula and also the computer program and calculate the formula. This table shows data base
at 06:00 a.m. - 08:00 p.m. on 3 December 2015 for a while the transformer load had been over
80% until over limit of this as following.
386
6
Interval of Current Data (15 minutes)
03 Deccember 2015 - 16 January 2016
Customer ID : 020001176306 Customer Name : MR. Wiratchai Arrom
PEA.Number : 27681412
Tariff : TOU
CT Ratio : 150:5 A.
VT Ratio : 1:1 V.
วัน/เดือน/ปี /เวลา
03/12/2015 06.00
03/12/2015 06.15
03/12/2015 06.30
03/12/2015 06.45
03/12/2015 07.00
03/12/2015 07.15
03/12/2015 07.30
03/12/2015 07.45
03/12/2015 08.00
03/12/2015 08.15
03/12/2015 08.30
03/12/2015 08.45
03/12/2015 09.00
03/12/2015 09.15
03/12/2015 09.30
03/12/2015 09.45
03/12/2015 10.00
03/12/2015 10.15
03/12/2015 10.30
03/12/2015 10.45
03/12/2015 11.00
03/12/2015 11.15
03/12/2015 11.30
03/12/2015 11.45
03/12/2015 12.00
PHASE A
0.01
0
0
0.05
0.17
1.22
2.77
3.2
3.12
4
3.32
3.14
3.07
3.06
3.61
4.47
3.52
3.14
3.3
3.23
3.23
5.39
4.49
4.79
4.44
PHASE B
0.02
0.02
0.01
0.02
0.09
1.09
2.57
3.25
3.63
4.59
3.69
3.61
3.57
3.56
4.15
5.43
4.29
3.75
4.13
4
3.97
6.47
5.55
5.64
5.37
PHASE C
0
0
0
0
0.03
0.89
2.3
2.77
4.2
5.38
4.9
4.37
4.59
4.77
5.39
6.54
5.53
5.1
5.39
5.05
4.95
7.3
6.21
5.84
5.15
I_Max
0.02
0.02
0.01
0.05
0.17
1.22
2.77
3.25
4.2
5.38
4.9
4.37
4.59
4.77
5.39
6.54
5.53
5.1
5.39
5.05
4.95
7.3
6.21
5.84
5.37
% LOAD
0.42
0.42
0.21
1.04
3.53
25.36
57.57
67.55
87.30
111.82
101.84
90.83
95.40
99.14
112.03
135.93
114.94
106.00
112.03
104.96
102.88
151.73
129.07
121.38
111.61
03/12/2015 12.15
03/12/2015 12.30
03/12/2015 12.45
03/12/2015 13.00
03/12/2015 13.15
03/12/2015 13.30
03/12/2015 13.45
03/12/2015 14.00
03/12/2015 14.15
03/12/2015 14.30
03/12/2015 14.45
03/12/2015 15.00
03/12/2015 15.15
03/12/2015 15.30
03/12/2015 15.45
03/12/2015 16.00
03/12/2015 16.15
03/12/2015 16.30
03/12/2015 16.45
03/12/2015 17.00
03/12/2015 17.15
03/12/2015 17.30
03/12/2015 17.45
03/12/2015 18.00
03/12/2015 18.15
03/12/2015 18.30
03/12/2015 18.45
03/12/2015 19.00
03/12/2015 19.15
03/12/2015 19.30
03/12/2015 19.45
03/12/2015 20.00
0.68
0.35
0.36
2.65
2.76
2.55
2.61
2.53
2.52
2.52
2.48
2.43
2.39
2.44
2.45
2.39
2.43
2.55
2.51
2.5
2.5
2.97
2.39
2.4
2.4
2.18
2.1
2.36
2.43
2.37
2.15
1.53
0.75
0.3
0.5
3.56
4.11
4.07
4.05
4.14
4.21
4.19
4.13
4.07
3.62
3.7
3.69
3.67
3.9
4.05
4.02
4.09
4.08
4.72
4.12
4.14
4.12
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3.49
4.07
4.19
4.06
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0.92
0.45
0.41
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4.94
4.97
5.25
5.27
5.33
5.09
5.22
5.01
5.21
5.24
5.21
5.3
5.43
5.37
5.37
5.43
5.71
5.49
5.48
5.51
4.49
4.22
5.01
5.41
5.26
4.62
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0.45
0.5
4.26
4.91
4.94
4.97
5.25
5.27
5.33
5.09
5.22
5.01
5.21
5.24
5.21
5.3
5.43
5.37
5.37
5.43
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5.49
5.48
5.51
4.49
4.22
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5.41
5.26
4.62
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19.12
9.35
10.39
88.54
102.05
102.68
103.30
109.12
109.53
110.78
105.79
108.50
104.13
108.29
108.91
108.29
110.16
112.86
111.61
111.61
112.86
118.68
114.11
113.90
114.52
93.32
87.71
104.13
112.44
109.33
96.02
57.16
Figure 7 The interval data of current and % Load
4. Conclusion
In this case, for analyzing period at 06:00 a.m. - 08:00 p.m. on 3 December 2015 and
the period at 11.15 p.m., the maximum percentage of transformer load is 151.73% with
transformer 100 kVA. At this time the customer used transformer load over 80% (PEA’s
technical standard) and over 100% of transformer capacity. This article focuses on Over
Current because the alarm exceeds the AMR meter, damage and also effect to Protection
System, Distribution System too. The technician should meet the customer after alarm. The
interval data benefits to AMR meter means you can use it for Preventive Maintenance (PM)
and it can solve many engineering problems. Nowadays, there are more complications in the
Distribution System that effect the STRONG GRID.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Gellings, C.W. “The concept of demand-side management for electric utilities” (IEEE Xplore
Digital Library, October 1985, page 1468 – 1470)
T Ahmed “Automatic Electric Meter Reading System: A Cost-Feasible Alternative Approach in
Meter Reading for Bangladesh Perspective Using Low-Cost Digit Wattmeter and Wimax
Technology” (http://arxiv.org/ftp/arxiv/papers/1209/1209.5431.pdf, 2012, page 1).
TS52: Power Supply and Demand CEPSI 2010. “SAP Value Added for Key Account
Management” (October 1992 Page 1)
The Automatic Meter Reading (AMR) Project Phase 2 Manual (Provincial Electricity
Authority. Thailand, 2012).
AMR Monitor System Manual (Provincial Electricity Authority. Thailand, 2013).
The Business Continuity Institute. “What is BC?” (http://www.thebci.org/ index.php/resources/
what-is-business-continuity, 2016)
Vadim Kotelnikov “Cross-functional Management (CFM)” (http://www.1000ventures.com/
business_guide/mgmt_cross-functional.html, 2016)
Schneider Electric United States “Frequently Asked Questions” (http://www.schneiderelectric.us/sites/us/en/support/faq/faq_main.page, 2016)
387
7
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
AORC& Technical
Meeting
2016
International
Conference
ofCIGREPower Transmission
Distribution Systems
including
Smartand
Grid, 24-26
Feb. 2016, New
Delhi, India
on
SUCCESSFUL
IMPLEMENTATION
OF of
HOTLINE
FOR HIGH
“Global Trends
in the Development
Power MAINTENANCE
T&D System including
Smart Grid”
VOLTAGE TRANSMISSION LINES AND SUBSTATIONS IN MALAYSIA
SUGUMAR SHUNMUGAM
Tenaga Nasional
Berhad MAINTENANCE FOR HIGH
SUCCESSFUL IMPLEMENTATION
OF HOTLINE
Malaysia
VOLTAGE TRANSMISSION LINES
AND SUBSTATIONS IN MALAYSIA
SUGUMAR SHUNMUGAM
Tenaga Nasional Berhad
Malaysia
SUMMARY
In this digital age, electricity plays an important role in driving our daily activities. It has
transformed the world in many ways since the day it was discovered. Today, we are depended heavily
on electricity to run our daily activities. In order to meet the electricity demand, utilities around the
world built extensive networks of power generations as well as transmission and distribution systems.
Besides meeting local demand, these networks are also used to interconnect with neighbouring
SUMMARY
countries either to export or import electricity supply.
In this digital age, electricity plays an important role in driving our daily activities. It has
In line with this, the key to become successful and reputable power utility company is to ensure
transformed the world in many ways since the day it was discovered. Today, we are depended heavily
continuous availability and reliability of power supply to meet customers’ demand. This is achievable
on electricity
run oureffective
daily activities.
In order
meetcompetent
the electricity
demand,
utilitiesofaround
by havingto highly
maintenance
regimetowith
workforce.
Application
new the
worldtechnologies
built extensive
networks of power
generations
wellworld
as transmission
distribution
systems.
and benchmarking
maintenance
practicesaswith
class utilities and
provide
opportunity
to
Besides
meeting
local
demand,
these
networks
are
also
used
to
interconnect
with
neighbouring
enhance existing capabilities and resources.
countries either to export or import electricity supply.
One of such world-class maintenance practice implemented by Tenaga Nasional Berhad (TNB),
hotline
maintenance
or live
maintenance.
This maintenance
practicecompany
has opened
In Malaysia,
line with isthis,
the key
to become
successful
and reputable
power utility
is tonew
ensure
chapter
in
TNB’s
quest
to
ensure
uninterruptible
power
supply
to
customers
ever
since
being
continuous availability and reliability of power supply to meet customers’ demand. This is achievable
introduced
in 1998.
It covers
wide range ofregime
activitieswith
fromcompetent
as small as repairing
‘hot-spots’
to as bigof
as new
by having
highly
effective
maintenance
workforce.
Application
replacing crossarms on transmission towers and replacing surge arrestors in substations. With hotline
technologies
and benchmarking maintenance practices with world class utilities provide opportunity to
maintenance, defects identified especially on transmission towers and primary equipment in
enhance
existingcan
capabilities
resources.
substations
be rectifiedand
safely
and within short period of time.
One of
such
world-class
implemented
by Tenaga
Nasional
Berhad
(TNB),
This
paper
highlights maintenance
the successfulpractice
implementation
of hotline
maintenance
for high
voltage
500/275/132kV
and substations
in Malaysia.
It highlightspractice
various has
maintenance
Malaysia,
is hotline transmission
maintenancelines
or live
maintenance.
This maintenance
opened new
methods
appliedquest
in maintaining
electrical
equipment power
and apparatus
live environment.
Besidesbeing
chapter
in TNB’s
to ensure
uninterruptible
supplyunder
to customers
ever since
that, safety
measures
are also
as they play
important
aspect
of hotline‘hot-spots’
maintenance.
introduced
in 1998.
It covers
widehighlighted
range of activities
from
as small
as repairing
to This
as big as
paper
also
discusses
the
benefits
and
achievements
gained
by
the
utility
as
well
as
the
impact
towards
replacing crossarms on transmission towers and replacing surge arrestors in substations. With hotline
interruption free maintenance practices.
maintenance,
defects identified especially on transmission towers and primary equipment in
substations can be rectified safely and within short period of time.
This paper highlights the successful implementation of hotline maintenance for high voltage
500/275/132kV transmission lines and substations in Malaysia. It highlights various maintenance
methods applied in maintaining electrical equipment and apparatus under live environment. Besides
sugumars@tnb.com.my
that, safety measures are also highlighted as they play important aspect of hotline maintenance. This
paper also discusses the benefits and achievements gained by the utility as well as the impact towards
interruption free maintenance practices.
388
KEYWORDS
Hotline Maintenance, Hot-Spots, Substations, Transmission Lines
1. INTRODUCTION
Hotline maintenance has been practiced by number of utilities around the world to ensure their
plants and installations operate under healthy conditions. Though hotline maintenance is categorized
as high risk, but with the availability of comprehensive procedures and safety guidelines, hotline
maintenance works being carried out successfully without interruption to the system or unwanted
incidents towards the workers.
As for TNB, hotline maintenance being introduced at time when Malaysia is experiencing
economic expansion with massive infrastructural development around the country, especially in Kuala
Lumpur, Penang and Johor. To be specific, hotline maintenance assisted TNB to address the issues of :
a) Outage constrain to conduct inspection or rectification of defects, mainly for critical or very
important overhead lines and substations.
b) Ensuring network availability and reliability, in-line with increase in power demand.
The transmission system of TNB consists of three (3) voltage levels, 132kV, 275kV and 500kV.
Currently, electrical installations (overhead lines and substations) under these voltage levels are being
maintained using hotline maintenance techniques.
Conventional method of maintaining overhead lines and substations is by using de-energizing or
shutdown method. With substantial increase in electricity demand, de-energizing method of
maintaining electrical installations is no longer a viable choice for maintenance practices. This is
because it involves re-routing the supply from affected network to another network, modifying
generation output and in isolated cases, shutting down supply to large number of customers.
2. TRANSFER OF TECHNOLOGY
The technology of practicing hotline maintenance started in Malaysia in 1998 for 500kV overhead
lines. TNB received transfer of technology from Hydro Quebec Int., Canada. Two pioneer teams were
trained and given complete technical knowledge and skills in performing hotline maintenance on
500kV towers.
Proven successful start-up, hotline maintenance practices were then expanded to 275kV and 132kV
overhead lines in 2002 with establishment of one new maintenance crew. Hydro Quebec Int., Canada,
provided technical support and the expertise. One of the unique hotline maintenance for overhead lines
in Malaysia is the replacement of defective wooden crossarms with composite crossarms.
Over the course of six years (2002-2008), TNB successfully established additional three new teams
for overhead lines maintenance by using internal trainers and experts. These pools of internal experts,
groomed from years of hotline working experience, capable to provide trainings, technical
consultations, providing solutions for hotline maintenance issues, as well as establishing new hotline
maintenance procedures for overhead lines up to 500kV.
As for substations, hotline maintenance practice was introduced in 2010, with transfer of
technology and collaboration from Reseau de Transport d’Electricite (RTE), France. The collaboration
covers wide range of activities including feasibility study, supply of hotline tools, identification of
work methods, training, formation of pioneer team and assessment on team performance.
389
1
The entire process of technology transfer divided in five (5) stages. First stage started with
feasibility study, conducted at selected 132kV and 275kV substations to ascertain possibility of
performing hotline work with respect to the design of TNB substations. This is followed with second
stage, preparation of rules and regulations for hotline maintenance suitable for local environment.
Third stage involved supply of hotline maintenance tools and accessories from CATU, France. Fourth
stage comprised of hotline trainings and transfer of knowledge to TNB’s maintenance crew. The final
fifth stage covered assessment by RTE experts on team’s performance and execution of hotline
maintenance work according to approved rules and regulations.
To further enhance expertise in hotline maintenance, TNB upgraded its capabilities with
collaboration from Terex-Ritz, Brazil, in 2015, to perform hotline maintenance in 500kV substations.
Maintaining 500kV substation is a challenge for crew members as it involves larger installations,
longer hotline tools as well as higher intensity of electromagnetic field.
With this final project, it completes TNB’s journey into hotline maintenance on 500kV, 275kV and
132kV overhead lines and substations. Though faced with its own set of challenges, hotline
maintenance proved to be a successful venture, by improving the availability and reliability of the
electricity network.
3. WORK PROCEDURES AND SAFETY
The framework of activities and programs for hotline works are divided into four categories as
follows :
a) Legal regulations and standards.
b) Maintenance strategies.
c) Policies prepared by respective departments.
d) Procedures described by the experts.
When maintenance works are conducted under hotline condition, aspects of safety become foremost
priority for the team members. In fact all procedures of safety will be nurtured from initial training and
will be part and parcel of their working environment. These safety trainings will then be conducted
and assessed periodically to close the gaps of any shortcomings.
Besides safety, team’s technical knowledge and skills are continuously monitored and upgraded
from time to time. This is done through refresher trainings and exchange of working experience from
other hotline experts.
All overhead lines and substations hotline maintenance works are supervised by a trained and
certified supervisors. These supervisors must able to judge the capabilities of each team member and
maintain continuous surveillance over their physical and mental conditions while performing hotline
works. The supervisors are also responsible to ensure that detailed preliminary works are carried out in
advance before start of actual hotline works. Among the particulars that need to be taken into account
in preparing proper work plans are safe working distances at work site, location of all grounded and
energized installations, condition of apparatus to be worked-on, weather forecast, previous work
records, availability of spares and appropriate working tools.
4. METHODS OF PERFORMING HOTLINE MAINTENANCE
There are two methods of performing hotline maintenance works on overhead lines and substations.
Both methods have their respective work procedures, safety requirements and working tools.
390
2
Details of the two hotline maintenance methods are as follows :
a) Barehand Method
Work performed by team member in direct contact with energized component i.e. busbar. The
team member shall wear special conductive attires while conducting hotline work and shall
respect working distance either from energized components or from ground potential.
b) Hot Stick Method
Work performed by team member at ground potential either on the ground or standing on noninsulated platform and perform work using insulated hand held sticks or tools. The team
member shall always maintain a specified working distance according to system voltage.
5. TYPES OF WORK CONDUCTED
Currently there are number of inspection and rectification works performed using hotline
maintenance methods for 500kV, 275kV and 132kV overhead lines and substations.
Details of hotline works carried out on overhead lines are as follows :
a) Replacement of insulators on suspension and tension towers.
b) Replacement of wooden cross-arm on suspension towers.
c) Replacement of tower fittings and accessories, example : vibration dampers and spacers.
d) Repair of hot-spots at jumper/bypass connections on tension towers.
Details of hotline works carried out at substations are as follows :
a) Repair of hot-spots at disconnectors and clamps.
b) Replacement of disconnectors, busbars, conductors and clamps.
c) Application of temporary shunting for critical hot-spots.
d) Removal of foreign objects on electrical apparatus.
e) Cleaning and servicing of components and accessories of electrical apparatus.
f) Removal of earth mast / overhead shield wire of substations.
g) Replacement of Surge Arresters.
6. HOTLINE WORK ON OVERHEAD LINES
Conducting hotline replacement of wooden cross-arms on suspension type transmission towers
(275kV and 132kV) require systematic approach as it involves :
a) a number of temporary hotline tools and equipment to be fixed on tower.
b) comprehensive work procedures and safety guidelines.
The installation of temporary hotline tools is to support the load of conductor during the removal of
insulator string and wooden cross-arms.
391
3
Figure 1. Installation Of Temporary Hotline Tools
Figure 1 shows an example of installation of temporary hotline tools on suspension 132kV tower for
the purpose of replacing wooden cross-arm.
The hotline tool named ‘wire tong’ is installed from tower body to the conductor at an upward angle
of about 300 – 450. The wire tong will experience compression load from the conductor.
The hotline tool named ‘swivel stick’ is installed from tower body to the conductor at downward
angle of about 300 – 450. The swivel stick will experience tension load from the conductor.
Once the load of the conductor is transferred to the wire tong and swivel stick, the insulator string
will be removed followed by the wooden cross-arm. The entire span load of the conductor will be
supported by the temporary hotline tools (wire tong and swivel stick) until the replacement work is
completed. The activity of replacing per phase wooden crossarms to composite crossarms under
hotline method will take about two hours.
7. HOTLINE WORK IN SUBSTATIONS
Among the various hotline maintenance works conducted, repairing hot-spots at disconnecting
switches are among the highest number of hotline works performed annually. The hot-spots usually
occur at the attachment of rotating rod and the clamp as well as at the connectors. Temperature of the
hot-spots mostly detected in the range of 900C to 2000C. Among the factors that determine
temperature of the hot-spots are loading of the network and environment temperature.
Unattended hot-spots could possibly lead to power interruption since high and prolonged
temperature at certain point could weaken the metallic component of the disconnecting switch.
