PCS 6000 Leaflet
Dynamic Reactive Compensation – MV STATCOM
Providing stability, security, and reliability to the grid.
Installing a STATCOM at one
or more suitable points on
the network is a powerful
and cost effective method
to increase the grid
transfer capability and
enhance voltage stability.
What is a STATCOM?
A STATCOM or Static Synchronous Compensator is a votage
regulating device. It is based on a power electronics voltagesource converter and can act as either a source or sink of reactive
AC power. It is a member of the Flexible AC transmission system
(FACTS) family which detects and instantly compensates for voltage fluctuations or flickers as well as corrects unbalanced loads
and controls the power factor.
The most advanced solution to compensate reactive power is to
incorporate a Voltage Source Converter (VSC) as a variable source
of reactive power. These systems offer advantages compared to
standard reactive power compensation solutions in demanding
applications, such as wind farms and arc furnaces. In the more
demanding applications, the normal reactive power control generated by generators or capacitor banks alone are too slow for the
sudden load changes.
Electrical loads both generate and absorb reactive power. Since
the transmitted load often varies considerably from one hour to
another, the reactive power balance in a grid varies as well. The
result can be unacceptable voltage amplitude variations, a voltage
depression, or even a voltage collapse.
STATCOM applications examples:
• Utilities with weak grids
• Fluctuating reactive loads
• Wind Farms
• Car Crushers & Shredders
• Harbor cranes
• Mining hoists
• Industrial mills & welding operation
• Single phase control for unbalanced loads
• Active harmonic cancellation
As a fully controllable power electronic device, the STATCOM is
capable of providing both capacitive and inductive VARs. ABB’s
MV STATCOMs are typically rated at up to +/-30 MVAR although
larger sizes are possible.
The electrical utilities and heavy industries face a number of challenges related to reactive power. Heavy industrial applications can
cause disturbances like voltage unbalance, distortion or flicker
on the electrical grid whereas in electrical utilities, they may be
confronted with voltage sags, poor power factor or even voltage instability. Reactive power control can resolve these issues
by improving the power factor or compensating for the voltage
instability.
Technology and Packaging:
• IGCT – Power Electronics
• Voltage Source Converter
• Indoor/Outdoor
• Walk-in Control Buildings
• Closed-loop liquid cooling
Contact us
ABB Inc.
High Power Rectifiers & Advanced Power Electronics
16250 West Glendale Drive
Phone:
262-780-8904
Fax:
514-635-6200
E-Mail: pes@us.abb.com
Bus Configuration
Reactive Power Generation
Support line: 1-800-665-8222
www.abb.com/powerelectronics
Project Capabilities:
ABB‘s qualified engineers can help design and build a STATCOM
solution that‘ll meet your company‘s stringent needs. We have
complete project handling resources to ensure successful project
execution including system studies, mechanical engineering,
protection, and full “Turn Key” installations.
ABB Inc.
High Power Rectifiers & Advanced Power Electronics
10300 Henri Bourassa West
St-Laurent, Quebec CANADA H4S 1N6
Phone:
514-332-5350
Fax:
514-635-6200
E-Mail: pes@us.abb.com
Support line: 1-800-665-8222
www.abb.com/powerelectronics
Document ID
New Berlin, WI 53151
Ultra High Voltage DC Systems
The use of HVDC at 800 kV,
has been found efficient,
environmentally friendly
and economically attractive for large point to point
power transmissions of
the order of 6400 MW and
more, with distances of
more than 1000 km. Worldwide there is an increasing
interest in the application
of HVDC at 800 kV.
800 kV UHVDC
UHVDC test circuit, Ludvika, Sweden
Financial benefits and built-in
advantages
Two main driving forces justify the use of 800 kV
HVDC.
• First, significantly lower total cost of investment
and losses.
• Second, this technology takes up significantly
less space, which often is as important as the
evaluated capital cost.
Financial
There are three main aspects to the financial
evaluation:
• Transmission system losses
• The investment cost for the line
• The investment cost for the converter station
and associated AC switchgear
The diagram below illustrates the cost differences
between 765 kV AC, 500 kV DC and 800 kV DC.
The example is for a 2 000 km long line to transmit
6 000 MW.
Pole bus arrester testing
Transmission of 6000 MW over 2000 km.
Total evaluated costs in MUSD
MUSD
3500
3000
2500
2000
Losses
1500
1000
Station cost
Line cost
500
0
765 kV AC
2
500 kV DC
800 kV DC
ABB
800 kV UHVDC
Artist view of 800 kV UHVDC switchyard
Inherent environmental advantages
Narrow tracks
With 800 kV HVDC the right of way of the power line is minimal. Where conventional means
of transmission are used, two or more lines are
needed and in most cases the right of way for
each one of them will be wider. The sketch below shows the approximate differences:
Low losses
As mentioned under “Financial” above, the line
losses for HVDC lines are significantly lower than
those for AC lines for a practical design.
765 kV AC
Low magnetic fields
Contrasted with normal AC transmission lines,
HVDC lines have an almost negligible alternating magnetic field. This means that HVDC
lines, unlike AC lines, can easily satisfy the
stricter magnetic field requirements (<0.4 μT)
increasingly being enforced in the western
countries.
Remote renewable energies can be utilized
Using 800 kV HVDC it is possible to use remote environmental friendly hydro power, today
located too far from the load centers for using
other transmission alternatives.
500 kV DC
800 kV DC
Number
of lines:
Right of way
(meter)
ABB
~ 240
~ 110
~ 90
3
800 kV HVDC
By-pass breaker, disconnector and
RI capacitor installed at the 800 kV
UHVDC test circuit at STRI, Ludvika
Transformer bushing testing
Dielectric testing of 800 kV UHVDC valve hall bushing
Basic research
More than twenty years have passed since the
voltage used for HVDC transmission was last
increased. The reason why it took so long time
is that this development step required further
basic research:
• The development of new materials for insulators in an outdoor environment. Using a
higher voltage means that there must be a
larger air clearance between live parts and
ground. For the past 100 years, insulators to
provide these gaps were primarily made of
porcelain. However, the past fifteen years
have seen the development of new polymeric
materials which make it possible to abandon
porcelain, especially for silicone rubber.
This material has been proven to possess very
favorable properties for outdoor insulation.
4
• Advanced computer-aided design tools for
three-dimensional field calculations, primarily
for transformer design.
• Refined measurement methods using advanced
laser technology to determine the characteristics
of insulating materials and insulation systems.
• Advanced control systems that control the entire
installation. This calls for an extremely high
calculation capacity, exploiting state-of-the art
computer processors and information technology
to the limit. For this, the Mach2 system developed
in-house by ABB is used.
There was a development project aimed at raising
the voltage to 800 kV in the mid-1990s, but the basic
research needed to achieve this was not finalized
at the time. While the project was in progress, the
market lost the interest and the project was halted.
ABB
800 kV UHVDC
The 800 kV project
Since the basic research
was in place, extensive
product development has
taken place over the past
two years. Most of this
development work has
been done at ABB’s facility
at Ludvika, backed by the
Corporate research laboratory at Västerås.
* STRI is an independent
technology consulting
company and accredited
high-voltage laboratory
located in Ludvika,
Sweden.
www.stri.se
UHVDC test circuit, Ludvika, Sweden
The key issues handled in the project
1. With up to 9 000 MW being carried on one
pair of overhead lines, extreme reliability is
obviously essential. Therefore a completely
new station design has been developed to
achieve these requirements. The converters
must not fail more than once every twenty-five
years. Increased availability is achieved by extensive sectioning of both the main circuit and
the auxiliary systems. In addition, all control
and protection systems are duplicated, as well
as auxiliary systems such as auxiliary power
and emergency battery systems.
2. New types of all the high-voltage devices subject
to DC have been developed and fitted with
newly-developed polymer insulating materials.
Examples of such devices are voltage dividers,
bypass switches, radio interference capacitors,
disconnectors and post insulators.
3. One of the main goals of the project was to develop a transformer and a bushing for 800 kV.
The foundation for this was the basic research
mentioned above. Prototype bushings were
produced and type-tested. For the transformer,
a mock-up was built to simulate the parts of
ABB
the transformer subject to high DC voltages.
The photos on pages 4 and 7 show the
transformer and wall bushing during test.
4. Design criteria for air clearance have been established. Extensive tests were done at extremely high, previously unused voltages. The
photo to the right show a discharge at over
2 million volts. These flashes are more than
ten meters long. The photo is taken during
an insulation gap test in one of the high-voltage laboratories in Ludvika.
Valve hall clearance testing. Testing
of multiple air gap in corner. Several
flashovers superimposed in one photo.
5. The DCC 800 control and protection system
is a futher development of the proven Mach2
system. Focus has been to satisfy the extreme
reliability demands.
6. A new thyristor and thyristor valve have been
developed to handle the increased voltage
and current.
7. Finally, all critical devices are undergoing
endurance testing in a special endurance
testing station built by ABB at STRI* in Ludvika. The elevated voltage test extends over a
year. The purpose of the test is to verify the
long-term characteristics of the components
used.
5
800 kV UHVDC
Artist view of 800 kV UHVDC switchyard
The market today and tomorrow
In China and India, the demand for energy is
growing dramatically. Every year, China installs
new power generating capacity equivalent to
the entire installed capacity of Sweden. Major
expansion of available hydro power will be
needed to satisfy this demand.
For China, this means to further exploit large
hydro resources in the West of the country.
However, the power is needed in the eastern
and southern parts of the country, so the generated electricity must be transmitted 1 500 to 2 000
kilometers (up to 1 200 miles). Up until now, 600 kV
DC has been used for long-distance transmission
of electric power, over distances of around 1 000
kilometers (about 600 miles).
With the introduction of 800 kV DC it will be possible
to transmit power as far as 3 000 kilometers (over
1 850 miles) with reasonable transmission losses.
China is currently planning to build one 800 kV
Disconnector and RI capacitor
installed at the 800 kV UHVDC test
circuit at STRI, Ludvika
Dielectric testing of 800 kV
UHVDC wall bushing
6
ABB
800 kV UHVDC
Artist view of 800 kV UHVDC switchyard
DC line per year over the next ten years, with a
capacity of between 5 000 and 6 400 MW per line.
India plans to expand hydro power in the northeastern part of the country. As in China, the demand for power is far away from the resources,
so also here the power will have to be transmitted
as far as 2 000 km (up to 1 200 miles). India is
currently planning to build one 800 kV DC line
every two years over the next ten years, with a
capacity of 6 000 MW per line.
Apart from China and India, investigations are
going on to use 800 kV lines in southern parts
of Africa and Brazil.
The conclusion is that 800 kV DC will account
for a significant part of world growth in power
transmission capacity over at least the next ten
years.
Transformer prototype in test room
ABB
7
ABB Power Technologies AB
Grid Systems - HVDC
SE-771 80 Ludvika, Sweden
Tel: +46 240 78 20 00
Fax: +46 240 61 11 59
www.abb.com/hvdc
Pamphlet no POW-0043
It’s time to connect
on
diti
e
d
e
s
evi
r
New
- Technical description of HVDC Light® technology
2
ABB
Table of Contents
1.Introduction
2.Applications
3.Features
4.Products
5.Descriptions
6.System engineering
7.References
8.Index
After the huge blackout in August 2003, a federal order allowed the
first use of the Cross Sound Cable HVDC Light® Interconnector.
The cable interconnection made a major contribution to getting
Long Island out of the dark and restoring power to hundreds
of thousands of customers across Long Island. LIPA Chairman
Richard Kessel heralded Cross Sound Cable as a “national
symbol of how we need to enhance our infrastructure”.
ABB
3
Proven technology in new applications
Our need for energy as a naturally integrated part of society is increasing,
and electricity is increasing its share of the total energy used. It is truer than
ever that electricity is a base for building a modern society, but also a principal tool for increasing well-being in developing countries. As a result, greater
focus is directed at how the electricity is generated and distributed. In addition, society requests less environmental impact from transmission and generation along with higher reliability and availability. To combine these goals
there is a need for new technologies for transmitting and distributing electrical
energy.
In this book we present our response to these needs, the HVDC Light® technique. HVDC Light® makes invisible underground transmission systems technically and economically viable over long distances. The technology is also
well suited for a number of applications such as power supply to offshore platforms, connecting offshore wind farms, improving grid reliability, city infeed and
powering islands. In these applications, specific characteristics of the technology such as compact and light weight design, short installation and commissioning time, low operation and maintenance costs and superior control of voltages, active and reactive power can be utilized.
It is my true belief that the HVDC Light® technique will actively contribute to
the development of transmission systems, in line with the requests given from
our society.
March 2008
Per Haugland
Senior Vice President
Grid Systems
4
ABB
INTRODUCTION
1 Introduction
1.0 Development of HVDC technology
– historical background
1.1 What is HVDC Light®?
Direct current was the first type of
transmission system used in the very
early days of electrical engineering. Even though the AC transmission system later on came to play a
very important role, the development
of DC transmission has always continued. In the 1930s, the striving for
more and more power again raised
the interest in high voltage DC transmission as an efficient tool for the
transmission of large power volumes
from remote localities. This initiated
the development of mercury arc converters, and more than 20 years later,
in 1954, the world’s first commercial HVDC link based on mercury arc
converters went into service between
the Swedish mainland and the island
of Gotland. This was followed by
many small and larger mercury arc
schemes around the world. Around
20 years later, in the early 1970s, the
thyristor semiconductor started to
replace the mercury converters.
ABB has delivered more than 60
HVDC projects around the world
providing more than 48,000 MW
capacity. The largest bipole delivered is 3150 MW.
Ê£
HVDC Light® is the successful and
environmentally-friendly way to
design a power transmission system
for a submarine cable, an underground cable, using over head lines
or as a back-to-back transmission.
HVDC Light® is HVDC technology
based on voltage source converters
(VSCs). Combined with extruded DC
cables, overhead lines or back-toback, power ratings from a few tenths
of megawatts up to over 1,000 MW
are available. HVDC Light® converters are based on insulated gate
bipolar transistors (IGBTs) and operate with high frequency pulse width
modulation in order to achieve high
speed and, as a consequence, small
filters and independent control of
both active and reactive power.
HVDC Light® cables have extruded
polymer insulation. Their strength
and flexibility make them well suited for severe installation conditions,
both underground as a land cable
and as a submarine cable.
HVDC Light® has the capability to
rapidly control both active and reactive power independently of each
other, to keep the voltage and frequency stable. This gives total flexibility regarding the location of the
converters in the AC system, since
the requirements for the short-circuit
capacity of the connected AC network are low (SCR down to zero).
The HVDC Light® design is based
on a modular concept. For DC voltages up to ± 150 kV, most of the
equipment is installed in enclosures
at the factory. For the highest DC
voltages, the equipment is installed
in buildings. The required sizes of
the site areas for the converter stations are also small. All equipment
except the power transformers is
indoors.
Well-proven and equipment tested
at the factory make installation and
commissioning quick and efficient.
The converter station designs are
based on voltage source converters
employing state-of-the-art turn on/turn
off IGBT power semiconductors.
ÊÓ
Installation of an HVDC Light® station
ABB
5
INTRODUCTION
The stations are designed to be
unmanned. They can be operated
remotely or could even be automatic, based on the needs of the interconnected AC networks. Maintenance requirements are determined
mainly by conventional equipment
such as the AC breakers, cooling
system, etc.
The cable system is supplied complete with cables, accessories and
installation services. The cables are
operated in bipolar mode, one cable
with positive polarity and one cable
with negative polarity.
The cables have polymeric insulating material, which is very strong
and robust.
This strength and flexibility make
the HVDC Light® cables perfect for
severe installation conditions:
- The submarine cables can be laid
in deeper waters and on rough
bottoms.
- The land cables can be installed
less expensively with the ploughing technique.
The environmental benefits are:
- Magnetic fields are eliminated
since HVDC Light® cables are laid
in pairs with DC currents in opposite directions. The magnetic field
from a DC cable is not pulsating
but static - just as the earth’s natural magnetic field. The strength
of the field is 1/10th of the earth’s
natural magnetic field one meter
above the ground immediately
above the cable. Thus there are
no relevant magnetic fields when
using HVDC Light® cables.
- Risk of oil spill, as in paper-oil
insulated cables, is eliminated.
- The cable insulation is an environmentally friendly recyclable
PE based material.
A pair of HVDC Light® land cables
1.2 Reference projects
1.2.1 Gotland HVDC Light®,
Sweden
- Client need
An environmentally-friendly way of
connecting wind power to the load
centre of the grid and high functional
requirements on performance in the
network.
- ABB response
50 MW / ± 25 MVar HVDC Light®
converters and 140 km (2 x 70 km)
± 80 kV HVDC Light® land cables.
Project commissioned 1999.
- The cable metals can be recycled.
- Low smoke generation and no
halogen is emitted if burning.
Power transmission via cables gives
- no visual impact
- no ground current
- no relevant electromagnetic fields.
6
ABB
INTRODUCTION
- Summary – Gotland HVDC Light®
For the Gotland scheme it was possible to develop and implement
practical operational measures
thanks mainly to the experienced
flexibility of HVDC Light®. Essential
aspects to consider were:
• Flicker problems were eliminated
with the installation of HVDC Light®.
Apparently, the transient voltage
control prevents the AC voltage from
locking to the flicker.
• Transient phenomena at which
faults were dominant. This was the
most significant problem.
The parallel connection of HVDC
with the AC grid and the weak grid
in one station make the response
time very important. Even the asynchronous generator behavior has
an impact during AC faults. It has
been shown that a standard voltage
controller cannot be used to manage these situations. The parameter
settings have to consider that the
system must not be too fast in normal operation, and that it has to act
rapidly when something happens,
which has been easily accomplished
with HVDC Light®.
Studies of fault events in the AC
system have shown considerable
improvements in behavior both
during the faults and at recovery,
including improved stability.
HVDC Light® station in Näs, Gotland
ABB
• Stability in the system.
1.2.2 Directlink, Australia
• Power flows, reactive power
demands, as well as voltage levels
in the system. To meet the output
power variation from the wind turbines, an automatic power flow control system has been developed to
minimize the losses and avoid overload on the AC lines. In normal conditions the overall SCADA system
determines the set points for active
and reactive power to minimize the
total losses in the whole system.
This function is important, so that
there is no need for the operators to
be on line and to carry out the control manually.
- Client need
Environmentally-friendly power link
for power trading between two
states in Australia.
Overall experiences are that the
control of the power flow from the
converters makes the AC grid easier to supervise than a conventional
AC network, and the power variations do not stress the AC grid as
much as in normal networks. Voltage quality has also improved with
the increased wind power production. Sensitive customers, such as
big industrial companies, now suffer
less from disturbances due to voltage dips and other voltage quality
imperfections. Even if the network
cannot manage all AC faults, the
average behavior over a year points
to much better voltage quality.
- ABB response
3 x 60 MW HVDC Light® converters and 390 km (6 x 65 km) ± 80kV
HVDC Light® land cables.
Project commissioned 2000.
- Summary – Directlink
Directlink is a 180 MVA HVDC Light®
project, consisting of three parallel
60 MVA transmission links that connect the regional electricity markets
of New South Wales and Queensland. Directlink is a non-regulated
project, operating as a generator
by delivering energy to the highest
value regional market.
The Directlink project features three
innovations which minimize its environmental, aesthetic and commercial impact: the cable is buried
underground for the entire 65 km;
it is an entrepreneurial project that
was paid for by its developers, and
the flow of energy over HVDC Light®
facilities can be precisely defined
and controlled. The voltage source
converter terminals can act independently of each other to provide
ancillary services (such as VAR support) in the weak networks to which
Directlink connects.
Experience with the operation of
Directlink with three parallel links
started in the middle of 2000 and
confirms the expected excellent
behavior of the controllability of the
transmission.
7
INTRODUCTION
1.2.3 Tjæreborg, Denmark
- Client need
A small-scale HVDC Light® system
to be used for testing optimal transmission from wind power generation.
- ABB response
8 MVA HVDC Light® converters and
9 km (2 x 4.5 km) ± 9 kV HVDC Light®
land cables. Project commissioned
2000.
- Summary – Tjæreborg
HVDC Light®
The purpose of the Tjæreborg HVDC
project was to investigate how the
controllability of HVDC Light® could
be used for optimal exploitation of
the wind energy by using the converter to provide a collective variable
frequency to the wind turbines. The
Tjæreborg wind farm can either be
connected via the AC transmission
only, or via the DC transmission only,
or via the AC and the DC cables in
parallel. The HVDC Light® control
system is designed to connect via
the AC transmission automatically if
the wind power production is below
500 kW, and via the DC cables if the
power is higher than 700 kW.
Experience has been gained of the
successful use of HVDC Light® for:
• Starting and stopping the wind turbines at low and high wind speeds.
• Smooth automatic switching
between the AC and DC transmission by automatically synchronizing
the wind turbines to the AC grid.
• Start against black network. This
was tested, as an isolated AC grid,
e.g. an islanded wind farm has to be
energized from the DC transmission.
• With a connected wind turbine
generator, the frequency was varied
between 46 and 50 Hz. A separate
test without connected wind turbines demonstrated that the HVDC
Light® inverter frequency could be
varied between 30 Hz and 65 Hz
without any problems.
The Tjæreborg HVDC Light® station
Directlink HVDC Light® station 3 x 60 MW
8
ABB
INTRODUCTION
1.2.4 Eagle Pass, US
1.2.5 Cross Sound Cable, US
- Client need
Stabilization of AC voltage and possibility to import power from Mexico
during emergencies.
- Client need
Environmentally-friendly controllable
power transmission to Long Island.
- ABB response
36 MVA HVDC Light® back-to-back
converters. Project commissioned
2000.
- Summary – Eagle Pass
HVDC Light® back-to-back was
chosen since other alternatives
would have been more expensive,
and building a new AC line would
have faced the added impediment
of having to overcome difficulties
in acquiring the necessary rights
of way. Furthermore, if an HVDC
back-to-back based on conventional technology had been considered,
there were concerns that such a
solution might not provide the necessary level of reliability because of
the weakness of the AC system on
the U.S. side of the border.
To mitigate possible voltage instability and, at the same time, to allow
power exchange in either direction
between the U.S. and Mexico without first having to disrupt service to
distribution system customers, an
HVDC Light® back-to-back rated at
36 MVA at 138 kV was installed and
commissioned.
- ABB response
330 MW MW HVDC Light® converters and 84 km (2 x 42 km) ±150 kV
HVDC Light® submarine cables.
Project commissioned 2002.
The two HVDC Light® power cables
and the multi-fiber optic cable were
laid bundled together to minimize
the impact on the sea bottom and to
protect oysters, scallops and other
living species. The cables were buried six feet into the sea floor to give
protection against fishing gear and
ships’ anchors. The submarine Fiber
Optic cable is furnished with 192
fibers.
- Summary – Cross Sound Cable
The Cross Sound Cable project is
a 42 km HVDC Light® transmission
between New Haven, Connecticut and Shoreham on Long Island
outside New York. It provides the
transmission of electric energy to
Long Island. The rating is 330 MW
with the possibility of both local and
remote control.
Testing of the Cross Sound Cable
project was completed in August
2002. The big blackout in the northeastern states happened on August
14 2003, and the Cross Sound
transmission became an important
power supply route to Long Island
when restoring the network during
the blackout.
Some hours after the blackout, a
federal order was given to start
emergency operation. In addition to
providing power to Long Island, the
AC voltage control provided by the
link of both the Long Island and the
Connecticut networks showed that
it could keep the AC voltages constant. During the thunderstorms that
occurred before the networks were
completely restored, several +100
to –70 Mvar swings were noticed
over 20 seconds. AC voltage was
kept constant. The transmission
remained in emergency operation
during the fall of 2003. The owner
has concluded that the cable interconnection made a major contribution to getting Long Island out of the
dark and restoring power to hundreds of thousands of customers
across Long Island.
HVDC Light® station at Shoreham
Steady-State 100 MW CT —> LI
during thunderstorm. ACVC APC SHM.
Measurement in Shoreham Converter
Station (DASH-18) Sunday 17 August
2003 – 18:48:00.000
ABB
9
INTRODUCTION
1.2.6 MurrayLink, Australia
- Client need
Environmentally-friendly power link
for power trading between two
states in Australia.
- ABB response
200 MW HVDC Light® converters
and 360 km (2 x 180 km) ±150 kV
HVDC Light® land cables. Project
commissioned 2002.
- Summary – MurrayLink
MurrayLink is a 180 km underground 200 MW transmission system between Red Cliffs, Victoria and
Berry, South Australia. It links regional
electricity markets and uses the ability of HVDC Light® technology to control power flow over the facility. The
voltage source converter terminals
can act independently of each other
to provide ancillary services (such as
var support and voltage control) in
the weak networks to which it is connected. Operating experience is that
its AC voltage control considerably
improves voltage stability and power
quality in the connected networks. In
addition, shunt reactors in neighboring networks can normally be disconnected when the link’s AC voltage control is on.
Cable transport for MurrayLink project
On the loss of an AC line, there is a
run-back from 200 MW to zero.
The project has won the Case
EARTH Award for Environmental
Excellence.
Cable laying for MurrayLink project
10
ABB
INTRODUCTION
1.2.7 Troll A, Norway
- Client need
Environmentally-friendly electric power to feed compressors to
increase the natural gas production
of the platform, combined with little
need of manpower for operation.
- ABB response
2 x 40 MW HVDC Light® converters and 272 km (4 x 68 km) ±60
kV HVDC Light® submarine cables.
Project commissioned 2005.
- Summary – Troll A
With the Troll A pre-compression
project, HVDC transmission converters are, for the first time, being
installed offshore on a platform. The
transmission design for this first
implementation is for 40 MW,
ABB
±60 kV, and converters for two
identical transmissions have been
installed and tested. On the Troll A
platform, the HVDC Light® transmission system will directly feed a highvoltage variable-speed synchronous
machine designed for compressor
drive with variable frequency and
variable voltage, from zero to max
speed (0-63 Hz) and from zero to
max voltage (0-56 kV).
The inverter control software has
been adapted to perform motor
speed and torque control. The control hardware is identical for rectifier
and motor converters.
always maintained. There is no telecommunication for control between
the rectifier control on land and the
inverter motor control on the platform - the only quantity that can be
detected at both ends of the transmission is the DC-link voltage.
However, the control system has
been designed so that, together with
a telecommunication link, it could
provide for land-based operation,
faultfinding and maintenance of the
platform station.
Over the entire motor operating
range, unity power factor and low
harmonics are assured, while sufficiently high dynamic response is
11
INTRODUCTION
1.2.8 Estlink HVDC Light® link,
Estonia - Finland
- Client need
Improved security of the electricity
supply in the Baltic States and Finland.
Reduced dependence of the Baltic power systems and an alternative electricity purchase channel to
cover potential deficits in generating
capacity.
- ABB response
350 MW HVDC Light® converters and
210 km (2 x 105 km) ± 150 kV HVDC
Light®‚ submarine/land cables. Project commissioned 2006.
