Guidance Document
Traditional Planning Considerations for
Power Electronics Devices
Guidance Document
Traditional Planning Considerations for Power Electronics Devices
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Guidance Document
Traditional Planning Considerations for Power Electronics Devices
Abbreviations
ACB
BAU
DINIS
DNO
DNV
ENA
FUN-LV
GIS
HV
LCNF
LPN
LV
MSS
NOP
PED
RTU
SDRC
SPN
UKPN
Air Circuit Breaker
Business As Usual
Distribution Network Information Systems
Distribution Network Operator
Distribution Network Visibility
Energy Networks Association
Flexible Urban Networks – Low Voltage
Geographical Information Systems
High Voltage
Low Carbon Networks Fund
London Power Networks
Low Voltage
Main Substation - LPN term for Primary Substation (secondary voltage of 11kV)
Normal Open Point (for LV systems – either a Link box or LV distribution board)
Power Electronics Device
Remote Telemetry Unit
Successful Delivery Reward Criteria
South Eastern Power Networks
UK Power Networks
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Guidance Document
Traditional Planning Considerations for Power Electronics Devices
Contents
1
2
3
4
5
6
7
8
9
10
Purpose ............................................................................................................................................6
Planning Considerations ..................................................................................................................6
2.1
UK Power Networks Planning Processes ............................................................................6
2.2
Traditional Planning Systems ...............................................................................................6
2.3
Network Analysis/Studies ...................................................................................................12
Business As Usual Comparison Case Studies – London Sites .....................................................16
LPN Method 1: Albert Embankment Camelford House North (90008) – Radial Network .............17
4.1
Connection Driven Reinforcement – Planners Log ............................................................17
4.2
Load Growth Driven Reinforcement ...................................................................................22
4.3
Proposed FUN-LV Method 1 ..............................................................................................23
LPN Method 2: Piccadilly Ritz Hotel (31529) – Interconnected Network ......................................26
5.1
Connection Driven Reinforcement – Planners Log ............................................................26
5.2
Load Growth Driven Reinforcement ...................................................................................29
5.3
Proposed FUN-LV Method 2 ..............................................................................................30
LPN Method 3: Shaftesbury Ave 125 (24410) – Interconnected Network ....................................34
6.1
Connection Driven Reinforcement – Planners Log ............................................................34
6.2
Load Growth Driven reinforcement.....................................................................................38
6.3
Proposed FUN-LV Method 3 ..............................................................................................39
Trial Site Case Studies – Brighton Sites ........................................................................................42
SPN Method 1: Regent Hill (523461) – Radial Network ................................................................42
8.1
Example FUN-LV Method 1 ................................................................................................42
SPN Method 2: Duke Street (523338) – Radial Network ..............................................................44
9.1
Example FUN-LV Method 2 ................................................................................................44
SPN Method 3: New Road (523230) – Radial Network ................................................................47
10.1 Example FUN-LV Method 3 ................................................................................................47
Table of Figures
Figure 1- ENMAC/PowerOn Screenshot of the LV Network ................................................................... 7
Figure 2 - Distribution Network Visibility Geographical Map Screenshot ................................................ 8
Figure 3 - Distribution Network Visibility Utilisation Screenshot .............................................................. 9
Figure 4 – SPN NETMAP Screenshot ................................................................................................... 10
Figure 5 - WinDebut Screenshot ........................................................................................................... 11
Figure 6 - DINIS Screenshot ................................................................................................................. 12
Figure 7 - Google Maps View – Albert Embankment Camelford Hs N ................................................. 17
Figure 8 – LV Geoview – Albert Embankment Camelford House N ..................................................... 18
Figure 9 – DNV Utilisation– Albert Embankment Camelford House N (90008) .................................... 19
Figure 10 – DNV Utilisation– Albert Embankment-Tintagen House (90007) and ................................. 20
Figure 11 – NETMAP Webview– Albert Embankment Camelford House North ................................... 21
Figure 12 – Proposed PED Solution – Albert Embankment Camelford House North........................... 23
Figure 13 – Method 1 Variant – no link box switches ............................................................................ 23
Figure 14 – Method 1 Variant – with link box switches ......................................................................... 24