Occurrence of the hot-spots may be contributed by many factors, but mainly due to pollution, wear
and tear, poor quality of material and aging.
Prior to perform hot-spot repair, thorough analysis is conducted to ensure work can be performed
safely. A number of parameters are taken into account in this analysis. These parameters include :
392
4
a) The “Voltage Influence Cone”.
The voltage risk zone that can be assimilated to a double cone area within which there is a risk
of flashover due to the vicinity of the High Voltage. The principle in the safety analysis is to
avoid in any case team member’s body passing through the cone [1].
b) Insulated Scaffolding
Insulated scaffolding is the place where team members will position their self to proceed with
hotline work. The movement of the scaffolding and the resulting position of the working
platform are the two parameters to be verified in the work preparation process. Position of
scaffolding with respect to the Voltage Influence Cone is shown in Figure 2.
c)
Phase to ground distance (t).
This is distance or clearance between live component and the ground potential.
d)
Phase to phase distance (T).
This is distance or clearance between live component to another live component (between
different phases).
The hot-spots repair usually conducted either using barehand method or hot-sticks method,
depending on availability of working clearance. In both methods, the disconnecting arm will be
dismantled from its housing, serviced thoroughly and re-installed to its original position.
Worker
Busbar
Voltage
Influence
Cone
Insulated
Scaffolding
Column
Figure 2. Position of scaffolding with respect to Voltage Influence Cone.
Figure 3. Position of worker with respect to Voltage Influence Cone when performing
hotline work using Hot-Stick Method.
393
5
8. CONCLUSION
From a promising start in 1998, TNB’s high voltage overhead lines and substations hotline
maintenance practices progressed consistently throughout the years by adopting new technologies and
enhancing working methods. With inputs from various utilities and hotline tools manufacturers, TNB
has continuously developed and improved hotline maintenance methods to suit the requirements and
designs of local overhead lines and substations.
Throughout the years, initiatives have been undertaken to create pool of in-house technical experts
and trainers to solve any issues pertaining hotline maintenance works. These experts work hand-inhand with other hotline practitioners in sharing and developing new or improved working methods.
A lot of researches, studies and improvements have been conducted to enhance the work
procedures, safety aspects and technical know-how of the maintenance works to ensure each job is
executed efficiently and effectively. All new work procedures are properly recorded, documented and
applied to the team members through a series of technical follow-ups and refresher trainings. Teams’
performance are also constantly assessed, leading to improved productivity and efficiency.
Implementation of hotline maintenance works in TNB proved to be successful investment in
ensuring reliability and availability of electricity supply to consumers. Hotline maintenance has
significantly reduced the time and work force required to conduct maintenance of electrical
installations. Besides that, hotline maintenance has also assisted in reducing interruption to the
transmission grid system in Malaysia.
BIBLIOGRAPHY
[1] RTE, “Feasibility study for the setting up a Live Working Maintenance Team”, July 2008.
[2] Electricity Supply Act, Malaysia, 1990.
[3] Occupational Safety & Health Act, Malaysia, 1994.
[4] Transmission Electrical Safety Rules, TNB, 2009
394
CIGRE- AORC Technical Meeting 2016 and International Conference
on
CIGRE- AORC Technical Meeting 2016 – International
Conference on Global Trends in the Development
of Power
Transmission
& Distribution
Systems
24-26 including
Feb. 2016, New
Delhi,
India
“Global
Trends
in the
Development
ofincluding
Power Smart
T&DGrid,
System
Smart
Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
on
A“Global
Comprehensive
Data
Governance
the Pragmatic
Guideline
for Grid”
Trends in the DevelopmentFramework,
of Power T&D
System including
Smart
Big Data Analytic in Smart Utility
DR. SURAT TANTERDTID, THEPMONGKOL SIGHSATIEN, RUJ TIEENTONGDEE
A Comprehensive
Data
Governance
the Pragmatic
Guideline
for
Communication System
Department,
ElectricityFramework,
Generating Authority
of Thailand (EGAT),
Thailand
Big Data Analytic in Smart Utility
DR. SURAT TANTERDTID, THEPMONGKOL SIGHSATIEN, RUJ TIEENTONGDEE
Communication System Department, Electricity Generating Authority of Thailand (EGAT), Thailand
SUMMARY
During the past years, all power utility play much attention in Smart Grid (SG) vision and started to do
their roadmap for being smart power utility in a very short future. Therefore, many technology have
been investigated whether to apply in their SG roadmap, generation, transmission, distribution and
operation/control system.
SUMMARY
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management
technology.
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Therefore the topic of applying Big Data analytic in SG roadmap is much talking in
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animplementation
guideline,
the
process
of
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Governance,
key
activity
as
well
currently. Most of the Big Data analytic papers usually shown the key feature and benefit whenasthey
role/responsibility of Data Governance participant are also presented.
apply in their Big Data in power utility operation system. Unfortunately, there have no any publication
or study presents about Data Governance which is a very important success factor for Data analytic.
This article addresses the problem of the Data Governance and proposes a comprehensive Data
Governance framework which is a pragmatic guideline for successful information management in Big
Data environment of smart utility. We address the challenge of Data management and summarize
the impact
of Data management in term of Data quality, consistency and accuracy. To be
KEYWORDS
animplementation guideline, the process of Data Governance, key activity as well as
Smart Grid, Big
Data, Governance
Data Governance,
Information
Management
role/responsibility
of Data
participant
are also
presented.
surat.t@egat.co.th
KEYWORDS
395
Smart Grid, Big Data, Data Governance, Information Management
1. Introduction
21st Century electric networks are rapidly evolving on multiple dimensions, including
the development of energy information and operational platforms, in response to the adoption
of a wide array of sensors, the penetration of significant distributed energy resources
(including renewable resources and load management), and the enabling of market
participation by millions of customers. This transition from vertically oriented value chain to
a hybrid, more horizontal industry structure creates the need for the convergence of data,
controls, and transactions into a unified energy platform enabling reliable and secure market
and grid operations. The resulting platform is an emerging Enernet.
In this new context, data includes a wide range of types to enable both use by electric
systems for planning, operations, asset management, and electricity markets applications, and
new services for end customers and other market participants. When combined with an
exponential growth in volume and diversity of data sources and in variety of uses and related
latency requirements, developing an effective data management strategy presents a very large
challenge.
Recently, most of power utility play much attention in order to achieve their Smart
Grid(SG) target. Importantly, information management is a key principle technology that they
use as a strategic tools for monitoring evaluating and managing their performance. Now a
day, the requirement of information management capability are changing from supportive to
be predictive and analytic capable system. The requirement of information analytic of huge
data and unstructured data are much talking and introducing into smart utility. This system is
called Big Data analytic. Conceptually, basic principle of Big Data Analytic is the system that
capable to store, process, analyze and visualize the high volume and velocity of data.
Moreover Big Data analytic principle is able to support an analyzing of non structure data
such as picture, text file and html file format. Therefore the topic of applying Big Data
analytic in SG roadmap is much talking in many symposium currently. Most of the Big Data
analytic papers usually shown the key feature and benefit when they apply in their Big Data in
power utility operation system. Unfortunately, there have no any publication or study presents
about Data Governance which is a very important success factor for Data analytic.
This article addresses the problem of the Data Governance and proposes a
comprehensive Data Governance framework which is a pragmatic guideline for successful
information management in Big Data analytic of smart utility. The organization of this article
are summarized as follows. Section 2.Is about the Big Data architecture and application in
smart utility. The important of data governance and key challenge are presented in Section 3.
Our proposed data governance framework as well as governance process are presented in
Section 4. The guideline for successful data governance implementation is introduced in
section 5. Conclusion and suggestion are shown in the last section.
2. Architecture and Application of Big Data Analytic
In order to present the whole picture of Big Data system, the system architecture of
Big Data have been shown in Figure 1
396
1
Figure 1: The architecture of Big Data Analytic system
As presented in Figure 1, the architecture of Big Data Analytic is separated into
difference 3 layer, visualization, services and infrastructure layer respectively.
 Visualization layer: This layer is about the analytical model and outcome of
calculation. The key capability of this layer is to present as a predictive results.
 Service layer: This layer present the services capability to handle many kind of
system such as batch processing, real time structured database, interactive
analytics as well as source of data, structure and unstructured data.
 Infrastructure layer: This layer is about the infrastructure of Big Data provided
such as computing, storage and cloud infrastructure.
To summarize the benefit of Big Data in power utility, the application in many area of
smart utility have been introduced as follows.
 Data Management in Advanced Metering Infrastructure (AMI)
 Data Management in aMeter Data Management Systems (MDMS)
 Information management in Outage Management Systems (OMS)
 Information management in Distribution Management Systems (DMS)
 Enterprise Asset Management Systems (EAS)
All of those application are dealing with the difference types of Data class. The table 1
presented shown the 5 difference of Data class that be classified in smart utility point of view.
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2
Table1: Data Classification
3. Key Challenge of Data Governance
As shown in Table 1, the business value of each class is not necessarily equal to that
of other classes. It is important that each utility understand this concept and define the
business value of each data class, perhaps to the point of subdividing the classes as
appropriate for the specific utility’s drivers and constraints, so that proper data management
solutions may be derived that reflect the utility’s business requirements. Also, data often is
used by multiple departments within a utility and may have quite different perspectives on the
classifications above. It is critical that a holistic approach is utilized along with an effective
governance process to reconcile and differences. The governance process used for enterprise
business process management should be utilized as the potential prioritization and ownership
issues with data are part of this domain.
From our experiences, utility, mostly, play much attention in technology point of
view. They were not familiar with data governance process which is a critical factor for data
management in Big Data implementation. We have summarized the key challenge of data
governance base on our practical experiences as follows.
• Cultural barriers: There still have a culture of data ownership. No any data sharing
or reusing in the organization.
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3
•
•
•
•
•
•
•
•
Lack of senior-level sponsorship: The executive did not aware the important of
data governance.
Underestimating the amount of work: The organization did not understand the
project footprint and stakeholder involved.
Lack of business commitment: Each function in the organization did not aware the
important of data governance.
A lack of cross-organizational data governance structures, policy-making, risk
calculation or data asset appreciation, causing a disconnect between business goals
and IT programs.
Governance policies are not linked to structured requirements gathering,
forecasting and reporting.
Risks are not addressed from a lifecycle perspective with common data
repositories, policies, standards and calculation processes.
Metadata and business glossaries are not used as to track data quality, bridge
semantic differences and demonstrate the business value of data.
Few technologies exist today to assess data values, calculate risk and support the
human process of governing data usage in an enterprise.
4. Data Governance Framework and Process
To be a pragmatic guideline for data governance implementation, a comprehensive
framework as well as suggested process has been presented as Figure 2
Figure 2: Data Governance Process
Section 1 Obtain Executive Buy-In and Support: Here is a very important step
which have a direct impact to the success or failure of data governance. The good understand
as well as critically of data governance to information management are the key message for
this section. The expected outcome of this section is executive sponsorship of the project.
Section 2 Establish Management Structure and Control: This section is about the
governance body as well as responsibility/accountability of governance body assignment. The
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4
right governance body should come from all business area of utility such as operation, control
center as well as substation line of business.
Section 3 Define Key Performance Indicator: The governance body should find the
performance indicator that reflexing to data quality. All the indicator should be measurable
and follow the performance management of the utility.
Section 4 Develop Target Information Management and Data Quality: This
section is about the desirable information management and data quality which correspondence
with the organization vision.
Section 5 Develop Baseline Data Quality: This section is the assessment of current
information management as well as current data quality.
Section 6 Develop the Sequencing Plan: This section is all about the activity or
initiative we may need in order to achieve the target of information management and data
quality.
Section 7 Use the Data Governance: This section is about the implement and
deployment of data governance policy to all the business area of utility.
Section 8 Maintain the Data Governance: This section is about the maintain the
process of data governance as well as embedded the process into each line of business.
Table 2: Data Governance Body
Body
Data Governance Steering
Committee
Data Governance Working
Committee/ LOB Manager







Data Quality Assurance




Responsibility
Determine enterprise data needs and data
strategy
Establish data professional roles and
organizations
approve data policies, standards, and procedures
Understand and assess current state data
management maturity level
Establish future state data management
capability
Develop data policies, standards, and
procedures
Plan and sponsor data management projects and
services
Coordinate data governance activities
Manage and resolve data related issues
Monitor and enforce conformance with data
policies, standards, and architecture
Communicate and promote the value of data
assets
5. Data Governance Pragmatic Guideline
Not all data governance efforts yields expected results. Major obstacles exist that
affect the value and success of the program. They include cultural, political, and
organizational challenges that can lead to resistance to the changes that are required to move
forward with the governance initiatives.
Here are some steps that help bring success and address the above-mentioned
challenges.
400
5
•
Take a holistic approach but start small
As was illustrated in the earlier section of this article, data governance is an
iterative process. Start with the people, politics and culture, and then move on to the data
governance and stewardship processes as well as technology. It takes a number of steps to
gradually move up the maturity scale. However, start with an end in mind. Balance out
strategic objectives and tactical compromises to ensure the overall program is moving towards
the desired direction at reasonable pace.
• Obtain executive sponsorship
Data governance involves significant behavioral and cultural changes. Funding
for projects and technology tools are also required. Without strong backing from the executive
level, none of the above will happen. Analyze your stakeholders and align and get on board
key decision makers who represent core functional areas and lines of businesses, who have
the strong influence and decision-making power. With them as your champion, the
foundational changes have a higher possibility to be successful.
• Define data stewardship during early stage
The main responsibility of the data stewards is to ensure effective control and
use of data assets. The best data stewards are found, not made. Take your time to identify and
build a data steward team that includes subject matter experts from all business areas.
Difference of opinion exists with regards to whether or not to establish an
official position and title for this role. The answer is: it depends. It depends on the stage you
are in developing your data governance program and it depends on the political and cultural
environment of your organization. What’s most important is that the definition of this role is
included in the job descriptions of these individuals and proper time allocation is applied to
the stewardship work.
• Establish quantifiable benefits by building business case
An effective data governance program brings tremendous benefits to an
organization in a long run. However, some of the effects might or might not be visible
immediately. As a result, it is not always easy to obtain and justify funding for the program
cost. Focus on the relationship of the key data elements and the business processes they
support. Calculate the cost of managing these data elements through repeated and duplicated
manual integration and validation. Quantify the business risk of such data elements becoming
unavailable or incorrect such as missing transaction or loss of customer. Identify clearly the
opportunities quality data brings in terms of generating and improving revenue through better
customer service and insight, through up-sale and cross-sale.
In short, building a business case to articulate and highlight quantifiable
benefits is essential to get buy-ins and support towards the program.
• Establish, collect, and report on metrics to measure the progress
Choose a combination of tactical quick wins and longer-term strategic
improvements as a starting project. Measure the immediate returns of the quick wins to gain
positive feedback, sustain engagement, and obtain more support. Measures should be
determined at the beginning of the project and focus on quantitative metrics that support the
objectives of the project as well as the overall program. Metrics need to covey business values
and some sample metrics include data value, data management cost (before and after), number
of decisions made, and data management process maturity. A data governance KPI dashboard
is a good way to automate the reporting of the progress.
• Link and build in incentives to award and re-enforce participation
One of the most challenging aspects of data governance is adequate
participation at an on-going basis. Data stewards are usually tasked with multitude of
operational duties and business units often vary significantly on resource allocation. The
collaborative nature of a data governance program, however, depends heavily on leveled and
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6
prioritized commitment from all business functions. Building an incentive-based reward
system that links performance to participation can re-enforce priority and thus gain more and
sustained commitment from all required parties. It is also important to note that incentives do
not have to be all financial-based. Formal and Informal recognitions go a long way in
showcasing good examples, instilling sustained enthusiasm, and promoting desired cultural
changes within an organization.
6. Conclusion
Forwarding to smart utility, data governance is one of the most important of effective
Information management. Generally, most of utility focus to the technology to handle and
manage the huge of data from their operation system, AMI, EMS, SCADA and ERP. Big
Data is one of most popular analytic technology which was introduced as a performance
management tools. One basic principle that very important to successful Big Data
implementation is the data quality (accuracy, consistency, timely etc. All of this data quality
shall be obtained by the data governance. This article address the key issue of data
governance and propose a comprehensive framework as a pragmatic guideline for data
governance implementation. The problem of the Data Governance and proposes a
comprehensive Data Governance framework which is a pragmatic guideline for successful
information management in Big Data environment of smart utility. We address the challenge
of Data management and summarize the impact of Data management in term of Data quality,
consistency and accuracy. To be an implementation guideline, the process of Data
Governance, key activity as well as role/responsibility of Data Governance participant are
also introduced.
BIBLIOGRAPHY
[1]
[2]
Jeffrey Taft, PhDPaul De Martini, Newport Consulting GroupLeonardo von Prellwitz(2012).
“Utility Data Management & IntelligenceA Strategic Framework for Capturing Value from
Data”. Cisco Systems, Inc. (May 2012, pages 2-4)
Helen Sun (2011). “Enterprise Information Management: Best Practices in Data Governance”.
U.S.A: Oracle.
402
7
The Grid I
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
Operation
and
Dynamics
ofSystems
VSC-HVDC
Transmission
of Power
Transmission
& Distribution
including
Smart
Grid,International
24-26 Feb.system
2016,Conference
New Delhi, India
CIGREAORC
Technical
Meeting
2016
and
on
TIRUPATHI
REDDY*,
SANJEEV
SHRIVASTAVA,
GULATI,
RENUKA
“Global Trends in the Development of PowerARUNA
T&D System
including
SmartGERA
Grid”
Bharat Heavy Electricals Limited
India
Operation and Dynamics of VSC-HVDC Transmission system
TIRUPATHI REDDY*, SANJEEV SHRIVASTAVA, ARUNA GULATI, RENUKA GERA
Bharat Heavy Electricals Limited
India
SUMMARY
Indian Power System is growing with a rapid pace. In recent years, there has been huge
planning for development and deployment of renewable energy resources to meet the ever
increasing electric power demand and to limit the use of fossil fuels. Wind generation poses
SUMMARY
grid integration challenge such as long distance under sea transmission and managing the
variability of wind power variation on in the power grid. These challenges can be properly
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deals with the modelling of Voltage Source Converter High Voltage Direct Current (VSC
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power flow and dynamic analysis. Control systems, DC circuit and converter transformers are
advantages
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For demonstrating
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are discussed
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HVDC) systems for power system analysis. Proposed VSC HVDC model can be used for
power flow and dynamic analysis. Control systems, DC circuit and converter transformers are
part of the dynamic model. For demonstrating the ability of VSC HVDC in regulating and
improving stability of power grid, simulation of Indian power system with VSC based HVDC
is envisaged. From simulation, list of controls are discussed in detail for easy understanding.
KEYWORDS
VSC HVDC- Dynamics –PWM - MMC
KEYWORDS
VSC HVDC- Dynamics –PWM - MMC
*ttreddy@bhel.in
*ttreddy@bhel.in
405
1. Introduction
1.1 Background
Power is the most vital input for the growth of any economy. Therefore, it is considered as a
core industry as it facilitates development across various sectors, such as manufacturing,
agriculture, commercial, education, railways etc. to achieve economic growth. Energy needs
of the country is growing at a very fast pace to meet high GDP growth rate. Present peak
electricity demand of the country is 135GW which is expected to grow to about 200 GW &
283 GW by the end of 2016-17 (12th plan) & 2021-22 (13th plan) respectively as envisaged
in the 18th EPS report of CEA. To meet growing demand and to reduce supply-demand gap,
there is a need of large capacity addition through conventional as well as from renewable
energy sources.