- Summary – Estlink
Estlink is a 350 MW, 31 km underground/ 74 km submarine cable
transmission between the Harku
substation in Estonia and Espoo
substation in Finland. It links the
Baltic power system to the Nordpool market and uses the ability of
HVDC Light® technology to control
the power flow over the facility. The
voltage source converter terminals
can act independently of each other
to provide ancillary services (such
as var support and voltage control),
thereby improving the voltage stability of the Estonian grid. The blackstart capability is implemented at
the Estonian side i.e. the converter
is automatically switched to household operation if the AC grid is lost
making a fast energization of the
network possible after a blackout
in the Estonian network. The implementation phase of the project was
19 months, and the link has been in
operation since the end of 2006.
The HVDC Light® station at Harku on the Estonian side of the link.
12
ABB
INTRODUCTION
1.2.9 Valhall Re-development
Project
- Client need
Supply of electric power from shore,
to replace existing gas turbines
offshore and feed the entire existing field, as well as a new platform.
The important issues are to minimize
emissions of CO2 and other climate
gases and, at the same time, to
reduce the operating and maintenance costs of electricity offshore.
- ABB response
HVDC Light® converter stations
onshore and offshore rated 78 MW
at 150 kV. The project will be commissioned 2009.
- Summary - Valhall
Re-development project
As a part of the redevelopment of the
Valhall field in the Norwegian sector,
ABB will provide the converter stations to enable 78 MW to be supplied
over a distance of almost 300 km from
shore to run the entire field facilities,
including a new production and living
quarters platform.
The main factors behind the decision
to choose power from shore were:
- reduced costs
- improved operational efficiency
- minimized greenhouse gas emissions
- improvement of all HSE elements
These factors contribute to the customer BP’s vision of a safe, intelligent,
maintenance-free and remotely controllable field of the future. In addition,
the HVDC Light® system will provide
a very high quality electric supply
with respect to voltage and frequency, including during direct online
start-up of the large gas compressor
motors, thereby eliminating the need
for additional soft start equipment.
The onshore station will be located
at Lista on Norway’s southern coast.
Here the alternating current will be
taken from the Norwegian grid at
300 kV and converted to direct current. This will be transmitted at 150 kV
over a distance of 292 km via a single power cable with an integrated
metallic return conductor to the new
Valhall platform. There it will be converted back to AC power at 11 kV
in the HVDC module and distributed to
all the platforms in the Valhall field.
Valhall Power from shore project
Offshore Station, Valhall
ABB
13
INTRODUCTION
1.2.10 NordE.ON 1 offshore
wind connection - Germany
- Client need
A 200 km long submarine/land cable
connection from an offshore wind park
to be operational within 24 months.
- ABB response
400 MW HVDC Light® converters,
one offshore on a platform and one
land-based and 400 km (2 x 200
km) ±150 kV HVDC Light® submarine/land cables. The project will be
commissioned 2009.
- Summary - NordE.ON 1 offshore
wind connection
The NordE.ON 1 offshore wind farm
cluster will be connected to the German grid by a 400 MW HVDC Light®
transmission system, comprising 75
km underground and 128 km submarine cable. Full Grid Code compliance
ensures a robust network connection.
For both the offshore and the onshore
part, most equipment will be installed
indoors, thus ensuring safe operation
and minimal environmental impact.
Independent control of active and
reactive power flow with total control
of power from zero to full power without filter switching enables smooth
and reliable operation of the offshore
wind farm.
A proven extruded cable technology
is used that simplifies installation on
land and at sea allowing very short
time for cable jointing. The oil-free
HVDC Light® cables minimize the
environmental impact at sea and on
land.
In operation, the wind power project
will reduce CO2 emissions by nearly
1.5 million tons per year by replacing
fossil-fuel generation.
The transmission system supports
wind power development in Germany.
1.2.11 Caprivi Link
Interconnector
- Client need
Import of hydro power and coalfired power from Zambia to ensure
a secure power supply in Namibia
utilizing an HVDC Light® interconnection of two weak AC networks
through a 970 km long ±350 kV
overhead line.
In addition:
- Accurate AC voltage control of
the weak interconnected AC
networks.
- Feed of a passive AC network in
the Caprivi strip.
- ABB response
HVDC Light® converter stations
designed for a DC voltage of
±350 kV to ground, to be built
in two stages:
- first stage: a monopole 300 MW
(-350 kV to ground)
- second stage: an upgrade to
2 x 300 MW bipole (±350 kV).
The monopole will be put into operation at the end of year 2009. Electrode stations about 25 km from the
converter stations.
- Summary – Caprivi Link
Interconnector
The Caprivi Link Interconnector will
be a 2 x 300 MW interconnection
between the Zambezi converter station in the Caprivi strip in Namibia, close to the border of Zambia,
and the Gerus converter station,
about 300 km North of Windhoek
in Namibia. The AC voltages are
320 kV and 400 kV at Zambezi and
Gerus respectively.
The converter stations will be interconnected by a 970 km long, bipolar ±350 kV DC overhead line. The
conductors of both the negative
and positive polarity will be mounted on the same poles. There will be
double-circuit electrode lines with a
length of about 25 km.
The NordE.ON 1 offshore wind connection
14
ABB
INTRODUCTION
In the monopole stage, the link will
be operated with parallel DC lines
and earth return to reduce line losses. In the bipole stage, the link will
be operated as a balanced bipole
with zero ground current.
The condition for the upgrade to a
2 x 300 MW bipole is that the AC
networks at Zambezi and Gerus are
reinforced, including a new connection to the Hwange coal fired power
station in Zimbabwe.
In the event of outage of the connecting AC lines to Zambezi during
power import to Namibia, the power
transmission can be reversed rapidly
in order to re-energize and feed the
black AC network at Zambezi.
The AC networks of today are
extremely weak at both ends, with
short-circuit power levels of around
300 MVA and long AC lines which
connect to remote generator stations. Due to this fact, the AC networks are also exposed to a risk of
50 Hz resonance. ABB has studied
the crucial AC and DC fault cases
and verified that the dynamic performance of the HVDC Light® is in line
with the requirements of the client.
The Zambezi and Gerus converter
stations will control the AC voltages
in the surrounding grids rapidly and
accurately over the entire range of
active power capability, by a continuous adjustment of the reactive power
absorption and generation between
- 130 Mvar and + 130 Mvar.
The client evaluated possible transmission alternatives and found that
the HVDC Light® technology is the
most feasible economically and
technically solution.
The Caprivi Link
Interconnector
Station Layout, Caprivi Link Interconnector
ABB
15
APPLICATIONS
2 Applications
2.1 General
A power system depends on stable
and reliable control of active and
reactive power to keep its integrity. Losing this control may lead to
a system collapse. Voltage source
converter (VSC) transmission system technology, such as HVDC
Light®, has the advantage of being
able almost instantly to change its
working point within its capability,
and to control active and reactive
power independently. This can be
used to support the grid with the
best mixture of active and reactive
power during stressed conditions.
In many cases, a mix of active and
reactive power is the best solution compared with active or reactive power only. VSC transmission
systems can therefore give added
support to the grid.
2.2 Cable transmission systems
2.2.1 Submarine cables
- Power supply to islands
The power supply to small islands
is often provided by expensive local
generation, e.g. diesel generation.
By installing an HVDC Light® transmission system, electricity from the
mainland grid can be imported.
Another issue is the environmental benefits to the island by reducing
emission from local generation.
Since HVDC Light® is based on VSC
technology, the converter can operate without any other voltage source
on the island, i.e. no local generation
on the island is needed for proper
operation of the system.
- Remote small-scale generation
As an example, simulations done at
ABB have shown that, for a parallel case (AC line and DC transmission), where the VSC transmission
system is connected in parallel with
an AC system, the VSC transmission system can damp oscillations
2-3 times better than reactive shunt
compensation.
Remote small-scale generating facilities are very often located on islands
that will not need all the generated
power in all situations. This power
can then be transmitted by HVDC
Light® to a consumer area on the
mainland or an adjacent island.
The benefits with a VSC transmission system during a grid restoration can be considerable, since it
can control voltage and stabilize frequency when active power is available at the remote end. The frequency control is then not limited
in the same way as a conventional
power plant where boiler dynamics
may limit the operation during grid
restoration.
The advantages of HVDC Light®
are of high value when connecting
between individual power systems,
especially when they are asynchronous. This refers to the possibilities
for controlling the transmitted power
to an undertaken value, as well as
being able to provide and control
reactive power and voltage in both
the connected networks.
With the above benefits, HVDC
Light® is the preferred system to
be used for a variety of transmission applications, using submarine
cables, land cables and back-toback.
16
- Interconnecting power systems
- from the shore to the platform
- from platform to shore
- between platforms
The most important and desirable
characteristics for offshore platform
installations are the low weight and
volume of the HVDC Light® converter.
Offshore, the converter is located
inside a module with a controlled
environment, which makes it possible to design the converter even
smaller for an offshore installation
than for a normal onshore converter
station.
2.2.2 Underground cables
- Interconnections
The environmental advantages of
HVDC Light® are of high value when
connecting two power systems. This
refers to the possibilities for controlling the transmitted power to the
desired value, as well as improving
AC network stability by providing and
controlling reactive power and voltage support in the connected networks. Other important factors are:
avoiding loop flows, sharing of spinning reserve, emergency power etc.
The rapid AC voltage control by
HVDC Light® converters can also be
used to operate the connected AC
networks close to their maximum
permitted AC voltage and in this way
to reduce the line losses in the connected AC networks.
- Power to/from/between Offshore
platforms
With its small footprint and its possibilities to operate at low short-circuit
power levels or even to operate with
a “black” network, HVDC Light® has
made it possible to bring electricity:
ABB
APPLICATIONS
- Bottlenecks
In addition to the power transmitted by
the HVDC Light® system, an HVDC
Light® transmission in parallel with
an existing AC line will increase the
transmitting capacity of the AC line
by the inherent voltage support and
power stabilizing capability of the
HVDC Light® system.
- Infeed to cities
Adding new transmission capacity
via AC lines into city centers is costly and in many cases the permits
for new right-of-ways are difficult to
obtain. An HVDC Light® cable needs
less space than an AC overhead line
and can carry more power than an
AC cable, and therefore it is often
the only practical solution, should
the city center need more power.
Also, the small footprint of the HVDC
Light® converter is of importance for
realizing city infeed. Another benefit of HVDC Light® is that it does not
increase the short-circuit current in
the connected AC networks.
2.3 DC OH lines
HVDC Light® converters can operate in combination with DC overhead lines forming a proper transmission system. An example of this
is the Caprivi Link Interconnector in
Namibia.
- see 1.2.11
2.4 Back-to-back
A back-to-back station consists of
two HVDC Light® converters located
close to each other, i.e. with no DC
cables in between.
ABB
2.4.1 Asynchronous Connection
If the AC network is divided into different asynchronous areas, connection between the areas can easily
be done with HVDC back-to-back
converters. This gives a number of
advantages:
- Sharing of spinning reserve.
- Emergency power exchange
between the networks
- Better utilization of installed generation in both networks
- Voltage support
- etc.
In many cases, the connection
between two asynchronous areas
is made at a weak connection point
in AC systems on the borders of
the areas. With its possibilities of
operating at low short-circuit ratios,
HVDC Light® is very suitable for this
type of connection.
2.4.2 Connection of important
loads
For sensitive loads, an HVDC Light®
back-to-back system is of importance for keeping the AC voltage
and AC frequency on proper levels if
the quality of those properties of the
connected AC network is not sufficient for the connected load. The
fast reactive power control properties of HVDC Light® can be used for
flicker mitigation.
2.5 HVDC Light® and wind power generation
This is contrary to conventional AC
transmission systems, which normally
require a high SCR compared with
the power to be entered. With the
imminent arrival of wind power farms
and accounting for a considerable
share of the total power generation
in a network, wind power farms will
have to be as robust as conventional
power plants and stay online during
various contingencies in the AC network. Various types of compensation will then be needed to preserve
power quality and/or even the stability of the network.
HVDC Light® does not require any
additional compensation, as this
is inherent in the converters. It will
therefore be an excellent tool for
bringing wind power into a network
2.6 Comparison of AC, conventional HVDC and HVDC Light®
- Comparison of DC cable system and AC cable system
DC cable system
- No limit on cable length
- No intermediate station needed
- No increase of capacitance in the
AC network (avoids low-order resonances)
- Lower losses
AC cable system
- Cable capacitance limits the practical cable length
- Reactive compensation is needed
HVDC Light® is a transmission system which has characteristics suitable for connecting large amounts
of wind power to networks, even at
weak points in a network, and without having to improve the short-circuit ratio.
17
APPLICATIONS
Comparison of HVDC Light® and conventional HVDC
- HVDC Light®, power from
50 – 1100 MW
IGBT used as active component
in valves
The pulse width controls both
active and reactive power
- The IGBT can be switched off with
a control signal. Fully controllable.
=forced commutation up to 2000 Hz
- Each terminal is an HVDC
converter plus an SVC
- Suitable both for submarine and
land cable connections
- Multi-chip design
- Advanced system features
- Forward blocking only
- Footprint (e.g. 550 MW):
120 x 50 x 11 meters
- Current limiting characteristics
- Short delivery time
- Gate turn-off and fully controllable;
forced commutation
- High-speed device
- Conventional HVDC, power up
to 6400 MW
Thyristor used as active
component in valves
Phase angle control
Pmax
Pmin
- The thyristor cannot be switched
off with a control signal.
- Most economical way to transmit
power over long distances.
- Long submarine cable
connections.
- Around three times more power in
a right-of-way than overhead AC
- Footprint (e.g. 600 MW):
200 x 120 x 22 meters
18
- It automatically ceases to conduct
when the voltage reverses.
- Single silicon wafer
= line commutated, 50/60 Hz
- Both forward and reverse blocking capability
- Very high surge current capability
- No gate turn-off; line commutated
ABB
APPLICATIONS
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- Lower trace: DC Voltage
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- Middle trace: Valve voltage
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- Lower trace: DC voltage
ABB
19
APPLICATIONS
- Simplified single-line diagram for HVDC Light®
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20
ABB
APPLICATIONS
- An HVDC Light® can control both active and reactive power
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- Reactive power exchange for conventional HVDC
- Continuously variable power from
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- Emergency power support
- Increase power in parallel AC lines
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- Additional reactive shunt compensation is not required. (Only small
harmonic filters are needed.)
- The HVDC Light® stations can be
operated as STATCOMs, even if
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connected to the DC line (staged
implementation: build one or two
stations for voltage stabilization
– connect them later with cables
and you have an interconnection).
21
APPLICATIONS
2.7.2 Undergrounding by cables
2.8 HVDC Light® cables
- No visible impact of overhead lines
– underground cables instead
2.8.1 Long lifetime with HVDC
- Easier to get permission
- No relevant electromagnetic fields
- No audible noise, unlike OH lines
2.7.3 Required site area for
converters
- Less space per MW required than
for conventional HVDC
- Indoor design - reduced risk of
flashover
- Small space requirement and low
weight are very important for offshore applications
2.7.4 Environmentally sound
- Audible sound reduced by indoor
design
- Stations look like any ordinary
industrial building, no outdoor
switchyards
- Low building height
- Bipolar operation – no need for
electrodes
2.7.5 Energy trading
- Fast and accurate power control –
you get the power you want
- No filter switching at power change
- Smooth power reversal (step less
power transfer around zero MW)
22
The inherent lifetime of insulating
materials is better for HVDC than
for AC.
2.8.2 Submarine cables
- Low losses
HVDC cables are generally much
more efficient for long-distance
transmissions than AC cables, in
particular for high powers.
The reason is that AC cables must
be rated for the capacitive charging current, in addition to the transmitted active current. The capacitive
charging current is proportional to
the length and the voltage of the AC
cable and beyond a certain distance
there is no capacity left for the active
power transmission. DC cables have
no capacitive charging current, i.e.
all the transmission capacity of the
cable is available for active power
transmission. The capacitive reactive
power generated by long AC cables
must be taken care of.
To avoid ferromagnetic losses AC
submarine cables need non-magnetic material for the wire armor,
thus copper or aluminum alloy or
non-magnetic stainless steel wires
are used.
For DC cables, there are no magnetic losses, hence galvanized steel
wires, can be used for the tensile
armor.
The following example shows the
difference:
Transmission of 550 MW by submarine cables for a distance of 75 km:
HVDC cable:
150 kV HVDC Light® cables, 2
cables with copper conductor
cross-section of 1400 mm2 and
steel wire tensile armor. The weight
of the two cables is 2 x 32 kg/m =
64 kg/m.
AC cable:
220 kV XLPE cable, 3 cables with
copper conductor cross-section
of 1600 mm2 and copper wire tensile armor. The weight of the three
cables is 3 x 60 kg/m = 180 kg/m.
- Deep sea waters
HVDC Light® cables are suitable for
large water depths, for the following
reasons:
- The polymeric insulation is
mechanically robust.
- The HVDC cables are generally less heavy than AC cables for
the same transferred power. This
gives lower tensile force during
laying of the cables.
- It is advantageous to use galvanized steel wires for tensile armor.
A galvanized steel wire has better tensile properties than most
non-magnetic materials that can
be used.
ABB
APPLICATIONS
- Laying and repair
HVDC Light® cables are very flexible
with respect to various installation
methods, due to their robust and
flexible insulation material. Should a
repair be required, the availability of
suitable cable ships is thus good.
- The cable can be coiled on a
cable laying ship (except for
cables with double cross laid
armor for large depths). The possibility of coiling the cables makes
it possible to lay the cable from
small barges and transport the
cable by cargo ships without turntables for the cables.
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Typical laying and trenching operation
- It is possible in most cases to lay
the two cables of the bipole close
to each other (e.g. by bundling of
the cables) in one common trench.
- The bending radius of the polymeric insulated HVDC Light® cable
is smaller compared with paperinsulated cables, which makes it
possible to use laying ships with
a smaller pay-off wheel, and also
smaller trenching equipment.
- Good resistance when installed
Particularly when comparing with
paper-oil insulated cables, the HVDC
Light® cables can resist repeated bending without fatigue of the
insulation. This is critical for cables
hanging in spans over an uneven
sea bed.
Coiled cable on small cable laying barge
ABB
23
APPLICATIONS
2.8.3 Underground Cables
- Permitting
In many cases it is easier to get
right of way for underground cables,
compared with overhead transmission lines. The main reasons are:
- Less visual impact
- Smaller width of the required right
of way.
- Handling
HVDC Light® cables have many
advantages compared with other
cable types, e.g.:
- HVDC Light cables have smaller bending radius compared
with paper insulated cables. This
makes it possible to use smaller
cable drums for transportation,
and makes it possible to use compact installation, e.g. on offshore
platforms. The smaller bending
radius also makes it possible to go
around obstacles such as rocks,
etc.
- Minimum bending radius for
standard designs
During installation, the bending radius
should exceed 18 x De.
When the cable is installed (no force
applied to the cable), the bending
radius must exceed 12 x De.
De is the external diameter of the cable.
- Maximum pulling forces for land
cables
When the pulling nose is attached to
the conductor, the following tensile
forces should not be exceeded:
- 70 N/mm2 for Cu conductors
®
- HVDC Light® cables are possible
to handle at lower temperatures
compared with paper insulated
cables.
- 40 N/mm2 for Al conductors
- Jointing
HVDC Light® cable joints are usually installed inside a portable jointing
house, which is placed in the joint
bay. This pre-built jointing house
provides adequate light, dust control, clean work surfaces and cable
stands to place the joint within comfortable reach of the cable jointers.
A crew of two cable jointers usually works together as a team. A joint
crew can complete one of these
joints in one working day.
- No magnetic fields of power frequency
There is no power frequency magnetic field from a DC cable; there is
only a static magnetic field, similar to
the earth’s magnetic field.
Recommended levels of static magnetic field strength are significantly higher than for power frequency
fields (from AC power lines), since
there is no induction effect, and the
magnetic fields are similar to that of
the earth itself.
A conventional mono-polar HVDC
cable scheme with a current of 1000
amps gives a magnetic field of 20
micro-Tesla magnitude at a distance
of 10 meters. This is approximately
half the magnitude of the earth’s natural magnetic field. With HVDC Light®
Cables, the magnetic field is reduced
to less than 0.2 micro-Tesla, which
is less than 1% of the natural magnetism.
Jointing container, placed over the
cables during jointing at MurrayLink.
24
ABB
FEATURES
3 Features
3.1 Independent power transfer
and power quality control
3.2 Absolute and predictable power transfer and voltage control
The HVDC Light® system allows
fully independent control of both
the active and the reactive power
flow within the operating range of
the HVDC Light® system. The active
power can be continuously controlled from full power export to full
power import. Normally each station controls its reactive power flow
independently of the other station.
However, the flow of active power
to the DC network must be balanced, which means that the active
power leaving the DC network must
be equal to the active power coming into the DC network, minus the
losses in the HVDC Light® system. A
difference in power would imply that
the DC voltage in the system would
rapidly increase or decrease, as the
DC capacitor increases its voltage
with increased charge. In a normal
design, the stored energy is equivalent to around 2 ms power transmission on the system. To attain this
power balance, one of the stations
controls the DC voltage.
The active power flow can be determined either by means of an active
power order or by means of frequency control.
This means that the other station
can arbitrarily adjust the transmitted power within the power capability limits of the HVDC Light® system,
whereby the station that controls
the DC voltage will adjust its power
to ensure that the balance (i.e. constant DC voltage) is maintained. The
balance is attained without telecommunication between the stations,
quite simply based on measurement
of the DC voltage.
Unlike conventional HVDC converters, the HVDC Light® converter can
operate at very low power, and even
at zero power. The active and reactive powers are controlled independently, and at zero active power the
full range of reactive power can be
utilized.
ABB
The converter stations can be set to
generate reactive power through a
reactive power order, or to maintain
a desired voltage level in the connected AC network.
The converter’s internal control loop
is active and reactive current, controlled through measurement of the
current in the converter inductor and
using orders from settings of active
and reactive power which an operator can make.
In an AC network, the voltage at
a certain point can be increased/
reduced through the generation/
consumption of reactive power. This
means that HVDC Light® can control the AC voltage independently in
each station.
3.3 Low power operation
3.4 Power reversal
The HVDC Light® transmission system can transmit active power in
any of the two directions with the
same control setup and with the
same main circuit configuration. This
means that an active power transfer can be quickly reversed without
any change of control mode, and
without any filter switching or converter blocking. The power reversal
is obtained by changing the direction of the DC current and not by
changing the polarity of the DC voltage as for conventional HVDC. The
speed of the reversal is determined
by the network. The converter could
reverse to full power in milliseconds
if needed.
The reactive power controller operates simultaneously and independently in order to keep the ordered
reactive power exchange unaffected
during the power reversal.
3.5 Reduced power losses in connected AC systems
By controlling the grid voltage level,
HVDC Light® can reduce losses in
the connected grid. Both transmission line ohmic losses and generator magnetization losses can be
reduced. Significant loss reductions
can be obtained in each of the connected networks.
3.6 Increased transfer capacity
in the existing system
- Voltage increase
The rapid and accurate voltage control capability of the HVDC Light®
converter makes it possible to operate the grid closer to the upper limit.
Transient overvoltages would be
counteracted by the rapid reactive
power response. The higher voltage level would allow more power to
be transferred through the AC lines
without exceeding the current limits.
25
FEATURES
- Stability margins
Limiting factors for power transfer in the transmission grid also
include voltage stability. If such grid
conditions occur where the grid is
exposed to an imminent voltage collapse, HVDC Light® can support
the grid with the necessary reactive
power. The grid operator can allow
a higher transmission in the grid if
the amount of reactive power support that the HVDC Light® converter
can provide is known. The transfer
increase in the grid is larger than the
installed MVA capacity of the HVDC
Light® converter.
3.7 Powerful damping control
using P and Q simultaneously
As well as voltage stability, rotor
angle stability is a limiting factor for
power transfer in a transmission
grid. HVDC Light® is a powerful tool
for damping angle (electro-mechanical) oscillation. The electromechanical oscillations can be rather complex with many modes and many
constituent parts. It is therefore
not always possible to find robust
damping algorithms that do not
excite other modes when damping
the first ones. Many control methods that influence the transmission
capacity can experience difficulties
in these complex situations. Modulating shaft power to generators,
switching on and off load demand
or using an HVDC Light® connected
to an asynchronous grid are methods that can then be considered.
These methods have the advantage
that they actually take away or inject
energy to damp the oscillations.
26
HVDC Light® is able to do this in a
number of ways:
- by modulating the active power
flow and keeping the voltage as
stable as possible
- by keeping the active power constant and modulating the reactive
power to achieve damping (SVCtype damping)
Line current, power flow or local frequency may be used as indicators,
but direct measurement of the voltage angle by means of Phasor Measurement Units can also be a solution to achieve observability.
3.8 Fast restoration after blackouts
HVDC Light® can aid grid restoration in a very favorable way. Voltage support and frequency support
are much needed during such conditions. This was proven in August
2003, when the north-east USA
experienced a blackout, by the
excellent performance of the Cross
Sound Cable Project that interconnects Connecticut and Long
Island. A black-start capability can
be implemented. It can be beneficial for an HVDC Light® operator to
speed up grid restoration because
the lack of energy (typically the first
6-24 hours) may initiate considerably
higher prices for energy. The blackstart facility is implemented on the
Estonian side of the Estlink HVDC
Light® Project.
3.9 Islanded operation
The HVDC Light® converter station normally follows the AC voltage
of the connected grid. The voltage
magnitude and frequency are determined by the control systems of the
generating stations. In the event of a
voltage collapse, a “black-out”, the
HVDC Light® converter can instantaneously switch over to its own internal voltage and frequency reference
and disconnect itself from the grid.
The converter can then operate as
an idling “static” generator, ready
to be connected to a “black” network to provide the first electricity to
important loads. The only precondition is that the converter at the other
end of the DC cable is unaffected by
the black-out.
3.10 Flexibility in design
The HVDC Light® station consists of
four parts:
- The DC yard, with DC filtering and
switches
- The converter, with the IGBT
valves and the converter reactors
- The AC filter yard
- The grid interface, with power
transformer and switches
The different parts are interconnected with HV cables, which make it
easy to separate the parts physically,
so as to fit them into available sites.
ABB
FEATURES
3.11 Undergrounding
Except for back-to-back, HVDC
Light® always employs HV cables for
DC power transmission. The cables
are buried all the way into the DC
part of each converter building. When
the landscape has been restored
after the cable laying, the transmission route quickly becomes invisible.
3.12 No relevant magnetic fields
The two HVDC Light® cables can
normally be laid close together. As
they carry the same current in opposite directions, the magnetic fields
from the cables more or less cancel
each other out. The residual magnetic field is extremely low, comparable to the level of the earth’s magnetic field.
Magnetic fields from DC cables are
static fields, which do not cause any
induction effects, as opposed to the
fields from AC cables and lines.