Figure 15 –Method 1 LV Circuit Breakers ............................................................................................. 24
Figure 16 - Google Maps View – Piccadilly Ritz Hotel .......................................................................... 26
Figure 17– LV Geoview- Piccadilly Ritz Hotel ...................................................................................... 27
Figure 18 – DNV Utilisation – Piccadilly Ritz Hotel ............................................................................... 27
Figure 19 – HV Geoview – Piccadilly Ritz Hotel ................................................................................... 29
Figure 20 – DINIS Network View – Piccadilly Ritz Hotel ....................................................................... 30
Figure 21 – Proposed PED Solution – Piccadilly Ritz Hotel .................................................................. 31
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Figure 23 – Method 2 general arrangement .......................................................................................... 32
Figure 22 – Method 2 Free Standing Cabinet ....................................................................................... 32
Figure 24 - Google Maps View – Shaftesbury Ave 125 ........................................................................ 34
Figure 25 – LV Geoview – Shaftesbury Ave 125 .................................................................................. 35
Figure 26 – DNV Utilisation– Shaftesbury Ave 125 .............................................................................. 36
Figure 27 – HV Geoview – Shaftesbury Ave 125 .................................................................................. 37
Figure 28 – DINIS Network View – Shaftesbury Ave 125 ..................................................................... 38
Figure 29 – Proposed PED Solution – Shaftesbury Ave 125 ................................................................ 39
Figure 30 – Method 3 general arrangement .......................................................................................... 40
Figure 31 – Method 3 Control Panel and Power Electronics Panel (1 of 3) .......................................... 40
Figure 32 – Traditional Planning for PED Solution – Regent Hill .......................................................... 42
Figure 33 – Traditional Planning for PED Solution – Duke Street......................................................... 44
Figure 34 – New Cable Installation Boyces’ Street ............................................................................... 46
Figure 35 – Traditional Planning for PED Solution – New Road ........................................................... 47
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Guidance Document
Traditional Planning Considerations for Power Electronics Devices
1
Purpose
The purpose of this guidance document is to outline traditional planning processes and
considerations, summarising how these relate to the connection of PED on urban LV networks. PEDs
provide a sophisticated method of interconnecting LV networks and enabling access to the
latent/spare capacity from neighbouring substations. During a trial rollout of these devices it is
necessary to understand the capability of current planning systems in context of device selection,
design and installation. These considerations are detailed as evidence in accordance with the Flexible
Urban Networks – Low Voltage (FUN-LV) project, a Low Carbon Networks Fund Tier 2 project. This
document concerns urban LV networks and accordingly focuses only on underground cables networks
and not overhead line networks. Radial (SPN/LPN) and interconnected (LPN only) underground
networks are referenced being that both network types are present within the FUN-LV trial areas.
2
Planning Considerations
Many business as usual planning considerations for typical planning solutions are also relevant when
selecting, designing and installing PEDs. These include costs, longevity, security/quality of supply,
fault level, space constraints, planning and installation time and planning permission/consent. The
following sections on traditional planning systems and network analysis/studies will explore these
considerations in more detail as well as discussing their application to connecting PEDs.
Examples of these considerations are investigated further in Section 3.
2.1
UK Power Networks Planning Processes
The UK Power Networks distribution planning department are responsible for planning work at
voltages of 11kV and below on the network, typical undertakings include customer connection
referrals, reinforcement and asset replacement works.
Reinforcement of the network can be initiated from each of these various areas i.e. requirement to
connect a new customer on an overloaded network, requirement to reinforce due to natural load
growth and opportunistic reinforcement due to other required works such as new asset installations.
Traditional reinforcement could involve replacing transformers to an increased capacity rating,
replacing cables to a higher current rating or building a new secondary substation, this is dependent
on the critical limitation of that network area.
PEDs can be considered as a method of deferring the traditional reinforcement for an appreciable
period of time (up to 8 years). As with any reinforcement solution, selection will be based on providing
the ‘minimum cost solution’ taking into account the particular network requirements, cost efficiency
and time/space constraints specific to a given case.
2.2
Traditional Planning Systems
Several tools/applications are currently used to analyse the LV network in the context of planning
work, these include ENMAC/PowerOn, DNV, NETMAP, WinDebut and DINIS, each of these is
described below. An additional tool being trialled by the project (DPlan) is not currently used as part of
the business as usual planning systems.)