India is endowed with abundant renewable potential which presents an excellent solution to
meet challenges like meeting long term energy requirements, attaining energy security along
with affordability, addressing climate change concerns etc. government is also promoting
development of renewable generation through an attractive mix of fiscal and financial
incentives as well as conducive policy environment. MNRE has envisaged about 175 GW
renewable capacity through solar (100 GW) & Non solar (75 GW) by 2022 [1].
The renewable energy resources are located at remote locations, e.g. offshore wind
generation. The on-shore (receiving) converter station can be located close to the shore or
further inland. The grid is sometimes rather weak (radial structure) along the coastline. The
new HVDC technology based on Voltage Source Converter (VSC) is a feasible and attractive
solution to interconnect these renewable energy sources to main Indian powergrid. It is also
easy to bring the connection point to a major substation at some distance from the shore by
means of DC cables. The main advantages to compared as the LCC alternative are smaller
converter size, smaller filters, possibility to use XLPE cables, independent control of active
and reactive powers, fast control response and black start capability and reliable operation in
weak system.
1.2 VSC- HVDC Projects under planning in India
A number of voltage source converter projects are under planning in India. The projects have
been planned as VSC based HVDC technology due to feasibility issues [2]:
1) India –Srilanka -2X500MW HVDC system: the line shall transmit power from/to
India to/from island of Srilanka which has a weak AC grid and further undersea cable
shall be used for interconnection
2) Pugalur –Trichur -2000 MW HVDC System: Trichur in kerala has severe right of way
issues, therefore a combination of Hybrid AC-DC line (existing as line can be
reconfigured to lay DC lines) and underground cable (XLPE cable) shall be a part of
the transmission system.
3) As per the Desert power india -2050 report, power from solar parks, identified in the
region of Rann of Kutch, Thar, Laddakh and Lahul & Spiti. The transmission system
planned to evacuate this bulk solar power shall also comprise of approximately
eighteen nos. (18) of VSC HVDC Links
406
1
1.3 Power transmission by Cable/transmission line
Undersea cable is used for power evacuation from offshore renewable (or) power
transmission between two islands. Further if the power transmission link is onshore but right
of way is a limitation such as urban areas, then underground cable can also be selected for
interconnection. In VSC HVDC scheme, the power reversal is done by reversing the direction
of current without changing the polarity of voltage. Therefore XLPE Cables can be used for
VSC HVDC System instead of Mass Impregnated (MI) cables used in LCC HVDC system.
As the XLPE cable is much cheaper than MI cables, the VSC technology is being preferred
for the systems that uses long distance DC cable transmission. The highest voltage rating of
the XLPE cable commonly used is 320kV [2].
1.4 Outline
This paper gives an overall introduction of VSC HVDC technologies in section 2. Section 3
discusses about the modelling in PSSE software. Section 4 shows the results of simulation
2. VSC -HVDC
The fundamental operation of a VSC-based HVDC converter implies the presence of a
voltage source on the DC side. The voltage source maintains a prescribed voltage across its
terminals regardless of the magnitude or polarity of the current flowing through the converter.
There are three types of VSCs used in HVDC applications, two-level, three-level and modular
multilevel converters. The categorization is done based on the voltage levels produced in the
AC output of the converter, before it is filtered. Configuration of VSC-HVDC system with
two level converter is shown in Fig 1.
Fig 1. Typical configuration of VSC - HVDC with level converter [3]
Main components of VSC HVDC Converter is as follows
Transformers :- Usually, the converters are connected to the AC system via transformers. The
transformer has the main purpose of transforming the AC voltage to a level suitable to the
converter.
Converter reactor :- The AC side of the converter bridge is connected to a series reactor, the
Converter Reactor, providing low-pass filtering of the PWM-switched converter voltage, to
give the desired fundamental-frequency voltage, and providing impedance between the
407
2
converter voltage and the AC filter bus voltage. The power flow between the AC and DC side
is defined by the fundamental-frequency voltage across the reactor. The amplitude and phase
of the voltage on the AC side of the converter reactor is determined by grid.
DC Capacitor :- A capacitor bank on the DC side of the converter bridge provides energy
storage and a low-inductance path for the turn-off current. The capacitor bank is connected
between the positive and negative DC pole, and it is mid-point grounded to provide a ground
reference for the converter.
AC filters :- In addition to the series inductance of the reactor, AC filters can be used to
eliminate the voltage harmonics entering into the AC system. A typical AC filter is a shunt
connected high pass filter containing two or three earthed or unearthed filter branches tuned in
the order of the PWM frequency [3].
Valve: Typically, many series-connected IGBTs are used for each semiconductor shown (see
Fig 1) in order to deliver a higher blocking voltage capability for the converter, and therefore
increase the dc bus voltage level of the HVDC system. It should be noted that an antiparallel
diode is also needed in order to ensure the four-quadrant operation of the converter.
2.1 Two level converter
Two level converter is shown in Fig 1. The converter’s two-level topology means that, by
turning the valve transistors (IGBT) on and off, the AC connection point of the converter
bridge is switched between +Vd/2 and –Vd/2. The valve switching method uses Pulse Width
Modulation (PWM) as shown in Fig 2. The AC side of the converter bridge is connected to a
series reactor, providing low-pass filtering of the PWM-switched converter voltage, to give
the desired fundamental-frequency voltage (VAo), and providing an impedance between the
converter voltage and the AC filter bus voltage.
Fig 2. Upper: Principle of using PWM switching and
Lower: Sinusoidal output voltage generated by PWM switching [4]
408
3
2.2 Modular multilevel converter
The MMC converter, or sometimes referred to as Cascaded Two-Level converter (CTL), is
based on the same operating and control principles as the VSC, but each phase-arm consists
of several two-level submodules, as can be seen in
Fig 3. Compared to the other two types of converters, the difference is that there is not
common capacitor of MMC connecting buses.
The operation principle of MMC is that each switch module consisting of two valves can be
switched in three modes as described below:
 S1 is turned on and S2 is turned off, the capacitor is inserted into the circuit. The module
contributes with voltage to the phase voltage.
 S1 is turned off and S2 is turned on, the capacitor is bypassed.
 S1 and S2 are both turned off; the module is blocked when the capacitor voltage is higher
than outside voltage.
MMC is attractive to the HVDC application, in contrast to two- or three-level converters,
because cascaded connection method permits each module theoretically only needs to switch
on and off only once per period, which greatly reduces the switching losses. The output
waveform can be closely sinusoidal when the number of modules is large enough (usually
more than 100 modules of each leg for HVDC application). This results in a very small
harmonic content of the voltage, and means that the ac filter is not necessary any more in the
HVDC stations [3].
Fig 3. Upper: modular multilevel converter topology, a) Structure of one module (SM) and (b) Phase leg.
Lower: AC Line voltage waveform [3]
409
4
3 VSC HVDC MODEL IN PSSE SOFTWARE
The VSCDCT, PSSE model is a time-averaged model and is therefore intended to be used in
order to study the effect of the VSC-HVDC on the network on the electromechanical time
frame. In general VSC-HVDC models can be either detailed or time-average. In detailed
models, all the components of the VSC-HVDC line, such as all the semiconducting
components, are modeled. Special electromagnetic transient software tools, such as PSCAD,
ATP etc, are needed in order to perform simulations with these models.
These models can be used to study the behavior of different HVDC topologies, PWM
techniques or high frequency component harmonics. On the other hand, time-average models
do not model in such detail the HVDC components. Also there is no distinction made between
different topologies or switching techniques. All phenomena related to the fundamental
switching frequency can be studied adequately. The main principle of time-average models is
that the HVDC line is represented as controllable three-phase voltage sources on the AC side
and a controllable current source on the DC side. Time-averaged models can be used both by
electromagnetic transient programs as well as power flow simulation tools, such as PSSE,
SIMPOW etc.
Since the VSCDCT model is used for electro-mechanical time frame studies only the outer
controllers are represented. The inner control loop and the DC side characteristics have a
much faster response than the time scale of PSSE. Therefore the DC side dynamics are
modeled in an approximate way while the inner current controller is not modeled at all. The
active and reactive current components are assumed to take instantaneously their reference
values created by the outer controllers.
The VSCDCT model consists of three modules, two of which represent the VSCs (VSCDYN)
and the other the DC line (DCLINE) shown in Fig 4. The converter modules have modeled
the outer controllers and enable the user to control AC voltage or reactive power, DC voltage
or active power as well as to apply current limitation strategies. Additional features are active
power ramping and converter blocking. Regarding active power control, the DC line module
coordinates the power flow between the two converters and is therefore responsible for
creating a power order for each converter and assigning it to each VSC module. In the case of
a current limitation in the network of a converter, e.g a fault in the AC system close to one of
the converters, an imbalance in the power flows of the converters will occur resulting in a
change of the DC voltage. The active power reference of the VSC modules will be lowered
appropriately, by the DC line module, in order to bring the active power exchange between
the converters in balance once again. The DC line module also is responsible for taking into
account the DC transmission losses. It creates the appropriate active power reference in order
to compensate these losses. The losses are compensated in the DC voltage controlling
converter. By changing the appropriate set point value in the VSCDCT model, active power
ramping is performed by the DC line module [5].
3.1 Time step
For the dynamic simulations with VSC HVDC, the time step has to be reduced compared to
simulations of normal AC systems. A time step of 10 ms is normally used for AC systems in
PSSE, while for simulation with VSC HVDC a time step of (¼ cycle) 5 ms (or) less will give
a good representation of the dynamic response close to the VSC HVDC converters [5].
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5
Fig 4. VSCDCT PSSE Model [5]
4
Simulation and Results
Bulk renewable energy resources are located at remote locations. VSC based HVDC
transmission technology is required for interconnection of these renewable resources to Indian
powergrid. To demonstrate the key features of VSC HVDC, typical 320 kV 500MW VSC
HVDC from Pugalur to Trichur is modelled for study and its parameters are given in below
Table 1.
Table 1. VSC HVDC Parameters
Description
Power
DC Voltage
DC Line
DC line resistance
AC Series reactor
Value
500MW
320 kV
250 km
2.02
0.17 pu on Converter MVA rating
PSSE software is used for simulation and prepared Single Line Diagrams (SLD) of VSC
HVDC area shown in Fig 5, where VSC HVDC is connected between sending PUGALUR4
(54413) bus and receiving NTRICUR (534011) bus. Power flow in the HVDC link is 500
MW measured at sending end.
Normal control philosophy is, sending converter is in DC voltage control mode, while the
receiving converter is in active power control mode. AC side is AC Voltage control mode on
both the converters i.e. Converters are set to control the voltage of their respective filter buses.
In a traditional HVDC system, a communication link between the two converter stations is
needed in order to control the power flow. The voltage is measured in one end, and the DC
voltage is controlled in the other end so that the voltage difference divided by the DC-line or
cable resistance equals the set point of the DC-current. A VSC HVDC system does not
require any communication between the two converters. The converters communicate through
the measured DC voltage at each end.
411
6
Fig 5. Single line diagram of indian power system around the VSC HVDC link
1) Case 1 Step change in DC power flow :DC Power shown in below Plot 1, is in pu on 100MVA system base. A step change is applied
at time =0.1 sec from 500 MW to 400 MW and at time=0.5 sec from 400 MW to 500 MW.
Final value is reached in 0.2 sec, which is fast and final value is reached without any
overshoot.
Plot 2 shows the converter bus voltage response for step change in DC power reference input.
Since VSC HVDC has capability of independent control of active power and reactinve power
control, converter voltages are not much effected by step change in DC power.
412
7
Plot 1. DC Power response for step change in DC power reference input
Plot 2. Converter bus voltage response for step change in DC power reference input
413
8
2) Case 2, three phase to ground fault on inverter side bus (COCHIN4):3 phase to ground fault is applied at time = 0.1 sec. on COCHIN4 (53404) bus, which is one
bus level away from converter bus. Fault duration is 100 msec and voltage response is shown
in below Plot 3.
Plot 3. Voltage response of converter buses for 3 phase to ground fault COCHIN4 bus
Since the fault is created near to inverter bus, inverter bus voltage is dropped to almost 0.3 pu,
where as rectifier bus voltage is dropped to approx. 0.9 pu. Rectifier and inverter buses are
interconnected through parallel AC transmission lines, fault has propogated through the
parallel AC lines instead of through DC Transmission line could be observed from the plot.
When the HVDC is working in AC voltage control the link provides reactive power in order
to support the voltage at their filter bus. Plot 4 shows the response of reactive power fed to
bus for above case.
QELE_VSC1 and QELE_VSC2 are reactive power (pu on 100 MVA base) fed into respective
buses of converters. By improving the AC system voltages through reactive power injection
during a fault, the impact of a fault on the system’s dynamic response becomes less severe.
414
9
Plot 4. Reactive power response for 3 phase to ground fault at COCHIN4 bus
Plot 5 shows the active power response and DC power response for 3 phase to ground fault at
COCHIN4 bus. When the fault occurs on inverter side bus, the DC voltage will increase
immediately because of the power imbalance between the two converters. The power fed into
the DC system from the sending converter is quickly reduced as a response to this in order to
reduce the DC voltage. This is how the HVDC control is possible without the
telecommunication between converters. PELE_VSC1 and PELE_VSC2 are active power (pu
on 100 MVA base) fed into respective buses of converters and P_REF is DC power flow in
pu on 100 MVA base. The results show that the HVDC systems stabilize without problems
after the fault clearance and are smoothly damped in a short time. The HVDC link has shown
a fast recovery response to reach again pre-contingency conditions.
415
10
Plot 5. Active power response for 3 phase to ground fault at COCHIN4 bus
5
Conclusion
 The paper has discussed the accelerated growth of Indian power sector and the
importance of VSC - HVDC in growing Indian power system. An overview of state of
art of VSC HVDC technology is introduced. The VSC HVDC converters have black
start capability. In order to interconnect the offshore renewable energy resources to
Indian powergrid, VSC HVDC is the feasible solution.
 Model for a 320kV 500MW VSC HVDC is developed in PSSE software
 The control capability of VSC HVDC is demonstrated under two common
disturbances
 From simulation results, it is clear that VSC HVDC have excellent performance at
disturbances in the connecting AC networks. The system recovers fully very fast after
faults.
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
I.S. Jha, Subir Sen, Kashish Bhanbhani, Sandeep kumawat; “Integration of large scale
renewables – An indian perspective”, GridTech 2015, New Delhi, India
Ebin Cherian Mathew, Khirad dhabhar, Vishwajeet singh, M.S.Rao, M.M.Goswami, Oommen
Chandy;” Planning of a VSC HVDC System –Utilities’ Perspective”, GridTech 2015, New
Delhi, India
Feng Wang, Lina bertling, Tuan le, Anders Mannikoff, Anders Bergman; “An Overview
Introduction of VSC-HVDC State-of-art and Potential Applications in electric power systems”,
CIGRE BOLOGNA 2011
Mohan, N., Undeland, T. M., Robbins W. P. (2003), Power electronics – Converters,
Applications and Design, John Wiley & Sons, Inc.
PSSE 33.5 User manual
416
11
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGREAORC
Technical
Meeting
2016
and International
Conference
Ongoing
efforts
and
Future
ASEAN
Power
Grid
CIGRE- AORC
Technical
Meeting
2016Directions
– on
International on
Conference
on Global
Trends
in the Development
on
of Power Transmission & Distribution Systems
including Smart Grid, 24-26 Feb. 2016, New Delhi, India
“Global
Trends
in inthe
Power
System
including
Smart Grid”
“Global
Trends
theDevelopment
Development of of
Power
T&DT&D
System
including
Smart Grid”
Woraporn Tanbhibal
Electricity Generating Authority of Thailand
Thailand on ASEAN Power Grid
Ongoing
effortsand
and Future
Future Directions
Ongoing
efforts
Directions on ASEAN Power Grid
Woraporn Tanbhibal
Electricity Generating
Authority
of Thailand
Woraporn
Tanbhibal
Thailand
Electricity Generating Authority of Thailand
Thailand
SUMMARY
As the ASEAN Economic Community (AEC) will come into effect by the end of 2015, it is
expected that the economic growth in the region will happen at a remarkably fast pace.
Consequently, ASEAN as a whole will be likely to witness a significant rise in power
SUMMARY
consumption. This situation will call for more efficient, secure, harmonious and economical
electrical power supply throughout the region.
As the ASEAN Economic Community (AEC) will come into effect by the end of 2015, it is
expected that the economic growth in the region will happen at a remarkably fast pace.
The ASEAN Power Grid (APG) is a project aimed at establishing the electrical
SUMMARY
Consequently, ASEAN as a whole will be likely to witness a significant rise in power
interconnection system via transmission line, which allows for electricity transfers between
consumption. This situation will call for more efficient, secure, harmonious and economical
the ten countries
of ASEAN.
Not only
providing
and sustainable
electrical
As the electrical
ASEAN
Economic
Community
(AEC)
willgreater
comesecure
into effect
by the end
of 2015, it is
power
supply throughout
the region.
energy for the Member States, but this cross-border power grid would also help optimising
expectedthethat
the economic growth in the region will happen at a remarkably fast pace.
use of energy resources available in the region.
The ASEAN
PowerasGrid
(APG) will
is a be
project
aimed
at establishing
the electrical
Consequently,
ASEAN
a whole
likely
to witness
a significant
rise in power
interconnection system via transmission line, which allows for electricity transfers between
Since itThis
is located
in the will
centrecall
of mainland
Southeast
Asia secure,
and is theharmonious
second-largestand
energy
consumption.
situation
for more
efficient,
economical
the ten countries of ASEAN. Not only providing greater secure and sustainable electrical
consuming
countrythroughout
in the region, there
is the possibility that Thailand could become the
electrical
power
supply
energy
for the
Member States, butthe
thisregion.
cross-border power grid would also help optimising
regional hub of ASEAN Power Grid. The Electricity Generating Authority of Thailand
the use of energy resources available in the region.
(EGAT) has been undertaking preliminary preparation to support the realisation of APG and
The ASEAN
Power
(APG)
a project
aimed improvement
at establishing
the electrical
the potential
role ofGrid
Thailand
in APG.isApart
from accelerating
of the national
Since
it
is
located
in
the
centre
of
mainland
Southeast
Asia
and
is
the
second-largest
energy
interconnection
system
viafortransmission
line,
allowsEGAT
for electricity
transfers
transmission
network
greater reliability
andwhich
sustainability,
has been working
on between
consuming country in the region, there is the possibility that Thailand could become the
several
interconnection
projects
in
order
to
support
APG.
the tenregional
countries
of ASEAN. Not only providing greater secure and sustainable electrical
hub of ASEAN Power Grid. The Electricity Generating Authority of Thailand
energy (EGAT)
for thehas
Member
States, but
this cross-border
gridrealisation
would also
help
been undertaking
preliminary
preparation to power
support the
of APG
and optimising
The main objectives of this paper are two-fold: to present a brief overview of EGAT’s role in
potential resources
role of Thailand
in APG.
Apart
from accelerating improvement of the national
the usethe
of
available
inpotential
the region.
theenergy
realisation of APG, and
to discuss
benefits of the APG to ASEAN.
transmission network for greater reliability and sustainability, EGAT has been working on
several interconnection projects in order to support APG.