The electromagnetic field around
an HVDC Light® converter installation is quite low, since all apparatus
is located in a building designed to
provide a very efficient shield. The
shielding is needed to minimize emissions in the radiofrequency range, i.e.
radio interference. The background
is that HVDC Light® operates with
high internal current derivatives and a
commutation frequency in the order
of 1-2 kHz. Such transients and fre-
ABB
quencies might cause radio interference if not properly controlled and
shielded. Considering these conditions, the overall and detailed design
has been aimed at ensuring proper mitigation of radio interference
and corresponding fields. The electromagnetic field levels around the
installation are therefore well below
the values stipulated in the relevant
standards for human exposure.
The performance is verified through
measurements.
The HVDC Light® converter installation is connected to the AC power
grid/system through AC overhead
lines or AC cables. Effective filtering prevents current harmonics from
loading into the connected AC lines/
cables. This means that they can
be considered as normal AC lines/
cables installed within the power
grid/system.
3.13 Low environmental impact
The fact that no electric or magnetic clearance from the cables is
needed, and that the converter stations are enclosed in a building,
makes the impact of the transmission system on the environment very
low. The building can be designed
to resemble other buildings in the
neighborhood, and the cables are
not even visible.
3.14 Indoor design
To avoid tall steel supporting structures, to facilitate maintenance and
to improve personal safety, the AC
filters, converter reactors and DC
filters are mounted directly on low
foundations/supports and are kept
within a simple warehouse-style
building with lockable gates and
doors. The building will keep highfrequency emissions and acoustic
noise low and protect the equipment
from adverse weather.
3.15 Short time schedule
The converter valves and associated control and cooling systems
are factory-assembled in transportable enclosures. This ensures rapid
installation and on-site testing of the
core systems.
The building is made up of standardized parts, which are shipped to
the site and quickly assembled.
A typical delivery time from order
to hand-over for operation is 20
months or less, depending of course
on local conditions for converter
sites and cable route.
27
PRODUCTS
4 Products
4.1 General
4.1.2 Typical P/Q diagram
Id
4.1.1 Modular concept
The modular concept of the ABB
IGBT valves and standard voltage
levels of the DC transmission cables
permit different power levels and
mechanical setups to be matched
optimally to each application.
The modularization of HVDC Light®
aims to achieve the most cost-effective technical and topological solution for a specific project, combined
with a short delivery time.
The various configurations provide
the most economical overall solution. The chosen DC voltages are in
line with the ABB High Voltage Cable
(HVC) product range, i.e. 80 kV, 150 kV
and 320 kV. The chosen valve currents are in line with the ABB Semiconductors product range. The
StakPakTM-type IGBTs from ABB
Semiconductors are of a modular design, i.e. the active parts, the
IGBT and diode chips, are organized
in sub-modules. Thus, the current
rating of the device is flexible, ranging in steps, i.e. 2 sub, 4 sub and 6
sub. Each sub-module comprises six
IGBT chips and three diode chips.
HVDC Light® modules
Voltages
28
± 80 kV
± 150 kV
± 320 kV
Sb
Ud
Power transformer
$U
Uc
IR
X tr
UF
If
It
Ut
n
UL
Xc
Simplified circuit diagram
The fundamental base apparent
power at the filter bus between the
converter reactor and the AC filter is
defined as follows (see figure above):
Where:
δ = phase angle between the filter
voltage UF and the converter voltage UC
L = inductance of the converter
reactor
The active and reactive power
components are defined as:
P
U F s U C s sin D
WL
Q
U F s (U F U C ) s cos D
WL
580A (2 sub)
M1
M4
M7
Currents
1140A (4 sub)
M2
M5
M8
1740A (6 sub)
M3
M6
M9
Changing the phase angle controls
the active power flow between the
converter and the filter bus and consequently between the converter
and the AC network.
Changing the amplitude difference
between the filter voltage UF and
the converter voltage UC controls
the reactive power flow between the
converter and the filter bus and consequently between the converter
and the AC network.
ABB
IL
PRODUCTS
,iV̈vˆiÀ
˜ÛiÀÌiÀ
$U
$U
UF
UC
D
UC
UF
D
With the OPWM (Optimized-PulseWidth-Modulation, ref. Section 5.2.3)
control strategy, it is possible to create any phase angle or amplitude
(up to a certain limit) by changing the
PWM pattern. This offers the possibility of controlling both the active
and reactive power independently.
The P/Q diagram shown is for a
back-to-back, i.e. with no distance
between the two stations. The 1st
and 2nd quadrants represent the
rectifier, and the 3rd and 4th the
inverter. A positive value of Q indicates the delivery of reactive power
to the AC network. It should be
noted that the reactive power can
be controlled independently in each
station.
The typical P/Q diagram, which is
valid within the whole steady-state
AC network voltage, is shown in the
figure below.
IR
Note that there are limitations that
have been taken into account in the
calculation of this typical P/Q diagram.
IR
Active power flow
*‡+ʈ>}À>“Ê­Ü…œiÊۜÌ>}iÊÀ>˜}i®
If the UC is in phase-lag, the active
power flows from AC to DC side
(rectifier)
£°Óx
£°Óx
£
If the UC is in phase-lead, the active
power flows from DC to AC side
(inverter)
ä°Çx
ä°x
V̈ÛiÊ*œÜiÀÊ­*°1°®
,i>V̈ÛiÊ«œÜiÀÊ
,i>V̈ÛiÊ«œÜiÀÊ ,i>V̈ÛiÊ«œÜiÀÊ
Vœ˜ÃՓ«Ìˆœ˜
Vœ˜ÃՓ«Ìˆœ˜
}i˜iÀ>̈œ˜
$U
ä°Óx
* ­F ®
£°Óx
£
ä°Çx
ä°x
ä°Óx
ä
ä°Óx
ä°x
ä°Çx
£
£°Óx
ä°Óx
$U $U
ä°x
UF UF
UF
UC
ä°Çx
UC UC
IR
£
IR
IR
Reactive power flow
If UF > UC, there is reactive power
consumption.
•
£°Óx
£°Óx
•
£°Óx
+ ­F ®
£°Óx
,i>V̈ÛiÊ*œÜiÀÊ­*°1°®
Typical P/Q diagram within the whole voltage range. Y-axis: Active power
If UC > UF, there is reactive power
generation.
ABB
29
PRODUCTS
4.2 HVDC Light® modules
For a specific project, the appropriate HVDC Light® module and cable
(if any) have to be selected.
The different HVDC Light® modules
are presented below. The typical
power capacity and total losses for
different cable lengths are also given
for each module. Note that a typical
cable size has been chosen for the
figures in the tables. The procedure
generally used for the selection of a
cable size leads to the minimum permissible cross-sectional area, which
also minimizes the initial investment
cost of the cable.
4.2.1 - 80 kV modules
- Data sheet (power) and power capacity vs. cable lengths
Converter types
Max. DC voltage (pole to ground)
Base power
DC current (IdcN)
M1
M2
M3
kV
80
80
80
MVA
101
199
304
A
627
1233
1881
Data for 80 kV modules, typical values
Converter
DC
voltage
DC
current
DC cable
Sending
power
types
kV
A
Cu in mm2
MW
Receiving power (MW)
Back-to-back
50 km
100 km
200 km
M1
80
627
300
102.0
98.7
96.0
93.0
M2
80
1233
1200
200.5
194.0
191.0
188.5
183.0
M3
80
1881
2800
306.1
296.0
293.0
290.5
285.0
400 km
800
km
274.0
Transfer capability for different cable lengths, typical values 80 kV modules
30
ABB
PRODUCTS
- Typical layout
Example of a 78 MW land station
Converter transformer
AC equipment
Converter reactors
4.5 m
8m
13.2 m
23.5 m
DC equipment
IGBT valves
A- Typical layout of an offshore
module
The offshore station is designed for
compactness, i.e. space and weight
capacities are very expensive and
scarce resources on an offshore
installation in a marine environment.
The offshore environment is very
tough. The high-voltage equipment
is installed inside a module with a
ventilation system designed to protect the high-voltage equipment and
electronics from salt and humid air.
12 m
Example of a 78 MW offshore station
30 m
16 m
Approximate weight: 1280 tonnes
ABB
31
PRODUCTS
4.2.2 - 150 kV modules
- Datasheet (power)
Converter types
Max. DC voltage (pole to ground)
kV
Base power
DC current (IdcN)
M4
M5
M6
150
150
150
MVA
190
373
570
A
627
1233
1881
Data for 150 kV modules, typical values
Converter
DC
voltage
DC
current
DC cable
Sending
power
types
kV
A
Cu in mm2
MW
Back-to-back
50 km
100 km
200 km
M4
150
627
300
191.3
185.0
182.0
179.0
174.0
M5
150
1233
1200
376.0
363.7
361.0
358.0
353.0
342.0
M6
150
1881
2800
573.9
555.1
552.0
549.5
544.0
533.0
Receiving power (MW)
400 km
800 km
Transfer capability for different cable lengths, typical values for 150 kV modules
Typical layout
HVDC Light® 350 MW block
80 x 25 x 11.5 meters
32
ABB
PRODUCTS
4.2.3 - 320 kV modules
- Datasheet (power)
Converter types
Max. DC voltage (pole to ground)
Base power
M7
M8
M9
kV
320
320
320
MVA
405
796
1216
A
627
1233
1881
DC current (IdcN)
Data for 320 kV modules, typical values
Converter
DC
voltage
DC
current
DC
Cable
Sending
power
types
kV
A
Cu in
mm2
MW
Back-toback
50 km
100 km
200 km
400 km
M7
320
627
300
408.1
396.4
391.4
388.8
382.9
370.6
M8
320
1233
1200
802.2
775.7
772.8
770.1
764.2
752.5
729.0
M9
320
1881
2800
1224.4
1184.1
1180.8
1178.1
1172.2
1160.5
1137.0
Receiving power (MW)
800 km
Transfer capability for different cable lengths, typical values for 320 kV modules
ABB
33
PRODUCTS
- Typical layout
11 m
43 m
24 m
HVDC Light® 1000 MW block
90 m
34
ABB
PRODUCTS
4.2.4 Asymmetric HVDC Light®
As an alternative to balanced (±)
DC voltages from the converter, an
alternative has been introduced in
the valve configuration to make an
asymmetric DC voltage possible, i.e.
DC voltage from ground to +DC or
–DC. A monopolar or bipolar HVDC
Light® configuration as used for conventional HVDC can be obtained
by this means. Two fully insulated
DC cables and one medium voltage
cable are needed in the scheme.
The asymmetric HVDC Light® is beneficial for transmission systems with:
- Very high requirements of reliability
and/or availability, i.e. only infeed
to important loads
HVDC Light®
asymmetric modules
Voltages
- Staged increase of transmitted
power for systems with long distances between terminals
- Fulfillment of N-1 criteria. In an
HVDC or HVDC Light® system,
each individual system or pole is a
controllable transmission system,
i.e. the remaining system or pole
will not be subject to overload if
the other system or pole is subject to an outage. Therefore, it is
not necessary to reserve capacity
margins on a DC system in order
to fulfill the N-1 criterion, DC links
can rather be operated at their
rated power, while still fulfilling the
N-1 criterion.
Bipolar HVDC Light® scheme
- Applications with OH lines and
ground electrodes
Currents
580A (2 sub)
1140A (4 sub)
1740A (6 sub)
150kV
M1A
M2A
M3A
320 kV
M4A
M5A
M6A
Matrix of HVDC Light asymmetric modules
®
Converter types
M1A
M2A
M3A
kV
150
150
150
Base power per pole
MVA
94.6
186.5
285
DC current (IdcN)
A
627
1233
1881
Max. DC voltage
(pole to ground)
Data for asymmetric 150 kV modules, typical values per pole
DC
DC
voltage
current
types
kV
M1A
DC cable
Sending
power
A
Cu in
mm2
MW
Back-toback
50 km
100 km
150
627
300
95.6
92.5
90.0
87.1
M2A
150
1233
1200
187.9
181,0
179.0
176.7
171.5
M3A
150
1881
2800
286.9
277.5
274.6
272.3
267.1
Converter
Receiving power per pole (MW)
200 km
400 km
800 km
256.8
Transfer capability for different cable lengths, typical values asymmetric 150 kV modules per pole
ABB
35
Converter types
M4A
M5A
M6A
Max. DC voltage
(pole to ground)
kV
320
320
320
Base power per pole
MVA
202
397
608
DC current (IdcN)
A
627
1233
1881
Data for asymmetric 320 kV modules, typical values per pole
DC
DC
voltage
current
types
kV
M4A
DC cable
Sending
power
A
Cu in
mm2
MW
Back-toback
50 km
100 km
200 km
320
627
300
204.0
197.3
194.1
190.9
185.6
M5A
320
1233
1200
401.0
387.9
385.0
381.8
376.5
364.8
M6A
320
1881
2800
612.1
592.1
588.8
586.1
580.2
568.5
Converter
Receiving power per pole (MW)
400 km
800 km
Transfer capability for different cable lengths, typical values for asymmetric 320 kV modules per pole
4.2.5 Selection of modules
The optimization of the entire project, including both converters and
cables, must be performed individually for each project, since active/
reactive power demand, cable length,
sea/land cable and cable installation
must be considered. In general, it is
more economical to choose a lower
voltage and higher current for short
distances. For longer distances, it is
more economical in most cases from
the point of view of cable cost and
losses to choose a higher voltage,
even if a higher DC voltage increases
the cost of the converters. A choice
of either a balanced or an asymmetric converter type shall be used
based on the distance between terminals, reliability/availability requirements, staged increase of power
capacity, etc. This must also be done
for each specific project.
36
4.3 HVDC Light® Cables
4.3.1 Insulation
The HVDC Light® polymer cables
for HVDC are similar to XLPE AC
cables, but with a modified polymeric insulation. XLPE cables have been
used for AC since the late 1960s.
4.3.2 Submarine Cable Data
Cable data (capability, losses, etc.,
for submarine cables installed in different tropical and moderate climate
zones) are set out below.
ABB
PRODUCTS
HVDC Light® Cable bipole data
Submarine cables
Tropical climate, submarine cables with copper conductor
Area
Ampacity
±80 kV bipole
Weight
Con- Close Spaced Close Spaced
per
ductor laying laying laying laying
cable
mm² Amps Amps MW
MW
kg/m
95
282
338
45
54
4,7
120
323
387
52
62
5,5
150
363
436
58
70
6,7
185
411
496
66
79
7,4
240
478
580
76
93
8,4
300
544
662
87
106
9,4
400
626
765
100
122
11
500
722
887
116
142
13
630
835
1030
134
165
15
800
960
1187
154
190
17
1000 1092 1355
175
217
21
1200 1188 1474
190
236
24
1400 1297 1614
208
258
27
1600 1397 1745
224
279
30
1800 1490 1860
238
298
32
2000 1589 1987
254
318
35
2200 1676 2086
268
334
40
2400 1764 2198
282
352
42
Diam.
over
cable
mm
42
44
47
49
52
56
61
66
71
76
81
85
89
92
96
99
103
106
Close
laying
MW
85
97
109
123
143
163
188
217
251
288
328
356
389
419
447
477
503
529
±150 kV bipole
Weight
Spaced
per
laying
cable
MW
kg/m
101
8,5
116
9,4
131
10
149
11
174
12
199
13
230
16
266
18
309
21
356
24
407
26
442
29
484
32
524
35
558
38
596
41
626
45
659
48
Diam.
over
cable
mm
60
61
63
64
67
69
75
78
83
88
96
100
103
107
110
113
118
121
Close
laying
MW
180
207
232
263
306
348
401
462
534
614
699
760
830
894
954
1017
1073
1129
±320 kV bipole
Weight
Spaced
per
laying
cable
MW
kg/m
216
15
248
16
279
17
317
18
371
20
424
22
490
24
568
26
659
30
760
33
867
37
943
40
1033
43
1117
47
1190
50
1272
53
1335
58
1407
61
Diam.
over
cable
mm
90
91
93
95
99
102
105
108
114
118
122
126
130
133
137
140
145
148
Sea soil: Temperature 28 degrees C, Burial 1.0 metre, Thermal resistivity 1.2 K × W /m
Cable: Copper conductor, HVDC polymer insulation, Steel wire armour
Bipolar power transmission is
Bipolar transmission losses are
Voltage drop at 100% load is
Area
Copper
Conductor
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
ABB
Resistance
per phase
20 deg.C
ohm/km
0,193
0,153
0,124
0,0991
0,0754
0,0601
0,0470
0,0366
0,0283
0,0221
0,0176
0,0151
0,0126
0,0113
0,0098
0,0090
0,0080
0,0073
P = 2×U×I×10-3
P = 2×R×10-3×I2
U = R×I MW
W/m
V/km
Voltage drop
Losses at 50%
Losses at 100%
Close laying
Spaced laying
Close laying
Spaced laying
Close laying
Spaced laying
V/km
65
59
54
49
43
39
35
32
28
25
23
21
20
19
17
17
16
15
V/km
78
71
65
59
52
48
43
39
35
31
29
27
24
24
22
21
20
19
W/m
8
9
9
9
9
9
10
10
11
11
11
11
11
12
12
12
12
12
W/m
12
12
13
13
14
14
15
15
16
17
17
18
18
18
18
19
19
19
W/m
37
38
39
40
41
42
44
46
47
48
50
50
52
53
51
54
54
53
W/m
53
55
57
59
60
64
66
69
72
74
79
80
77
84
82
83
83
84
37
PRODUCTS
Moderate climate, submarine cables with copper conductor
Area
Ampacity
Conductor
Close
laying
Spaced
laying
Close
laying
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
Amps
343
392
441
500
583
662
765
883
1023
1175
1335
1458
1594
1720
1830
1953
2062
2170
Amps
404
463
523
596
697
797
922
1072
1246
1438
1644
1791
1962
2123
2265
2407
2540
2678
MW
55
63
71
80
93
106
122
141
164
188
214
233
255
275
293
312
330
347
±80 kV bipole
Weight
Spaced
per
laying
cable
MW
kg/m
65
4,7
74
5,5
84
6,7
95
7,4
112
8,4
128
9,4
148
11
172
13
199
15
230
17
263
21
287
24
314
27
340
30
362
32
385
35
406
40
428
42
Diam.
over
cable
mm
42
44
47
49
52
56
61
66
71
76
81
85
89
92
96
99
103
106
Close
laying
MW
103
118
132
150
175
199
230
265
307
353
401
437
478
516
549
586
619
651
±150 kV bipole
Weight
Spaced
per
laying
cable
MW
kg/m
121
8,5
139
9,4
157
10
179
11
209
12
239
13
277
16
322
18
374
21
431
24
493
26
537
29
589
32
637
35
680
38
722
41
762
45
803
48
Diam.
over
cable
mm
60
61
63
64
67
69
75
78
83
88
96
100
103
107
110
113
118
121
Close
laying
MW
220
251
282
320
373
424
490
565
655
752
854
933
1020
1101
1171
1250
1320
1389
±320 kV bipole
Weight
Spaced
per
laying
cable
MW
kg/m
259
15
296
16
335
17
381
18
446
20
510
22
590
24
686
26
797
30
920
33
1052
37
1146
40
1256
43
1359
47
1450
50
1540
53
1626
58
1714
61
Diam.
over
cable
mm
90
91
93
95
99
102
105
108
114
118
122
126
130
133
137
140
145
148
Sea soil: Temperature 15 degrees C, Burial 1.0 metre, Thermal resistivity 1.0 K × W /m
Cable: Copper conductor, HVDC polymer insulation, Steel wire armour
Bipolar power transmission is
Bipolar transmission losses are
Voltage drop at 100% load is
Area
Copper
Conductor
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
38
Resistance
per phase
20 deg.C
ohm/km
0,193
0,153
0,124
0,0991
0,0754
0,0601
0,0470
0,0366
0,0283
0,0221
0,0176
0,0151
0,0126
0,0113
0,0098
0,0090
0,0080
0,0073
P = 2×U×I×10 -3
P = 2×R×10-3×I2
U = R×I MW
W/m
V/km
Voltage drop
Losses at 50%
Losses at 100%
Close laying
Spaced laying
Close laying
Spaced laying
Close laying
Spaced laying
V/km
79
72
65
59
53
48
43
39
35
31
28
26
24
23
21
21
20
19
V/km
93
85
78
71
63
57
52
47
42
38
35
32
30
29
27
26
24
23
W/m
12
12
12
13
13
14
14
15
15
16
16
16
16
17
17
18
17
18
W/m
16
17
17
18
19
20
21
22
23
23
24
25
25
26
26
27
26
27
W/m
54
56
57
59
62
64
66
69
72
73
75
76
77
79
77
82
82
82
W/m
75
79
82
85
88
91
96
101
105
109
115
115
118
123
122
125
122
123
ABB
PRODUCTS
4.3.3 Land Cable data
Cable data (capability), losses etc for land cables installed in different tropical and moderate climate zones) are set out
below.
HVDC Light® Cable bipole data
Land Cables
Tropical climate, land cables with aluminium conductor
For higher transmission capacity, see submarine cables with copper conductor
Area
Conductor
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
Ampacity
Close
laying
Amps
211
240
269
305
351
400
456
536
591
711
811
888
980
1044
1129
1198
1265
1330
Spaced Close
laying laying
Amps
258
298
332
378
439
503
581
672
744
898
1026
1123
1242
1326
1434
1524
1600
1681
MW
34
38
43
49
56
64
73
86
95
114
130
142
157
167
181
192
202
213
±80 kV bipole
Weight
per
cable
MW
kg/m
41
1,2
48
1,3
53
1,5
60
1,6
70
1,9
80
2,1
93
3
108
3
119
3
144
4
164
5
180
6
199
6
212
7
229
8
244
8
256
9
269
10
Spaced
laying
Diam.
over
cable
mm
33
34
36
38
40
43
46
50
53
57
61
65
69
72
75
78
81
84
Close
laying
MW
81
92
105
120
137
161
177
213
243
266
294
313
339
359
380
399
±150 kV bipole
Weight
per
cable
MW
kg/m
100
2
113
3
132
3
151
3
174
4
202
4
223
5
269
5
308
6
337
7
373
8
398
9
430
9
457
10
480
11
504
11
Spaced
laying
Diam.
over
cable
mm
50
52
54
57
60
63
67
71
75
79
83
86
89
92
95
98
±320 kV bipole
Weight
per
cable
MW
kg/m
281
5
322
6
372
6
430
7
476
8
575
8
657
9
719
10
795
11
849
12
918
13
975
14
1024
15
1076
16
Close Spaced
laying laying
MW
225
256
292
343
378
455
519
568
627
668
723
767
810
851
Diam.
over
cable
mm
80
82
86
89
93
97
101
105
108
112
115
118
121
123
Sea soil: Temperature 28 degrees C, Burial 1.0 metre, Thermal resistivity 1.2 K × W /m
Cable: Aluminium conductor, HVDC polymer insulation, Copper wire screen
Bipolar power transmission is
Bipolar transmission losses are
Voltage drop at 100% load is
P = 2×U×I×10-3
P = 2×R×10-3×I2
U = R×I MW
W/m
V/km
Area
Resistance
Voltage drop
Aluminium
conductor
per pole
20 deg. C
Close laying
Spaced laying
Close laying
Spaced laying
Close laying
Spaced laying
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
ohm/km
0,32
0,253
0,206
0,1640
0,1250
0,1000
0,0778
0,0605
0,0469
0,0367
0,0291
0,0247
0,0208
0,0186
0,0162
0,0149
0,0132
0,0121
V/km
81
73
66
60
52
48
42
39
33
31
28
26
24
23
22
21
20
19
V/km
99
90
82
74
66
60
54
49
42
39
36
33
31
30
28
27
25
24
W/m
8
8
8
8
8
9
9
9
9
10
10
10
11
11
11
11
11
11
W/m
11
12
12
13
13
14
14
15
14
16
16
17
17
17
18
19
18
18
W/m
34
35
36
37
37
38
38
42
39
44
45
46
47
48
50
50
51
51
W/m
51
54
54
56
58
60
63
66
62
70
74
74
77
80
80
82
80
81
ABB
Losses at 50%
Losses at 100%
39
PRODUCTS
Moderate climate, land cables with aluminium conductor
For higher transmission capacity, see submarine cables with copper conductor
Area
Ampacity
Conductor
Close
laying
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
Amps
258
294
330
374
432
492
565
659
727
877
1001
1096
1211
1291
1395
1482
1571
1652
Spaced Close
laying laying
Amps
310
357
402
458
533
611
705
816
964
1094
1252
1371
1517
1621
1752
1866
1963
2066
MW
41
47
53
60
69
79
90
105
116
140
160
175
194
207
223
237
251
264
±80 kV bipole
Weight
per
cable
MW
kg/m
50
1,2
57
1,3
64
1,5
73
1,6
85
1,9
98
2,1
113
3
131
3
154
3
175
4
200
5
219
6
243
6
259
7
280
8
299
8
314
9
331
10
Spaced
laying
Diam.
over
cable
mm
33
34
36
38
40
43
46
50
53
57
61
65
69
72
75
78
81
84
Close
laying
MW
99
112
130
148
170
198
218
263
300
329
363
387
419
445
471
496
±150 kV bipole
Weight
per
cable
MW
kg/m
121
2
137
3
160
3
183
3
212
4
245
4
289
5
328
5
376
6
411
7
455
8
486
9
526
9
560
10
589
11
620
11
Spaced
laying
Diam.
over
cable
mm
50
52
54
57
60
63
67
71
75
79
83
86
89
92
95
98
Close
laying
MW
276
315
362
422
465
561
641
701
775
826
893
948
1005
1057
±320 kV bipole
Weight
per
cable
MW
kg/m
341
5
391
6
451
6
522
7
617
8
700
8
801
9
877
10
971
11
1037
12
1121
13
1194
14
1256
15
1322
16
Spaced
laying
Diam.
over
cable
mm
80
82
86
89
93
97
101
105
108
112
115
118
121
123
Sea soil: Temperature 15 degrees C, Burial 1.0 metre, Thermal resistivity 1.0 K × W /m
Cable: Aluminium conductor, HVDC polymer insulation, Copper wire screen
Bipolar power transmission is
Bipolar transmission losses are
Voltage drop at 100% load is
P = 2×U×I×10-3
P = 2×R×10-3×I2
U = R×I MW
W/m
V/km
Area
Resistance
Aluminium
conductor
per pole
20 deg. C
Close laying
Spaced laying
Close laying
Spaced laying
Close laying
Spaced laying
mm²
95
120
150
185
240
300
400
500
630
800
1000
1200
1400
1600
1800
2000
2200
2400
ohm/km
0,32
0,253
0,206
0,1640
0,1250
0,1000
0,0778
0,0605
0,0469
0,0367
0,0291
0,0247
0,0208
0,0186
0,0162
0,0149
0,0132
0,0121
V/km
99
89
81
73
65
59
53
48
41
39
35
32
30
29
27
26
25
24
V/km
119
108
99
90
80
73
66
59
54
48
44
41
38
36
34
33
31
30
W/m
11
11
12
12
12
12
13
13
13
14
15
15
16
16
16
17
17
17
W/m
16
17
17
18
18
19
20
21
22
23
23
24
25
25
26
27
26
27
W/m
51
52
53
55
56
58
60
63
60
68
70
70
73
75
75
77
79
79
W/m
74
77
80
82
85
89
93
96
104
105
110
112
115
117
119
123
122
124
40
Voltage drop
Losses at 50%
Losses at 100%
ABB
DESCRIPTIONS
5 Descriptions
5.1 Main circuit
- Single-line diagram
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Single-line diagram of an HVDC Light® Converter
5.1.1 Power transformer
The transformer is an ordinary singlephase or three-phase power transformer, with a tap changer. The secondary voltage, the filter bus voltage,
will be controlled with the tap changer to achieve the maximum active
and reactive power from the converter, both consumption and generation.