ENMAC/PowerOn
This software displays the network connectivity at EHV, HV and LV levels. The LV ‘Geoview’
geoschematics, as shown in Figure 1, are used by distribution planners to observe existing cable
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routes, cable size/type, secondary substations and link boxes, network configuration, basic operational
information/status, building outlines, customer location and certain items of asset information.
This system can enable the selection of substation sites for PEDs by displaying the LV connectivity
and subsequently potential routes for power transfer between substations. The power transfer might
utilise sharing between two or three substations and potential LV mains between them. These
geoschematics can also indicate what installation arrangements may be possible in order to gain the
required power transfer e.g. retrofitting link boxes or cross jointing between LV mains.
Due to PEDs being capable of remote network reconfiguration, a representation of the devices and
networks would need to be present in the connectivity model. Under the current system, there is no
automated visibility of the LV network configuration i.e. switching operations in link boxes and
substation LV distribution boards must be recorded into the system manually, however, PEDs are
capable of relaying such information. The ENMAC/PowerOn connectivity diagrams will be utilised to
assess the feasibility of connecting secondary substations via the LV network i.e. link boxes or LV
distribution boards, as well as marking network boundaries (primary substation/feeder group/block).
However, there is a limitation in automatically tracing LV feeders to their donor substations (although
this functionality is currently present in the HV diagram), and this would better facilitate viewing
connections in dense networks. Automatic LV feeder tracing would save time in planning BAU works
as well as planning for PEDs. Transformer utilisation data is available (for substations with RTUs) in
graph format as well as data tables, however, coordinating the desired data into this format is
complex.
Figure 1- ENMAC/PowerOn Screenshot of the LV Network
DNV (Distribution Network Visibility) Tool
The DNV Tool is used to gather and display data, on demand, from a number of disparate databases,
to obtain a better representation of how the network is performing. DNV is applied by planners both as
a geographical map of the network assets (see Figure 2) as well as an indicator of asset utilisation
(maximum demand) and load profiles (see Figure 3). Data is communicated from RTUs installed in the
primary and secondary substations to a server database and illustrated in a user friendly, discernable
visual format in the DNV Tool. This tool has a particular relevance in planning new customer points of
connection as it can display secondary substations according to their available capacity using a colour
key.
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This tool can be used to identify overloaded secondary substations and recognise load profiles
(residential/ commercial/night). These two factors are critical in selecting and matching sites that
would benefit from installing PEDs. The utilisation view (shown in Figure 3) is not only used to identify
the substation that would become overloaded and require power transfer but also the load profiles of
potential donor substation nearby. By measuring the extent of overloading, it is possible to select a
suitable Method capable of transferring an amount of power e.g. a multi terminal device is capable of
transferring more capacity than a dual terminal PED. Additionally these load profiles illustrate the time
and duration for which the maximum demand typically occurs, this information is considered in
designing the control processes of the PED.
The implementation of this tool largely depends on the installation of RTUs in secondary substations
and the availability of historical data. For example in LPN, 54% of secondary substations have RTUs
as compared to only 26% in SPN. Moreover, the RTU data in SPN only reflects the HV network (i.e.
measurement current transformers around HV cables) and cannot be captured retrospectively (only
illustrates live readings). In addition to RTU data (where available), an asset management system
(Ellipse) is used by LPN and SPN to log the MDI (Maximum Demand Indicator) readings through a
regular programme of substation inspections.
Figure 2 - Distribution Network Visibility Geographical Map Screenshot
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Figure 3 - Distribution Network Visibility Utilisation Screenshot
NETMAP
This application provides a scaled geographical map of the LV and HV cable routes. There are various
layers that can be superimposed onto the Ordnance Survey background map, providing more detailed
information on cable joint locations, cross sections for cable positions in the ground, substation
position, LV service cables/SRC (service record cards), link box locations, building outlines and
road/pavement layouts. These layers include older hand sketched raster-based drawing plans as well
as some vectorised digital information e.g. some cable routes. An example of this overlay is illustrated
in Figure 4 with the vectorised cable routes represented as blue lines and raster drawings/annotations
in grey. The business typically uses NETMAP drawings (commonly 1:500 scale) when assessing
practicalities of works (particularly underground).