Since it is located in the centre of mainland Southeast Asia and is the second-largest energy
KEYWORDS
consuming
country
in the
region,
there
is the
possibility
that Thailand
could
become the
The main
objectives
of this
paper are
two-fold:
to present
a brief overview
of EGAT’s
role in
woraporn.tan@egat.co.th
Grid,and
interconnection
system,
Optical
Ground
telecommunication
regionaltheASEAN
hub
ofPower
ASEAN
Power
Grid.
Thebenefits
Electricity
Generating
Authority of Thailand
realisation
of APG,
to discuss
potential
of the
APG
toWire,
ASEAN.
(EGAT) network
has been undertaking preliminary preparation to support the realisation of APG and
the potential role of Thailand in APG. Apart from accelerating improvement of the national
transmission
network for greater reliability and sustainability, EGAT has been working on
woraporn.tan@egat.co.th
several interconnection projects in order to support APG.
417
The main objectives of this paper are two-fold: to present a brief overview of EGAT’s role in
the realisation of APG, and to discuss potential benefits of the APG to ASEAN.
1. Introduction
Despite the global economic downturn, it is expected that the official onset of ASEAN
Economic Community (AEC) at the end of 2015 will contribute positively to economic
activities in the region as the AEC will become the third largest consumer market in
the world. One of the crucial factors for regional economic integration is the development of
cross-border infrastructure, which will facilitate intra-regional flows of goods, services,
investment, capital, and skilled labour.
Along with the growth of regional economy, the electricity demand is projected to rise
accordingly. In ASEAN, the approach to interconnecting power grids was launched way back
in 1997 under the name ASEAN Power Grid (APG). This project was aimed primarily at
optimising the use of energy resources as well as ensuring reliable and secure supply of
electricity in the region. The APG is considered to play a significant role in AEC since the
energy sector is an integral part for economic integration endeavour.
With respect to the location of Thailand, which is at the central of Southeast Asia, the country
has potential to serve as a regional hub of power trading through the APG. As Thailand’s
main electricity utility, it then fell under the responsibility of Electricity Generating Authority
of Thailand (EGAT) to transform this envision into reality. The main objectives of this paper
are to overview briefly EGAT’s approach to support the realisation of APG and to discuss
potential benefits of the APG to the region.
2. ASEAN Power Grid: Background and Current Status
The ASEAN Power Grid (APG) is one of ASEAN flagship interconnectivity projects which
was announced under the declaration of ASEAN Vision 2020 by the ASEAN Heads of
States/Governments in 1997. The main objectives of this project were to enhance security,
availability, and reliability of regional electricity supply and to optimise the utilisation of
energy resources in Southeast Asia. In order to materialise the programme, a working group
of ASEAN Interconnection Master Plan Study (AIMS) was established in 2000 by the Heads
of ASEAN Power Utilities/Authorities (HAPUA) to conduct the master plan study for the
APG. The study confirmed that the APG would help the member countries reduce
significantly the amount of investment needed to implement and to operate new power
projects. Moreover, the findings indicated that the integrated network could provide a net
saving of US$ 788 million and reduce installed capacity by 2,013 MW.
It was originally estimated that the APG will be accomplished by 2020. However, power grid
integration is a complex practice; therefore, the progress of the project has been quite slow.
The APG is currently at the stage of establishing fully physical cross-border interconnection
system, with the presence of bilateral electricity trading activities. The major barriers to the
realisation are legal and regulatory issues related to bilateral and cross-border power
interconnection and trade, technical compatibility and operational coordination among
member countries, and financial viability.
418
2
3. EGAT’s role on the APG
EGAT is Thailand’s state enterprise which is responsible for power generation and
transmission in the whole country. In 2014, Thailand’s total installed capacity was 38,814.95
MW, and 39.98% of which (15,518.13) was generated by EGAT. That means the remaining
60.02% were supplied by power purchase from domestic private power producers and
neighbouring countries.
Even though current total installed capacity is more than sufficient to cover national peak
demand (26,942.10 MW in 2014), EGAT has been striving relentlessly to source more power
in order to secure the electricity supply to meet the potentially rising demand of the country.
Since power resources are relatively limited in Thailand, whereas the neighbouring countries,
such as Laos PDR and Cambodia, have a wealth of natural energy resources that are capable
of generating electricity that is considerably more than their actual demand and requirement;
therefore, purchasing surplus power from these countries will not only help to strengthen
Thailand’s energy security and deliver economic benefits to sellers, but also ensure the
efficient utilisation of regional electricity resources.
EGAT, as the leading organisation responsible for the APG in Thailand, has been taking
several efforts to advance the realisation of regional interconnections. Currently, there are 17
ongoing transmission system development projects, taking place throughout four regions in
Thailand, being undertaken by EGAT to support the interconnected network that will become
larger and more complicated of the APG. Several MOUs have been signed to allow for
bilateral power trading between EGAT and the neighbouring countries, including Laos PDR,
Myanmar, Cambodia, Malaysia, and China. This has enabled an electricity trade of 2,111
MW through existing grid network. Furthermore, the project of 300 MW Thailand –
Malaysia High Voltage Direct Current (HVDC) interconnection is considered as a major
stepping stone towards the realisation of the APG since it is the first cross-border DC link in
the region. The construction of this HVDV transmission system in Thailand was completed
by EGAT in September 2001 at a total cost of THB 4,980 million.
4. APG and OPGW for ASEAN telecommunication network
EGAT, as well as many electric utilities around the world, installed high capacity optical fibre
cables on overhead transmission lines in order to facilitate internal communications. These
cables enabled an opportunity for EGAT to generate additional revenues by leasing excess
capacity in the fibre network to third party communications ̶ that is telecommunication
network providers. Consequently, EGAT entered telecommunication business as network
provider and wholesaler in 2007 after being granted a Telecom Business License from the
National Broadcasting and Telecommunications Commission (NBTC), with the main purpose
of optimising its asset utilisation.
EGAT integrated optical fibre cables into overhead power transmission lines to establish an
effective internal communication system by encasing them within the ground wire (Optical
419
3
Ground Wire, OPGW). These compact lines were placed on the topmost position of power
transmission towers. With such a location, the composite wire not only serves as a traditional
overhead ground wire, but also delivers the added benefit of providing a high capacity and
reliable internal communications path, which is capable of withstanding electrical faults on
the transmission line. Currently, EGAT owns optical fibre network with a length of more than
10,000 kilometres, which provides nationwide coverage with 200 substations as nodes that
connect the entire network across the country.
Since officially joining the telecommunications industry in 2007, EGAT’s revenues from
telecommunications business has increased continuously. What is more interesting is that the
annualised growth rates of EGAT’s telecommunications sales were higher than those of our
core business, electric energy sales, over the past nine years. Therefore, with respect to its
distinct attributes and potential, EGAT has put a lot of efforts to bring our OPGW
communications system to become a national core (backbone) network in the near future. If
this goal is realised, EGAT will not only contribute greatly to the GDP of the country, but will
also help to avoid a redundant investment in telecommunication infrastructure by other
companies in this sector.
In Southeast Asia, internet penetration has been growing rapidly in recent years. The figures
extracted from the ITU World Telecommunication/ ICT Indicators Database 2014 revealed
that the number of internet users in the region increased twofold from 81 million in 2009 to
162 million in 2013. Moreover, an explosive growth in smartphone sales and adoption across
Southeast Asia have resulted in soaring mobile data usage. All these call for high network
capacity and performance to cope up with heavy data traffic in the region.
Nowadays, submarine cables are the main supply of international bandwidth of Southeast
Asia. Two major hubs that provide international gateways to this region are Hong Kong and
Singapore. Singapore, which is considered by many to be a “choke point” due to its
concentration of submarine network infrastructure, serves as a regional hub that facilitates
global interconnectivity for ASEAN member countries via 16 undersea cables. However,
despite its continued expansion and dominance of international telecommunications network,
submarine system is not without complications. Underwater cables are quite vulnerable.
Incidents of cable cuts worldwide occur from time to time due to trawler nets, vessel
anchoring, natural disaster, and even shark attack. Worsening the situation is the fact that the
maintenance and restoration of underwater cables is a painstaking and time-consuming task
that is subjected weather and sea conditions. Therefore, terrestrial fibre optic networks could
bring more reliable to global interconnectivity of ASEAN by providing backup to the main
systems and an alternate route that enable an interconnection with another global hub in Hong
Kong. The inland networks will also benefits landlocked Laos PDR and low-income
countries, such as Myanmar and Cambodia.
In tandem with the APG, the interconnecting system could help strengthen telecommunication
network in the region. With respect to Thailand’s geographic advantage, EGAT expects that
our OPGW network will be able to provide a highly reliable terrestrial route to global hubs in
Singapore and Hong Kong for Southeast Asia in the near future (figure 1). After
420
4
implementing several strategies to expand our telecommunication business into neighbouring
countries, EGAT is currently leasing the network to telecommunications service providers in
Malaysia.
Figure 1: Potential route of OPGW and network interconnection plan
5. Conclusion and Discussion
Apart from ensuring electricity security and promoting optimise utilisation of energy
resources within the region, the realisation of APG will also benefit Southeast Asian
telecommunication network. The interconnecting systems could become the ASEAN
telecommunications grid, which will consequently deliver more reliable telecommunication
network to ASEAN as a whole.
421
5
BIBLIOGRAPHY
[1] TRPC and the Internet Society, “Unleashing the Potential of the Internet for ASEAN
Economies” (2015)
[2] B. Hermawanto, “ASEAN power grid: Road to multilateral Power Trading” (ERC Forum
2015, Bangkok, Thailand, 1 October 2015)
[3] S. Kaewchan, “Thailand benefits from demand diversity in ASEAN Power Grid” (2013)
[4] P.Vongthanet, “ASEAN Power Grid & EGAT Smart Grid development plan” (TNCCIGRE Seminar 2015, Bangkok, Thailand, 4 December 2015)
[5] T. Doshi, “ASEAN energy integration: interconnected power and gas pipeline grids”
(2013)
[6] G. Ryder, “Behind the ASEAN power grid” (2003)
[7] United Nations ESCAP, “An In-Depth Study of Broadband Infrastructure in the ASEAN
Region” (2013)
[8] K. Ko, “Development of submarine cables in Asia-Pacific” (2014)
422
6
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE- AORC Technical Meeting 2016 and International Conference
on Renewable Energy Generations in
Power Grid Management for the Increased
“Global Trends in the Development
of Power T&D System including Smart Grid”
Thailand
W. WONGLIMAMORNLERT1, C. ACHAYUTHAKAN2
1Electricity Generating Authority of Thailand, Power Purchase Agreement Division,
Power Grid Management for the Increased
Renewable Energy Generations in
Thailand
Thailand
W. WONGLIMAMORNLERT1, C. ACHAYUTHAKAN2
1Electricity Generating Authority of Thailand, Power Purchase Agreement Division,
Thailand
SUMMARY
Renewable energy (RE) in Thailand are rapidly rising to become a major portion in the
electricity generations portfolio by the support of Thai government's policies. Those policies
encourage and promote the use of RE. However, the nature of electricity generations from RE
such as Solar and Wind generation are intermittent and more volatility than conventional
power generations by several factor such as variance of energy source issues which have the
SUMMARY
direct effects on reliable of power generation.
Renewable
energy
in Thailand
rapidly
rising
to become(REG)
a major
portionthe
in the
This paper
aims(RE)
to assess
the effects are
of season
to the
RE generation
load profile,
electricity
generations
portfolio
by
the
support
of
Thai
government's
policies.
Those
policies
concept of impact from increased REGs and the generation forecast model shall be proposed
encourage
and promote
of RE.method
However,
the nature
of electricity
generations
in technical
aspect. the
The use
analysing
consists
of the two
years (1 January
2014 –from
31 RE
such as
Solar and
are statistical
intermittent
and The
more
volatility
than Deviation
conventional
December
2015)Wind
actual generation
load profile and
methods.
statistical
Standard
shall be used
to analyze
the collected
for variability
observation.
power(S.D.)
generations
by several
factor
such as data
variance
of energy
source issues which have the
direct effects on reliable of power generation.
The study found that, Grid management policy shall consider the season effect on load profile
of solar and wind generations. Therefore, in the short-term power grid planning for reserve
This paper
aims toshould
assesstake
thethe
effects
of season
to season
the REinto
generation
load profile,
management
volatility
from the
account. (REG)
Furthermore,
results the
concept
of impact
from
REGs
generation
forecast
model
shall
be proposed
prove
that when
theincreased
power grid
has and
morethe
penetration
from
volatility
REGs.
Overall
of
in technical
aspect.
The
analysing
method
consists
of
the
two
years
(1
January
2014
volatility from REGs should be lower which is helpful to the promotion of RE to electricity – 31
December
2015)sector.
actualConsequently,
load profile the
andconcept
statistical
methods.
The
statisticalinStandard
generation
of REG
capacity
forecasting
this paperDeviation
shall
beneficial
to to
theanalyze
management
of power data
grid for
in the
reserve management
aspect. That will
(S.D.)beshall
be used
the collected
variability
observation.
lead to the technical comply, policy abide and economical of spinning reserved model for
powerfound
grid inthat,
bothGrid
of short
term operation
andshall
long consider
term planning
in considerate
of stability
The study
management
policy
the season
effect on
load profile
and
generation
costs
of
power
grid.
of solar and wind generations. Therefore, in the short-term power grid planning for reserve
management
should take the volatility from the season into account. Furthermore, results
KEYWORDS
prove that when the power grid has more penetration from volatility REGs. Overall of
volatility
from Energy
REGs Generation,
should bePower
lower
which
is helpful
to Effects,
the promotion
RE to electricity
Renewable
Grid
Management,
Season
Aggregateof
Renewable
Energysector.
Generation,
Capacity Forecasting
generation
Consequently,
the concept of REG capacity forecasting in this paper shall
be beneficial to the management of power grid in the reserve management aspect. That will
lead to the technical comply, policy abide and economical of spinning reserved model for
chira.a@egat.co.th
powerworrapong.wo@egat.co.th,
grid in both of short term
operation and long term planning in considerate of stability
and generation costs of power grid.
KEYWORDS
423
Renewable Energy Generation, Power Grid Management, Season Effects, Aggregate Renewable
Energy Generation, Capacity Forecasting
1. THAILAND’S RENEWABLE ENERGY POLICY
Thai government established the roadmap as strategy to promote renewable energy (RE)
through the Alternative Energy Development Plan 2012-2021 (AEDP 2012-2021), promulgated and
later revised to Alternative Energy Development Plan 2015-2036 (AEDP 2015-2036).
Energy Resource
2014 (MW)
2036 Target (MW)
Municipal Solid Waste
65.72
500
Industrial Waste
0
50
Biomass
2,451.82
5,570
Biogas (Waste Solid/Water)
311.5
600
Mini hydro
142.01
376
Biogas (Energy Crop)
0
680
Wind Energy
224.47
3,002
Solar Energy
1,298.51
6,000
Hydropower
0
2,906.4
Total Capacity (MW)
4,494.03
19,684.4
Energy Generation from RE (%)
9.87%
20.11%
Table 1: Target Electrical Generation Capacity from Renewable and Alternative Resource in 2021
(from AEDP 2015-2036)1
As the result from AEDP and others supporting policies, it causes the rapid growth of
electricity generation from RE. However, the RE purchase structure in Thailand is non-firm
basis, providing first priority to purchase
power from RE. With the nature of
intermittency and volatility in power
output, difficulties in managing RE exist.
With the aforementioned and
EGAT’s obligations to maintaining the
stability of Thailand power grid. This
paper aims to assess the effects of season
to RE, the concept of RE impact and
generation forecast model in technical
aspect.
Fig.1: Daily Power Generation of Wind Power Plant
2. CASE STUDY AND DATA COLLECTION
The methodology concerning with technical evaluation of RE can be described as follows.
2.1 Case study
Consists of seven sites of RE generation (REG) described in Table 2.
No.
1
2
3
4
5
6
7
Name
Natural Energy Development (NED)
Bang Chak Petroleum Generation (BCPG)
EA Solar Nakonsawan (EAN)
Sermsang Palangngan (SSP)
EA Solar Lamphang (EAL)
First Korat Wind (FKW)
KR Two (KRT)
Type of Generation
Solar
Solar
Solar
Solar
Solar
Wind Power
Wind Power
Contracted Capacity (kW)
55,000
30,000
90,000
40,000
90,000
90,000
90,000
Table 2: Type and capacity of case study
424
1
The term of power generating of each REG or aggregate REG shall be hereafter
denoted using “CC” or Contracted Capacity.
The actual load profiles (kW) of 15 minute time interval are collected from metering
equipment for two years (1 January 2014 – 31 December 2015). In case of wind power
generation analysis, the load profiles for 24 hours per day or equivalent to 8,760 operating
hours/year is used. In case of solar power generation analysis, the load profiles from 6:00
A.M. to 6:00 P.M. or equivalent to 4,380 operating hours/year is used to eliminate the effects
of solar source absence in the night time.
2.2 Analysis Tools and Methods
The statistical Standard Deviation (S.D.) shall be
used to analyze the collected data which have a
considerable amounts of population, so we assumed it to
distribute in Normal Distribution Curve. From
characteristic of Normal Distribution, S.D. shall be
arbitrary set to cover around 68.2% of entire population
with the Band of + 1 S.D. and – 1 S.D. which shall be
Fig.2: Normal Distribution Curve3
used to further analysis in this paper for variability observation.
3. PERFORMANCE REVIEW: OBSERVATION ON SEASON EFFECTS
The characteristics of solar source and wind source intensity in Thailand are fluctuated
by each month due to the influenced of the regular season wind which the important one are
divided in two types such as the Southwest Monsoon also known as the "Summer Monsoon"
and the Northeast monsoon that is also known as the "Winter Monsoon".
The "Summer Monsoon” is more notably blow during the second week of May to the
second week of November, thus approximately six months of blowing. Due to the wind
blowing through the ocean, it features a warm wind and moisture (more cloud). So when
Thailand is under the influence of the southwest monsoon, it brings wet weather and rain
throughout the season.
The "Winter Monsoon” features cool and dry air masses which are blowing for a
shorter period of time. But there is more speed compare to the southwest monsoon. Thus,
when these masses of air are blowing through the country it shall cause the decrease of
temperature and humidity of the air (less cloud). Generally this regular season wind will begin
to blow in late November to early February.
The results of our study for season effect shall be shown as follow;
Solar: January
Solar: September
Wind: April
Wind: December
Fig.3: Season effect on load profile and 1 S.D. of Solar and Wind Power Generation
425
2
2014
Avg. Generate (kW)
Avg. Generate (%CC)
Solar
Avg. S.D. (kW)
Avg. S.D. (%CC)
Avg. Generate (kW)
Wind Avg. Generate (%CC)
Avg. S.D. (kW)
Avg. S.D. (%CC)
January
23,528.91
26.14%
2,376.21
2.64%
28,001.01
31.11%
23,633.01
26.26%
April
23,384.44
25.98%
5,566.96
6.19%
9,036.70
10.04%
9,770.39
10.86%
September December
20,643.10 22,335.43
22.94%
24.82%
7,084.42
5,295.52
7.87%
5.88%
11,439.77 44,255.26
12.71%
49.17%
13,250.39 25,121.85
14.72%
27.91%
Table 3: Season effect on Average kW and Average S.D. of Solar and Wind Generation
As the results from observation shown in Fig.3 and Table 3, they can be seen that the
season affects the capacity and the volatility of MW on both of solar and wind power
generation. Such as the effect of clear weather under the influence of Winter Monsoon in
January which can cause smooth profile of solar generation. On the other hand, the load
profile of solar generation in September has suffered from cloud and rain cause by Summer
Monsoon which resulted in more volatility of MW than in January as more the Average S.D.
shown in Table 3.