The tap changer is located on the
secondary side, which has the largest voltage swing, and also in order
to ensure that the ratio between the
line winding and a possible tertiary
winding is fixed.
ABB
The current in the transformer windings contains hardly any harmonics
and is not exposed to any DC voltage. In order to maximize the active
power transfer, the converter generates a low frequency zero-sequence
voltage (<0.2 pu), which is blocked
by the ungrounded transformer secondary winding.
The transformer may be provided
with a tertiary winding to feed the
station auxiliary power system.
41
DESCRIPTIONS
5.1.2 Converter reactors
The converter reactor is one of the
key components in a voltage source
converter to permit continuous and
independent control of active and
reactive power.
The main purposes of the converter reactor are:
• to provide low-pass filtering of the
PWM pattern to give the desired
fundamental frequency voltage. The
converter generates harmonics related to the switching frequency. The
harmonic currents are blocked by
the converter reactor, and the harmonic content on the AC bus voltage is reduced by an AC filter.
• to provide active and reactive
power control. The fundamental frequency voltage across the reactor
defines the power flow (both active
and reactive) between the AC and
DC sides. Refer to Typical P/Q diagram and active and reactive power
definitions.
• to limit the short-circuit currents
There is one converter reactor per
phase. They consist of vertical coils,
standing on insulators. They are several meters tall and several meters in
diameter. Shields eliminate the magnetic fields outside the coils.
The short-circuit voltage of the converter reactor is typically 15%.
The stray capacitance across the
reactor should be kept as low as
possible in order to minimize the
harmonics coupled to the filter side
of the reactor. The high dv/dt on the
bridge terminal at each switching will
42
result in current pulses through all
capacitances to ground. These current pulses should be minimized as
they pass through the valve. The filter side of the reactor can be considered as ground at high frequen-
cies, and the capacitance across
the reactor should therefore be low.
These requirements have led to the
design of converter reactors with air
coils without iron cores.
ABB
DESCRIPTIONS
5.1.3 DC capacitors
5.1.4 AC filters
The primary objective of the valve
DC side capacitor is to provide a
low-inductance path for the turnedoff current and also to serve as an
energy store. The capacitor also
reduces the harmonics ripple on the
direct voltage. Disturbances in the
system (e.g. AC faults) will cause DC
voltage variations. The ability to limit
these voltage variations depends on
the size of the DC side capacitor.
Voltage source converters can
be operated with different control
schemes, most of which use pulse
width modulation to control the ratio
between the fundamental frequency voltage on the DC and AC side.
Looking at the AC side converter
terminal, the voltage to ground will
be anything but sinusoidal, as indicated in the figures on the following pages. The most frequent application of voltage source converters
is as machine drives (in industrial
applications), where this is of less
or no concern. However, connecting a voltage source converter to
a transmission or distribution system requires the voltage to be made
sinusoidal. This is achieved by
means of the converter reactor and
AC filters.
The DC capacitor is an ABB DryQ
capacitor. For high voltage applications, this technology makes possible capacitors of a dry, self-healing, metallized film design. The DryQ
design has:
• Twice the capacity in half the
volume
• Corrosion-free plastic housing
The distorted waveform of the converter terminal voltage can be
described as a series of harmonic
voltages E E h cosh7 1t A h ¤
h 1
where Eh is the h:th harmonic EMF.
The magnitude of the harmonic
EMFs will, naturally, vary with the DC
voltage, the switching frequency (or
pulse number) of the converter, etc.
But it will also depend on the chosen PWM technology of the converter. To illustrate this, the figures below
contain two examples:
• A converter utilizing a sinusoidal PWM with 3rd harmonic injection (that is when a 3rd harmonic is
added on the fundamental frequency modulator to increase the power
rating of the converter).
• A converter using a harmonic cancellation PWM or OPWM.
• Low inductance
• Shortened production time and
simplified installation
ABB
43
DESCRIPTIONS
Converter Terminal Phase to Ground Voltage, E
v
1
0
−1
0
50
100
150
200
250
300
Harmonic content of phase voltage, excluding zero sequence components
350
1
0.5
0
0
10
0
10
20
30
40
50
60
70
80
Harmonic content of phase voltage, zero sequence components only
90
100
90
100
1
0.5
0
20
30
40
50
60
70
80
Voltage source converter operated with a sinusoidal PWM with 3rd harmonic
injection. The blue dotted line shows the fundamental frequency voltage component of the converter terminal to ground voltage.
44
ABB
DESCRIPTIONS
Converter Terminal Phase to Ground Voltage, Ev
1
0
−1
0
50
100
150
200
250
300
Harmonic content of phase voltage, excluding zero sequence components
1
350
0.5
0
0
10
0
10
1
20
30
40
50
60
70
80
Harmonic content of phase voltage, zero sequence components only
90
100
90
100
0.5
0
20
30
Both the above figures give the converter terminal phase-to-ground voltage (with the fundamental component indicated) together with the
corresponding harmonic spectrum.
The spectrum is given as positive
and negative sequence components
and zero-sequence components.
The power transformer between the
filter bus and the connecting AC
bus will effectively prevent the latter
entering the AC network.
In a typical HVDC Light® scheme,
AC filters contain two or three
grounded or ungrounded tuned filter
branches.
40
50
60
70
80
Voltage source converter operated
with a harmonic cancellation PWM.
The blue dotted line shows the
fundamental frequency voltage component of the converter terminal to
ground voltage.
C
1
C
1
L
1
L
1
R
1
Example of an HVDC Light® AC filter.
ABB
45
DESCRIPTIONS
5.1.5 DC filters
Depending on filter performance
requirements, i.e. permissible voltage distortion, etc., the filter configuration may vary between schemes.
But a typical filter size is somewhere
between 10 to 30% of the rated
power. Typical requirements on filter
performance are
For HVDC Light® converters used
in combination with HVDC Light®
cables, the filtering on the DC side by
the converter DC capacitor and the
line smoothing reactor on the DC side
are considered to provide sufficient
suppression of any harmonics.
Individual harmonic distortion,
U
D h h ≈ 1%
U1
Total harmonic distortion,
THD ¤D
2
h
≈ 1.5% to 2.5%
h
Telephone influence factor,
TIF ¤5hf C
1
messagehf1 D h
2
≈ 40 to 50
h
The above indices are all based on
the voltage measured at the point of
connection of the DC scheme. The
first two are direct measures of voltage quality, whilst the third, TIF, is a
weighted measure and is a commonly
used indication of expected telephone
interference. The TIF value is based
on the Cmessage weight presented in
E.E.I. Publication 60-68.
However, under certain circumstances, if the DC cable route shares the
same right of way or runs close by
subscribers telephone wires, railroad
signaling wires or similar, there is a
possibility of exposure to harmonic
interference from the cable. Under
these circumstances and for conditions where a local preventive measure is not feasible, e.g. improving the
shielding of subscriber wires, the third
party (telephone company, railway
company, etc.) should be consulted
for permissible interference limits.
A typical requirement can be
expressed as an equivalent weighted
residual current fed into the cable pair
at each station. The current is calculated as
I eq (1 / P800 ) *
( Phf1 * I h ) 2 where:
¤
h
• Ieq is the psophometrically weighted, 800 Hz equivalent disturbing
current.
• Ih is the vector sum of harmonic currents in cable pair conductors
and screens at harmonic h
• Phf1 is the psophometric weight at
the frequency of h times the fundamental frequency.
The weighting factor in this example is
the UIT (CCITT) psophometric weighting factor.
Sometimes the C-message factor
mentioned above is used instead.
If additional filtering is required, the
remedy is to add a filter on the DC
side, consisting of either a common
mode (zero-sequence) reactor or/ and
a single-tuned filter or filters.
C−message weight vs frequency.
1
0.9
0.8
0.7
−
0.6
0.5
0.4
0.3
0.2
0.1
0
0
500
1000
C-message weight
46
1500
2000
2500
Hz
3000
3500
4000
4500
5000
ABB
DESCRIPTIONS
Psophometric weight vs frequency.
1.4
Psophometric weight
1.2
1
−
0.8
0.6
0.4
0.2
0
0
500
1000
1500
2000
2500
Hz
3000
5.1.6 High-frequency (HF) filters
In voltage source converters, the
necessarily high dv/dt in the switching of valves means that the high
frequency (HF) noise generation is
significantly higher than for conventional HVDC converters. To prevent
this HF noise spreading from the
converter to the connected power
grids, particular attention is given
to the design of the valves, to the
shielding of the housings and to
ensuring proper HF grounding con-
3500
4000
4500
5000
nections. For example, the valves
contain HF damping circuits on both
the AC and DC sides to ensure that
as little HF disturbance as possible
will spread from the valve area.
To further limit HF interference, a
radio interference (RI) filter capacitor
is connected between the AC bus
and earth, and an AC line filter reactor is installed. With these measures,
the scheme will meet the requirements of applicable standards for
emissions.
If a power line carrier (PLC) is used
nearby in the connected power
grid, additional PLC filters may be
required, i.e. an additional AC line
filter reactor and a properly tuned
capacitor to earth.
R I d ef ens e l i n es
U V alve and reactor enclosures
U E nclosure cable connections
U EM C ROX
U F errites
U RI - Filtering
U House
U E arthing system
U EM C approved aux. systems
Applicable standards
• CISPR 11
• ENV50121-5
ABB
47
DESCRIPTIONS
5.1.7 Valves
- The IGBT position
The semiconductor used in HVDC
Light® is the StakPak™ IGBT from
ABB Semiconductors. The IGBT
(insulated gate bipolar transistor) is
a hybrid of the best of two worlds.
As a conducting device, the bipolar transistor with its low forward
voltage drop is used for handling
high currents. Instead of the regular current-controlled base, the IGBT
has a voltage-controlled capacitive gate, as in the MOSFET device.
To increase the power handling, six
IGBT chips and three diode chips
are connected in parallel in a submodule. A StakPak™ IGBT has
two, four or six sub-modules, which
determine the current rating of the
IGBT.
A complete IGBT position consists
of an IGBT, a gate unit, a voltage
divider and a water-cooled heat sink.
Each gate unit includes gate-driving circuits, surveillance circuits and
optical interface. The gate-driving
electronics control the gate voltage
and current at turn-on and turn-off,
in order to achieve optimal turn-on
and turn-off processes of the IGBT.
The voltage across the IGBT during switching is measured, and the
information is sent to the valve control unit through an optical fiber. The
voltage divider connected across the
IGBT provides the gate unit with the
current needed to drive the gate and
feed the optical communication circuits and the control electronics.
The StakPak™ IGBT with four and six sub-modules.
48
ABB
DESCRIPTIONS
- Valve function
To be able to switch voltages higher than the rated voltage of one
IGBT, several positions are connected in series in each valve. The most
important factor is that all IGBTs
must turn on and off at exactly the
same moment, in order to achieve
an evenly distributed voltage across
the valve. ABB has a well-proven
solution that regulates each IGBT
position individually in the valve to
the correct voltage level. The flexibility of the IGBT as a semiconducting device also makes it possible to
block the current immediately if a
short circuit is detected, and thus
to prevent damage to the converter.
A single valve for a 150 kV module
consists of around 300 series-connected IGBTs.
- Valve bridge
HVDC Light® is based on a two-level topology, meaning that the output voltage is switched between
two voltage levels. Each phase has
two valves, one between the posi-
tive potential and the phase terminal
and one between the phase terminal
and the negative potential. Thus, a
three-phase converter has six valves,
three phase reactors and a set of
DC capacitors. The diagram below
shows the schematics of an HVDC
Light® converter in principle.
- Mechanical design
The HVDC Light® converter valves
are for DC voltages up to 150 kV
assembled inside an enclosure
made of steel and aluminum. The
shielded enclosure helps to improve
the electromagnetic compatibility of
the converter. Another advantage
is that the enclosure is made as a
standard container, which simplifies
the transport of the converter to the
site. With this method, most of the
HVDC Light® converter parts can
be pre-assembled at the production location to minimize the assembly work on site. Some of the testing
can also be done before transportation, thereby reducing the installation
and commissioning time on site.
All IGBTs and coolers in a stack are
mounted tightly together under very
high pressure, in order to minimize
contact resistance and to increase
cooling capacity.
The stacks are pressed together with glass fiber bolts, which fulfill both insulation and mechanical
strength criteria. Circular aluminum
shields are mounted around the
IGBT stacks to smooth the electrical
field around the high-voltage equipment. The stacks are suspended
on an insulator from the ceiling of
the valve enclosure. This installation
method makes the converter resistant to earthquakes and other movements.
Overall, the assembling method with
shielded stacks hanging in enclosures with controlled humidity levels makes it possible to reduce the
distances between the high-voltage parts and the surroundings.
This makes HVDC Light® a compact
power transmission technology.
³
6°6£
6°6£
6
°6£
·«…>ÃiÊ
6°6Ó
6°6Ó
6
°6Ó
‡
Principle schematic of a three-phase two-level HVDC Light® converter.
ABB
49
DESCRIPTIONS
5.1.8 Valve cooling system
All HVDC Light® positions are
equipped with water-cooled heat
sinks providing high-efficiency cooling. The valve cooling systems are
manufactured by SwedeWater, a
member of the ABB group.
To be able to use water as cooling
liquid in direct contact with high voltage potentials, it is of great importance that the water has very low
conductivity. The water is circulating through the heat sink in close
contact with each IGBT, which efficiently transports the heat away
from the semiconductor. The cooling water circuit is a closed system,
and the water is cooled through
heat exchangers using either air or
a secondary water circuit as cooling
medium.
Inside a Valve Enclosure
Today, there are no issued standards that fully cover the testing of
an HVDC Light® converter valve.
In this process, the IGBT, the voltage
divider and the gate unit are tested
together.
The AC and DC voltage applications
are tested according to IEC 60700-1
and IEC 61954, to the extent that the
standard is applicable. The switching and lightning impulse tests are
performed according to IEC 60060.
However, standard IEC 62501 for
testing of VSC Valves is under preparation, and as soon as it is valid testing of
the HVDC Light® valves will be based
on that standard.
Afterwards, parts of the converter
valves are type tested in an H-bridge
test setup. The tests are performed
on a downscale of the converter
valves, with only a few positions in
series and with a reduced AC voltage. Four valves are connected in an
H-bridge configuration, which makes
it possible to test both rectifier and
inverter operation. Phase angles,
voltages, current and filters can be
adjusted to simulate most of the
HVDC Light® operation modes.
All IGBT positions are tested before
the stacks are assembled, in a
sophisticated routine test line.
50
The water in the valve cooling system passes continuously through a
de-ionizing system, to keep the conductivity of the water low. The temperature of the water in the valves
is controlled by a MACH-2-based
cooling control system, for example regulating the number of fans to
be operated in order to achieve the
necessary cooling capacity. In addition to temperature measurements,
the cooling system is also equipped
with sensors for pressure, water
flow, level and conductivity, and
it controls motor-operated valves,
pumps and fans. If necessary, electrical heaters or glycol can be added
to prevent the water from freezing if
the converter station is located in a
cold area.
ABB
DESCRIPTIONS
Valve cooling system.
All major parts of the valve cooling
system are provided with redundant
equipment. The control system consists of two separate systems that
measure all parameters using different transmitters, all in order to minimize the risk of an unwanted stop.
Both systems are able to control
the two main pump motors, and the
low-voltage switchgear has switchover functions to ensure uninterruptible operation. The software also
performs weekly changeovers of
the pumps in operation, in order to
ensure equal wear of the equipment.
ABB
The redundancy of all the equipment
also simplifies the maintenance of
the valve cooling system. If maintenance is necessary, it is possible to
change which pump will run manually directly from the operator computer,. Some parts of the cooling
system can be closed and disconnected to allow maintenance to be
carried out without interrupting the
power transmission.
The valve cooling system used for
HVDC Light® is based on the valve
cooling system used for thyristor
valves in conventional HVDC converters since 1980.
51
DESCRIPTIONS
5.1.9 Station service power
The station service power system
is vital for reliable operation of the
HVDC Light® station. The design of
station service power is focused on:
- Redundant power supplies, one
from the internal AC bus and one
from an external source.
The supply to the internal AC bus
can be taken from a yoke winding
on the converter transformer.
In this way, the power supply is
guaranteed at all times when the
station is in operation. The output
voltage is 6 –10 kV, which means an
intermediate transformer is necessary to provide a 400 V system.
The external power supply is taken
from a local AC system provided by
the customer and is used as a backup source.
- Duplication of all critical parts,
valve cooling pumps, station batteries and battery chargers.
- Automatic changeover
The incomers to the 400 V switchgear have automatic changeover
control. The supply coming from the
internal AC bus is pre-selected as a
primary supply, and the supply from
the external local AC system is preselected as a backup supply. If the
pre-selected supply fails, changeover to the backup supply takes
place within a pre-set time. When
the pre-selected supply returns, the
changeover system changes back
to the primary supply within the preset time.
52
- Duplication of all critical equipment
- valve cooling pumps
The duplicated valve cooling pumps
are controlled by frequency converters for maximum flexibility for the
flow control of cooling water. The
frequency converter also makes it
possible to use a DC backup source
to keep the pump running if auxiliary
power is lost for a long time.
- station battery system
The control equipment and other
station DC loads are supplied from
a duplicated station battery system
with a backup time of at least two
hours.
Critical AC loads within the control
equipment, such as servers, computers, LAN switches, etc., are supplied from a DC/AC inverter fed from
the station battery and with an automatic switchover to the alternative
AC supply in the event of inverter
failure or overload.
5.1.10 Fire protection
For HVDC Light® projects, the fire
protection area is generally smaller than for conventional HVDC, but
the requirements are the same. The
design of fire-fighting and fire protection is in accordance with NFPA
(National Fire Protection Association) and with the requirements of all
authorities having jurisdiction over
any parts of the works.
The valve enclosures, the control
enclosure and all areas that have a
high demand because of sensitive
equipment are detected with air sampling systems. The air sampling system can detect smoke at a very early
stage. Being able to detect smoke at
an early stage is an advantage, since
this can prevent unnecessary tripping
or shutdown of the station.
The power transformer is isolated
by firewalls. Depending on the local
regulations or client requirements,
the transformer may or may not be
protected by a sprinkler system.
The converter reactors have smoke
detectors.
If necessary, the valve enclosures
and other detected areas with air
sampling systems can be protected
with total flooding by gas or water
mist extinguishing systems in accordance with NFPA 2001 or NFPA 750.
If a water pumping system is
required, it consists of one electric
pump and one standby diesel-driven pump. A ring main water loop will
then be located on the site (underground) for a fire-fighting water supply. It is connected to an isolation
valve that will bring redundancy
in the ring main loop for fire fighting water. Fire hydrants will be positioned at strategic locations around
the site area close to the main loop.
Water supply storage will be connected to the fire fighting water loop.
The signals from the detection system and the pumps will be connected to a fire alarm panel in the operator control room.
ABB
DESCRIPTIONS
5.1.11 Civil engineering work,
building and installation
- General
For HVDC Light® systems up to 150 kV,
land-based stations are built without
a dedicated valve hall. The converter
station has a compact layout, with
the majority of equipment housed
in a typical warehouse-style building. The buildings are made of sheet
steel and are provided with doors,
stairs and catwalks.
The IGBT’s valves are installed in
steel enclosures, which are placed
on a concrete slab. The control and
cooling equipment is normally also
installed in enclosures. Concrete
slabs are also used for locating the
AC filters and DC equipment. A simple steel building is erected over all
the equipment. The main functions
of the building are HF shielding,
noise reduction and weather protection. All the enclosures (valves, control and cooling) have a controlled
indoor environment as regards temperature, humidity and cleanness.
The wall cladding of the building is
normally metal sheeting, which can
be insulated with sound barriers to
achieve the required noise level. The
building can be fitted with a ventilation system if required.
Transformers and cooling fans are
located outside the building. The
power transformers are placed on
solid foundations. The transformer
is connected to the indoor AC filter
by cables. If required, conventional
AC switchgear with breakers, etc.,
can be added to connect the power
transformer to the AC network.
Both the civil engineering works and
equipment installation are normally
contracted to a local contractor, who
will perform the works under the
supervision of ABB engineers.
ABB
- Site inspection and testing
System testing is normally the last
test activity prior to handing over the
HVDC system to the client for operation. Prior to system testing, several other test activities will have been
performed.
System tests of the HVDC system.
• Terminal test
- High-voltage energizing
- Terminal operation
• Transmission test
The general philosophy is that all
tests must be performed as early
as possible in order to allow early
remedial work to be done. The onsite inspection and test activities
comprise:
Verifications and tests during civil
engineering work and during installation of individual equipment/unit.
• Verifications and inspection
during civil engineering work.
In addition to the tests specified
above, acceptance tests will be performed according to the specification and contract agreement.
All verifications and tests on site are
listed in the inspection and test plan
for field tests (ITP).
During inspections, the environmental impact requirements specified in
the various design drawings will also
be verified.
• Pre-installation verifications.
• Verifications during installation.
• Equipment tests.
Testing of subsystems of the HVDC
system.
• Subsystem functional (circuit)
tests.
• Start up of auxiliary systems,
including building systems.
All tests will be performed or supervised by ABB commissioning engineers and ABB experts.
All tests under high-voltage conditions, terminal tests and transmission tests will be directed by ABB’s
test manager with the assistance of
ABB commissioning engineers, but
under full operational responsibility
of the customer’s operational organization.
53
DESCRIPTIONS
5.1.12 Availability
in the figure below. Since the number of installed items of equipment
is less for an HVDC Light® scheme
compared with a conventional
HVDC scheme, the target value for
availability is equal or even better for
HVDC Light® compared with conventional HVDC.
• the design must allow maintenance activities (forced and scheduled) to be performed with minimum
curtailment of the system operation
When designing a modern HVDC
Light® transmission system, one of
the main design objectives is to minimize the number of forced outages and the down time due to forced
outages and scheduled maintenance.
• scheduled maintenance that
requires link shut-down must be
minimized
• the scheduled maintenance time
has been kept low thanks to few
mechanical parts
The HVDC Light® transmission is
designed according to the following principles in order to assure high
reliability and availability:
Maintainability is increased by the
introduction of redundancy up to
an economically reasonable level.
The maintenance times, especially for work that requires curtailment
of the HVDC Light® transmission,
should be minimized by the use of
exchange modules or components
instead of repair.
• simple station design
• use of components with proven
high reliability
• automatic supervision
• use of redundant and/or back-up
control systems and equipment
such as measurements, pumps, etc.
Observed energy availability from
two of our projects in commercial
operation is above 98%, as shown
• available spare units
Availability, Cross Sound and Murray Link
99,4
99,2
99
Availability in %
98,8
98,6
Guarantee Value
98,4
Average availability
98,2
98
97,8
97,6
2003
Year & month
December
November
October
September
August
July
June
May
April
March
February
January
December
November
October
September
August
July
June
97,4
2004
1) October 2003, Average availability is decreased by annual preventive maintenance in MurrayLink
54
ABB
DESCRIPTIONS
5.1.13 Maintainability
The unavailability due to scheduled maintenance depends both
on the design of the HVDC Light®
transmission and on the organization of the maintenance work. The
modern design, which incorporates
extensive redundancies for essential systems such as cooling systems, duplicated control systems
and station service power, allows
most of the maintenance work to be
done with no interruption of operation. This work will require 200-400
man-hours per year, depending on
the size of the transmission system.
As an example, the remaining maintenance effort for a 350 MW module that requires curtailment of the
HVDC transmission is estimated
to require approximately 160 manhours per station every second year.
The time to do this work is estimated
to be 60 hours, the necessary workforce will then be six persons, and
the minimum scheduled unavailability will then be a maximum of 0.35%
on average per year. However, with
increased staff and proper planning,
the maintenance work can be performed in a shorter time.
5.1.14 Quality Assurance/
Standards
ABB has developed an effective
and efficient quality assurance program complying with ISO 9001 and
other applicable standards and
an environment management system complying with ISO 14000. The
know-how acquired by long experience with HVDC projects of different kinds, solid technical resources
and closely developed relations with
key sub-suppliers, ensures reliable
products in compliance with specifications.
ABB
The quality assurance program provides the tool to ensure that the
work in different phases is executed
in a predictable manner.
Several systems for feedback of
experience are used, including follow-up and testing during equipment
manufacturing (type testing and routine testing for equipment, factory
system testing for control equipment),
installation, commissioning and commercial operation. The included
equipment is in line with applicable
IEC standards.
5.1.15 Acoustic noise
A major part of the equipment that
generates noise is located inside the
buildings, and this noise can be successfully attenuated by appropriately designed acoustic properties of
the walls and roof. The station layout
should also be adapted to fit acoustical requirements.
There may be several different
sound requirements for an HVDC
Light® station.
Identifying which of them are valid
and may be critical for the design
of the plant is a major task at the
beginning of the acoustic design
process.
- Decibel scale
Sound is measured as the sound
pressure level (usually referred to as
the sound level) and is stated as a
decibel (dB) value, which represents
a value related to a certain reference
sound pressure level.
It is normal that the value used is
corrected for the spectral sensitivity of the human ear; this is known
as dB(A).
- Sound requirements
The most common sound requirements for the areas outside the station area are set at the following
locations.
• At the station fence.
(typically 60 dB)
• At the property line.
• At a given distance /radius from
the station;
• At the nearest residences.
(typically 40 dB)
- Acoustic design
To ensure that noise requirements for
the plant will be met, it is necessary
to design and construct the station
correctly from the very beginning.
The sound requirements usually
apply to the areas outside the station, the space inside the station,
and the inside of the buildings/enclosures.
Sound requirements for the outside
area may vary depending on state
regulations, or on local regulations
or industry practices.
55
DESCRIPTIONS
The process of acoustic design
of the plant includes the following
steps:
• Identify the noise requirements for
the plant
• Identify the real constraints for the
noise design
• Influence the layout design so that
the noise requirements will be fulfilled
• Predict the expected noise level
around the equipment used and the
entire plant
• Decide the maximum permissible
noise levels for the most significant
pieces of equipment
• Decide the acoustic properties
of the enclosures, buildings and
expected attenuation screens
• Work out the verification procedures for final compliance with the
noise requirements for the plant
- Noise sources in an HVDC Light®
station
Typical noise sources in the HVDC
Light® station are:
• Power transformers;
• Cooling fans for cooling systems;
All significant sound sources in the
plant are included in such a model.