In wind power generation aspect, the average generate MW in April is significant less
than the one in December. The reason for that is the absence of regular season wind in period
of late February to early May
Because of reason mentioned on above, it can assume that the season has the directly
effects on load profile of solar and wind generations.
4. PERFORMANCE REVIEW: AGGREGATE REG AND COINCIDENCE EFFECT
ON POWER GRID
From the power grid
demand to reduce the impact of
REGs from the volatility and
intermittent nature, this paper
shall propose the concept for
reduction of that impact by
connecting more REGs into the
power grid. With our hypothesis,
that
more
penetration
of
intermittent REGs into power grid
shall cause the compensation of
individual volatility.
Fig.4: The examples of group sampling for Coincident S.D. calculation
This concept has been proven by the use of actual load profile in 2014 of five REGs to
calculate the S.D. that shall be used as volatility indicator between the average individual S.D.
and average values of S.D. from grouped power generations of the same type in a form that is
at all possible arrangement (all group Samplings). In this paper, the S.D. from grouped one
shall be defining as the “Coincident S.D.” The examples of group sampling are determined
by Fig.4.
426
3
The proposed concept verified results shall be shown as follows:
2015
March
July
October
December
Individual S.D.
1 Power Plant
8.91%
11.46%
11.99%
9.72%
2 Power Plants
10.65%
11.24%
11.93%
10.47%
Coincident S.D.
3 Power Plants
4 Power Plants
8.23%
6.51%
8.32%
6.51%
8.89%
7.03%
7.90%
6.21%
5 Power Plants
5.33%
5.30%
5.75%
5.08%
Table 4: Average Individual S.D. vs. Average Coincident S.D. from Solar power generation in October 2015
Fig.5: Average Coincident S.D. from Solar Power
generations in October 2015
Fig.6: Compensated MW from more penetrated
Solar power Generation in October 2015
The observation alleviate that more penetration of solar power plant shall be reduce
the volatility in power output from the reduced in S.D. and hopefully, we expect the wind
power generations shall behave the similar. But in present, our country has only 2 large (more
than 10 MW) wind power generations so the study result will not mention in this paper.
5. PROPOSED IMPERATIVE FORECASTING MODEL
To serve the obligations for stability maintaining in power grid, EGAT has a desire for
forecasting tools or forecasting models to deal with the increasing non-dispatch REG. But
presently in Thailand, there is no system in forecasting aspect for RE existed. Also the data
required in forecasting such as the intensity of daily solar ray and daily wind speed are not
adequate. So in this study, Simple Forecasting Model that can be easily used and do not need
much data shall propose in three individual approaches as follows.
Model 1: Preceding Year
This Forecasting model shall forecast the monthly load profile by using the load
profile data in preceding year of the same month and same power generation, such data
including monthly average MW and calculated monthly average Individual S.D. to generate a
forecasted model with the error tolerance band (+1 S.D.,-1 S.D.) to use in that desired month.
Model 2: 7 Days
This Forecasting model shall forecast the daily Load Profile by using the Load Profile
data in preceding 7 days ago of the same power generation, such data including MW Output
of 15 minute time interval and calculated Individual S.D. of 15 minute time interval to
generate a forecast model with the error tolerance band (+1 S.D.,-1 S.D.) to use in that desired
day.
427
4
Model 3: 30 Days Model
This Forecasting model shall forecast the daily Load Profile by using the Load Profile
data in preceding 30 days ago of the same power generation, such data including MW Output
of 15 minute time interval and calculated Individual S.D. of 15 minute time interval to
generate a forecasted model with the error tolerance band (+1 S.D.,-1 S.D.) to use in that
desired day.
The approach verified results shall be shown as follows:
Table 5: Result of propose model: Preceding Year Model
Table
Table7:6:Result
Resultofofpropose
proposemodel:
model:307 Days
Days Model
Model
With our observation on these model results, we can summarize the analyzed result
into these following;
1. Solar power generation is easier to forecast than Wind power generation.
2. Preceding Year Model and 30 Days Approach have %Frequency of Error around
31.8% which be similar to error from +1 S.D. and -1 S.D. band of Normal
Distribution.
3. In these three different model, from the result can assume that 30 Days Model is
the most suitable to use in forecasting
the capacity of REG due to the minimum
428
percent of average forecast error outside tolerance band (+ 1 S.D. and – 1 S.D.).5
But the differences between the Preceding Year model and the 30 Days model are
negligible. So the Preceding Year model may be useful for imperative situation or
Table 7: Result of propose model: 30 Days Model
With our observation on these model results, we can summarize the analyzed result
into these following;
1. Solar power generation is easier to forecast than Wind power generation.
2. Preceding Year Model and 30 Days Approach have %Frequency of Error around
31.8% which be similar to error from +1 S.D. and -1 S.D. band of Normal
Table 7: Result of propose model: 30 Days Model
Distribution.
3. Inour
these
three different
model,
from
the result
can summarize
assume thatthe
30analyzed
Days Model
With
observation
on these
model
results,
we can
resultis
the most suitable to use in forecasting the capacity of REG due to the minimum
into these following;
1. Solar
power
generation
is easier
to outside
forecasttolerance
than Wind
power
percent
of average
forecast
error
band
(+ 1generation.
S.D. and – 1 S.D.).
2. Preceding
Year
Model
and
30
Days
Approach
have
%Frequency
Error
around
But the differences between the Preceding Year model and the 30 of
Days
model
are
31.8%
which
to Year
error model
from may
+1 S.D.
and -1
band of
Normal
negligible.
So be
the similar
Preceding
be useful
for S.D.
imperative
situation
or
Distribution.
use in annually energy forecast.
3. In these three different model, from the result can assume that 30 Days Model is
6. CONCLUSION:
CHALLENGES
OPPORTUNITIES
the most suitable
to use in AND
forecasting
the capacity of REG due to the minimum
percent of average forecast error outside tolerance band (+ 1 S.D. and – 1 S.D.).
REGs become the significant elements in power grid management, so that it can be
differences
the Preceding
and thepolicy
30 Days
model
are
integrated But
into the
power
grid withbetween
sustainable
harmony. Year
Grid model
management
shall
consider
So the
Preceding
Year
be usefulTherefore,
for imperative
or
the seasonnegligible.
effect on load
profile
of solar
andmodel
wind may
generations.
in thesituation
short-term
use
in
annually
energy
forecast.
power grid planning for reserve management should take the volatility from the season into
account.
6. CONCLUSION:
CHALLENGES
OPPORTUNITIES
The results prove
that when theAND
power
grid has more penetration from volatility REGs.
Overall of volatility from REGs should be lower which is helpful to the promotion of RE to
REGs
become sector,
the significant
elements
in power
gridfurther
management,
can be
electricity
generation
more ideas
from this
paper can
develop so
intothat
the itvolatility
integrated
into
power
grid
with
sustainable
harmony.
Grid
management
policy
shall
consider
management scheme in the country level (Coincident Country-wise or Whole Country) or the
the
seasonmanagement
effect on load
profile
of solar
wind generations.
Therefore,
volatility
in the
regional
leveland
(Coincident
region-wise
or Zonal)in the short-term
power grid
planning
for
reserve
management
should
take
the
volatility
season
Consequently, the concept of REG capacity forecasting in from
this the
paper
shallinto
be
account.
beneficial to the management of power grid in the reserve management aspect. That will lead
The results
prove that
when
the and
power
grid has more
penetration
from model
volatility
to the technical
comply,
policy
abide
economical
of spinning
reserved
forREGs.
power
Overall
volatility
should
be long
lowerterm
which
is helpful
to the promotion
of REand
to
grid in of
both
of shortfrom
termREGs
operation
and
planning
in considerate
of stability
electricity
generation
sector,
more
ideas
from
this
paper
can
further
develop
into
the
volatility
generation costs of power grid.
management scheme in the country level (Coincident Country-wise or Whole Country) or the
volatility management in the regional level (Coincident region-wise or Zonal)
BIBLIOGRAPHY
[1] DEDE,
AEDP, http://www.dede.go.th/download/files/AEDP2015_Final_version.pdf
(accessed:
Consequently,
the concept of REG capacity forecasting in this paper shall
be
6
1 September
2015)
beneficial
to the management
of power grid in the reserve management aspect. That will lead
[2]theEGAT,
EGAT
Data Center,
http://meter.egat.co.th
(accessed:
6 September
2015)
to
technical
comply,
policy Datagyr,
abide and
economical of spinning
reserved
model for
power
[3]
Wikipedia,
Wikipedia,
Standard
Deviation,
https://en.wikipedia.org/wiki/Standard_deviation
grid in both of short term operation and long term planning in considerate of stability and
(accessed
October
generation
costs8of
power2015)
grid.
429
6
CIGREAORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016 and International Conference
on
on
CIGREAORC
Technical
Meeting 2016 – International
Conference
on Global
Trendsincluding
in Smart
the Development
Trends
in the
Development
ofof
Power
T&DT&D
System
including
Grid”
“Global“Global
Trends
in the
Development
Power
System
Smart Grid”
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
Optimal Operation Method Considering Supply-Side Uncertainty
Optimal Operation
Method
for Forecast
Error in Considering
Plural Regional Supply-Side
Power Systems Uncertainty
for Forecast Error in Plural Regional Power Systems
Shota Tobaru, Cirio Celestino Muarapaz, Mohammad Masih Sediqi,
and Tomonobu Senjyu,
Shota Tobaru, Cirio Celestino
Mohammad Masih Sediqi,
UniversityMuarapaz,
of the Ryukyus
and Tomonobu
Japan Senjyu,
University of the Ryukyus
Toshihisa Funabashi
Japan
Institute of Materials and Systems for Sustainability (IMaSS)
NAGOYA UNIVERSITY
Japan
Toshihisa
Funabashi
Institute of Materials and Systems for Sustainability (IMaSS)
NAGOYA UNIVERSITY
Japan
SUMMARY
Japan has many power systems because there are many isolated islands. However, the renewable
energy facilities are introduced into isolated island from the large economic burden caused by the high
generation cost. Nevertheless, it is very difficult to predict renewable energy facility output because
this output fluctuates with weather. Therefore, there is a need to consider the uncertainty associated
with power demand and supply when introducing the renewable energies in large amount. As a
SUMMARY
countermeasure to the fluctuating output of renewable energy facilities, battery energy storage system
(BESS) is often introduced. However, it is necessary to reduce BESS capacity because it is costly.
electricity
market
is booming
with electricity
in Japan.
In Japan
electric power
Japan hasThe
many
power
systems
because
there aresystem
manyreform
isolated
islands.
However,
the renewable
exchange (JPEX), spot market, forward market (fixed form products), forward market (bulletin board
energy facilities
are
introduced
into
isolated
island
from
the
large
economic
burden
caused
products) are provided. It is expected to deal with uncertainty associated with power demand and by the high
generationsupply
cost.byNevertheless,
it is markets.
very difficult to predict renewable energy facility output because
using these electricity
paper proposes
optimal operation
method
thatiscan
coped
the forecast
error of load associated
this outputThis
fluctuates
with the
weather.
Therefore,
there
a be
need
to with
consider
the uncertainty
demand
and
the
increase
in
uncertainty
caused
by
introducing
renewable
energy
facilities
in large
with power demand and supply when introducing the renewable energies in large
amount. As a
amount, by considering the electricity market and the regional real-time pricing (RP). The proposed
countermeasure
to
the
fluctuating
output
of
renewable
energy
facilities,
battery
energy
storage
system
method can contribute to reduce the operational cost in plural regional power systems by using the
(BESS) isshortage
often introduced.
However,
it isday-ahead
necessary
to reduce
BESSmarket.
capacity because it is costly.
and surplus power
through the
market
and hour-ahead
The electricity market is booming with electricity system reform in Japan. In Japan electric power
exchange (JPEX), spot market, forward market (fixed form products), forward market (bulletin board
KEYWORDS
products) are provided. It is expected to deal with uncertainty associated with power demand and
supply byUnit
using
these electricity
markets.
commitment,
Uncertainty,
Day-ahead market, Hour-ahead market, Real-time pricing
This paper proposes the optimal operation method that can be coped with the forecast error of load
demand and the increase in uncertainty caused by introducing renewable energy facilities in large
amount, by considering the electricity market and the regional real-time pricing (RP). The proposed
method can
contribute to reduce the operational cost in plural regional power systems by using the
125573j@gmail.com
shortage and surplus power through the day-ahead market and hour-ahead market.
KEYWORDS
430
Unit commitment, Uncertainty, Day-ahead market, Hour-ahead market, Real-time pricing
INTRODUCTION
In Japan, a large number of small-scale power systems are present because many isolated islands exist.
The generation equipment in isolated island is mainly composed of an internal combustion power
generation facility. However, the economic burden is large because the unit price for generation is
expensive in isolated island because not only the fuel cost but also the transportation cost takes as
generation cost. The renewable energies such as photovoltaic (PV) and wind generator (WG) are
actively introduced to small-scale system because isolated-island has vast natural energy and good
locational conditions. However, it is very difficult to predict the output of PV and WG because this
output is fluctuating with weather such as solar radiation and wind speed. As a countermeasure to the
fluctuating output of the renewable energy generation facilities, the BESS is often introduced. Since
BESS can compensate the surplus and shortage power by charging and discharging of the BESS, it is a
very effective facility. However, it is necessary to reduce BESS capacity because it is costly [1–5].
The power transaction market is also becoming more active with the power system reform in Japan. In
JPEX, spot market, forward market (fixed form products), forward market (bulletin board products) are
provided. The spot market is the market which performs electricity transaction for the next day, and the
forward market (fixed form products) delivers electricity for after certain period of time, and the
forward market (bulletin board products) performs electricity transaction by posting on bulletin board
freely [6]. It is expected to deal with uncertainty associated with power supply-demand by using these
electricity transactions market in plural trading period. We had proposed optimal operation method that
can be achieved high efficiency operation and the reduction in operational cost, by effectively utilizing
the renewable energy, and interchanging the power between microgrids and controllable loads [7-9].
However, it is necessary to consider the uncertainty associated with the power demand and supply when
introducing the renewable energies in large amount. Moreover, it is necessary to consider the influence
on unit commitment of generators caused by interchanging power with other power systems through
electricity market in accordance with electric power liberalization.
This paper proposes an optimal operation method that is possible to cope with the forecast error of
power demand and the increase in uncertainty caused by introducing renewable energy facilities, by
considering the electricity market and the regional RP. As electricity market, it is assumed two markets:
(i) day-ahead market and (ii) hour-ahead market. In day-ahead market, the electricity transaction for 24
hours of next day is traded on before-day. In hour-ahead market, the electricity transaction is conducted
every 3 hours. In the regional RP, the load demand is levelized by giving incentive to customers by
changing the electricity price in every hour. The proposed method can contribute to reduce the
operational cost in plural regional power systems by using the shortage and surplus power through the
day-ahead and hour-ahead market.
POWER SYSTEM AND OPTIMIZATION METHOD
A. Power System Model
The flow of operational planning in this paper is shown in Fig. 1. At first, scheduling the operational
planning, and bidding on the day-ahead market, from the forecast load demand data. During day,
calculating the shortage and surplus power caused by forecast error, it is performed by replanning the
operational planning, bidding on the hour-ahead market, and RP every 3 hours. Furthermore, Fig. 2
shows the expected plural regional power systems model. In addition to, the regional power systems
perform transaction among each power systems (PS) through the electricity market. The power system
of PS1 is shown in Fig. 3. Moreover, Table I indicates the installed capacity of each PSs. The objective
function, the constraint condition and the optimization method are described in this section. Here, it is
assumed that the forecast data of the power demand, wind speed and solar radiation for each hour are
obtained, and the forecast data are updated every 3 hours. However, the forecast error for power demand
and the renewable energy generation facilities has been also taken into the account.
431
1
Fig. 1. Operation scheduling flow.
Fig. 2. Plural power systems model.
TABLE I
INSTALLED CAPACITY OF EACH PS.
TABLE II
PARAMETERS OF OBJECTIVE FUNCTION.
Fig. 3. Configuration of power system 1 (PS1).
B. Objective Function
The objective function is set to minimize the total operational cost of the plural power systems. The
unit commitment of generator, charging and discharging schedule, amount of power transaction has
been determined as to the objective function is minimized. The objective function is shown in Eq. (1). In
addition, the operational cost in each PS is shown in Eq. (2).
100
𝑁
min ∶ 𝑇𝐶 = 𝑝� � 𝑇𝐶𝑃𝑆1 + 𝑇𝐶𝑃𝑆2 + 𝑇𝐶𝑃𝑆3
�=1
24
(1)
𝑇𝐶𝑃𝑆 = � �[𝐹� (𝑡)�𝑃𝐷𝐺� (𝑡)� + 𝑆𝑈� (𝑡) ∙ 𝐼� (𝑡) + 𝑆𝐷� (𝑡) + 𝐶�� (𝑡) + 𝐶𝑑�� (𝑡) + 𝐶ℎ��� (𝑡)] (2)
�=1 𝑡=1
where, 𝑝� is the probability of error; 𝑁 is the number of generator; 𝐹� (𝑡)(𝑃𝐷𝐺� (𝑡)) is the fuel cost [￥] of
𝐷𝐺� at time 𝑡; 𝑃𝐷𝐺� (𝑡) is the output [kW] of 𝐷𝐺� ; 𝐼� (𝑡) is the state of 𝐷𝐺� ; 𝑆𝑈� (𝑡) is the start-up cost
[￥]; 𝑆𝐷� (𝑡) is the shutdown cost [￥] of 𝐷𝐺� ; 𝐶�� is the cost of storage energy. 𝐶𝑑�� (𝑡) and 𝐶ℎ��� (𝑡)
are the electricity transaction costs that is traded in the day-ahead market and hour-ahead market.
Furthermore, the fuel cost is shown in Eq. (3).
𝑄 × 𝑃𝐷𝐺� × 𝑃𝑅�
𝐹� (𝑃𝐷𝐺� ) =
(3)
𝑄� × 𝜂�
where, the parameters of fuel cost are listed in Table II. 𝜂� (𝑡) represents the efficiency of the generation.
C. Constraints
1. System power balance limit
The sum of the output of DG, the charging and discharging output of BESS, and the trading power
must be equal to the load power at each times 𝑡.
𝑁
� 𝑃𝐷𝐺� (𝑡) + 𝑃�� (𝑡) + 𝑃𝑅𝑒 (𝑡) + 𝑃𝑑�� (𝑡) + 𝑃ℎ��� (𝑡) = 𝑃���𝑑 (𝑡)
�=1
(4)
where, 𝑃���𝑑 (𝑡) is the load demand [kW]; 𝑃𝐷𝐺� (𝑡) is the output [kW] of DG; 𝑃�� (𝑡) is the charging and
discharging output [kW] of the BESS; 𝑃𝑅𝑒 (𝑡) is the total output [kW] of the PV and WG; 𝑃𝑑�� (𝑡) is the
trading power [kW] in the day-ahead market; 𝑃ℎ��� (𝑡) is the trading power [kW] in the hour-ahead
market.
432
2
2.
Controllable load limits (RP limits)
���𝑥
����
The controllable load 𝑃𝑅𝑃���𝑑 after RP must be within the limit of 𝑃���𝑑
and 𝑃���𝑑
each hour.
���� (𝑡)
���� (𝑡)
(𝑡)
𝑃���𝑑
≤ 𝑃𝑅𝑃���𝑑
≤ 𝑃���𝑑
(5)
���𝑥
����
where, 𝑃𝑅𝑃���𝑑 is the modified load demand by RP. In addition, 𝑃���𝑑 and 𝑃���𝑑 represents the
���𝑥
����
and 𝑃���𝑑
are :
maximum and minimum load demand respectively. 𝑃���𝑑
𝑃�𝑝
���𝑥 (𝑡)
�
+
(6)
𝑃���𝑑
= 𝑃���𝑑
𝑃𝑅𝑃���𝑑 (𝑡)
𝑃�𝑝
���� (𝑡)
�
𝑃���𝑑
+
(7)
= 𝑃���𝑑
𝑃𝑅𝑃���𝑑 (𝑡)
�
where, 𝑃�𝑝 and 𝑃���𝑑
are the response power and the load power before modify. Furthermore, the load
consumption after RP should be equal to the load consumption before RP.
𝑇
𝑇
𝑊�𝑒 (𝑇) = �� 𝑃�� (𝑡)𝑑𝑡 − � 𝑃𝑑𝑒 (𝑡)𝑑𝑡� = 0
0
0
(8)
where, 𝑊�𝑒 (𝑇) is the controlled load consumption [kW]; 𝑃�� (𝑡) is the increased load power [kW];
𝑃𝑑𝑒 (𝑡) is the decreased load power [kW] as follows:
�
�
(𝑃𝑅𝑃���𝑑 ≥ 𝑃���𝑑
) (9)
𝑃�� (𝑡) = 𝑃𝑅𝑃���𝑑 (𝑡) − 𝑃���𝑑
�
�
𝑃𝑑𝑒 (𝑡) = 𝑃���𝑑 (𝑡) − 𝑃𝑅𝑃���𝑑 (𝑃���𝑑 ≥ 𝑃𝑅𝑃���𝑑 ) (10)
3.
Upper/Lower limit for output of DG
���
��𝑥
The output power of the 𝐷𝐺� is within the limits 𝑃𝐷𝐺�
and 𝑃𝐷𝐺�
.
���
��𝑥
𝑃𝐷𝐺�
≤ 𝑃𝐷𝐺� (𝑡) ≤ 𝑃𝐷𝐺�
(11)
���
��𝑥
where, 𝑃𝐷𝐺� and 𝑃𝐷𝐺� are the minimum output power [MW] and the maximum output power [MW] for
the DG.
4.
Spinning reserve limit
To deal with the fluctuation of load demand, in the DG is installed spinning reserve.
��𝑥
𝑃𝐷𝐺� (𝑡) + 𝑃�𝑒� ≤ 𝑃𝐷𝐺�
where, 𝑃�𝑒� is the spinning reserve for the 𝐷𝐺� .
5.
State of charge and output limits for BESS
(12)
���
��𝑥
The charging and discharging output of BESS is within the 𝑃��
and 𝑃��
.
���
��𝑥
(13)
𝑃�� ≤ 𝑃�� (𝑡) ≤ 𝑃��
���
��𝑥
where, 𝑃�� and 𝑃�� are the maximum charging output [MW] and the maximum discharging output
[MW] for the BESS. Furthermore, the state of charge is limited as shown in Eq. (14).
���
��𝑥
𝜉��
≤ 𝜉�� (𝑡) ≤ 𝜉��
(14)
���
��𝑥
where, 𝜉�� and 𝜉�� are the minimum and maximum limits for the state of charge [%]. The state of
charge is controlled within 20~80% to cope with the fluctuating wind speed and solar radiation.
D. Optimization Method
In this paper, the unit commitment for the DG, the charging and discharging plan for the BESS, and the
trading power are determined by using this optimization method, tabu-search. The optimization flow
chart is shown in Fig. 4.
STEP1: The forecast data of the load demand and the generated power of the PV and WG are inputted.
Furthermore, the end condition is set.
STEP2: The unit commitment plan of DG are determined by the forecast data in each power systems,
and determined the bid for electricity amount in day-ahead market by calculating the shortage and
surplus power from the determined plan.
STEP3: The contract processing is conducted from the bidding price and amount in day-ahead market,
and the electricity is traded by determining the contract price and amount. In addition, the operation
plan is created considering the day-ahead market.
STEP4: The reforecast and replanning is conducted, and calculated the shortage and surplus power
caused by the forecast error of the power demand and supply. Furthermore, the bid for electricity
amount in hour-ahead market is determined by calculating the shortage and surplus power from the
determined plan.
STEP5: The operation plan is determined considering the hour-ahead market. Furthermore, if forecast
data is updated, the algorithm proceeds to STEP 4, or it ends.
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3
(a) Price
(b) State of charge
(c) Active power
Fig. 5. Membership functions.
Fig. 4. Optimization algorithm.
DAY-AHEAD AND HOUR-AHEAD MARKET
In the day-ahead and hour-ahead market, the bidding price and amount is considered by using fuzzy
inference. Furthermore, the membership function is used in the selling bid as follows:
𝑆𝐹�𝑒 = 𝑘�𝑒 𝑃𝑑𝑙 (𝑃𝑑𝑙 ≤ 0) (15)
𝐶𝑅ℎ�𝑒 = 𝐶𝑅ℎ�𝑒 + 𝑆𝐹�𝑒 (16)
𝐶𝑅𝑙�𝑒 = 𝐶𝑅𝑙�𝑒 + 𝑆𝐹�𝑒 (17)
(𝑃𝑅�� − 𝐶𝑅𝑙�𝑒 )
(𝐶𝑅𝑙�𝑒 < 𝑃𝑅�� ≤ 𝐶𝑅ℎ�𝑒 ) (18)
𝑀𝑆�𝑒 =
𝐶𝑅ℎ�𝑒 − 𝐶𝑅𝑙�𝑒
where, 𝑆𝐹�𝑒 is the function of the selling; 𝑘�𝑒 is the coefficient; 𝑃𝑑𝑙 is the difference between the load
demand and the scheduled generation amount; 𝐶𝑅ℎ�𝑒 is the maximum reference price; 𝐶𝑅𝑙�𝑒 is the
minimum reference price; 𝑀𝑆�𝑒 is the membership function; 𝑃𝑅�� is the transaction price. The
adaptability is evaluated from membership function as shown in Fig. 5. In addition, the bidding price
and amount is determined by using the center of gravity method. Furthermore, it is assumed the contract
price and amount when the difference between the bidding amounts in each power systems is minimum
value. These equations are as follows:
𝑁
𝑃𝑆
min : � 𝑃��𝑑
(𝑡)
𝑃𝑆=1
(19)
𝑁
𝑃𝑆
𝑃𝑆 (𝑡)
�𝑃𝑆 (𝑡)
�𝑃𝑆
𝑃𝑆
(𝑡)� + 𝑘�� × 𝑀𝑆��
× 𝑃��
(20)
= 𝑘𝑙 × �𝑃𝑙��𝑑
− � 𝑃𝐷𝐺�
𝑃𝑑𝑙
�=1
𝑃𝑆
𝑃𝑆 (𝑡)
��S
(𝑡) = MS�𝑒
𝑃��𝑑
× 𝑃𝑑𝑙
(21)
𝑃𝑆
𝑃𝑆
where, 𝑃��𝑑 is the bidding amount in each PS; 𝑃𝑑𝑙 is the difference between the load demand and the
scheduled generation amount; 𝑘𝑙 is the bidding weight function relating load; 𝑘�� is the bidding weight
function relating the state of charge for the BESS; 𝑀𝑆 �𝑃𝑆 is the adaptability of the state of charge for the
BESS.
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4
Fig. 6. Sigmoid function.
REAL-TIME PRICING
In this paper, the sigmoid function is used as the demand response model to the electricity price. The
load demand of the customer is modeled as the macro model by the sigmoid function as shown in Fig. 6
and Eq. (22). Furthermore, the load demand is levelized by modifying the electricity price (RP). The
method of the demand response amount is calculated as follows:
1
ℎ�𝑝 (𝑡) =
+ 𝑆𝐹2 (22)
1 + 𝑒𝑥𝑝 (𝑃𝑅�𝑝 (𝑡) − 𝑆𝐹1 )
�
∑𝑇𝑡=1 𝑃���𝑑
(𝑡)
�
(𝑡) −
∆𝑃���𝑑 (𝑡) = ℎ�𝑝 (𝑡) × �𝑃���𝑑
� (23)
𝑇
�
(𝑡) + ∆𝑃���𝑑 (𝑡) (24)
𝑃𝑅𝑃���𝑑 (𝑡) = 𝑃���𝑑
where, ℎ�𝑝 is the change rate of the load demand; 𝑆𝐹1 is the right and left shift function for the sigmoid
function; 𝑆𝐹2 is the upper and lower shift function for the sigmoid function. The demand response
amount of the customer is determined based on this sigmoid function.
SIMULATION RESULTS
In this section, the conventional method is compared with the proposed method, to confirm the
effectiveness of the proposed method. The conventional method creates the operation planning from the
forecast data. In contrast, the proposed method considers the day-ahead market, the RP, the reforecast,
and the replanning. In the simulation, the operation planning for one day is created, and the forecast date
is obtained every 3 hours. Furthermore, the uncertainty relating the power demand and supply is
considered by using the scenario-based method. In the scenario-based method, the scenarios of 50 types
are considered in the load demand and the renewable energy facilities respectively. Each method is
operated in each scenario so that the error ratio is from 10% to 50%, and the method for confirming the
effectiveness is to calculate the expectation value of the operational cost. The operation example of the
conventional method and proposed method are illustrated in Figs. 7 and 8. In the conventional method,
the number of starts and stops of the DG in PS2 are many at the morning, and the number of starts and
stops of the DG in PS3 are many at the night as shown in Fig. 7. This is because the DG is required to
start and stop due to deal with the forecast error for the load demand and the generated output of the
renewable energies. In particular, in the PS3, the state of charge reaches 80% after 16:00 because the
surplus power is occurred in large amount by the forecast error. Thereby, the DG starts and stops
frequently because the BESS can not charge. It can be seen that the number of start and stop of the DG
in PS1 in proposed method is less than the number of start and stop of the DG in PS1 in conventional
method as shown in Figs. 7 and 8. Fig. 10 shows the simulation results for RP in each power systems.
The load demand decreases when the electricity price is expensive, while the load demand increases
when the electricity price is cheap as shown in Fig. 10. Thereby, it is accomplished to level the load
demand. This is because the forecast error of the load demand and the renewable energies are
compensated by hour-ahead market and RP. Furthermore, in PS2 and PS3, the load demand in the
daytime is satisfied by the day-ahead and hour-ahead market, and BESS. The forecast error is
compensated by interchanging electricity through the hour-ahead market.
The expected values of the operation cost are shown in Fig. 11 and Table III. Thus, the high-efficiency
operation of the DG is achieved and the operation cost is reduced even when the forecast error increased.
435
5
CONCLUSION
In this paper, it was accomplished to create the operation planning that is possible to deal with the
increase in uncertainty associated with the power demand and supply by considering the day-ahead and
hour-ahead market, and RP. The proposed method restrains the shortage and surplus power caused by
forecast error, and utilizes the renewable energies. As a consequence, it is achieved to reduce the
operation cost remain the high-efficiency operation of the DG even when increase the forecast error
relating the power demand and supply.
BIBLIOGRAPHY
[1]
Tomonbu Senjyu, Daisuke Hayashi, Yoshinari Sakamoto, Naomitsu Urasaki, and Toshihisa
Funabashi, “Generating Power Leveling of Renewable Energy for Small Power System in
Isolated Island”, T. IEEJapan, Vol .125-B, No. 12, pp. 1209-1215, 2005. (in Japanese)
[2] J. L. Rodriguez-Amenedo, S. Armalte, and J. C. Burgos, “ Automatic Generation Control of Wind
Farm With Variable Speed Wind Turbeines”, T. IEEE Trans. on Energy Conversion, vol 17, no. 2,
pp. 279-284, 2002.
[3] Tomonobu Senjyu, Motoki Tokudome, Atsushi Yona, and Toshihisa Funabashi, “A Frequency
Control Approach by Decentralized Controllable Loads in Small Power Systems”, Power and
Energy Conference, 2008.
[4] T. Senjyu, Y. Kikunaga, M. Tokudome, A. Uehara, A. Yona, and T. Funabashi :”Coordinate
Control of Wind Turbine and Battery in Wind Turbine Generator System”, IEEJ Trans, Vol. 129,
No. 1, pp. 1-7 (2009).
[5] Kyouhei Kurohane, Tomonobu Senjyu, Atsushi Yona, Naomitsu Urasaki, E. B. Muhando, and
Toshihisa Funabashi, “ A High Quality Power Supply System with DC Smart Grid”, Generation,
Transmission & Distribution Conference & Exposition, 2010.
[6] Japan Electric Power Exchange, JEPX, http://www.jpex. org/index.html
[7] Wang Mengyan, Shota Higa, Atushi Yona and Tomonobu Senjyu, “Optimal Operation of Power
Systems with Power Players”, The International Conference on Renewable Energy Research and
Applications, p63, Nagasaki, Japan, 11-14 November 2012.
[8] Kazuki Ogimi, Shota Kamiyama, Michael Palmer, Atsushi Yona, Tomonobu Senju, and
Toshihisa Funabashi, “Optimal Operation Planning of Wind Farm Installed BESS Using Wind
Power Forecast Data of Wind Turbine Generators Considering Forecast Error”, International
Journal of Emerging Electric Power Systems, vol. 14, Issue 3, pp. 207-218, 2013.
[9] Shota Higa, Wang Mengyan, Atsushi Yona, Tomonobu Senjyu, and Toshihisa Funabashi,
“Optimal Operation Method Considering Uncertainly of Renewable Energy and Load Demand in
Micro-grids”, the 5th International Conference on Advanced Power System Automation and
Protection, Jeju, Korea, October 28-31, 2013.
[10] Shota Higa, Adbul Motin Howladar, Yuhei Shiroma, Atsushi Yona, Tomonobu Senjyu, and
Toshihisa Funabashi, “Optimal Operation Method Considering Replanning and Uncertainly in
Power Systems”, The International Conference on Electrical Engineering 2014, Jeju, Korea, June
15-19, 2014.
[11] Antonio Bracale, Guido Carpinelli, Annarita Di Fazio, and Shahab Khormali, “Advanced, CostBased Indices for Forecasting the Generation of Photovoltaic Power”, International Journal of
Emerging Electric Power Systems, vol. 15, Issue 1, pp.77-91, 2014.
[12] S. Surender Reddy, A. R. Abhyankar and P. R. Bijwe, “Co-optimization of Energy and DemandSide Reserves in Day-Ahead Electricity Markets”, International Journal of Emerging Electric
Power Systems, vol. 16, Issue 2, pp. 195-206, 2015.
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6
(a) DG schedule (PS3)
(a) DG schedule (PS1)
(b) DG schedule (PS2)
(b) DG schedule (PS2)
(c) DG schedule (PS3)
(c) DG schedule (PS3)
Fig. 8.Simulation results for proposed method.
Fig. 7. Simulation results for conventional method.
(a) Trading power in day-ahead market
(a) PS1
(b) Trading power in hour-ahead market
(b) PS2
Fig. 9. Simulation results for electricity markets.
TABLE III
FUEL COST AND OPERATIONAL COST.
(c) PS3
Fig. 10.Simulation results for RP.
Fig. 11. Operational cost for uncertainty.
437
7
CIGRE - AORC Technical Meeting 2016 and International Conference on
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
“Global Trends
in the Development of Power T&D System including Smart Grid”
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE - AORC Technical Meeting 2016 and International Conference on
“Global Trends in the Development of Power T&D System including Smart Grid”
SVC PLUS – The Way to Improve Stability and Power Quality of Power Systems
P. THEPPARAT1, G. PILZ2, P. ERNST2, B. RUTRECHT2, V. HILD2
1
Limited,
Energy
Management
SVC PLUS – The Way toSiemens
Improve
Stability
and
Power Quality of Power Systems
Thailand
2
Siemens AG, Energy Management
P. THEPPARAT1, G. PILZ2, P. ERNST2, B. RUTRECHT2, V. HILD2
Germany
1
Siemens Limited, Energy Management
Thailand
2
Siemens AG, Energy Management
Germany
SUMMARY
Power demand starts continuously increasing in this decade and near future, therefore many power
system developing plans are under discussion. Expansion of power transmission system by keeping
stability and power quality of power systems becomes a challenge for transmission system operator.
SUMMARY
Voltage stability, power imbalance, requirement of proper voltage profile, harmonic, flicker, voltage
dips are some of the criteria which need to be taken into account for system integration.
Power demand starts continuously increasing in this decade and near future, therefore many power
Focusing
on parallel
applicationExpansion
of Flexible
Transmission
System
(FACTS),
system
developing
planscompensator
are under discussion.
of AC
power
transmission
system
by keeping
Mechanical
Switched
Devices,
SVC
(Static
Var
Compensator)
and
STATCOM
(Static
Synchronous
stability and power quality of® power systems becomes a challenge for transmission system operator.
Compensator)
SVC PLUS
are frequently
used. of
Which
typevoltage
of technology
provide flicker,
the greatest
Voltage
stability,- power
imbalance,
requirement
proper
profile,will
harmonic,
voltage
benefit for the network depends on different criteria’s. The operator of the network has to evaluate the
dips are some of the criteria which need to be taken into account for system integration.
decisive parameters of the installing FACTS devices. The criteria of choosing the application are
voltage profile,
harmonic
impact on network,
activeofpower
losses AC
and dynamic
behaviour.
Focusing
on parallel
compensator
application
Flexible
Transmission
System (FACTS),
Mechanical
Switched
SVC (Statictechnology
Var Compensator)
and
STATCOM
(Static capability
Synchronous
The progress
in the Devices,
power® semiconductor
introducing
a turn-on
and turn-off
Compensator)
SVC
PLUS
are
frequently
used.
Which
type
of
technology
will
provide
devices called IGBTs (Insulated Gate Bipolar Transistors) provides the capability to build the
up greatest
AC
benefit
for
the
network
depends
on
different
criteria’s.
The
operator
of
the
network
has
to
evaluate
voltages itself and it is possible to connect a weak/very weak network or even passive networks. SVC the
decisive
of theconverter
installing
FACTS so-called
devices.Modular
The criteria
of choosing
application
PLUS®parameters
using innovative
technology
Multilevel
Converterthe
(MMC)
is with are
voltage
profile,
harmonic
impact on
power losses
and dynamic
behaviour.
cascaded
IGBT
Full Bridge
andnetwork,
isolatedactive
capacitors.
Each converter
module
consists of a
semiconductor arrangement and a DC capacitor as well as two terminals for the connection to the
Theneighboring
progress in
the power
introducing
turn-on
and turn-off
capability
modules
of thesemiconductor
converter. Usingtechnology
MMC technology,
designa of
SVC PLUS
is compact
and
devices
calledBoth
IGBTs
(Insulated(±25,
Gate±35
Bipolar
Transistors)
the building
capability
to build
up AC
adaptable.
containerized
and ±50MVAr)
and provides
conventional
(±75,
±100 and
±125MVAr)
solutions
are available
with low
space requirement.