The most essential elements of station surroundings which may influence the sound propagation from
the station are also included in the
model. The 3-D model makes it possible to study different possible layouts and different configurations of
the equipment for the future station.
The result of the prediction may be
shown as a sound contribution map
for the area around the station and
can also be supplemented with the
tables containing the exact sound
level values for the chosen locations
of interest.
5.2 HVDC Light® control and protection
5.2.1 Redundancy design and
changeover philosophy
- Active/standby systems
The redundant PCP systems are
designed as duplicated systems acting as active or hot standby. At any
time only one of the two control systems is active, controlling the converter and associated equipment.
If a fault is detected in the active
system, the standby system takes
over control, becoming the new
active system. The faulty system
(the previously active system) should
be checked before being taken into
operation as the standby system.
- System changeover
The system switchover commands
can be initiated manually or automatically. The manual commands
are initiated by a push-button in the
active system, while the automatic
commands are initiated by extensive internal supervision functions
of the subsystems, or on a protection order.
The switchover commands are
always initiated from the currently
active system. This switchover philosophy means that a fault or testing
activity in the standby system cannot result in an unintentional switchover. Furthermore, a manual switchover order to a faulty standby
system is not possible.
The other system, the standby system, is running, but the “outputs”
from that system are disabled.
• Ventilation openings and facades
of the equipment buildings;
• PLC filter components;
• Air-conditioning equipment.
- Prediction model
The calculation for prediction of the
sound contribution from the HVDC
Light® equipment is usually done in
a three-dimensional (3-D) model of
the plant and its surroundings. The
3-D model is created in the qualified
software, which is also used for calculations.
An example of a 3D model and a result map for a typical HVDC Light® station.
56
ABB
DESCRIPTIONS
- Changeover from protections
Control problems may initiate protection actions. To improve the overall reliability performance of the
HVDC Light® transmission by avoiding unnecessary trips in connection with control problems, some of
the converter and pole protections
initiate a fast changeover from the
active to the standby control system.
Before a trip order is issued from
the DC protection system, a system changeover is performed if the
fault type could have been caused
by a control failure, and the inherent delay in such a changeover is
acceptable. If the redundant control
system is healthy and successfully
re-establishes undisturbed power
transfer on the HVDC link, the protections in both systems will reset
and not time out to trip. To achieve
proper coordination between block/
trip orders, both time and level separation is used.
• Duplicated inputs and comparison
in the software.
- Protection redundancy
Both AC and DC protection trip
actions are active in both systems,
but only some of the DC protections,
i.e. those that may have been initiated due to a control problem, can
order a changeover.
• Supervision of data bus communications.
• Supervision of auxiliary power.
Any detected failures in the control
and protection hardware will result in
a request for changeover, which will
be executed if a standby system is
available and ready to take over.
Both systems are equipped with
identical protections fed from separate primary sensors where practically possible.
- Self supervision
Inadvertent trips are avoided as
each system is provided with extensive self-supervision, which further
enhances system security. Examples
of methods for self-supervision are:
5.2.2 Converter control
Each HVDC Light® converter is able
to control active and reactive power
independently by simultaneously
regulating the amplitude and phase
angle of the fundamental component of the converter output voltage.
The general control scheme of one
converter station is shown in the figure below.
• Inherent supervision in measuring
systems (e.g. DCCT, DCOCT).
• Comparison in the software
between actually measured zero
sequence components and zero
sequence components calculated
in the software in the case of threephase current measurement.
=WP1
=U
-T1
=WZ
=WT
i_pcc
-U1
tap_pos
i_dc_p
u_dc_p
i
AC_BRK_OPEN
PCC
Q1
-T1
-T2
-T11
-T11
=WP2
u_f
u_pcc
u_dc_n
i_dc_n
-U1
tap_pos
u_pcc
i_pcc
i
u_f
u_dc_p
u_dc_n
i_dc_p
-T1
Valve Control
i_dc_n
INTERFACE
AD conversion, Anti-Aliasing Filters, Resampling, Decimation Filters &
Normalization
U_PCC_Alpha/Beta
I_PCC_Alpha/Beta
U_DC_pos/neg
INC_TAP_POS
Y_Alpha/Beta
DEC_TAP_POS
Delta_IREF_Q
U_Alpha/Beta
P_PCC_REF
Q_PCC_REF
$P_PCC_REF
$Q _PCC_REF
U_PCC_REF
UDC_CTRL
UAC_CTRL
AC_BRK_OPEN
OUT_TEMP
PQU ORDER CONTROL
Pac Ctrl
Qac Ctrl
Uac Ctrl
TCC
Temp. Limitation
Runback Control
I_MAX_TEMP
p_ref
q_ref
DCVC_enable
Runback
udc_ref
Runback
BLOCK
BLOCK
ABB
CURRENT CONTROL
AC Current Control
Voltage Seq. Estimator
DQPLL
DC Voltage Balance Ctrl
3PWM
Sync. PLL
3Ix
u_dq_pos
CURRENT ORDER
CONTROL
UDCCOL
UACCOL
DCVC
PQ2IDQ
u_dc_pos/neg
i_dc_pos/neg
i_d_ref
i_q_ref
block
Control block diagram with
simple Single-line diagram
57
DESCRIPTIONS
5.2.3 Current control
The purpose of current control is to
allow the current through the converter phase reactors and the transformer to be controlled. The control operates in a coordinate system
phase synchronous to the fundamental frequency in the network,
referred to as a dq-frame. The control reference object is the transformer current.
- Voltage sequence decomposition
The voltage sequence decomposition provides the true positive voltage sequence, u_dq_pos, for the
phase-locked loop, the quasi-positive sequence, u_pcc_p, and the
true negative sequence voltage, u_
pcc_n, for the AC current control
feed-forward voltages.
- DQPLL and SYNCPLL
The phase-locked loop (PLL) is used
to synchronize the converter control with the line voltage. The input of
the PLL is the three-phase voltages
measured at the filter bus.
- AC current control
Controls the currents through the
converter phase reactors and provides a symmetrical three-phase
current to the converter, regardless
of whether the AC network voltage
is symmetrical or not. The current
order is calculated from the power
order.
58
- OPWM
The OPWM (optimal pulse width
modulation) function must provide
two functions: calculate the time to
the next sample instant, and modulate the reference voltage vector.
OPWM is a modulation method that
is used for harmonic elimination and
for reducing converter losses. The
harmonic elimination concentrates
the harmonics to a narrow bandwidth, which is beneficial for the filter
design. Thus, the filters can be made
smaller. The converter losses are
reduced by switching the valves less
frequently when the current is high.
Using pulse width modulation makes
it possible to achieve rapid control of
the active and reactive power. This
is beneficial when supporting the AC
network during disturbances. The
control is optimized to have a rapid
and stable performance during AC
system fault recovery.
5.2.4 Current order control
The current order control provides
the reference current for the current control and acts as an interface
between the PQU order control that
operates on RMS values and the
momentary control signals within the
current control.
- DCVC and UDCCOL
The DC voltage control provides
control of the DC voltage using the
current order.
- UACCOL
The AC voltage-dependent current
order limiter provides control to keep
the AC filter bus voltage within its
upper and lower limits.
- PQ2idq
The pq2idq calculates the dq current orders with respect to the positive-sequence voltage.
5.2.5 PQU order control
The PQU order control object must
mainly calculate and provide the current order control block with active
and reactive power references.
- Active power control/frequency
control
The active power control controls
the active power flow by generating a contribution to the DC voltage
reference depending on the active
power reference. In isolated mode,
the frequency control will control the
frequency of the isolated network.
- Reactive power control
The reactive power control controls
the reactive power.
- AC voltage control
The AC voltage control controls the
AC voltage.
- Tap changer control
The tap changer control is used to
keep the filter bus voltage, and thus
the modulation index, within suitable limits.
ABB
DESCRIPTIONS
5.2.6 Protections
- Protective actions and effects
- Protection system philosophy
The purpose of the protection system is to cause a prompt removal of
any element of the electrical system
from service in the event of a fault,
for example when it suffers a short
circuit or when it starts to operate
in any abnormal manner that might
cause damage or otherwise interfere with the effective operation of
the rest of the system. The protective system is aided in this task by
the AC circuit-breakers, which disconnect the AC network from the
converters and are capable of deenergizing the converter transformer,
thereby eliminating the DC current
and voltage.
Alarms
Alarms are generally generated as
a first action by some protections to
notify the operator that something is
wrong, but the system will still continue to run as before the alarm.
The protection system has extensive self-supervision. Any failures
detected in the control and protection hardware result in appropriate
actions depending on the severity of the fault. Failures may result
in a request for changeover to the
redundant system, which is executed if there is a standby system ready
to take over.
When a protection operates, the
following fault clearing actions are
taken depending on the type of fault:
• Transient current limitation by
means of temporary blocking of the
converter control pulses on a per
phase basis
• Permanent blocking of the converter
• Tripping of the AC circuit-breakers
ABB
Transient current limiter
The transient current limiter stops
sending pulses to the IGBTs corresponding to the phase with high current. The pulses are re-established
when the current returns to a safe
level (i.e. temporary blocking on a
per phase basis). Overvoltage protection temporarily stops the pulses
in all three phases simultaneously.
Permanent blocking
Permanent blocking means that a
turn-off control pulse will be sent to
all IGBTs and they will stop conducting immediately.
AC circuit-breaker trip
Tripping of the AC circuit-breaker
disconnects the AC network from
the converter equipment.
Set lockout of the AC circuit-breaker
If a trip order has been sent to the
AC circuit-breaker, an order to lock
out the breaker may also be executed. This is done to prevent the
breaker from closing before the
operator has checked the cause of
the trip. The operator can manually
reset the lockout of the breaker.
Pole isolation
The pole isolation sequence involves
disconnecting the DC side (positive and negative poles) from the DC
cable. This is done either manually during normal shutdown or automatically by order from protections
in the case of faults which require
that the DC side is disconnected, for
example a cooling water leakage.
Start breaker failure protection
At the same time as a trip order is
sent to the AC breaker, an order
may also be sent to start the breaker
failure protection. If the breaker does
not open properly within a certain
time, the breaker failure protection
orders re-tripping and/or tripping of
the next breaker.
This prevents the AC system from
feeding a fault on the valve side of
the converter transformer.
In addition, the removal of the AC
voltage source from the converter valves avoids unnecessary voltage stresses, especially when the
valves have suffered severe current
stresses.
All protective trip orders to the AC
circuit-breakers energize both the A
and B coils of the breakers through
two redundant devices. Two redundant auxiliary power supplies also
feed the redundant trip orders.
59
DESCRIPTIONS
Protection overview
The figure below shows the protections included in an HVDC Light®
station
PROTECTION OVERVIEW
-T11
-L1
-Q11
-U1
V1
-T1
-Q1
-T11
-L1
-X1
-T1
-T3
V2
-Z11
-T2
-T11
-L1
-C1
-Q11
-U1
-L1
-R1
-T1
TRANSFORMER
DIFFERENTIAL
PROTECTION
TRANSFORMER
AND MAIN AC BUS
OVER CURRENT
PROTECTION
TRANSFORMER
PROTECTIVE
RELAYS
CIRCUIT BREAKER
FAILURE
PROTECTION
CONVERTER BUS
DIFFERENTIAL
PROTECTION
CONVERTER
OVER CURRENT
PROTECTION
DC ABNORMAL
VOLTAGE
PROTECTION
AC BUS
ABNORMAL
VOLTAGE
PROTECTION
AC TERMINAL
SHORT CIRCUIT
PROTECTION
DC CABLE
FAULT
INDICATION
AC FILTER
CAPCITOR
UNBALANCE
PROTECTION
AC FILTER
RESISTOR/REACTOR
OVERLOAD
PROTECTION
VALVE
SHORT CIRCUIT
PROTECTION
VALVE
CURRENT
DERIVATIVE
PROTECTION
IGBT
POSITION
MONITORING
VALVE
COOLING
PROTECTION
60
ABB
DESCRIPTIONS
5.3 Control and protection platform - MACH 2
5.3.1 General
To operate a conventional HVDC
or an HVDC Light® transmission as
efficiently and flexibly as possible, a
powerful, flexible and reliable control and protection system is clearly
required. The control system should
not impose any limitations on the
control of the main system apparatus, such as the converter valves,
and should not prevent the introduction of new, advanced, control and
protection functions.
To fulfill the current and future
requirements of the HVDC and
HVDC Light® control and protection
system, ABB has developed a fully
computerized control and protection
system using state-of-the-art computers, micro-controllers and digital signal processors connected by
high-performance industrial standard buses and fiber optic communication links.
The system, called MACH 2, is
designed specifically for converters in power applications, meaning
that many compromises have been
avoided and that both drastic volume reductions and substantial performance improvements have been
achieved.
ABB
All critical parts of the system
are designed with inherent parallel redundancy and use the same
redundancy and switchover principles as used by ABB for HVDC
applications since the early 1980s.
Because of the extensive use of
computers and micro-controllers, it
has been possible to include very
powerful internal supervision, which
will minimize periodic maintenance
for the control equipment.
Developments in the field of electronics are extremely rapid at present, and the best way to make sure
that the designs can follow and benefit from this development is to build
all systems based on open interfaces. This can be done by using
international and industry standards, wherever possible, as these
standards mean long lifetimes and
ensure that spare and upgrade parts
are readily available.
As a consequence of placing all
functions in computers and microcontrollers, the software will play the
most important role in the design of
the system. By using a fully graphical functional block programming
language and a graphic debugging
tool, running on networked standard
computers, it is possible to establish
a very efficient development and test
environment to produce high quality
programs and documentation.
To achieve high reliability, quality is
built into every detail from the beginning. This is assured by careful component selection, strict design rules
and, finally, by he extensive testing
of all systems in a real-time HVDC
simulator.
61
DESCRIPTIONS
5.3.2 Control and protection
system design
The HVDC Light® Control and protection system, built with the MACH
2 equipment, consists of HMI, main
computer systems, I/O systems and
valve control (valve base electronics),
typically arranged as shown in the
figure below.
The design criterion for the control
system is 100% availability for the
transmission system. The way to
achieve this is that no single point
of failure should interrupt operation.
Therefore, redundancy is provided
for all system parts involved in the
power transfer of the HVDC Light®
transmission.
The redundant systems act as active
or hot standby. At any time, only one
of the two control systems is active,
controlling the converter and associated equipment. The other system, the standby system, is running,
but the outputs from that system
are disabled. If a fault is detected
in the active system, the standby
system takes over control, becoming the active system. The internal
supervision giving switchover orders
includes auxiliary power supervision,
program execution supervision (stall
alarm), memory testing and supervision of the I/O system communication over the field buses. The special ABB feature of using appropriate
protections for switchover between
systems further increases the control system reliability.
System
servers
Gateway
computer
Thanks to the high performance of
the MACH 2 equipment, the type of
hardware and system software used
for an ABB HVDC Light® control system are the same as in a classic
HVDC control system. In fact, only
the application software differs. This
is also the case with the valve control
(valve base electronics), including
the communication to the IGBT firing
unit, although a more advanced firing
logic is needed for the IGBTs.
Operator
Workstation
Maintenance
workstation
A
B
LAN
PCPB
PCPA
Main computer
System A
Main computer
System B
Field Bus Systems A
I/O
system 1A
I/O
system nA
Field Bus Systems B
Valve
Control A
Valve
Control B
I/O
system 1B
I/O
system nB
Valve Interface
Mach 2 Control and Protection system structure
62
ABB
DESCRIPTIONS
5.3.3 Main Computers
To take full advantage of the rapid
electronic developments, the main
computers of the Mach 2 system
are based on high-performance
industrial computer components.
This ensures that ABB can take full
advantage of the extremely rapid
developments in the field of microprocessors and always design the
control and protection system for the
highest possible performance.
The main computers are built
around COM Express modules with
Intel® Core™ Duo processors, giving the main computers very good
performance and, at the same time,
very low power consumption. The
low power consumption means
that the main computers can be
designed with self-convection cooling. Dust problems connected with
forced air-cooling are therefore
avoided.
The main computers are designed
for mounting in the rear-mounting
plane of control and protection cubicles. The operating status of the
computers/systems is clearly indicated on the front on all computers.
The main computers for control and
protection include one ore more PCI
boards, PS803, as an interface with
the I/O system. The PS803 boards
have a general-purpose processor
and four DSPs for high-performance
computing. Control and protection
functions are normally running in the
main computer, but the DSPs on the
PS803 boards are used for highperformance applications. As an
example, the firing control system,
including converter sequences, runs
in a single PS803 board.
The main computer may also include
one or more measuring boards for
optical current measurement.
High performance DSP board PS803
5.3.4 I/O system
The process interface of the redundant main computer systems is the
I/O systems, placed in the control
and protection cubicles or in separate cubicles or boxes. The field bus
connections between the different
levels of equipment (cubicles) are
always optical to avoid any possible
interference.
Main Computer
ABB
63
DESCRIPTIONS
5.3.5 Communication
The communication inside the converter station uses a hierarchy of
serial buses. A general rule for the
use of serial buses is that only industry (or international) standard buses
are used. This means that no proprietary buses are used. The objective
is to ensure a long economic lifetime
for the buses and to ensure that the
components used to build the bus
structures are available from independent sources.
- Local communication
• The local area network used in the
pole is based on the well-known IEEE
802.3 (Ethernet).
• The SCADA LAN is used to transfer
data between the control and protection main computers and the various
clients on the network, OWS, GWS.
Field Buses
CAN Bus
ISO standard buses, ISO 11898, also
known as CAN (Control Area Network), are used for communication
with binary type I/O devices (disconnectors and breakers etc.), within the
I/O systems. The CAN bus combines
a set of properties important for use in
an HVDC station.
• It is a high-speed bus with an efficient short message structure and
very low latency.
• There is no master/slave arrangement, which means that the bus is
never dependent on the function of
any single node to operate correctly.
• CAN also have efficient CRC
checksum and hardware features to
remove a faulty node from the network.
The CAN communication within an
I/O system is performed via the backplane of the I/O racks. Extension
cables with shielded, twisted pairs are
64
used for the connection of adjacent
racks in the cubicle. Fiber optic communications on eTDM are used for
communication outside of the cubicles or control room.
Any application (software function)
in a control, protection or I/O system
can readily communicate with other
applications, simply by connecting
their signals respectively to send and
receive software function blocks.
eTDM bus
The eTDM bus used in the Mach 2
system is primarily a high-speed, single fiber, optical data bus for digitized
analog measurements. Due to the
high-speed-performance of the bus, it
has been possible to include the binary data from the CAN bus of the I/O
systems as an “overlay” on the eTDM
bus communication.
The eTDM bus used is characterized
by large data carrying capacity, very
low latency and “no jitter” operation.
This is absolutely essential when used
to feed the HVDC controls with high
bandwidth measured signals. Each
eTDM bus is able to transmit over
300,000 samples per second (one
sample every 3 µS).
- Remote communication
If station-to-station communication is
included, it is handled by communication boards in the main computer of
the pole control and protection (PCP)
cubicles. This pole-level communication gives a more robust design than a
centralized station-level telecommunication unit. The communication is synchronous and conforms to ISO3309
(HDLC frames) for high security.
If available, a LAN/WAN type of communication can also be used which
eliminates the need for special communication boards and provides even
higher performance.
ABB has experience with all types of
telecommunication, ranging from 50
and 300 bps radio links, via the very
common 1200, 2400 or 9600 bps
communication links using analogue
voice channels, up to digital 64 kbps
or higher speed links obtained with
optical fiber connections.
5.3.6 Software
- Application software development
(HiDraw)
Most application software for the
HVDC control and protection system
is produced using a fully graphical
code-generating tool called HiDraw.
HiDraw is very easy to use, as it is
based on the easiest possible dragand-drop method. It is designed to
produce code either in a high level
language (PL/M or ANSI standard C)
or in assembly language. For functions not available in the comprehensive library (one for each type of processor board), it is very easy to design
a new block and to link this to the
schematic with a simple name reference. HiDraw can be run on any
industry-standard Windows-compatible computer.
A schematic drawn in HiDraw consists of a number of pages. One page
specifies cycle times and the execution order of the other pages. HiDraw
includes a first on-screen plausibility check of the drawn schematic and
automatic cross-reference generation between the pages. As output,
HiDraw produces code and a “make”
file ready to be processed.
The next step in the workflow is to run
this make file (on the same computer)
which means invoking the necessary
compiler/assembler and link locate
programs (these are usually obtained
from the chip manufacturers e.g. Intel
and Analog Devices). The result is a
file that is ready to be downloaded
from the computer to the target and
stored in the flash PROMs.
ABB
DESCRIPTIONS
29
EXT
UPDATE_FOSYS
Telecom Analog
RECEIVE
From Other:
SYSTEM
Application ID:
SEQ
Block No: 2
Board ID: PCID
Telecom Analog
SEND
SPEED_REF_FOSYS
To Other: SYSTEM
Application ID: SEQ
Block No: 2
Board ID: PCID
Hysteresis:
1.0
Cyclic update:
10
Enable
TRUE
39
29
EXT
EXT
48
48
EXT
EXT
11
EXT
48
EXT
29
EXT
48
EXT
EDS_IN_OPERATION
SPEED_REF_ENABLE
&
SPEED_RT_UP_NORMAL
SPEED_RT_UP_STARTUP
MAX_SPEED_REF_LIMIT
SPEED_REF ( PUBLIC )
PCDA_SPEED_REF
EXT
EXT
39
MIN_SPEED_REF_LIMIT
0.0
48
48
SPEED_REF_RT_UP
CONV_DEBLOCKED
p.u.
SPEED_RT_DOWN_NORMAL
SPEED_RT_DOWN_STARTUP
SPEED_REF_RT_DW
q
-1
Send PCI DPM
OMEGA_REF_PU
0.000556
rpm/pu
Note: speed reference in p.u.
motor shaft speed 1800 rpm <=> 1.0 pu
Design checked by
Name:
SPEED_CTRL
Motor Speed Control
Proc.type:
Rev Ind
Revision
Appd
Year Week
Type:
TASK
MainCPU
B Nordstrom
Board ID: PCIA
Board type: PS801
Area:
DSP1
Signal No: 9
Troll A
FUNCTIONAL DIAGRAM
Drawing checked by
H Blom
SEQUENCES
Drawn by
Iss by Dept
P Karreby
ABB POWER SYSTEMS AB
TCC
Year Week
02/44
1JNL100089-652
DSP1A : 51
Rev Ind
Sheet
Rev Ind
Sheet
00
38
Cont
39
HiDraw schematic
- Hierarchical design
HiDraw supports hierarchical design
in order to ease understanding of
complex applications and to encourage top-down design. Hierarchical
design means an organization of the
drawings in a hierarchical structure,
where symbols on the top layer represent functionality in rough outlines.
Double-clicking on such a symbol
opens a “hierarchical drawing” with
more details of that symbol, etc. (see
figure below).
ABB
65
DESCRIPTIONS
STEPPING
LOGIC
CURRENT
POWER_ORDER
CUR_ORD_LIM
CUR_ORD
166
ORDER
LIMITER
FUNCTION
UD
UD
CALC
Name:
Func
Space for explanation
Proc.type:
02
14
20
20
20
34
UPDATE_FOSYS
B_INTG_OSYS
PO_IO_OSYS
PPTS_OSYS
SEND
RECEIVE
SEND
RECEIVE
22
49
22
PO_IO4_FOP ( PUBLIC )
PO_IO4
14
PO_IO_FOSYS ( PUBLIC )
PO_IO_FOP
IOMAX_TYPE5
OVERLOAD_LIM
THYR_TEMPLIM
SEND
RECEIVE
SEND
RECEIVE
B_INTG_FOSYS ( PUBLIC )
B_INTG_FOP
34
IO_MAX
SEND
RECEIVE
SEND
RECEIVE
PPTS
POWER_ORDER
PPTS_FOP
BFOW11
IO_CFC_FOP ( PUBLIC )
IO_CFC
BFOW14
45
45
BPO_REF
BPO_RAMP
BFOW1
BPO_REF_FOSYS ( PUBLIC )
BPO_RAMP_FOSYS ( PUBLIC )
BPO_REF_FOP
BPO_RAMP_FOP
RECEIVE
SEND
&
IOMAX ( PUBLIC )
SLFR9
22
45
45
16
16
TYPE3_DP
TYPE4_DP
11
15
PWR_DIR_NORM
11
11
SLF_BPO_MAX
SLF_MAX
32
32
30
29
29
23
BFOW4
11
11
BFOW13
BFOB2
BPO_REF_FOSTA ( PUBLIC )
BPO_RAMP_FOSTA ( PUBLIC )
>1
RUNB1
INIT_TYPE5 ( PUBLIC )
>1
>1
RUNB2
23
31
RUNW1
SLFB1
13
19
SLFR10
SLFB2
RB2
RB2_FOSTA
>1
RUNB3
SLFB3
>1
RUNB6
TESR3
49
19
THYR_TEMP_UPDATE
THYR_TEMP_UPDATE_FOSTA
13
44
19
PROT_ORD_P_BAL
ORD_P_BAL
ORD_P_BAL_FOSTA
16
11
11
TYPE5_IOMAX
RB1_IOMAX
RB2_IOMAX
PACK
>1
RUNB4
RUNW2
MODMAX
TYPE34_DP
UD
TYPE34_NS
TYPE34_NORM
PROJECT_PWR
52
SLFMAX
SLFR1
MODMIN
UPDATE_SLF
NEW_SLF_VALUE
SLF_INPROG
PO_IO2 ( PUBLIC )
PO_IO1
PO_IO
SLF
FINAL_REF
34
RUNB7
>1
P_BAL ( PUBLIC )
40
RUNR2
CUR_ORD_LIM
31
32
FINAL_RAMP
B_CONT_ON
SLF_BPO_MIN
SLF_MIN
SLFMIN
SLFR8
SEND
RB1
RB1_FOSTA
34
34
BPO_REF_OSYS
BPO_RAMP_OSYS
RECEIVE
TYPE5_INIT
TYPE5_UPDATE
13
19
RUNI1
35
LEAD
STEP_SIZE
SLFR2
BFOW2
SEND
16
16
STEP_TIME
BFOB1
BFOW12
IO_MAX_TOSTA
1
UPDATE_TYPE5 ( PUBLIC )
STEP_TRIGG
27
BFOW9
BFOW10
35
1000
1002
SLFW1
STEP_TEST ( PUBLIC )
51
25
UD_FOP ( PUBLIC )
UD_FILT
00
4870 210-A
95 05
SEND
SLFR11
IO_MAX_FOSTA
B_INTG
BASE DESIGN
LKC
RECEIVE
BFOW8
26
OWN FUNCTION
JT
32
BFOW7
51
FUNCTIONAL DIAGRAM
G Odnegård
45
BFOW6
PO_IO
33
M Hyttinen
H Alerman
Type: TASK
PO_IO_TOSTA ( PUBLIC )
1
45
45
49
19
19
THYR_TEMP_LIM
THYR_TEMP_LIM_FOSTA
THYR_TEMPLIM ( PUBLIC ) 33
PO_IO_ABS ( PUBLIC )
29 31 32
36 52
RECEIVE
35
21
IO_CFC
IO_CFC_FOP
RUNR1
BFOW5
PO_IO ( PUBLIC )
BFOW3
20 21 30
36 41 42
BFOB3
Name: BIPFOP
signals to and from other pole
Type: SUBTASK
M Hyttinen
FUNCTIONAL DIAGRAM
G Odnegård
OWN FUNCTION
H Alerman
BASE DESIGN
LKC
95 05
4870 210-A
Name:
00
SLF
Stepping Logic Function
21
Proc.type:
22
BASE DESIGN
M Hyttinen
FUNCTIONAL DIAGRAM
G Odnegård
POLE POWER CONTROL
510
H Alerman
Type: SUBTASK
LKC
ID_100_PU
ICONT
ID_OVER_AMB
STOL0_9
STOL0_2
33
RUNBACK
runback handling
34
Type: SUBTASK
1
15
61
Name:
02
4870 210-A
95 05
STOL0_3
&
STOL_DISABLE ( PUBLIC )
ENABLE_START_STOL
&
LIM_OFS
M Hyttinen
FUNCTIONAL DIAGRAM
G Odnegård
OWN FUNCTION
H Alerman
BASE DESIGN
LKC
95 05
4870 210-A
00
63
START_STOL
SR6
HI_LIM
&
SR1
SR8
PO_10
INTG
1
SR12
64
64
INTG_FOSYS
SR5
LO_LIM
STOL0_1
DOWN_TIME_CONST
58
STOL0_5
1
ENABLE_LEV
TIME_CONST
UP_TIME_CONSTANT
EN_STOL
&
STOL0_14
STOL0_13
UPDATE_FOSYS_OLL
RESET_COUNTER
START_STOL
64
STOL_RUNNING_FOSYS
STO3B1
& S Q
1
STOL_NOT_RUNNING_FOSYS
STOL_RUNNING
STOL_RUNNING_TOSYS ( PUBLIC )
1
STOL_RUNNING_IND ( PUBLIC )
1
STO3B3
64
65
R
RESET
RESET
64
STOL_TIME_FOSYS
Itop
SR7
SR11
SEC_PER_TIC
ZERO_PER_TIC
STOL_TIME_TOSYS ( PUBLIC )
1
SR10
STOL_TIME
SR4
Table
Y
64
03
STOL_LIM ( PUBLIC )
63
X
SR9
SR3
time
OLD_STOL_TIME
Name:
STOL
short time overload limiter calc.