In addition,
SVCpassive
PLUS networks.
has fast andSVC
voltages
itself and
it is possible
to connect
a weak/very
weak network
or even
®
accurate
dynamic
response
of voltage
control. Itso-called
is also possible
to have
a hybridConverter
solution meaning
PLUS
using
innovative
converter
technology
Modular
Multilevel
(MMC)that
is with
SVC PLUS
with TSC
MSC (Mechanically-Switched
cascaded
IGBTis together
Full Bridge
and (Thyristor-Switched
isolated capacitors.Capacitor),
Each converter
module consists of a
Capacitor), TSR
(Thyristor-Switched
and as
MSR
(Machanically-Switched
semiconductor
arrangement
and a DCReactor)
capacitor
well
as two terminals forReactor).
the connection to the
neighboring
modules
of
the
converter.
Using
MMC
technology,
design
of
SVC
PLUS
is compact
To improve dynamic stability and power quality, the application of SVC PLUS with
offshore
wind and
adaptable.
Both
containerized
(±25,
±35
and
±50MVAr)
and
conventional
building
(±75,
±100
farm confirms the necessity of SVC PLUS to control the voltage at point of common coupling. The and
±125MVAr)
solutions
are cause
available
low space
requirement.
In addition,
SVC problem.
PLUS hasOther
fast and
volatility of
wind can
the with
fluctuation
of power,
in consequence
stability
accurate
dynamic
response
of
voltage
control.
It
is
also
possible
to
have
a
hybrid
solution
meaning
application of SVC PLUS with HVDC Classic show SVC PLUS acts as a booster to ensure the that
SVC
PLUS ofisHVDC
together
with TSC
(Thyristor-Switched
MSC (Mechanically-Switched
operation
and reduces
the voltage
dip during filterCapacitor),
switching, especially
in weak network
Capacitor), TSR (Thyristor-Switched Reactor) and MSR (Machanically-Switched Reactor).
pakorn.thepparat@siemens.com
To improve dynamic stability and power quality, the application of SVC PLUS with offshore wind
farm confirms the necessity of SVC PLUS to control the voltage at point of common coupling. The
volatility of wind can cause the fluctuation of power, in consequence stability problem. Other
438
application of SVC PLUS with HVDC Classic show SVC PLUS acts as a booster to ensure the
operation of HVDC and reduces the voltage dip during filter switching, especially in weak network
pakorn.thepparat@siemens.com
condition. Regarding power quality improvement, the application of traction system which causes
voltage unbalance is discussed. SVC PLUS having single-phase control and fast response becomes a
solution
In this paper, the requirement of using parallel compensation – SVC and SVC PLUS will be shortly
discussed. Furthermore, the benefits of SVC PLUS to improve system stability and power quality are
shown and project applications are presented.
KEYWORDS
SVC PLUS, Power Quality, Dynamic, Power System Stability
439
2
1
INTRODUCTION
Nowadays the power system is more complicated than the past due to e.g. high penetration of
Renewable Energy Resource (RES) shown in Fig. 1 for wind power, far energy resource, long HVAC
cable, environmental protection, complexity of loads, weak AC system integration. These challenge
network designers to fulfil stability and power quality of power systems with security, cost-efficiency
and environmental compatibility at the same time. The combination of these tasks can only be
achieved if ideas, intelligent solutions and innovative technologies meet.
Fig. 1. Wind Power Installed in Europe End of 2014 (Source: EWEA)
Since the commercial application of HVDC (High Voltage Direct Current) after the 2nd World War in
1945 (Germany), 1951 (Russia) and 1954 (Sweden) [1] and FACTS (Flexible AC Transmission
Systems) in 1988 [2], the development of transmission technology has started moving forward in big
steps. The use of FACTS for continuous control of AC power system was introduced since eighties.
Many areas used SVC (Static VAR Compensators) based on line-commutated thyristor technology
which its commutation process is depended on the connecting AC voltage. Fig. 2 shows the simple
configurations of SVC which consists of Thyristor Controlled Reactor (TCR), Thyristor Switched
Capacitor (TSC) and filters.
TCR, TSC, Filter
Fig. 2. Simple SVC Configuration
Filters are used to absorb harmonic currents generated by TCR. In case of severe imbalance network,
the filters should be designed to damp 3rd harmonics. This is a challenge for filter design in SVC. The
440
3
variation of reactive power can be controlled by changing of firing angle in TCR. Moreover, the
capacitive power can be additionally provided by switching on TSC. If the excessive capacitive power
from TSC is more than grid requirement, TCR will absorb this capacitive power. For this reason SVC
provides a continuous range of reactive power control, consequently the system voltage will be
controlled in desired range. Note that Thyristor Switched Reactor (TSR) can also be applied to get
more inductive power.
The progress in the power semiconductor technology introducing a turn-on and turn-off capability
devices called IGBTs (Insulated Gate Bipolar Transistors) provides the capability to build up AC
voltages itself and it is possible to connect a weak/very weak network or even passive networks. This
makes STATCOM (Static Synchronous Compensator) application adding more feature to the known
SVC application. Using innovative converter technology in high voltage transmission application, the
Modular Multilevel Converter (MMC) which is applied for SVC PLUS shows the benefit of VoltageSourced Converter (VSC).
In this paper, the overview of using parallel compensation and to enhance transmission system will be
shortly discussed. After that the detail of SVC PLUS and its benefits will be explained. Additionally,
the example of SVC PLUS projects to improve system stability and power quality are shown.
2
ENHANCEMENT OF TRANSMISSION SYSTEM WITH PARALLEL
COMPENSATIONS
With the change of power generation from nuclear power plants to renewable energies especially in
Germany, the transmission network has to be adapted to these new conditions. The development plan
of the future transmission network defines the modifications and improvement of the existing AC
network as well as the erection of new HVDC connections shown in Fig. 3. Due to the offshore wind
generation in the north and the load centres in the middle and south of the country and the increased
generation from solar power into low and medium voltage systems as well, the load flows in the
German network will change and respectively have already changed. This causes challenges for the
owners and operators of the transmission network. Power electronic devices applied in HVDC and
FACTS will have a decisive part for controlling the load flow and stabilizing the voltage in the
European transmission system.
Fig. 3. Change of Transmission Grid in Germany (NEP 2013, date July 2013)
441
4
Different types of FACTS devices exists for controlling power transfer in the network. In the
following the main focus is on parallel connected equipment. In general three different types can be
identified:
x
Mechanical switched devices (Mechanical Switched Capacitor, Mechanical Switched Reactor,
Mechanically Switched Capacitor with Damping Network)
x
Line – commutated “classic” Static Var Compensator (based on Thyristor technology)
x
Self – commutated STATCOM (based on multi – level technology)
Which type of technology will provide the greatest benefit for the network depends on different
criteria’s. The operator of the network has to evaluate the decisive parameters of the installing FACTS
devices. As an example the output capability of a line – commutated and self – commutated
compensator in dependency of the voltage on the connection point of the SVC is shown in Fig. 4. In
the chosen example the output for both technologies is equal at 1pu reference voltage. One main task
of a SVC is to operate during network contingencies mainly in two different scenarios (under- and
overvoltage). During a fault in the network the system voltage at the point of common coupling
decreases. The voltage sag depends on the location of the fault and on the short circuit level of the
network. The voltage control mode of the SVC will regulate the output of the SVC to capacitive
output. In case of a deep decrease of voltage below the steady state voltage band the full capacitive
capability of the SVC will be required. The current output of a SVC based on thyristor technology will
be linearly decreased with respect to the connected voltage on HV side. A STATCOM does not have
this limitation. Independent of the connected voltage a constant current can be injected into the
network. In case of a similar failure for both technologies the voltages on the nodes in the network
with installed STATCOM technologies will be higher during the failure as in the network with a SVC
based on thyristor technology. Simulations show also a faster voltage recovery for STATCOM
technologies after fault clearing.
The voltage at the PCC may rise above the steady state voltage band. During this event the control will
regulate to the full inductive output capability of the SVC. Due to the dependency to the connected
voltage thyristor based SVC technology will generate a higher inductive current as a STATCOM and
will achieve a higher reduction of the over voltage.
Fig. 4. Comparison of Operating Ranges between line-commutated and self-commutated compensator
For this reason, under- and overvoltage is one criteria for considering whether SVC or SVC PLUS
shall be applied. Additional evaluation criteria for choosing the kind of technology are:
442
5
3
x
Harmonic impact on network
x
Comparison of active power losses
x
Dynamic behavior
STATCOM WITH MMC TECHNOLOGY – SVC PLUS
Siemens developed an innovative system for dynamic voltage control referred to as SVC PLUS which
is based on the new generation of modular as well as compact multilevel converter technology which
poses an important step on the way to a Smart Grid technology [3]-[4]. The state-of-the-art highly
flexible MMC technology for SVC PLUS makes it possible to easily comply with all known voltage
quality requirement – Grid Codes for enhancement of transmission system.
The SVC PLUS converter is an MMC with cascaded IGBT Full Bridge and isolated capacitors shown
in Fig. 5 and 6. Each converter module consists of a semiconductor arrangement and a DC capacitor as
well as two terminals for the connection to the neighboring modules of the converter. Similarly to
reactive power control in HVDC, varying the amplitude of the converter voltage by switching on/off
power modules to get the voltage which is in phase with the system voltage at the point of common
coupling allow the change in reactive power. The details of switching sequence are depicted in Fig. 7.
It can be seen that the voltage at the module terminals can be zero and also with inverted polarity. The
output of voltage from converter is shown in Fig. 8. Obviously, the voltage output produced by MMC
technology has very small voltage step and consequently very small portion of harmonics and low
emitted high-frequency radiation. The switching frequency of individual semiconductors can be highly
reduced. This results in a small loss in converter.
Power Module 1
Power Module 2
Power Module 3
Power Module 4
Power Module n
VSC
v conv 12
AC Equivalent
SVC Voltage v12
i conv 12
Conv
Conv12
12
vconv 12
Xfmrs, Lines
v L12
VSC =
Loads
Electronic Generator
for Reactive Power
Voltage Stabilization
Fig. 5. MMC with Cascaded IGBT Full Bridge
Fig. 6. SVC PLUS – Voltage source Converter
“OFF” State - Capacitor bypassed
v
v
“ON” State - Capacitor charging/discharging
Fig. 7. SVC PLUS - Switching Sequences
Fig. 8. Modular voltage Generation
443
6
Using MMC technology, design of SVC PLUS is compact and adaptable. Both containerized (±25,
±35 and ±50MVAr) and conventional building (±75, ±100 and ±125MVAr) solutions are available
with low space requirement. In addition, SVC PLUS has fast and accurate dynamic response of
voltage control. It is also possible to have a hybrid solution shown in Fig. 9. It means that SVC PLUS
together with TSC (Thyristor-Switched Capacitor), MSC (Mechanically-Switched Capacitor), TSR
(Thyristor-Switched Reactor) and MSR (Mechanically-Switched Reactor).
Containerized Solutions:
Up to 4 equal L-Units in parallel: +/- 200 MVAr
SVC PLUS S: +/- 25 MVAr
SVC PLUS M: +/- 35 MVAr
SVC PLUS L: +/- 50 MVAr
HV
8 kV – 36 kV
LV
Open Rack Solution (Building):
SVC PLUS C: +/- 75 MVAr
SVC PLUS C: +/-100 MVAr
SVC PLUS C: +/-125 MVAr
SVC PLUS Hybrid Options:
Mechanically and/or Thyristor-Switched
Reactors and/or Capacitors
SVC PLUS
MSR/TSR
MSC/TSC
+/ -25 ... +/ -400 MVAr
Up to 4 equal C-Units in parallel: +/- 400 MVAr & more
Fig. 9. Hybrid Solution of SVC PLUS with TSC, MSC, TSR and MSR
4
IMPROVE DYNAMIC STABILITY AND POWER QUALITY WITH SVC PLUS
For grid access solution, when connecting the long submarine cable the reactive power control
becomes a concerned factor. In some offshore wind farm applications, the HVAC cable transmission
has shown a big impact of the excessive reactive current drawn by cable capacitance. The power
quality at the grid connection point must be considered. This requires the dynamic shunt stabilization
e.g. SVC PLUS to control the excessive reactive power of cable which can cause high overvoltages
and resonances. For submarine cable longer than 80km, HVDC solution will bring about significant
technological and economic advantages. The grid access solution with HVDC PLUS and SVC PLUS
shows in Fig. 10. Fig. 11shows the large scale wind farms in UK. Due to volatility of wind, SVC
PLUS is used to control voltage at point of common coupling.
SVC PLUS:
 3 x PLUS L in parallel
 132 kV / 13.9 kV
DC Solution for
Grid Access
33 kV AC
33 kV AC
HVDC PLUS
132 kV AC
132 kV AC
SVC PLUS:
 4 x PLUS L in parallel
” 320 kV DC
HVDC PLUS
SVC PLUS
33 kV AC
 150 kV / 13.9 kV
AC Solution for
Grid Access
… and London Array
World’s largest Offshore Wind Farm
630 MW & Upgrade up to 1 GW
132 kV AC
Fig. 10. Grid Access solution
2010
2011
Fig. 11. AC Grid Access of Large Wind Farm
The combination of HVDC classic and SVC PLUS shows in Fig. 12 and 13. HVDC Classic based
thyristors has a restriction in weak or very weak system condition since the converters always
consume reactive power, approximately 50-60% of active power transfer. AC filters and additional
capacitor banks are therefore designed to support the reactive power for converters otherwise HVDC
converter will take the reactive power from network which causes the further reduction of AC voltage.
Additionally in weak system condition, the switching of filters and capacitor banks can cause a large
disturbance to the connecting AC systems. This will take some efforts for control optimization. Also
during faults, commutation failures are more risky in this system condition.
444
7
In New Zealand, shown in Fig. 12, the inter-island Connector Pole 3 HVDC transmission project link
became fully operational in winter 2013. This upgrade expands the transmission capacity of the link
and ensures reliable power transmission between the country’s North and South islands with overhead
line and cable (40km), in total 649km. In addition, an SVC PLUS of ±60MVAr acting as
“Performance Booster” for the HVDC is installed at Haywards substation to supply reactive power,
stabilize 220kV during transients and reduce the commutation failure risk.
SVC PLUS for Haywards Substation
 1 x PLUS C
2013
 220 kV Dynamic Voltage Stabilization
 Reactive Power Control
HVDC and STATCOM
in parallel Operation
Fig. 12. Combination of HVDC Classic with SVC PLUS as Booster
In the UK, the Western HVDC Link 2,200MW shown in Fig. 13 with the World’s first 600kV DC MI
cable (Mass-Impregnated), 420km is currently installed. This project increases the power exchange
and bypasses the congested onshore AC overhead lines. This mitigates the instability which can cause
blackout. Moreover, two SVC PLUS of 2x125MVAr will be installed to strengthen the Northern Grid.
They will enhance the Scottish network in terms of dynamic voltage stability.
SVC PLUS C: 2 x 125 MVAr
 Dynamic Voltage Stabilization
 Reactive Power Control
Western HVDC Link, UK
HVDC and STATCOM
in parallel Operation
SVC PLUS – the Performance
Booster for HVDC “Classic”
World’s 1st
HVDC with
600 kV DC
Cable
6 hrs Overload 2,400 MW (Cable)
Customer:
National Grid / Scottish
Power
2016
Deesid
e
System Data:
Rating
2,200 MW
Voltage ± 600 kV DC
Thyristor
8 kV LTT
More Power Transfer
No Increase in
Short-Circuit Power
Increase in Grid Stability
Bypassing overloaded
Onshore Overhead Lines
Fig. 13. Western HVDC Link with 2xSVC PLUS
In Queensland, Australia, three new SVC PLUS systems are installed at the Wycarbah, Duaringa and
Bluff substation, as shown in Fig. 14. The capacity of each SVC PLUS is ±100 Mvar. There is a
substantial increase in the volume of coal exported from Central Queensland expected in the near
future. As the system is relatively weak, Static Var Compensators (SVCs) were installed coincidently
with the introduction of electric locomotives during the late 1970s, to maintain quality of supply for
other customers in the region. However, the existing SVCs cannot cope with the predicted increase of
the Queensland Railways load. This increase will affect the power quality and increase the unbalance
in the region [5]. Installation of these three SVC PLUS can efficiently solve the problem.
445
8
Fig. 14. Black Water SVC PLUS
5
CONCLUSIONS
The increase of power demand causes risks in power system stability and power quality. FACTS
becomes solution for AC power system. STATCOM technology is superior in case of undervoltage
scenarios in the network. On the other hand, SVC based on thyristor technology provides benefits for
overvoltage scenarios. Siemens developed an innovative system for dynamic voltage control referred
to as SVC PLUS which is based on the new generation of modular as well as compact multilevel
converter technology so-called MMC. It offers fast and robust control as well as the feature to
configure the system in a flexible way. As fast and accurate controllability can be fulfilled, power
system stability and power quality therefore improve.
BIBLIOGRAPHY
[1] D. Povh, P. Thepparat, D. Westermann, “Analysis of Innovative HVDC Control”,
PowerTech2009, Bucharest, Romania, June 2009
[2] N. G. Hingorani: “High Power Electronics and Flecible AC Transmission System” (Amercan
Power Conference 50th Annual Meeting, April 1988, Chicago. Published at the IEEE Power
Engineering Review, July 1988)
[3] W. Breuer, D. Povh, D. Retzmann, Ch. Urbanke, M. Weinhold, “Prospects of Smart Grid
Technologies for a Sustainable an Secure Power Supply”, The 20th World Energy Congress,
November 11-15, 2007, Rome, Italy
[4] J. Dorn, H. Huang, D. Retzmann, “Novel Voltage Sourced Converters for HVDC and FACTS
Applications”, CIGRE Symposium, November 1-4, 2007, Osaka, Japan
[5] A. Janke, et.al., “Queensland Railways Upgrade Project”, SCB4 CIGRE Colloquium 2011
446
9
The Grid II
CIGRE- AORC Technical Meeting 2016 and International Conference
CIGRE- AORC Technical Meeting 2016on
– International Conference on Global Trends in the Development
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
CIGRE- AORC Technical Meeting 2016 and International Conference
on
“Global Trends in the Development of Power T&D System including Smart Grid”
“Global Trends in the Development of Power T&D System including Smart Grid”
Mae Hong Son Smart Grid Pilot Project
JITTIPORN NAGAPRADIP
Mae
Hong
Son Smart
Grid
Pilot Project
Electricity
Generating
Authority
of Thailand
(EGAT)
THAILAND
JITTIPORN.N@EGAT.CO.TH
JITTIPORN NAGAPRADIP
Electricity Generating Authority of Thailand (EGAT)
THAILAND
JITTIPORN.N@EGAT.CO.TH
SUMMARY
The smart grid pilot project in Mae Hong Son (MHS) Province, Thailand was prepared under the
collaboration of 1. Energy Policy and Planning Office (EPPO), 2. Department of Alternative Energy
Development and Efficiency (DEDE), 3. Electricity Generating Authority of Thailand (EGAT), 4.
Provincial Electricity Authority (PEA), and 5. Chulalongkorn University. The main driving factor of
this project is to increase performance or energy efficiency, to stimulate the use of renewal energy, to
improve the system reliability, and to reduce the emission of greenhouse gas. With the “Smart Grid”
SUMMARY
concepts and technologies, the smart grid roadmap in Thailand was created and it’s now under the
pilot project.
The smart grid pilot project in Mae Hong Son (MHS) Province, Thailand was prepared under the
Mae
Son, a northern
of Thailand,
was selected
for 2.
the Department
pilot project because
of its area Energy
collaboration
ofHong
1. Energy
Policyprovince
and Planning
Office
(EPPO),
of Alternative
is
appropriate
to
the
education
of
Smart
Grid
implementation
in
many
aspects.