Proc.type:
510
Type: SUBTASK
M Hyttinen
FUNCTIONAL DIAGRAM
G Odnegård
POLE POWER CONTROL
H Alerman
BASE DESIGN
LKC
95 05
4870 210-A
02
62
63
Hierarchical symbols and drawings
5.3.7 Input to system studies
Code generation is performed by
means of the code definitions in
an HDF file (HDF = HiDraw Definition Format). Each graphical symbol
in a symbol library has a name, and
the name is used to define a piece
of code in a separate HDF file. This
open ABB approach is very advantageous in several aspects. One is from
the HVDC Light® system point of
view. The HiDraw drawings for con-
66
trol and protection, with the normal
definition files producing code in C,
PL/M, or DSP-assembler, are used
simply by switching the definition files
used to generate FORTRAN code.
The electromagnetic transient program PSCAD (previously PSCAD
(previously EMTDC) can use this
FORTRAN code directly, and an
exact representation of the control and protection functions is thus
achieved in the digital system studies.
ABB
22
23
33
DESCRIPTIONS
5.3.8 Debugging facilities
For debugging, a fully graphical
debugger, known as HiBug, operating under Windows is used.
HiBug allows the operator to view
several HiDraw pages at the same
time and look at any internal software “signal” in real time simply by
double-clicking on the line that represents the signal. Parameters can
be changed easily by double-clicking on their value.
For fault tracing, it is easy to follow a signal through several pages
because when a signal passes from
one page to another, a double click
on the page reference automatically
opens the new page and allows the
trace to continue immediately on the
new page.
There are also a number of supporting functions, such as single or multiple stepping of tasks (one HiDraw
page is normally a task) and coordinated sampling of signals.
The fact that HiBug allows inspection of signals while the application
system is running makes it very useful not only for debugging but also to
facilitate maintenance.
Because the debugger works in the
Windows environment, it is also possible to transfer sets of signal values to other Windows-compatible
programs, such as Excel, for further
analysis.
All these development and debug
tools are, of course, supplied to all
customers of our plants, to facilitate their maintenance and future
improvements of their HVDC Light®
control and protection systems.
5.3.9 Human-machine interface
(HMI)
A well-designed and flexible humanmachine interface (HMI) is clearly essential when it comes to more
demanding application areas such
as HVDC Light® power transmission.
To avoid human errors, all parts of
these systems must also be easy
to use. The HMI must be able to
announce alarms and perform operator controls in a safe and reliable
way. Incorrect operator actions due
to a bad HMI are not acceptable and
could be very costly.
The requirements for tools of this
type are therefore strict. For example, several thousands of measured
values, indications and alarms of different types need to be handled. All
changes in the state of these signals
must be recorded with high-time
resolution for accurate real-time and
post-fault analysis. Time resolution
down to one millisecond between
the stations is often required.
The new generation of integrated
HMIs adopted by ABB in MACH 2™,
the station control and monitoring
(SCM) system, employs the most
advanced software concepts with
regard to system openness and flexibility, as well as ergonomic aspects.
A number of power companies have
made valuable contributions to this
work.
HiBug
ABB
67
DESCRIPTIONS
Distributed over an Ethernet LAN,
the SCM system comprises several operator workstations (OWSs)
and SQL servers. The Windows NT
based OWSs are characterized by
high performance and an open software architecture based on the latest trends in data engineering supporting TCP/IP, SQL and OPC.
The SCM system integrates a large
number of features such as:
• Control of the HVDC Light® from
process images, see the figure
below
• Sequential Event Recorder, SER,
See the figure below
• Archiving of events
SLD for a typical HVDC Light® station
• Powerful alarm handling via list
windows
• Effective user-defined data filtering
• Flexible handling of both on-line
and historical trends
• On-line help functions and direct
access to plant documentation
• TFR analysis
• Remote control via Dispatch Gateway
• Instant access to standard applications such as e-mail, word processing, spreadsheet, Internet
• Automatic performance report
generation developed with the most
versatile graphical package
Event list
68
ABB
DESCRIPTIONS
5.3.10 Maintenance of MACH 2
- General
As far as possible, the ABB control
equipment is built to avoid periodic
maintenance and provide the shortest possible repair times. Due to its
redundant design, the maintenance
of the control equipment does not
require any periodic shutdown of
any main circuit equipment.
Maintenance is minimized by the
extensive use of self-supervision
built into all microprocessor-based
electronic units and the ability to
check all measured values during operation without disturbing the
operation.
The internal supervision of microprocessor-based systems includes
auxiliary power supervision, program
execution supervision (stall alarm),
memory test (both program and
data memory) and supervision of the
I/O system communication over the
field buses.
The operation of the field buses is
monitored by a supervisory function
in the pole control and protection
system, which continuously writes to
and reads from each individual node
of the system. Any detected fault
results in an alarm and switchover to
the standby system.
ABB
Another example of integrated selfsupervision is the switch control unit.
In this unit, the outputs to the breakers, etc., are continuously monitored
to detect failure of the output circuits
of the board. Very short repair times
are facilitated by the self-supervision, but another contribution to this
is the high degree of integration in all
units. As an example, the entire control computer, including the converter firing control system, etc., is easily changed in a couple of minutes,
as the whole system is a single-rack
unit with only a handful of connection cables.
As the TFR is an integrated part of
the HVDC control system, it also
runs in both the active and the
standby systems.
Any standard software analysis program interpreting the COMTRADE
format, (IEEE C37.111-1991), can be
used for post-fault analysis of the
stored TFR records.
- Transient fault recorder (TFR)
The TFR integrated in the HVDC
control system, as a part of the control and protection software, is an
invaluable tool for maintenance and
out-performs old-fashioned external
TFR’s, as it always gives a correct
representation of the important internal control signals. The TFR continuously samples the selected channels
to be monitored for fault analysis.
There is a predefined selection of
protection and control signals, but
also a number of channels which
are available to be chosen freely by
the operator. This makes it possible to monitor any internal signal in
the control and protection software.
Important external signals can, of
course, also be connected for monitoring by the TFR.
69
DESCRIPTIONS
5.4 HVDC Light® Cables
5.4.1 Design
The cables are designed to meet the
current and voltage ratings for the
specified power transmission capacity and for the specified installation
conditions.
5.4.2 Land cable
A general cutaway drawing of the
land cable design is shown below
Conductor
Aluminum or copper
Conductor screen
Semi-conductive polymer
Insulation
Cross linked HVDC polymer
Insulation screen
Semi-conductive polymer
Metallic screen
Copper wires
Swelling tape
Aluminum laminate
Outer covering/Sheath
Polyethylene
70
ABB
DESCRIPTIONS
5.4.3 Submarine cable
A general cutaway drawing of the
submarine cable design is shown
below
Conductor
Aluminum or copper
Conductor screen
Semi-conductive polymer
Insulation
Cross linked HVDC polymer
Insulation screen
Semi-conductive polymer
Swelling tape
Lead alloy sheath
Inner jacket
Polyethylene
Tensile armor
Galvanized steel wires
Outer cover
Polypropylene yarn
ABB
71
DESCRIPTIONS
5.4.4 Deep-sea submarine
cable
A general cutaway drawing of the
deep-sea submarine cable design
is shown below
Conductor
Aluminum or copper
Conductor screen
Semi-conductive polymer
Insulation
Cross linked HVDC polymer
Insulation screen
Semi-conductive polymer
Swelling tape
Lead alloy sheath
Inner jacket
Polyethylene
Tensile armor
Two layers of tensile armors
(laid in counter helix)
Galvanized steel wires
Outer cover
Polypropylene yarn
72
ABB
DESCRIPTIONS
5.5 General design of cables
Typical HVDC Light® cable designs
are previously shown.
5.5.1 Cable parts
- Conductor
The shape of the conductor is round
and built up of compacted stranded
round wires or, for large cross-sections, concentric layers of keystoneshaped wires.
On request, the conductor can be
water sealed, in order to block longitudinally water penetration in case of
damage to the cable
- Insulation system
The HVDC polymeric insulation system consists of:
- Conductor screen
- Insulation
- Insulation screen
The material, specifically developed
for HVDC cables, is of the highest
quality, and the insulation system is
triple-extruded and dry-cured. The
sensitive interface surfaces between
insulation and conductive screens
are not exposed at any stage of the
manufacture of the insulation system.
High-quality material handling systems, triple extrusion, dry-curing
and super-clean insulation materials
guarantee high-quality products.
ABB
- Metallic screen
Copper wire screen, for land cables,
with cross-section design for fault
currents.
- Metallic sheath
A lead alloy sheath is provided for
submarine cables.
A metal-polyethylene laminate may
be provided for land cables. The
laminate is bonded to the polyethylene, which gives excellent mechanical properties.
- Inner jacket (for submarine
cables)
A polyethylene sheath is extruded
over the lead sheath. The polyethylene sheath provides mechanical
and corrosion protection for the lead
sheath.
- Tensile armor (for submarine
cables)
The tensile armor consists of galvanized round steel wires close to
each other twisted round the cable.
The tensile armor is flooded with
bitumen in order to obtain effective
corrosion protection.
The tensile armor is needed when
the cable is laid in the sea. The tensile armor also offers mechanical protection against impacts and
abrasion for a cable that is not buried to safe depth in the seabed.
- Outer sheath or serving
The outer serving for submarine
cables consists of two layers of polypropylene yarn, the inner one impregnated with bitumen. The polypropylene yarn is a semi-wet covering.
The outer sheath on land cables is
normally a thermoplastic polyethylene (PE) sheath or an extruded PVC
sheath. PE is a harder material offering better mechanical protection,
and is the first choice for most applications.
PVC sheaths are classified as halogen material and are flame-retardant.
The surface of the outer sheath may
be provided with a thin conductive layer, which is simultaneously extruded with, and thus strongly bonded to, the non-conductive
underlying jacket. This is useful to
ensure the physical integrity of the
cable in the post-installation test.
5.5.2 Standards and
Recommendations
- Cigré, ELECTRA No. 171 Recommendations for mechanical tests
on sub-marine cables
- Cigré Technical Brochure Ref No
219 “Recommendations for testing DC extruded cable systems for
power transmission at a rated voltage up to 250 kV”
- IEC 60228 Conductors of insulated cables
- IEC 60229 Tests on extruded
over-sheaths which have a special
protective function.
- IEC 60287 Electric cables - Calculation of the current rating
- IEC 60840 Power cables with
extruded insulation and their
accessories
73
DESCRIPTIONS
5.5.3 Testing
Tests are performed according to
combinations of relevant parts from
- Cigré recommendations for
mechanical testing of submarine
cables published in Electra 171
- IEC 60840, Power cables with
extruded insulation and their
accessories
- Cigré “Recommendations for testing DC extruded cable systems for
power transmission at a rated voltage up to 250 kV”, published in
Cigré Technical Brochure Ref No
219
HVDC Light® Cable test voltages
U0 UT
kV kV
80 148
150 278
320 555
UTP1
kV
116
217
435
LIPL
kV
160
304
573
UP1
kV
185
350
660
SIPL
kV
143
275
541
UP2,S
kV
165
320
630
UP2,O
kV
92
175
350
Definitions
U0 Rated DC voltage.
UT Load cycle test voltage =
1.85U0 at test at works and
Factory Acceptance Test.
UTP1 Polarity reversal test voltage
= 1.45U0, also for
post-installation testing.
UP1 Lightning impulse voltage
> 1.15LIPL. Not applicable
for HVDC Light® System.
UP2,S
Same polarity switching
impulse voltage > 1.15SIPL.
UP2,O
Opposite polarity switching
impulse voltage
74
Peak values of UP1, UP2,S and UP2,O
are defined as maximum voltages
to ground when a suitable charge is
transferred from the impulse generator to the cable.
5.5.3.2 Routine and sample test
Routine testing will be performed on
each manufactured length of cable.
- Voltage test, UT during 15 minutes.
For land cables also:
5.5.3.1 Type test
The table below summarizes the
status of type-tested HVDC Light®
cable systems (up to year 2007). If
type tests have already been performed, they need not to be repeated for cables within the scope of
approval as defined by Cigré.
Voltage
U0
[kV]
80
80
80
150
150
150
320
Conductor
area
[mm2]
95
300-340
630
95
1000-1600
2000
1200
Total
Number of
performed
type tests
2
5
2
4
11
2
2
28
The electrical type tests are composed of following test items:
- Mechanical tests: Bending of land
cables as per IEC 60840. Submarine cables as per Cigré Recommendations, ELECTRA No. 171 –
clause 3.2.
- DC-testing of non-metallic sheath,
according to IEC 60229.
The following sample tests are performed (generally on one length from
each manufacturing series):
- Conductor examination
- Measurement of electrical resistance of the conductor
- Measurement of thickness of insulation and non-metallic sheath
- Measurement of diameters on
complete cable (for information)
- Hot set test of insulation material
5.5.3.3 Post-installation test
- Voltage test, UTP1 during 15 min.
For land cables also:
DC-testing on non-metallic sheath,
according to IEC 60229
- Load Cycle Test
- Superimposed impulse voltage
test: Switching Surge Withstand
Test, at UP2,S and UP2,O
ABB
DESCRIPTIONS
5.5.4 Cable drums
Land cables are typically transported on cable drums.
Cable lenghts in metres on Wooden drum K14 - K30 and Steel drum St 28 - St 34
Cable
dia.
mm
36
38
40
42
44
46
48
50
52
54
56
58
60
62
64
66
68
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
102
104
106
108
110
112
114
116
118
120
122
124
126
128
130
132
134
ABB
Wooden drum
K14
570
470
450
430
340
330
310
K16
760
630
610
500
480
450
360
360
340
320
260
240
K18
850
820
690
660
530
510
480
400
385
360
360
275
275
250
250
240
240
K20
1155
1075
900
870
720
690
660
550
530
505
475
385
365
365
345
345
320
250
250
250
230
230
K22
1560
1290
1100
1070
1030
860
820
670
670
640
610
510
480
480
450
370
345
345
345
320
320
320
230
230
210
210
210
210
K24 K26
2090 2860
1780 2490
1560 2220
1510 2160
1310 1830
1260 1780
1070 1540
1020 1490
910 1280
870 1280
825 1090
720 1040
680 990
680 460
545 825
545 825
515 785
515 670
480 635
400 635
400 625
400 600
325 500
325 470
300 470
300 470
275 440
275 440
355
325
325
325
325
Steel drum
K28
4000
3600
3200
3100
2800
2430
2360
2090
1830
1775
1715
1550
1490
1270
1270
1230
1025
1030
985
985
810
810
810
775
660
615
615
615
585
585
485
485
455
K30
5800
4900
4400
3950
3900
3460
3130
2820
2750
2450
2380
2090
2030
1770
1730
1535
1475
1475
1260
1260
1210
1210
1015
1015
1015
965
840
840
800
800
755
640
640
St 28
4600
4300
3700
3600
3000
2900
2450
2410
2300
1880
1840
1800
1760
1390
1350
1320
1280
1280
1010
980
940
910
910
885
880
660
630
630
610
610
585
580
580
560
560
385
380
380
365
360
360
345
340
340
325
325
325
325
305
305
St 30
6080
5335
5085
4485
3830
3695
3175
3120
2990
2520
2470
2410
2050
1940
1890
1575
1530
1530
1490
1440
1170
1130
1130
1090
1090
1050
820
820
785
785
755
755
755
725
725
530
530
530
505
505
505
480
480
480
450
450
450
450
305
305
St 32
7670
6830
6030
5850
5100
4500
4340
3880
3720
3200
3130
2740
2680
2540
2180
2125
2060
2060
1750
1690
1640
1590
1360
1310
1310
1270
1220
1220
970
970
930
930
930
900
900
690
690
690
660
660
660
625
625
625
595
595
450
450
430
430
St 34
9350
8420
7530
6820
6000
5800
5170
4670
4490
3920
3850
3410
3340
2850
2780
2710
2340
2340
2290
1950
1890
1830
1830
1540
1540
1490
1430
1430
1380
1180
1130
1130
1130
1080
1080
860
860
860
820
820
820
785
785
785
595
595
595
595
560
560
St 35
9930
8970
8050
7320
6475
6260
5600
5090
4890
4300
4220
3775
3690
3170
3100
2710
2640
2640
2290
2230
2160
2090
1840
1780
1780
1720
1430
1430
1380
1380
1330
1330
1140
1080
1080
1040
1040
1040
990
820
820
780
780
780
740
740
740
740
560
560
St 36
11130
10110
9130
8350
7400
6720
6040
5520
5300
4680
4600
4140
4050
3500
3420
3020
2940
2940
2580
2510
2430
2090
2090
2030
2030
1720
1660
1660
1600
1390
1330
1330
1330
1280
1280
1040
1040
1040
990
990
990
950
950
790
740
740
740
740
700
700
St 37
11750
10700
9680
8880
7940
7200
6490
5960
6730
5080
5600
4510
4050
3850
3420
3340
3250
2960
2880
2800
2430
2350
2350
2030
2030
1970
1890
1670
1600
1600
1540
1540
1340
1280
1280
1230
1230
1230
990
990
990
950
950
950
900
900
750
750
700
700
St 38
13000
11200
10250
9400
8450
7690
6950
6410
6165
5490
4990
4900
4430
4200
3675
3675
3250
3250
3190
2800
2720
2635
2370
2295
2295
2220
1890
1890
1835
1835
1540
1540
1540
1490
1490
1230
1230
1230
1180
1180
1180
1120
950
950
900
900
900
900
850
850
St 39
13600
12500
11400
9900
8900
8100
7400
7300
6600
5900
5400
5300
4800
4570
4100
4000
3580
3600
3190
3100
3000
2635
2635
2560
2310
2220
2140
2140
1835
1835
1760
1760
1760
1490
1490
1430
1430
1430
1180
1180
1180
1120
1120
1120
1070
900
900
900
850
850
St 40
14900
13100
12000
11100
9500
8600
7900
7800
7060
6340
5810
5710
5200
4570
4470
4010
3910
3910
3510
3420
3010
2920
2920
2560
2560
2495
2140
2140
2070
2070
1760
1760
1760
1710
1710
1430
1430
1430
1370
1370
1370
1120
1120
1120
1070
1070
1070
1070
850
850
St 43
17700
15700
14500
12900
11740
10840
9960
9330
8500
7690
7120
6560
6450
5730
5220
5100
4610
4610
4190
4080
3630
3520
3520
3140
3140
3050
2670
2670
2580
2340
2240
2240
2240
1930
1930
1860
1860
1860
1570
1570
1570
1500
1500
1320
1250
1250
1250
1250
1190
1190
75
DESCRIPTIONS
Sizes and weights of wooden drums
Drum type
Shipping volume
Drum weight incl. battens
m3
K14
K16
K18
K20
K22
K24
K26
K28
K30
2.14
2.86
3.58
5.12
6.15
7.36
10.56
13.88
17.15
kg
185
275
320
485
565
625
1145
1460
1820
mm
1475
1675
1875
2075
2275
2475
2700
2900
3100
b Flange diameter
mm
1400
1600
1800
2000
2200
2400
2600
2800
3000
c Barrel diameter
mm
800
950
1100
1300
1400
1400
1500
1500
1500
a Diameter incl battens
d Total width
mm
982
1018
1075
1188
1188
1200
1448
1650
1800
e Spindle hole diameter
mm
106
106
131
131
131
131
132
132
132
Sizes and weights of steel drums
Drum type
St 36
St 37
St 38
St 39
St 40
Shipping volume
m3
20.6
23.5
26.6
28.9
31.6
33.4
35.2
37
38.9
40.9
47.1
Drum weight incl. battens
kg
1500
1700
2200
2600
2700
2800
3000
3100
3300
3500
4000
a Diameter incl battens
mm
2930
3130
3330
3530
3630
3730
3830
3930
4030
4130
4430
b Flange diameter
mm
2800
3000
3200
3400
3500
3600
3700
3800
3900
4000
4300
c Barrel diameter
mm
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
d Total width
mm
2400
2400
2400
2400
2400
2400
2400
2400
2400
2400
2400
e Spindle hole diameter
mm
150
150
150
150
150
150
150
150
150
150
150
St 28
St 30
St 32
St 34
St 35
St 43
Steel drums with outer diameters up
to 4.5 m are available, but transport
restrictions have to be considered.
Special low-loading trailers and permits from traffic authorities may be
required, depending on local regulations and conditions. Special wooden drums with a larger barrel diameter or larger width (up to 2.5 m) are
also available, if needed.
5.5.5 Installation
- Land cables
The installation of cable systems
consists mainly of cable pulling,
clamping of cable and accessories
as well as mounting of accessories.
The installation design is an important part of the cable system design.
ABB certified erectors perform the
high quality work necessary for the
reliable operation of a cable system
during its lifetime.
ABB has long and good experience
of traditional installation technologies
including direct burial, duct, shaft,
trough and tunnel, but also trenchless technologies including directional
drilling, pipe jacking and others.
76
- Submarine cables
The cable can be installed on all
types of seabed, including sand,
sediment, rocks and reefs. For protection against anchors and fishing gear, the cable can be buried by
various methods, or can be protected by covers.
Submarine cable installation may
include the following items of work:
- Route survey
- Calculation of tensile forces
- Installation plans
- Cable laying vessels
The cables can be laid either separately or close together, and protection can be provided by means
of water jetting or ploughing, either
simultaneously with or after the
cable laying.
- Marine works
- Burial of the cable
- Equipment for cable pulling
- Directional drilling on shore
- Post-installation testing
ABB
DESCRIPTIONS
5.5.6 Repair
- Fault Location
It is important to perform a fairly fast
pre-location of a fault for the repair
planning. The converter protections
identify the cable that is faulty. If possible, the pre-location could start
with an analysis of the records in the
converter stations in order to give a
rough estimate the location of the
fault.
- Pre-location of fault with pulse
echo meter or fault location bridge
A fault in the HVDC cable is prelocated with an impulse generator (Thumper) and a Time Domain
Reflection meter (TDR). The thumper creates high voltage impulses,
and the time required for the pulse
to travel forth and back is measured
with the TDR.
A fault in the HVDC cable can also
be located with a fault location
bridge. The fault location bridge is a
high-precision instrument based on
the Wheatstone measuring bridge,
and a measurement with the fault
location bridge should give approximately the same distance to the fault
as the TDR.
- Accurate location of a fault
The principle for this method is to
use the powerful thumper to create
a flashover at the fault. The sound
from the flashover and/or the magnetic field from the pulse is picked
up with microphones or with spikes
connected to a receiver.
- Repair time
An HVDC Light® cable repair on a
land cable should take less than a
week, even if a section has to be
removed and replaced in a duct sys-
ABB
tem. A directly buried cable can easily be opened and repaired in a short
time by installing a new section of
cable and two joints.
The basic requirement in this case
would be to have some spare joints,
spare cable and jointing tools available in the customers’ stores.
5.5.7 Accessories
The only accessories required for
HVDC Light® cable systems are
cable joints and terminations.
- Cable terminations
Terminations are used to connect
the cables to the HVDC converters. The terminations are mounted
indoors in the converter stations.
The termination is made up of several prefabricated parts.
Cable termination for 150 kV HVDC
Light® cables.
- Cable joints
Joints for HVDC Light® are based on
field molding or pre-fabricated joint
techniques.
The field molding method uses a
mini process to restore the insulation, and it gives a joint with the
same diameter as the cable.
Pre-fabricated joints are used to
connect the cables. The design
involves a screwed conductor connector and a pre-fabricated rubber joint body. The body has a builtin semi-conductive deflector and a
non-linear resistive field control. The
one-piece design of the joint body
reduces the amount of sensitive
interfaces and simplifies pre-testing
of the joint bodies.
77
DESCRIPTIONS
Pre-fabricated 150 kV HVDC Light® cable joint.
5.5.8 Auxiliary equipment
Other auxiliary equipment may be
used for the cable system, e.g.:
- Cable Temperature Sensing
Systems
- Forced Cooling Systems
5.5.9 Environmental
The cable does not contain oil or
other toxic components. It does not
harm living marine organisms. Due
to its design, the cable does not
emit electrical fields. The magnetic
field from the cable is negligible. The
cable can be recovered and recycled at the end of its useful life.
78
5.5.10 Reliability of 150 kV
HVDC Light® Cable projects
Cross Sound Submarine Cable,
Connecticut – Long Island
83 km HVDC Light® Cables
with 1300 mm2 copper conductor
7 pcs
Flexible Cable Joints
4 pcs Cable Terminations
Delivery year 2002.
Operating experience very satisfactory. No faults.
MurrayLink Land Cable, Victoria
– South Australia
137 km HVDC Light® Cables
with 1400 mm2 aluminum conductor
223 km HVDC Light® Cables
with 1200 mm2 aluminum conductor
400 pcs Stiff Cable Joints
4 pcs Cable Terminations
Delivery year 2002
Operating experience very satisfactory. One fault attributed to external
damage.
ABB
SYSTEM ENGINEERING
6 System Engineering
6.1 Feasibility study
During the development of a new
project, it is common to perform a
feasibility study in order to identify
any special requirements to be met
by the system design. ABB can supply models of HVDC Light® transmissions in the PSS/E simulation
tool. For unusual applications, ABB
can perform feasibility studies using
a detailed control representation in
PSCAD (previously EMTDC).
For new applications, it is advisable
that ABB performs pre-engineering
studies, which include main circuit
design, system performance and
station layout design.
The main circuit design includes the
following design studies:
- Main circuit parameters
- Single-line diagram
The layout of the main circuit equipment is determined by the electromechanical design, and the station
design specifies buildings and foundations.
- Insulation coordination
- AC and DC filter design
- Radio interference study
6.3 Validation
- Transient overvoltages
- Transient currents
- Calculation of losses
- Availability calculation
- Audible noise study
6.2 System design
A suitable rating of converters and
DC cables is determined to satisfy
the system requirements. The HVDC
Light® system is adapted to fulfill the
requirements for the project. Some
engineering work needs to be done
to define the system solution, equipment and layout needed.
The flow diagram below illustrates
the types of engineering required.
The control system design specifies
the requirements to be met by the
control and protection system. During the detailed design, the control
system characteristics are optimized
to meet the requirements.
The equipment design specifies the
requirements of all the main circuit
apparatus. The rating includes all
relevant continuous and transient
stresses.
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The auxiliary system design includes
the design of auxiliary power, valve
cooling, air-conditioning system and
fire protection system.
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- DPS
The performance of the combined
AC and DC system is validated in a
dynamic performance study (DPS).
The setup includes a detailed representation of the main circuit equipment, and the control model is a
copy of the code that will be delivered to site (see 5.3.7 above). The
AC systems are represented with a
detailed representation of the immediate vicinity and an equivalent
impedance for the rest of the AC
system. Typical faults and contingencies are simulated to show that
the total system responds appropriately.
- FST
During the factory system test (FST),
the control equipment to be delivered is connected to a real-time simulator. Tests are performed according to a test sequence list in order to
validate that the control and protection system performs as required.
- Site test
During the commissioning of
the converter stations, tests are
performed according to a test
sequence list in order to validate the
specified functionality of the system.
79
SYSTEM ENGINEERING
6.4 Digital Models
- Load flow
During load flow calculations, the
converters are normally represented with constant active power and a
reactive power that is situated within the specified PQ-capability, in the
same way as generators. A load flow
model of a VSC HVDC transmission is included in the latest version
of PSS/E.
- Reference cases
The figure above shows a comparison between site measurement and
PSCAD (previously EMTDC) simulation of the DC voltage at a load
rejection of 330 MW. Even though
the transient is fast, the behavior is
quite similar.
80
- Stability
The dynamic model controls the
active power to a set-point in one
station and calculates the active
power in the other station, including
current limitations. The reactive power
or the AC voltage is controlled independently in each station. ABB can
supply dynamic models of HVDC
Light® transmissions in the PSS/E
simulation tool.
- Dynamic Performance
Detailed evaluation of dynamic performance requires an extensive
PSCAD (previously PSCAD (previously EMTDC) model that can be
supplied to the customer during the
project stage.
ABB
REFERENCES
7 References
7.1 Projects
7.3 CIGRÉ/IEEE/CIRED material
Gotland HVDC Light® Project
DC Transmission based on VSC
Directlink HVDC Light® Project
HVDC Light® and development of VSC
Tjæreborg HVDC Light® Project
VSC TRANSMISSION TECHNOLOGIES
Eagle Pass HVDC Light® Project
HVDC Light® experiences applicable
to power transmission from offshore
wind power farms
Cross Sound Cable HVDC Light®
Project
MurrayLink HVDC Light® Project
Troll A Precompression Project
Estlink HVDC Light Project
®
Valhall Re-development Project
NordE.ON 1 offshore wind connection
Caprivi Link interconnector
7.2 Applications
HVDC Light® as interconnector
HVDC Light® for offshore
Wind power and grid connections
Cross Sound Cable Project – secondgeneration VSC technology for HVDC
MurrayLink – the longest HVDC
underground cable in the world
Power system stability benefits with
VSC DC transmission system
New application of voltage source
converter HVDC to be installed on
the Troll A gas platform
The Gotland HVDC Light® project experiences from trial and commercial
operation
CIGRE WG B4-37-2004
7.4 General
For further material please refer to
ABB HVDC Light® on the Internet:
http://www.abb.com/hvdc
ABB
81
INDEX
8 Index
1 Introduction
1.0 Development of HVDC technology–
historical background
1.1 What is HVDC Light®?
1.2 Reference projects
1.2.1 Gotland HVDC Light®, Sweden 1.2.2 Directlink, Australia 1.2.3 Tjæreborg, Denmark 1.2.4 Eagle Pass, US 1.2.5 Cross Sound Cable, US 1.2.6 MurrayLink, Australia
1.2.7 Troll A, Norway 1.2.8 Estlink HVDC Light® link, Estonia - Finland 1.2.9 Valhall Re-development Project
1.2.10 NordE.ON 1 offshore wind connection Germany
1.2.11 Caprivi Link Interconnector
5
5
5
6
6
7
8
9
9
10
11
12
13
14
15
2 Applications
2.1 General
2.2 Cable transmission systems
2.2.1 Submarine cables
2.2.2 Underground cables
2.3 DC OH lines
2.4 Back-to-back
2.4.1 Asynchronous Connection
2.4.2 Connection of important loads
2.5 HVDC Light® and wind power generation
2.6 Comparison of AC, conventional
HVDC and HVDC Light® 2.7 Summary of drivers for choosing an
HVDC Light® application
2.7.1 AC Network Support
2.7.2 Undergrounding by cables
2.7.3 Required site area for converters
2.7.4 Environmentally sound
2.7.5 Energy trading
2.8 HVDC Light® cables
2.8.1 Long lifetime with HVDC
2.8.2 Submarine cables
2.8.3 Underground Cables
16
16
16
16
16
17
17
17
17
17
3 Features
3.1 Independent power transfer and
power quality control
3.2 Absolute and predictable power
transfer and voltage control
3.3 Low power operation
3.4 Power reversal
3.5 Reduced power losses in connected
AC systems
3.6 Increased transfer capacity in the
existing system
3.7 Powerful damping control using P and
Q simultaneously
3.8 Fast restoration after blackouts
3.9 Islanded operation
3.10 Flexibility in design
3.11 Undergrounding
3.12 No magnetic fields
3.13 Low environmental impact
3.14 Indoor design
3.15 Short time schedule
25
4 Products
4.1 General
4.1.1 Modular concept
4.1.2 Typical P/Q diagram
4.2 HVDC Light® modules
4.2.1 - 80 kV modules
4.2.2 - 150 kV modules
4.2.3 - 320 kV modules
4.2.4 Asymmetric HVDC Light®
4.2.5 Selection of modules
4.3 HVDC Light® Cables
4.3.1 Insulation
4.3.2 Submarine Cable Data
4.3.3 Land Cable data
28
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82
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27
5 Descriptions
5.1 Main circuit
5.1.1 Power transformer
5.1.2 Converter reactors
5.1.3 DC capacitors
5.1.4 AC filters
5.1.5 DC filters
5.1.6 High-frequency (HF) filters
5.1.7 Valves
5.1.8 Valve cooling system
5.1.9 Station service power
5.1.10 Fire protection 5.1.11 Civil engineering work,
building and installation
5.1.12 Availability
5.1.13 Maintainability
5.1.14 Quality Assurance/Standards
5.1.15 Acoustic noise
5.2 HVDC Light® control and protection
5.2.1 Redundancy design and changeover
philosophy
5.2.2 Converter control
5.2.3 Current control 5.2.4 Current order control
5.2.5 PQU order control
5.2.6 Protections
5.3 Control and protection platform - MACH 2
5.3.1 General
5.3.2 Control and protection system design
5.3.3 Main Computers
5.3.4 I/O system
5.3.5 Communication
5.3.6 Software
5.3.7 Input to system studies
5.3.8 Debugging facilities
5.3.9 Human-machine interface (HMI)
5.3.10 Maintenance of MACH 2
5.4 HVDC Light® Cables
5.4.1 Design
5.4.2 Land cable
5.4.3 Submarine cable
5.4.4 Deep-sea submarine cable
5.5 General design of cables
5.5.1 Cable parts
5.5.2 Standards and Recommendations
5.5.3 Testing
5.5.3.1 Type test
5.5.3.2 Routine and sample test 5.5.3.3 Post-installation test
5.5.4 Cable drums
5.5.5 Installation
5.5.6 Repair
5.5.7 Accessories
5.5.8 Auxiliary equipment
5.5.9 Environmental
5.5.10 Reliability of 150 kV HVDC Light®
Cable projects
41
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42
43
43
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47
48
50
52
52
6 System Engineering
6.1 Feasibility study
6.2 System design
6.3 Validation
6.4 Digital Models
79
79
79
79
80
7 References
7.1 Projects
7.2 Applications
7.3 CIGRÉ/IEEE/CIRED material
7.4 General
81
81
81
81
81
8 Index
82
ABB
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Brochure issued by:
ABB AB
Grid Systems - HVDC
SE-771 80 Ludvika, Sweden
Tel. +46 240 78 20 00
Fax. +46 240 61 11 59
www.abb.com/hvdc
Elanders, Västerås POW-0038 rev. 5, 2008-03
For additional information please contact your local ABB Sales Office
The Valley Group, Inc.
CAT-1TM Transmission Line Monitoring Systems
Increasing Reliability While Decreasing Operating Costs
Real Time Ratings Provides Real Time Benefits to CAT-1 System Users
The following graph shows how information from the CAT-1 Transmission Line Monitoring System
enables operators to make well informed decisions, resulting in increased grid reliability and reduced
operating costs.
Note where line load begins to rapidly approach the traditional static limit. On that day, one generation
unit was unavailable, so operational switching was performed to avoid operating the line beyond the static
limit. The real-time rating shows that the true thermal limit was somewhat higher than the static limit.
The same scenario occurred the following day, when weather conditions were such that the conductor
was, in fact, capable of safely supporting 1100 amps, or 26% above the static limit during the peak
demand period as seen in the real-time rating.
Operational switching, or “breaking up the grid”, to address a thermal constraint threatens overall system
reliability. Had the generation unit been available, rather than switching, operations would have opted to
call for generation to run at a cost of over $170,000. In fact, neither action was necessary.
With the CAT-1 Real-Time Rating System now in full operational use, this user will be able to maintain
system reliability while at the same time recovering the cost of the CAT-1 system in a matter of days.
Figure 1. Operational actions that could have been avoided using real time ratings.
The Valley Group, Inc.
Phone: (203) 431-0262
871 Ethan Allen Hwy. #104
Email: info@cat-1.com
Ridgefield, CT 06877 USA
Fax: (203) 431-0296
The Valley Group, Inc.
CAT-1TM Transmission Line Monitoring Systems
NERC Compliance to Increase Reliability
Real Time Ratings Provides Real Time Benefits to CAT-1 System Users
The following graph shows how information from the CAT-1 Transmission Line Monitoring System helps
improve reliability and ensure compliance with NERC standards for determining and operating within
facility limits.
The graph shows a contingency event where the line was loaded above it’s previous “static rating”, which
was based on a set of generally conservative meteorological assumptions. The blue (bottom) line is line load,
the red (middle) line is the static rating, and the green (top) line is the CAT-1 System real-time rating.
Under previous circumstances, this contingency would have been a NERC “reportable event”. During
this event, it would have been noted that the utility failed to comply with the NERC “Operate Within Limits”
standard, since the line was operated above its “limit” for an extended period of time.
With a real-time rating system deployed and documented as the facility rating methodology, the utility is in
full compliance with the NERC “Determine Facility Ratings” standard because the system continuously
monitors actual line capacity. During this event, it can now be proven that no violation of NERC
reliability standards occurred, since the load never exceeded the actual real-time capacity of the conductor.
In addition, the CAT-1 system helps users ensure reliability by enabling them to avoid exceeding
operating limits before they ever occur. Unlike voltage or stability limits which can occur in milliseconds,
thermal limits develop over time, providing operators with ample advance notice to take action before limits
are exceeded.
Figure 1. Real-time ratings show that contingency did not exceed actual facility rating.
The Valley Group, Inc.
Phone: (203) 431-0262
871 Ethan Allen Hwy. #104
Email: info@cat-1.com
Ridgefield, CT 06877 USA
Fax: (203) 431-0296
Increasing System Reliability/Availability and Reducing
Congestion with Real Time Line Ratings
IEEE Power Engineering Society – 2005 General Meeting
PSO System Control Subcommittee
Real time line ratings have been widely shown to increase the transfer capability of existing
transmission lines by 10% to 30% without violating safety clearances and without exceeding the line’s
design criteria including the conductor’s design temperature. The technology has been deployed to
remove system constraints, mitigate congestion, facilitate market deregulation, maximize wheeling
revenues, protect physical transmission assets, and to increase system reliability.
Real time rating systems have the advantage of being fully integrated with the existing SCADA system.
All functions are fully automatic; ratings are continuously displayed in a format familiar to system
operators, and are also available to design engineers, planning engineers, state estimating programs,
security analysis programs, etc.
The systems are both cost and time effective. The cost of a real time rating system on a typical 30 km
transmission line is 90% to 95% less than the cost of reconductoring the same transmission line. The
systems can be fully operational in 90 to 120 days from date of order.
Validity of Real Time Ratings
The temperature of a transmission conductor is the result of a thermodynamic balance between those
elements that add heat to the conductor and those that remove heat from the conductor. Heat is added
by the ambient air temperature, radiation from the sun, and energy losses generated by current flowing
in the conductor. Heat is removed from the conductor by natural radiation (still air) and convective
cooling (wind).
Transmission lines are designed to operate at a maximum conductor temperature that will not harm the
conductor and will not cause the conductor to sag below its safe clearance to ground.
That
maximum
permitted
operating
temperature is represented as the “Design
Capability” (isotherm) curve in Figure 1. The
MVA that can be carried by the conductor
without exceeding the design capability varies
with weather conditions. 80% of the time,
weather conditions are such that 125 MVA (or
more) can be carried without exceeding the
permitted operating temperature. 40% of the
time weather conditions are more favorable
and 160 MVA (or more) can be safely carried.
When real time monitoring is not available,
engineers have no knowledge of weather
conditions and must exercise good judgment
Figure 1 – Design Capability
by assuming the worst possible combination
of no wind, full sun, and high ambient temperature. Under those assumptions, an engineer will set the
static (fixed) rating in our example at 75 MVA to be certain that the conductor will never be overheated
The Valley Group, Inc.
Phone: (203) 431-0262
871 Ethan Allen Hwy. #104
E-mail: ron.stelmak@cat-1.com
Ridgefield, CT 06877 USA
Fax: (203) 431-0296
under any conceivable load and weather conditions. Since those worst conditions rarely occur, a
perfectly good transmission conductor is left significantly underutilized nearly all of the time.
Static Ratings are often increased by assuming that a cooling wind (typically 0.6 m/s) will continuously
blow 24 hours a day on every day of the year. The assumption yields the desired increase in static
rating as shown in Figure 2. Note that since the transmission line’s physical construction has not
changed, the Design Capability isotherm will
also remain unchanged. The static rating will
now intersect the isotherm at a point
representing the assumed wind speed. In the
real world, there is a certain percentage of the
time when the wind speed will be less than
the assumed wind speed. If the conductor is
operated at the static rating during that
percentage of time, the conductor will be
overheated. There is a risk associated with
assuming a continuous wind speed.
Real time transmission line rating methods
safely capture the underutilized design
capacity of the transmission line. Instruments
Figure 2 – Wind Assumption
installed on the conductor track the “Design
Capability” isotherm through changing weather conditions. The instruments determine exactly how
many MVA may be carried by the conductor without exceeding the permitted maximum operating
temperature. For example, on any given day conditions may be such that the conductor can safely
carry 125 MVA versus the fixed static rating of 75 MVA.
Elements Affecting Real Time Ratings
Real time ratings are affected by ambient temperature, solar radiation, wind speed, and wind direction.
At any given time of day, wind speed and direction have by far the greatest impact. The relative
importance of each element can be observed by examining a typical 30 km transmission line (795
ACSR) with a steady state thermal rating of 787 amperes at 40 oC ambient temperature, zero wind, and
mid-day in the summer.
Ambient temperatures are relatively stable over distance and seldom exhibit rapid changes. A typical 2
o
C temperature fluctuation along the 30 km transmission line would vary the rating by 2%. It would take
a sudden temperature drop from 40 oC to 30 oC to increase the rating to 874 amperes (11%).
Solar radiation is also relatively stable over distance and seldom exhibits rapid changes. Typical
shadowing from clouds produces rating changes of only a few percent. It would take a total eclipse of
the mid-day sun to increase the rating to 929 amperes (18%).
Wind speed behaves differently. It can cause significant changes in ratings in short time intervals.
Increasing wind speed from zero to only 1.0 m/s at a 45o angle increases the rating to 1060 amperes
(35%). Wind direction is also highly variable. The same 1.0 m/s wind perpendicular to the conductor
produces a 44% rating increase; a wind parallel to the conductor produces a negligible increase in
ratings.
Wind also exhibits spatial variability... there can be several meters/sec of wind at one spot and absolute
calm a short distance away. The phenomena can be easily observed in the waving grass of an open
field or the ripples on a lake. Several studies have attempted to quantify the spatial variability. Results
The Valley Group, Inc.
Phone: (203) 431-0262
871 Ethan Allen Hwy. #104
E-mail: ron.stelmak@cat-1.com
Ridgefield, CT 06877 USA
Fax: (203) 431-0296
have ranged from centimeters to nearly a kilometer, with 200 meters being an approximate median.
The implication for a transmission line is that one span can experience cooling winds while another
span 200 meters away can be in a dead calm.
Figure 3 contains the results of a study wherein 2 wind monitors were installed approximately 5-7 km
apart on a transmission line. Wind speeds were averaged every 10 minutes to remove some of the
spatial variability. One monitor is plotted on the x-axis; the other
monitor is plotted on the y-axis. Note that there is still very little
usable correlation between the wind speeds at the two locations.
One location reports an average wind speed of 2.5 m/s at the
same time that the second location reports an average wind speed
of 0.0 m/s.
Wind is clearly the weather element that has the greatest impact
on transmission line ratings. It is also the most volatile and
spatially dispersed.
There is one additional significant element in establishing a
conductor’s real time rating. It is the transmission line itself.
During the design phase, good engineering practice dictates that
all possible material and construction variances be treated as working against the ratings. Unless a
transmission owner is extremely unlucky, some of the actual variances will work in favor of the ratings.
Ratings are also affected by maintenance and aging elements. Splices may have been installed
increasing the slack of the conductor, or high temperature creep may have increased the sag of the
conductor.
Figure 3 – Wind Speed Comparison
Real Time Rating Methods
A successful real time rating method must address the elements in the preceding section, including all
the pitfalls and the opportunities. Since that is not an easy task, only a handful of methods are in
widespread use in the world today.
Ambient Adjusted Ratings
Ambient adjusted ratings are very common. Since ambient temperature does not vary much over
distance, very few instruments are required along the typical 30 km transmission line. System
operators receive information about the ambient temperature and typically use a look up table to
determine the conductor’s real time rating. Other elements (solar radiation, wind speed, wind direction)
are assumed to be constant. Conservative assumptions should include zero wind speed and full solar
radiation.
The method has the advantage of low cost instrumentation and well established calculation models by
IEEE, CIGRE, and others. Rating improvements are limited to the small changes in ratings attributable
to ambient temperature variation.
Day/Night (Solar Adjusted) Ratings
Conventional wisdom states that ratings will be higher at night because there is no solar energy to heat
the conductor.
The time of day graph that is inset in Figures 1 and 2 displays data showing that daytime ratings are
typically higher than nighttime ratings. That is the result of daytime winds being higher than nighttime
winds. Solar radiation creates wind. When the sun rises, it creates more wind than is needed to offset
The Valley Group, Inc.
Phone: (203) 431-0262
871 Ethan Allen Hwy. #104
E-mail: ron.stelmak@cat-1.com
Ridgefield, CT 06877 USA
Fax: (203) 431-0296
any solar heating of the conductor. That leaves additional wind to cool electrical losses in the
conductor. The result is that more current can be carried by the conductor during the day (when it is
needed most) than can be carried at night.
Wind Based Ratings
Real time ratings are a function of the conductor’s average temperature between dead-ends; they are
not a function of the conductor’s temperature at a single spot.
There are several good calculation methods to determine the temperature of a conductor at a particular
location based on ambient temperature, solar radiation, and wind. As previously described, wind has a
great deal of spatial variability. A rating calculated based on moderate wind reported by a monitor at
one span of a conductor, could be a dangerously high rating for another span located just a few
hundred meters away. The question becomes “How many wind monitors must be installed to obtain a
statistical average of the conductor temperature?”
Point Temperature Based Ratings
Devices that measure the temperature of a conductor at a single point have the same spatial variability
limitations as a wind monitor.
Tension Based Ratings
Rating methods based on tension monitoring technology address all of the elements affecting real time
ratings. The spatial variability of wind, solar energy, and ambient temperature are addressed. The
variances in transmission line materials, construction, maintenance, and aging are addressed. Plus the
technology accounts for variables such as conductor core temperatures exceeding surface
temperatures and heating introduced by magnetic losses when conductors are operated at high
currents.
Figure 4 depicts a transmission line section supported by suspension insulators and terminated by
dead-end insulators. A wind blows on some of the spans, while other spans exist in a dead calm.
In the spans cooled by wind, the conductor will contract and the mechanical tension in the conductor
will tend to increase to a level greater than the tension in adjacent spans. Since the suspension
insulators between spans are free
to move, they will swing inwards
toward the span having the higher
tension until the tensions on both
sides of the suspension insulators
are equal.
TENSION
Figure 4 – Tension Equalization
In the spans not cooled by wind,
the conductor will expand and the
mechanical tension will tend to
drop to a level less than the
tension in adjacent spans. The
suspension insulators will swing
away from the span until all
tensions are equalized.
The tension adjustments will
continue until all tensions are equalized. The spatial variability of wind, ambient temperature, and solar
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radiation will then have been resolved into a single variable (tension) that is a function of the average
temperature of the conductor between dead-ends.
Fully Integrated Real Time Rating Systems
Real time rating systems are completely automatic and fully integrated into the EMS/SCADA system.
On a typical transmission line, tension monitoring equipment is installed at multiple structures. Solar
powered transmitters send the tension and other data back to a substation using spread spectrum
radios. At the substation, a receiver translates the data into the EMS/SCADA protocol and sends the
data directly to the EMS/SCADA master. An algorithm in the EMS/SCADA calculates the real time
rating and displays the rating on the system operator’s existing console. The ratings are also available
to system planners, design engineers, security analysis programs, and state estimator programs.
Translating Real Time Ratings into Grid Operations
The primary objective of real time ratings is to fully utilize the true transfer capability of a transmission
line with deterministic safety. Or, as described by CIGRE, “The main purpose of real-time line
monitoring is to assist system operators in better utilization of the load current capacity of overhead
lines, ensuring that the regulatory clearances above ground are always met.”
Several methods have evolved to provide that assistance.
Day Ahead Dispatch – Business as Usual but with Less Congestion
What would be the impact of raising the
static rating from 235 MVA to 310 MVA
(90th percentile)? The available transfer
capability would go up, congestion would
be relieved, and there would be more
room with which to ensure system
reliability.
Operating practices would
remain unchanged since they would still
be based on a fixed static rating.
Manitoba SN 3112, July 2002
Ratings Probability,
New Rating
Method
Ratings Probability
– Upper
Midwest
– July 2002
700
650
600
550
500
Rating
Figure 9 depicts the available capacity of
a transmission line during its summer
peak. The 235 MVA static rating is based
on an assumed 2 ft/sec wind. This line is
capable of exceeding its static rating
more than 99% of the time, with more
than 30% additional capacity being
available 90% of the time.
450
400
350
300
250
200
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
% of Time
Actual Ampacity
Static
Figure 9 – Available Capacity
But, what would be the impact of the added risk? Most transmission lines are operated to survive a first
contingency event. The risk of a first contingency event occurring is 0.001 – 0.005. The risk that the
310 MVA rating will not be available is 0.10. The risk of both events occurring at the same time is
0.005 x 0.10 = 0.0005. 99.95% of the time the system operates (including first contingency events)
without operator intervention. What about the other 0.05% of the time? If a real time rating system is in
place, the operator will receive advance warning.
Figure 10 graphically portrays a real time rating system function known as a dynamic alarm. The static
rating has been set at a more realistic level as described above. The load can be actual load, or more
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typically the projected post contingency load output by the EMS’s security analysis. The real time
rating system will trend both the load and the real time rating. When the two trends are projected to
converge in 15 minutes, an alarm is triggered to alert the operator. The operator may then respond as
he deems appropriate. Responses might include:
1. Redispatching the system to accommodate any possible contingency event.
2. Taking no action, but having a remedial action plan at hand should a contingency event
actually occur.
Real time ratings coupled with dynamic alarms make it possible to garner all the economic and
operational benefits of a higher and more
realistic static rating with complete safety.
Raw Real-Time Rating
Dynamic Alarms
System Reliability and Safety
1500
Conventional static ratings are commonly
based on a probabilistic minimum amount
of wind (for example, 1 m/s) blowing 24
hours a day every day. Reality is that
calm periods do exist, and during those
Static Rating
calm periods the true rating of the line will
drop. If those calm periods coincide with
Load
high loads, the probability that the
conductor will overheat and violate
Dynamic Alarm
mandated clearances is significant…with
the obvious implications for reliability and
public safety. Real time ratings are not
probabilistic, they are deterministic; they
Figure 10 – Dynamic Alarms
report the true state of the conductor as it
responds to changing weather conditions. When poor cooling conditions and high loads combine to
present a threatening situation, the dynamic alarms of a real time rating system will alert the operator
and appropriate actions can be taken.
1250
Real Time Rating
1000
750
500
250
133
129
125
121
117
113
109
105
97
101
93
89
85
81
77
73
69
65
61
57
53
49
45
41
37
33
29
25
21
17
9
13
5
1
0
Safely Managing Contingencies and Reducing TLR’s
Unusual events can push line loads beyond their static ratings, but not necessarily beyond their true
rating. Figure 11 is an example of a safely managed 3 hour contingency event. Although the static
rating was exceeded, the line was operating within limits according to NERC standards (OWL/DFR).