This
province
Development and Efficiency (DEDE), 3. Electricity Generating Authority of Thailanddoesn’t
(EGAT), 4.
have any large capacity power sources but the location have the potential for renewable energy
Provincial Electricity
(PEA),
and
Chulalongkorn
University.
The
main driving
developmentAuthority
and its electrical
system
still5.unstable
and unreliable.
Currently, the
transmission
system factor of
this project in
is Thailand
to increase
or energyProvince,
efficiency,
to stimulate
theis use
of renewal
energy, to
is stillperformance
hardly get to Maehongsorn
the distribution
system
also not
strong
thatreliability,
area, becauseand
of itstolocation
is the
mountainous
province in Thailand.
Therefore,
if
improve thearound
system
reduce
themost
emission
of greenhouse
gas. With
the “Smart
Grid”
Smart
grid
is
a
good
and
sustainable
solution
so
Thailand
should
bring
this
technology
to
perform
a
concepts and technologies, the smart grid roadmap in Thailand was created and it’s now under the
Pilot project here.
pilot project.
The area of consideration can be divided into 3 parts. Firstly, the supply side, in Mae Hong Son
province
already hasprovince
some smallofhydro
power plants,
solar farm, for
diesel
and energy
Mae Hong Son,
a northern
Thailand,
was selected
thepower
pilotplant,
project
because of its area
storage. Secondly, the operation side such as Micro Energy Management System, demand forecast,
is appropriate
to the education of Smart Grid implementation in many aspects. This province doesn’t
and load forecast to monitor the data in many aspects. Finally, the demand side such as smart meter,
have any large
capacity
butthethe
location ofhave
the potential
for to
renewable
energy
intelligent
sign, power
and etc. sources
to encourage
participation
the public
sector in order
manage power
developmentusage
andtogether.
its electrical system still unstable and unreliable. Currently, the transmission system
in Thailand is still hardly get to Maehongsorn Province, the distribution system is also not strong
around that KEYWORDS
area, because of its location is the most mountainous province in Thailand. Therefore, if
Smart grid isSmart
a good
sustainable
solution
Thailand
should bring this technology to perform a
Grid,and
SG, EGAT,
Pilot Project,
Mae so
Hong
Son
Pilot project here.
The area of consideration can be divided into 3 parts. Firstly, the supply side, in Mae Hong Son
province already has some small hydro power plants, solar farm, diesel power plant, and energy
Jittiporn.n@egat.co.th
storage. Secondly, the operation side such as Micro Energy Management System, demand forecast,
and load forecast to monitor the data in many aspects. Finally, the demand side such as smart meter,
intelligent sign, and etc. to encourage the participation
449 of the public sector in order to manage power
usage together.
KEYWORDS
1. INTRODUCTION
Smart Grid is a technology provided in order to modernize and improve the electrical network to be
more intelligence. In other word, smart grid also referred to the process of bringing information and
technology to control and automate the electrical operation system. Basically, the design of the smart
grid should be based on the regional specific. Nowadays, the electrical network system all over the
world tends to develop according to the smart grid idea. In Thailand, we are also see the importance of
this technology and start the studied since 2010.
This article will focus on the basic knowledge that general people can easily understand the overview
content which will not focus on in-depth knowledge to analyze power supply system or mathematical
equation. It will focusing on case study in Mae Hong Son City to demonstrate a link from concept into
the guidelines in the development of the smart grid pilot project in Mae Hong Son (MHS) Province
including Supply Side, Operation & Control Side, and Demand Side. This project is aiming for
maximize the performance and efficiency of the electric system as well as improving the quality of
electrical service.
Figure 1.1 the guidelines in the development of the smart grid pilot project in Mae Hong Son
The key factor that makes the Mae Hong Son province becomes the Smart grid project are divided into
2 parts:
Internal factors which are:
- The potential of electricity production from renewable energy sources within the area
including small hydro-power plant, biomass-power plant, and solar energy.
- The good collaboration between relevant agencies within the area in production planning and
electric distribution
- People in MHS province are well aware about the problems of electric power quality and
reliability of electrical distribution systems. They are ready to cooperate to help reduce the
impact and damage caused by a power failure in the area.
- MHS province development strategies towards sustainable development which also focuses on
ecotourism, society of learning, and the sustainable conservation and rehabilitation of natural
resources
- There is no high voltage transmission line of the Electricity Generating Authority of Thailand
(EGAT) accessing to the area due to the topography was engulfed by water conservation
forest district which made serious restrictions for the pole line and vertical line expansion.
450
1
-
The unfavorable climate, which permitting occurrence of frequently electrical outages in both
the rainy season and the dry season all resulted in electrical distribution systems into MHS
have the higher chance to be easily isolated.
External factors which are:
- The Government encourages the development of a pilot project with the Smart Grid network,
in order to make a research and development prototype to find the appropriate technologies for
other Smart Grid project in Thailand.
- The budget for research and development from both the Government and other related parties
is ready to support this project.
2. Driving Force for Smart Grid Pilot Project
The development of electric infrastructure systems in the form of Smart Grid in all regions of the
world is driven by four sustainable development keys to support the challenges of energy security
issues and the concern of climate change around the world. However, each country may weigh the
importance of each driving key in a different aspect. The Four driving force keys are:
1. Energy Efficiency is the reduction of energy loss in transmission, distribution, and production
systems includes learning to limit the energy consumption, provide the cost-effective method,
and find the flexible solution for electric power consumption in each interval to reduce costs
on investment (Capital Expenses, CAPEX), construction, or expansion of the main electricity
grid system. Moreover, to help reduce the expenses related to maintenance (OPEX Expenses,
Operational) and commissioning, this leads to the appropriate electricity prices for consumers
or the affordable price in the long term.
2. Renewable Energy refers to the electricity grid that can connect and utilize the energy from
renewable energy production system in high proportion through the supportive mechanism for
the impact on the power system stability due to the variability of climate. The electrical
production from renewable energy sources such as solar, wind power and etc. will leading to
sustainable energy and are environmentally friendly.
3. System Reliability refers to the ability of the system to maintain stability, security, and
reliability of the system. According to the dynamic changes of the electricity grid structure
that are likely to be more complex in planning, operation, and controlling. It’s both from the
effects of the electricity grid system expansion to Regional Interconnection which covers a
broader area and from the results of the Decentralized Micro Energy Management Systems
which are expected to have the number increases continuously. Moreover, we also should
focus on the durable of interference from natural disasters and terrorism.
4. Emission Reduction means the operation in accordance with the regulations about the
reduction of greenhouse gas that emits into the atmosphere from burning fossil fuels used in
the production of electricity such as coal, oil, and natural gas. By promoting the production of
electricity from renewable energy instead of fossil fuels altogether with the process of
increasing the awareness of consumers on the production performance and power
consumption which will helps bring to a low-carbon society to sustainability.[1]
The key driving factors that make Mae Hong Son (MHS) is appropriate to develops into a Smart grid
pilot project of the country are because of;
The potential of renewable energy sources in Mae Hong Son area which is sufficient to produce
electricity for the local area. The small hydro-power plant is the main energy sources (usually during
August-November, it will be a lot of water that can produce enough electricity up to 100% for this
area). In addition, solar energy and biomass can be used as auxiliary power, especially during the
451
2
summer between March-May which has less water, if it has a management system to effectively
implement biomass and agricultural waste in MHS area as a fuel source for generating the electricity
and combined-heat that will also help reducing air pollution from the smoke causing by waste burning
after the harvest.
The quality and reliability of the electric system in Mae Hong Son province is considered to be one of
the area with lowest index of electricity reliability in Thailand. Due to landscape features, that similar
to island surrounded by forest, which is one of conservation zones A1 and a National Park. The
transmission line must go along the route across long distances forest and with a climate that people
always faced with natural disasters such as monsoon storm, land or mud slide, flood in rainy-season,
and forest fires in the summer which is always caused potential difficulties for transmission system
such as short circuit or transmission tower falling more than other area in Thailand. Furthermore, in
order to restore the system, due the path is steep and winding road in several area, it’s hard for
transport to solve the issue and may require long periods of time.
Figure 2.1 Mae Hong Son map with Transmission line
Additionally, MHS also promote the strategy for ecotourism development with significant goals is to
cultivate the scenic area for ecotourism, enhance and distribute the revenues from tourism, and reduce
the impact of disasters [2].
3. Strategies on developing smart grid pilot project
Strategies on developing smart grid pilot project in Mae Hong Son are divided into four aspects as
follows:
Figure 3.1 Strategies on developing smart grid pilot project [3]
Smart Energy: To primarily support and rely on452
renewable energy and increase the quality and
reliability of the power system. The main elements are focusing on electrical production systems for
MHS such as Solar Farm & Rooftop, Biomass Power Plant, and Battery Energy Storage System
(BESS). Besides, secondary elements are improving automatic control system to help starting the
system that faced the power outage is a wide area (Black start) and the promotion of waste-to-energy
3
Figure 3.1 Strategies on developing smart grid pilot project [3]
Smart Energy: To primarily support and rely on renewable energy and increase the quality and
reliability of the power system. The main elements are focusing on electrical production systems for
MHS such as Solar Farm & Rooftop, Biomass Power Plant, and Battery Energy Storage System
(BESS). Besides, secondary elements are improving automatic control system to help starting the
system that faced the power outage is a wide area (Black start) and the promotion of waste-to-energy
project.
Smart System: Modernize the power management and forecasting system within the area and
enhancing the communication systems to support the electrical Smart Grid systems. The main element
for the communication system is to have Micro Energy Management System (Micro-EMS) that can
command and control the electrical production within the area altogether with electricity generation
from renewable energy forecasting module, demand forecast module, and ICT Infrastructure which is
integration and interoperability with the power plant, control center, and substation. Moreover, the
distribution management system (DMS), the Quality of service, and cyber security must be adequate.
Smart City: The consumer must be welled aware, educated, and using energy efficiently. Smart
Billboard and Mobile Application will provides information and awareness of energy consuming
within the area. Building energy management system (BEMS) will also provide starting with the
government office building and hospital within the area. Electric Vehicle and Intelligent Charging will
also provide in the form of public bus service for people in MHS.
Smart Learning: The research center of learning and training about Smart grid. It’s divided into zones
such as Sustainable Energy, Sustainable Environment, Sustainable Economy, and Sustainable Living.
The primary achievement expectations for smart grid pilot project in Mae Hong Son Province when
completed are as follows:
1. The quantity of electrical energy use throughout the year from renewable energy sources
produced within the area must be more than 95 percent (small hydro power plant 80 percent,
biomass 10 percent, and solar energy 5 percent).
2. The quality and reliability of the electric system must be met the country’s benchmark.
3. Electric power management system can manage the production and the utilization of energy
within the area efficiently with the self-reliant basis in energy consumption and be prepared
whenever natural disasters occur.
4. The consumer is welled aware, educated, and participate proactively in managing the city's
energy.
5. Be a low-carbon society, that cares about the environment altogether with the economic
development and improving the quality of life.
4. Conclusion
The project of developing Smart grid system in Mae Hong Son is considered as a pilot project to
research, development, and demonstration at the country level. The primary objective is to design
technical details for the supply side, operation side, and demand side by appropriately integrating the
knowledge and application of Smart Grid technology to various related aspects. In addition, every
party is expecting this pilot project to master in sustainable development projects for the ASEAN
region. According to the three main conceptual frameworks which are 1) consuming of electricity
from renewable energy sources more than other sources 2) increasing the reliability of the electric
system and alleviate the impact of the disaster and 3) allowing the consumer to participate in electric
power management of the city.
453
4
BIBLIOGRAPHY
[1]
[2]
[3]
Smart Grid development in Mae Hong Son, Assistant Professor Dr. Naebboon Hoonchareon,
2015.
Report on Smart grid project and renewable energy, Department of electrical and the
technological specialist center for electrical power, Chulalongkorn University, April 2011
NBTC - EGAT: Collaborate on Telecommunication Network of ASEAN Power Grid, 2015.
454
CIGRE- AORC Technical Meeting 2016 – International Conference on Global Trends in the Development
CIGRE- AORC Technical Meeting 2016 and International Conference
of Power Transmission & Distribution Systems including Smart Grid, 24-26 Feb. 2016, New Delhi, India
on
CIGRETechnical ofMeeting
2016
and International
“Global
Trends AORC
in the Development
Power T&D
System
including SmartConference
Grid”
on
“Global Trends in the Development of Power T&D System including Smart Grid”
SMART GRID IN THAILAND: TRENDS IN THE DEVELOPMENT OF POWER
TRANSMISSION & DISTRIBUTION SYSTEMS
SMART GRID IN THAILAND: TRENDS IN THE DEVELOPMENT OF POWER
TRANSMISSION
& DISTRIBUTION
SYSTEMS
Jatuporn
Vongmahadlek*
and Chatchawan Vongmahadlek
Electricity Generating Authority of Thailand
Thailand
Jatuporn Vongmahadlek* and Chatchawan Vongmahadlek
Electricity Generating Authority of Thailand
Thailand
SUMMARY
The development of smart grid is global trends. Various activities in different parts of the world reflect
the regional needs and resources. The increasing number of integration in a smart grid from renewable
energies to the power grid brings new visions and opportunities for the future power grids. However,
as the matter of smart grid is relatively new, there are many context and issues that are considered
SUMMARY
complex and unclear to many. Thailand is now facing challenges implementing efficiency, reliability,
and availability being taken part in the electric power supply industry. Accordingly, Thailand is
reacting to this development, as witnessed by various striving plans and promotion activities covering
The development
of smart grid is global trends. Various activities in different parts of the world reflect
energy efficiency as well as renewable power supply. For instance, under the Eleventh National
the regional
needs
resources.
ThePlan
increasing
number
of integration
in a smart
gridrequiring
from renewable
Economic
andand
Social
Development
(2012-2016),
government
policy specifies
that more
energies
to the
power
grid
brings
new visions
and
opportunities
for thus
the Thailand
future power
grids.
clean
energy
will be
used
and alternative
energy
should
be developed,
will lead
to anHowever,
in energy
efficiency.
In 2015,
rolled
out all and
of the
energythat
plans
as the overall
matterimprovement
of smart grid
is relatively
new,
thereThailand
are many
context
issues
areinto
considered
Thailand
Integrated
Energy
Blueprint
(TIEB)
as
the
core
of
the
long
term
energy
development.
In
complex and unclear to many. Thailand is now facing challenges implementing efficiency, reliability,
accordance with
thetaken
smart grid
Thailand
was released
masterindustry.
smart planAccordingly,
of Thailand smart
and availability
being
partplan,
in the
electric
power the
supply
Thailand is
grid development (2015-2036) by the Ministry of Energy. This plan will be used for implementation
reacting
to
this
development,
as
witnessed
by
various
striving
plans
and
promotion
activities
guidelines and regulatory framework development and also be aligned with TIEB. Consequently, it is covering
energyexpected
efficiency
as well
as renewable
supply.
instance,in under
thesectors.
Eleventh
that further
concrete
mitigation power
and adaptation
willFor
be launched
respective
Five National
Economic
and Social
Development
Plan
(2012-2016),
government
specifies
that
more requiring
strategies
and objectives
of Thailand
smart
grid master plan
are outlinedpolicy
and executed
in the
following
areas, (1)
Security;
(2) and
Sufficiency;
(3) Efficiency;
(4) Competitiveness;
andthus
(5) Awareness
by thelead to an
clean energy
will
be used
alternative
energy should
be developed,
Thailand will
related
stakeholders.
In
a
successful
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grid
system,
today
Thailand
has
launched
and
formulated
overall improvement in energy efficiency. In 2015, Thailand rolled out all of the energy plans into
smart grid development pilot projects in the various areas. The principal objectives of this paper are
Thailand
Integrated Energy Blueprint (TIEB) as the core of the long term energy development. In
three-fold. First, the paper is to explore the trends in the development of power transmission &
accordance
with systems
the smart
grid plan,
Thailand
was released
master
smart plan
Thailand smart
distribution
including
smart grid
in Thailand.
Second, thethe
paper
is to exemplify
the of
marketing
grid development
(2015-2036)
by
the
Ministry
of
Energy.
This
plan
will
be
used
for
implementation
strategies to implement smart grid systems. Third, the initial ideas for demonstration projects in the
Northern
of Thailand
are alsodevelopment
outlined. Following
this,be
successful
smart grid
guidelines
and region
regulatory
framework
and also
alignedapplications
with TIEB.ofConsequently,
it is
systems
are
further
discussed
and
presented.
expected that further concrete mitigation and adaptation will be launched in respective sectors. Five
strategies and objectives of Thailand smart grid master plan are outlined and executed in the following
KEYWORDS
areas, (1) Security; (2) Sufficiency; (3) Efficiency; (4) Competitiveness; and (5) Awareness by the
relatedSmart
stakeholders.
a successful
smart grid
system,
today Thailand has launched and formulated
Grid MasterInPlan,
Marketing Strategies,
PDP
2015, Thailand
smart grid development pilot projects in the various areas. The principal objectives of this paper are
three-fold. First, the paper is to explore the trends in the development of power transmission &
distribution
systems including smart grid in Thailand. Second, the paper is to exemplify the marketing
jatuporn.v@egat.co.th
strategies to implement smart grid systems. Third, the initial ideas for demonstration projects in the
Northern region of Thailand are also outlined. Following this, successful applications of smart grid
455
systems are further discussed and presented.
KEYWORDS
1. INTRODUCTION
The development of smart grid is global trends. Various activities in different parts of the
world reflect the regional needs and resources. The increasing number of integration in a smart grid
from renewable energies to the power grid brings new visions and opportunities for the future power
grids. However, as the matter of smart grid is relatively new, there are many context and issues that
are considered complex and unclear to many. As a result of the new load growth in today’s
environment at the center of the Indochina peninsula in the Southeast Asia, Thailand is now facing
challenges implementing efficiency, reliability, and availability being taken part in the electric power
supply industry in its country regions. Accordingly, Thailand is reacting to this development, as
witnessed by various striving plans and promotion activities covering energy efficiency as well as
renewable power supply.
For instance, under the Eleventh National Economic and Social Development Plan (20122016) [1], Thai’s government lead the country to the existing resilience of Thai society and economy
by paving the way toward well-balanced development under the Sufficiency Philosophy. One of the
key sectors and areas to focus is the energy security. With this regard, government policy specifies that
more requiring clean energy will be used and alternative energy should be developed, thus Thailand
will lead to an overall improvement in energy efficiency.
In 2015, Thailand rolled out all of the energy plans into Thailand Integrated Energy Blueprint
(TIEB) 2015-2036. It was the first long term master plan for Thai energy sectors to shape Thailand’s
future in twenty years as the core of the long term energy development [2]. Five principal objectives of
TIEB were (1) Supply security; (2) Cost competitiveness; (3) Environment; (4) Energy support
sustainability; and (5) Socio-economic support for the needed people/sectors. Notably, five master
plans of TIEB as the pillars of energy development were composed of (1) Power Development Plan
(PDP 2015); (2) Energy Efficiency Plan (EEP 2015); (3) Alternative Energy Development Plan
(AEDP 2015); (4) Gas Plan 2015; and (5) Oil Plan 2015 [2].
In accordance with the smart grid plan, Thailand was recently released the master smart plan
of Thailand smart grid development (2015-2036) by the Ministry of Energy [2][9]. This plan will be
used for implementation guidelines