Without real time ratings, such an event must be reported as a violation.
In the process of establishing the real time rating of a transmission line, the average temperature of the
conductor is determined. That temperature is a prerequisite to determining the real time transient
response of the conductor to a change in load. There are two forms of the transient response that are
very useful in contingency management; one before the event, and one after the event.
Figure 12 is an example of pre-contingency transient analysis. In this example, the conductor is not
permitted to exceed a design temperature of 100 C. Both the load on the line and the conductor’s
temperature are known at time zero. A real time rating system will answer the question: How large a
step in load will cause the conductor to reach its 100 C design temperature in 15 minutes, but not
before? The answer is the real time 15 minute short term emergency (STE) rating.
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In practice, an operator can dispatch the system to the STE rating, knowing that should a contingency
event occur, he will have a full 15 minutes to respond. After 15 minutes, load must be reduced to the
real time continuous rating.
Figure 11 – Safely Handling A Contingency Event
15 Minute Transient Rating
200
1600
180
1400
15 Minute Transient Rating
160
1200
Continuous Rating
140
Degrees C
100
800
80
Amperes
1000
120
600
Pre-contingency Load
60
400
Conductor Temperature
40
200
20
0
0
-5
0
5
10
15
20
Minutes
Figure 12 – Pre-contingency Transient Response Analysis
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Figure 13 is an example of post-contingency transient analysis where the conductor has just been
subjected to a large step current. The question answered by the real time rating system is: How many
minutes until the conductor reaches its 100 C design temperature? In this example, the time is 8.5
minutes. In practice, the operator must reduce load on the line to the real time continuous rating before
8.5 minutes elapse.
The time available to take corrective actions is valuable information to the operator. If time is short,
quick but expensive actions may be required. If a longer time is available, more economical or less
disruptive actions may be taken.
Facilitating Maintenance and Construction Outages
Maintenance and construction of transmission facilities are vital to system reliability and transfer
capability. Those activities are often curtailed because the very grid constraints that they are intended
to solve preclude the granting of outages. If the constraints are managed by a real time rating system,
outages can often be granted when they would otherwise be denied. Real time rating systems provide
the data to predict when the outages can be granted, and provide complete safety during the outage by
verifying that all is going to plan.
Transient Response Time to Design Temperature
1600
200
180
Post-contingency Load
1400
160
1200
140
Degrees C
800
100
80
Amperes
1000
120
600
Pre-contingency Load
Conductor Temperature Rises to the Design
Limit of 100 Degrees C in 8.5 Minutes
60
400
Conductor Temperature
40
200
20
0
0
-5
0
5
10
15
20
Minutes
Figure 13 – Post–contingency Transient Response Analysis
Conclusions
Transmission lines have traditionally been limited to a fixed (static) rating that will permit safe operation
under the worst possible conditions. Since the worst possible conditions rarely occur, a large part of
the transmission line’s true capacity has been unused. Real time rating systems make it possible to
use all of the line’s capacity while still maintaining a complete level of safety.
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The added capacity can be used to maximize transfer capability, mitigate constraints, manage
contingency events, avoid unnecessary service curtailments, permit outages for new line construction,
and enhance system reliability.
Real time rating systems are fully automated and integrated into the EMS/SCADA system. The ratings
are delivered to system operators on their existing consoles in the format specified by the operator.
Real time rating systems are structured to fold into and to enhance present operating practices. In its
simplest form, a real time rating looks like and is treated as a significantly higher fixed static rating.
Real time rating systems provide the system operator with tools to manage contingency events both
before and after the event. Real time short term emergency ratings are available before the event, and
the amount of time available for response after the event are both delivered to the operator.
Since real time rating systems monitor the actual response of the transmission line to changing weather
conditions, they are completely safe. System operators are given advance warning when load and the
transmission line’s true rating are converging, and appropriate actions can be taken.
The Valley Group, Inc.
Phone: (203) 431-0262
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New Orleans Project Profile
New Orleans, Louisiana is the site of the longest HTS cable project
in the world to date.
High-Temperature
Superconductor Powers New
Orleans Suburb
The Metairie area in New Orleans is a densely built
residential neighborhood that is encountering energy
growing pains. Older, smaller houses are rapidly being
replaced by larger dwellings that are pushing up power
demand. Existing distribution capacity is stretched to the
limit.
For Entergy Louisiana, which serves the area with electric
power, the traditional solution would be to bring in a
230 kV line and build a complete 13.8 kV step-down
substation. Community impact could possibly include
expanding substation footprint in a congested area or
use of expensive gas-insulated equipment. There are also
permitting issues, plus the costs of transformers and
construction.
Instead, Entergy has opted for a solution that uses hightemperature superconductor (HTS) power distribution
technology to bring 13.8 kV power directly into the
neighborhood. Benefits of the HTS Triax solution from
Southwire include much reduced community impact,
smaller equipment and rights-of-way.
Project Overview
Project: New Orleans HTS Triax Project
Location: New Orleans, Louisiana
Project Owner: Entergy Louisiana
Product Used: HTS Triax Superconducting Cable
In-service Date: March 2011
“ HTS Triax
installations can
provide power for
an entire substation
at distribution
voltages.”
POWER
MORE
TO
MOREPEOP L E
HTS Triax Eliminates
Substation Construction
The New Orleans HTS Triax® Superconducting Cable
installation lets Entergy Louisiana avoid a new step-down
substation in a congested area. The cable brings 13.8 kV
power, 2,000 A per phase, to a small-footprint “virtual
substation” that contains only the distribution bus and
protection equipment.
The New Orleans HTS Triax cable spans 1.1 miles–
the longest HTS cable project in the world to date.
Component installations will take place in 2010, with
operations scheduled for early 2011.
Replacing old cables adds capacity
Southwire HTS Triax delivers costeffective distribution
Southwire has been pioneering HTS projects since the
late 1990s. Southwire’s ability to adopt cost-reducing
advances such as pulse-tube cooling makes Southwire HTS
Triax systems even more attractive to budget-bound city
planners struggling to add power to urban centers.
“The New Orleans project is another demonstration of
the cost-effectiveness of distribution with HTS Triax cable
compared to a conventional transmission-voltage circuit
and step-down substation,” says David Lindsay, Director,
Distribution Engineering for Southwire.
“High-temperature” is Relative
Many densely populated areas suffer declining grid
reliability when demand overloads aging distribution
cables. Old cables can be replaced in existing ducts with
HTS Triax cables that add capacity.
“High-temperature” superconductivity (HTS) is relative:
HTS conductors run in liquid nitrogen at -320˚F (-196˚C).
Transmitting current with almost no resistance, HTS puts
high-density, low-loss capacity in existing duct banks. That’s
a key to cost-effectiveness in urban settings.
With HTS Triax cables, large transformers can move to
less-crowded areas of a city. That lets urban planners free
up valuable real estate for development or green space.
Partners Developed New Orleans
Components
Interconnection boosts urban grid
reliability
HTS Triax installations can provide power for an entire
substation at distribution voltages. Interconnecting urban
substations increases grid reliability by allowing loadsharing in case of component failure or peak loads. This is
not feasible with copper cables.
The New Orleans HTS Triax installation is being
developed by Southwire Company in partnership with
the U.S. Department of Energy’s Oak Ridge National
Laboratory (ORNL). The New Orleans project is one of
five projects that the Department of Energy has chosen
to advance the application of superconducting materials in
electric systems.
Costs dropping for established
technology
HTS is now commercial technology in the cost-reduction
stage. Current-generation HTS Triax systems use pulsetube cryogenic cooling technology with fewer parts,
lower cost, smaller footprint, less maintenance, and more
energy-efficiency than older systems.
The combined operational time of the three longestrunning commercial-scale HTS projects by Southwire
and joint venture partner nkt cables adds up to over 11
years of consistently reliable power delivery. Other HTS
projects in-power, or soon to be, include:
• Columbus, Ohio
• Carrollton, Georgia
• Copenhagen, Denmark
• Manhattan, New York
Entergy Louisiana employees meet at the Labarre Substation in New
Orleans.
Manhattan Project Profile
Project Hydra brings HTS Triax technology to densely populated
Manhattan.
High-Temperature
Superconductors Come
To Manhattan
Grappling with growing power demands in densely
populated Manhattan, Consolidated Edison Company
of New York (Con Edison) wanted to link an existing
substation with a new substation being built. They were
looking for an effective way to stage development to
match revenue flow and to defer expensive transformer
costs.
The solution is a 300-meter (984-foot), high-temperature
superconductor (HTS) cable from Southwire. The HTS
Triax cable will carry up to 4,000 A per phase at 13.8 kV
from the existing substation to the new site. As additional
transformers come to the new site, the HTS Triax cable
will serve as a bus link between the two substations,
increasing grid flexibility and system security. An added
innovation of this HTS Triax installation is a fault-current
limiting function that will further enhance distribution
reliability.
Project Overview
Project: Manhattan HTS Triax Project
Location: New York, New York
Project Owner: Con Edison
Product Used: HTS Triax Superconducting Cable
In-service Date: December 2010
“This HTS Triax substation
bus-tie application lets
Con Edison leverage
transformer assets with a
small equipment footprint,
smaller right-of-way and
avoidance of costly new
transformers.”
POWER
MORE
TO
MOREPEOP L E
Urban Density Requires
High Distribution Capacity
The Manhattan installation, known as Project Hydra, will
use Southwire’s HTS Triax® Superconducting Cable to
relieve distribution congestion and reduce power delivery
costs. The high-capacity HTS Triax cable lets the two
Project Hydra substations share excess capacity during
peak loads or emergencies. The project is scheduled for
completion by the end of 2010.
HTS Triax systems operate at -320˚F (-196˚C) for ultralow loss with high current. At 4,000 A per phase, this is the
highest capacity HTS cable built to date. The high capacity
is needed to meet expected power demands.
CRITICAL SURFACE PHASE DIAGRAM
Manhattan HTS Triax links substations,
limitsTfault Temperature
currents
C
When multiple
substations are linked in a network,
there must be fault current protection between stations.
Project Hydra’s HTS Triax installation includes a built-in
fault-current limiting function. “The distribution grid in
HC from fault currents
Manhattan is so dense that protection
is a significant engineering problem,” says David Lindsay,
Director, Distribution Engineering
forField
Southwire.
Magnetic
JC
The HTS Triax fault-protection function enhances the
action of standard protection devices.
Current Density
Costs dropping for established
technology
HTS is now commercial technology in the cost-reduction
stage. Current HTS Triax systems use pulse-tube cryogenic
cooling technology with fewer parts, lower cost, smaller
footprint, and more energy-efficiency than older systems.
The combined operational time of Southwire and joint
venture partner nkt cables longest-running commercial
HTS projects is over 11 years. HTS projects in-power, or
soon to be, include:
• Columbus, Ohio
• Carrollton, Georgia
• Copenhagen, Denmark
• New Orleans, Louisiana
Southwire HTS Triax delivers costeffective distribution
Southwire has been pioneering HTS projects since the
late 1990s. HTS Triax cable systems rely on Southwire’s
compact second-generation design, which puts all phase
conductors in one cable. These high-capacity, ultra-lowloss cables
can be retrofitted into existing infrastructure
HTS TRIAX™
GLOBAL
REACH bottlenecks in congested urban
to relieve
distribution
grids.
Lindsay says, “This HTS Triax substation bus-tie application
lets Con Edison leverage transformer assets with a small
equipment footprint, smaller right-of-way and avoidance of
costly new transformers.”
Partners Developed Manhattan HTS
Project
The Manhattan HTS Triax installation is being developed
by Southwire Company and its partners
American
Temperature
T
C
Superconductor, Con Edison of New York, Air Liquide, U.S.
Department of Energy Oak Ridge National Laboratory
and the U.S.
Department of Homeland Security. The HTS
CRITICAL SURFACE
Triax cable
was DIAGRAM
designed in the Ultera joint venture of
PHASE
HC
Southwire and nkt cables, a European cable manufacturer.
“High-temperature” is Relative
Magnetic Field
“High-temperature” superconductivity (HTS) is relative:
HTS conductorsJrun
C in liquid nitrogen at -320˚F (-196˚C).
Operating with almost no resistance, HTS puts highCurrent Density
density, low-loss capacity in existing duct banks. That’s a
key to cost-effectiveness in urban settings.
HV
MV distribution
110-230 kV
INCREASED RELIABILITY
AND RESILIENCE
HV
10-20 kV
HTS Triax™ Cable
MV distribution
110-230 kV
10-20 kV
HTS Triax cables provide high-capacity distribution-voltage links
between substations.
HTSTRIAX
®
superconducting cable
Columbus Project Profile
AEP’s Bixby substation in Groveport, Ohio
Columbus Superconducting
Power Project Reaching
Toward Third Anniversary
In 2006, American Electric Power (AEP) teamed up
with Southwire Company and nkt cables of Denmark to
demonstrate the viability of the newly created HTS Triax®
cable design in its Bixby substation in the Columbus, Ohio
suburb of Groveport. The HTS Triax cable provided the
link from a 138 kV - 13 kV step-down transformer to a
13 kV substation bus an eighth of a mile away when it was
energized in August 2006.
HTS Triax cables cooled by liquid nitrogen have become
commercial solutions to the challenge of adding power to
densely populated areas. Operating at 13 kV, the HTS Triax
system uses a single compact cable to carry 3,000 A. That
provides the equivalent of 18 conventional underground
cables with no new duct construction.
Project Overview
Project: Columbus HTS Triax Project
Location: Columbus, Ohio
Project Owner: American Electric Power (AEP)
Product Used: HTS Triax Superconducting Cable
In-service Date: August 2006
“ HTS Triax
systems are now
commercial
technology in the
cost-reduction
stage.”
POWER
MORE
TO
MOREPEOP L E
Exciting New Technology
Proves To Be Very Reliable
allows fewer parts, lower cost, smaller footprint, less
maintenance, and more energy-efficiency than older
systems.
HTS Triax Superconducting Cable termination at AEP’s Bixby Substation in
Groveport, Ohio.
Back in 2006, people saw HTS equipment as exotic
technology. But the HTS Triax system does what good
technology is supposed to do: It just quietly works. The
drama level is equivalent to watching paint dry.
The Columbus HTS Triax system is now in its third
year of operation. People viewing the system today are
considering HTS Triax facilities in their own cities. They
want high current-density distribution with the reliability
of a well-designed anvil. HTS Triax systems are on their
short lists.
The Columbus HTS Triax system carries the full 13 kV
station load, and it has been pushed hard: It saw 2,715
amps per phase during peak summer months, over 90
percent of its design rating. It has weathered lightning and
snow and ice, and ambient temperatures ranging from
0ºF to near 100ºF. Fault events coming in from the grid
have driven currents up to 17,700 A per phase for 222
milliseconds, with a repeated 17 kA fault peak six seconds
later. The system has never been out of service due to
one of these events.
Decreasing costs encourage commercial
adoption
Southwire has been pioneering HTS projects since the
late 1990s. Southwire’s ability to adopt cost-reducing
add-ons such as pulse-tube cooling makes Southwire HTS
Triax systems even more attractive to budget-bound city
planners struggling to add power to urban centers.
“High-temperature” is relative
“Engineering advances are continuing to cut HTS
Triax distribution costs,” says David Lindsay, Director,
Distribution Engineering for Southwire. “The long-term
cost-effectiveness of the Columbus HTS Triax project has
supported decisions to proceed with HTS Triax systems in
Manhattan and New Orleans.”
Urban areas benefit from
HTS Triax
Partners Developed Columbus Project
“High-temperature” superconductivity (HTS) is relative:
HTS conductors run in liquid nitrogen at -320˚F (-196˚C).
Transmitting current with almost no resistance, HTS puts
high-density, low-loss capacity in existing duct banks. That’s
a key to cost-effectiveness in urban settings.
Because HTS Triax cables carry very high currents
at distribution voltages in existing ducts, large power
transformers can be pushed out to less-crowded areas of
a city. That lets urban planners free up valuable real estate
for development or green space. HTS Triax technology
also allows increased interconnectivity among urban
substations.
The Columbus HTS Triax installation was developed by
Southwire Company and its partners, American Electric
Power, Praxair, American Superconductor and the U.S.
Department of Energy’s Oak Ridge National Laboratory.
HTS Triax performs worry-free
The combined operational time of the three longestrunning commercial-scale Southwire and nkt cable HTS
projects adds up to over 11 years of consistently reliable
power delivery. HTS is now commercial technology in
the cost-reduction stage. For example, Columbus uses
innovative pulse-tube cryogenic cooling technology that
HTSTRIAX
®
superconducting cable
PROJECT PROFILE: CenterPoint Energy
PROJECT OVERVIEW
Project: Hillje Project
Location: Houston, Texas
Project Owner: CenterPoint Energy
Electrical Contractor: InfoSource
Product Used: Southwire HS285®
In-Service Date: July 2007
High-Capacity Tie Line
Uses Low-Sag
Technology
When Houston-based CenterPoint Energy needed
to upgrade a tie line between two major generating
stations, their choice was a new product from
Southwire that delivers high-temperature, low-sag
capacity rivaling exotic composite-coredesigns –
without the exotic cost. The wire CenterPoint chose
puts an ultra-high-strength steel core inside an
ACSS/TW conductor architecture. (See box
for details of the HS285 ultra-high-strength
ACSS/TW architecture.)
CenterPoint’s challenge was to bring more power to
the greater Houston area. They needed increased
transmission capacity between a nuclear plant near
Bay City, Texas, and a generating facility in
Rosenberg, Texas. The solution was an $80 million,
60-mile, two-circuit 345kV transmission line. The
question was how to implement the circuits.
HS285
PROJECT PROFILE: CenterPoint Energy
Reduced tower height saved several hundreds of
thousands of dollars over the ACSR option, but even
then we didn’t make full use of HS285 economies.
HS285 will reduce maximum sag by yet another three
to four feet.”
HS285 rivals composite-core designs
The new HS285 is an enhanced version of Southwire’s
ACSS/TW. Like standard ACSS/TW, HS285 is rated for
continuous operation at 250°C. An ultra-high-strength
steel core puts HS285 sag performance on a par with
recently developed composite cores “…at a reasonable
cost, not 10 to 30 times the price,” according to Bennett.
High-temperature, low-sag HS285
won over many options
CenterPoint analyzed 60 different design
combinations, factoring in distance between
structures, land-use impacts, construction issues
and total installed costs. Circuit options included:
two conductors using ACSR (aluminum conductor,
steel-reinforced); three conductors using standard
ACSS/TW (aluminum conductor, steel-supported,
trapezoidal wires); and two conductors using
Southwire’s new HS285 ultra-high-strength
ACSS/TW high-temperature, low-sag design.
CenterPoint found that the new HS285 ACSS/TW
conductors would give 55 percent more capacity
than the ACSR conductors with a project cost
premium of only about four percent. That made
the decision clear. Forty miles of the line will
use new structures to carry two 1433.6 kcmil
ACSS/TW HS285 conductors. That installation
was energized in July 2007.
Chuck Bennett, Manager of Transmission
Engineering for CenterPoint, says, “We would
have used HS285 for the entire project, but
testing time and early product availability didn’t
quite meet schedule requirements for the first
phases. For the same scheduling reasons, we
originally designed our new structures for the
reduced sag of standard ACSS/TW.
The ultra-high-strength steel core material borrows
heavily from existing steel technology to develop high
tensile strength without loss of elongation, ductility or
stress corrosion properties.
The HS285 core is protected by a Galfan coating that
contains 95 percent zinc and about five percent
aluminum, with a small addition of rare earth elements,
primarily cerium and lanthanum. The Galfan coating
protects the steel core at operating temperatures that
would shorten the life of traditional galvanizing.
“The advanced HS285 steel core lets us get more
strength with tested and known technology,” says Nick
Ware, Vice President, Technical for Southwire’s Energy
Division. “The higher strength of HS285 ACSS/TW lets
us pull the cable tighter at installation. That helps
sag performance and allows shorter, less expensive
support structures.”
In addition to cost advantages, another advantage of
HS285 over exotic composite conductors is that it uses
the same installation techniques as standard ACSS.
HS285 is commercially available with lead times in line
with conventional ACSR conductors.
CenterPoint sees future uses
Bennett says, “We have a long history with the
ACSS/TW cable architecture. We have been using
ACSS/TW since 2000, and have installed over
3,000 miles of it.”
HS285
CenterPoint sees HS285 ACSS/TW conductors as an
economical solution for increasing capacity needs.
The additional mechanical strength will also meet
new needs. The 2007 National Electrical Safety Code
will require higher mechanical loading design criteria,
and the Texas PUC may be considering higher
hurricane storm-loading criteria. “This is a good
option to have in our toolbox,” says Bennett.
HS285 ACSS/TW:
High Temperatures with Low Sag
HS285 high-temperature, low-sag (HTLS) designs
use an ACSS (aluminum conductor, steel-supported)
architecture. In ACSS conductors, the weight of the
wire is taken almost entirely by the steel core. Sag
is determined by the low expansion rate of steel,
rather than the high expansion rate of aluminum.
That allows higher operating temperatures – and
more capacity. ACSS can operate continuously at
temperatures up to 250°C without loss of strength.
For the same conductor size and weight, ACSS can
carry up to 100 percent more power than ACSR,
with the same sag.
In addition, a form of ACSS that uses trapezoidallyshaped conductor strands packs more aluminum
into a given cable diameter. This is ACSS/TW, and
it multiplies the cost-benefits of ACSS technology in
upgrading transmission lines.
Strength Comparison of Steel Cores
• A typical steel core in a standard ACSR cable has a
tensile strength of about 210ksi.
• A traditional “high-strength” core delivers a
tensile strength of about 235ksi.
• Southwire’s HS285 steel core racks up 285ksi
before failure, 21 percent stronger than the usual
“high-strength” core, and 36 percent stronger
than a standard core.
PROJECT PROFILE: N1/Otra Danmark
PROJECT OVERVIEW
Project: Trige-Tange line upgrade
Location: Arhus, Denmark
Project Owner: N1/Otra Danmark
Electrical Contractor: Delpro A/S
Product Used: Southwire HS285®
In-Service Date: November 2006
Ultra-High-Strength
Steel Upgrades
Danish Grid
On Denmark’s Jutland peninsula, near Arhus, the
second-largest city in Denmark and a major
seaport, power needs for homes and industry are
growing just as quickly as in the U.S. But building
new towers to carry larger, heavier conductors
can push upgrade budgets past the breaking
point. The Danish utility operator N1 found an
alternative. They have reconductored existing
towers using Southwire’s ACSS/TW (aluminum
conductor, steel-supported, trapezoidal wire)
conductors with a new ultra-high-strength steel
core Southwire calls HS285.
HS285
PROJECT PROFILE: N1/Otra Danmark
Reconductoring Made Upgrade Affordable
and switch gear to the Danish utility market. Otra also
contributed engineering services that helped make the
upgrade both successful and cost-effective.
N1 and Otra spent a year considering several approaches to
the problem, including conductors manufactured in Europe.
They reviewed environmental impact, installation costs and
operating economy. In the end, the only alternative that
met the needs of price and performance was the newly
developed product from Southwire. The HS285 solution
required no structural modifications to the existing towers.
The ancient Vikings didn’t worry about
power grid capacity. Modern Danes do.
Facing challenges very similar to those in
the United States, Danish utilities need to
upgrade the capacity of their transmission
grids. And, as in the U.S., the problem is
how to increase grid capacity cost-effectively.
A new conductor design from Southwire
offers solutions.
N1’s HS285 project is a double-circuit 170kV line
stretching 22.5 miles (36 km) between the cities of
Trige and Tange. The line was built in 1963, using
ACSR (aluminum conductor, steel-reinforced)
conductors. By 2005, the original 980 amp capacity
just wasn’t sufficient. N1’s goal was to develop a
capacity of 1,500 amp down the same right-of-way.
The problem was finding a cost-effective approach to
the expansion.
Several approaches were considered
N1 worked with Otra Danmark and Delpro A/S,
supplier of overhead conductors, cables, transformers
N1 and Otra then took another full year testing and
confirming the performance of the new design. “Otra
helped N1 with technical assistance in sag, tension, and
tower strength calculations,” says Merete Neilsen,
Manager of Power and Networks for Otra.
Southwire ACSS/TW experience was a factor
N1’s Trige-to-Tange project was energized in mid-November
of 2006. The upgrade used a total of 137.5 miles (220
km) of 954 kcmil Cardinal ACSS/TW conductor with the
HS285 steel core.
“Southwire has 25 years of experience with the ACSS/TW
conductor architecture,” says Neilsen. “That was an
important factor in making the choice.” Mark Lancaster,
Senior Product Engineer, adds, “Southwire also brought
specialized conductor engineering expertise to the project,
to design a steel-core, high-temperature low-sag conductor
with specifications tailored to the application.”
In meeting the application requirements, the ACSS
architecture was a “must-have” to control sag due to
thermal elongation under a 1,500 A load. The HS285 core
was needed to handle the weight of the conductor spans
and expected ice loads. Ice loads can be heavy in
Denmark. One incident reported 1.15 inches (29.2 mm)
of conductor ice at 23°F (-5.2°C).
ACSS/TW use is expected to grow
N1’s project is the first installation of the ultra-high-strength
HS285 conductor in Europe. The ACSS/TW architecture in
general is relatively new to Europe. Conductors there
more commonly use ACSR or AAAC (All Aluminum Alloy
Conductor) designs.
HS285
The HS285 product installs just like other steel-core ACSS/TW
conductors, but because of the relative unfamiliarity of
the ACSS/TW design, a team from Southwire conducted a
pre-installation conference for the contracting crew doing
the job. The Southwire team inspected the site, trained
installers and consulted with Otra engineers.
“This project is the first of its kind in Denmark and this type
of upgrading is only carried out in a few places in Europe,”
Neilsen says. “We’re pleased with the results,” Lancaster
adds. “We’re expecting to see growth in the use of
ACSS/TW conductors in Europe as grid operators continue
to confront the cost of upgrade projects.”
HS285 ACSS/TW: High Temperatures
with Low Sag
HS285 high-temperature, low-sag (HTLS) designs
use an ACSS (aluminum conductor, steel-supported)
architecture. In ACSS conductors, the weight of the
wire is taken almost entirely by the steel core. Sag
is determined by the low thermal expansion rate of
steel, rather than the high thermal expansion rate of
aluminum. That allows higher operating temperatures
– and more capacity. ACSS can operate continuously
at temperatures up to 250°C without loss of strength.
In addition, a form of ACSS that uses trapezoidallyshaped conductor strands packs more aluminum into
a given cable diameter. This is ACSS/TW, and it
increases the cost benefits of ACSS technology in
upgrading transmission lines.
Strength Comparison of Steel Cores
• Typical steel core in a standard ACSR cable has a
tensile strength of 210ksi.
• Traditional “high-strength” core delivers a tensile
strength of about 235ksi.
• Southwire’s ultra-high-strength HS285 steel core
racks up 285ksi.