Although there is no substation equipment information and no utilisation information available, this
application provides detailed cable asset information, including size, type, positioning, ducting and
age. In terms of planning the installation of PEDs, these NETMAP drawings are important in verifying
the cable information shown in the LV ENMAC/PowerOn connectivity diagram ‘Geoview’ and
customer connection points with LV services information. The scaled map can provide a more refined
outline of potential installation sites, such as highlighting larger secondary substations (potential for
multi terminal device) and planning connections to the LV mains (retrofitting link boxes or using dual
terminal device).
Whilst the mapping continues to combine various layers of network information, there are areas of
potential inconsistency and outdated information. Within the LPN network, only new additions to the
network are being incorporated as vectorised drawings and therefore the raster images are often
used, however, in SPN the full LV network can be examined in the vectorised format. Considering that
this application is widely used across the business, it would be expected to include objects
representing PEDs.
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Figure 4 – SPN NETMAP Screenshot
WinDebut
WinDebut is primarily used in the SPN planning department to model single LV networks, providing
volt drop, earth loop impedance and predicted fault currents. It does not allow for import of data links
from other systems, rather it relies upon the designer to build the network based upon information
from other systems such as Netmap and customer usage information. Typically WinDebut is used to
perform basic studies on networks with supply quality issues, and longer feeders with undersized
cables/conductors, an example study is shown in Figure 5. It allows for the modelling of customers by
means of standard load profiles which can be scaled to customer annual usage, as well as motors,
welders, and from version 3.1 the modelling of various forms of LV connected generation, photovoltaic
cells etc., on the network.
Due to the lack of network information in WinDebut, building network models and apportioning
customer usage information is a time consuming exercise for planners. Additionally the accuracy of
the model is wholly dependent on the estimations and assumptions that are adopted by the planner
rather than being a direct reflection of the network.
This flexibility is useful for modelling simple direct services, rural overhead line networks and creating
local networks from scratch such as new housing estates. However, there are limitations on applying
this software to urban networks, encompassing implications to the wider network and geographical
referencing.
As it does not reflect the existing network, WinDebut has limited functions that will assist in selecting
and installing the PED. Utilising WinDebut for designing networks including PEDs will also prove to be
difficult as Windebut can only model from a secondary substation to the open point or customer, it
does not allow for the modelling of interconnected LV networks or the Power Transfers which would
occur.
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Guidance Document
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Figure 5 - WinDebut Screenshot
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Guidance Document
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DINIS (Distribution Network Information Systems)
The DINIS application is primarily used in the LPN planning department (not used in SPN or EPN) for
its network modelling capabilities. An output from the DINIS model network connectivity is reflected in
ENMAC/PowerOn, hence DINIS contains network information to conduct load flow analysis (including
voltage drop and network current), fault level analysis and model protection operation. Individual
feeder groups can be loaded from a master network for local analysis, a single LPN feeder group view
is shown in Figure 6, HV and LV cables represented in red and grey respectively. The LPN planning
department only typically run fault level analysis in DINIS for connections involving generation, starter
motors or where transformer capacity is upgraded in interconnected systems. The Fault Study
Package (FSP) is also available as an add-on within DINIS, which is used for large network
reinforcement planning schemes.
This system can be utilised in planning PED selection in a similar way to ENMAC/PowerOn. The LV
connectivity diagram is geographical and demonstrates potential routes of power transfer between
nearby substations. The diagram has a representation of link boxes and can therefore be used to plan
potential capacity sharing across these open points (retrofitting link boxes or using dual terminal
device). DINIS has additional facility through network modelling, which can provide a better
understanding of the existing load flows and fault level in the network.
There is the capability within DINIS to model interconnected systems, however, this can be a time
demanding process i.e. before retrieving results the model requires load information to be
imported/manually input and time allowed for running the analysis. Using the current DINIS modelling
function to conduct load flow and fault level studies on networks involving PEDs would prove difficult
as no function has yet been created that can represent a specified power transfer (as opposed to one
derived from system impedance) and also one that varies in time (as opposed to a snapshot of the
current demand).
Figure 6 - DINIS Screenshot
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2.3
Network Analysis/Studies
The following section details typical considerations involved in the planning process for connecting
new customers on to a fully loaded network. Comparable considerations apply when planning
reinforcement of the network following natural load growth (driven by the DNO). These contexts can
equally demonstrate the planning considerations that are important in the process of selecting,
designing and installing of PEDs.
LV Connection Options
To accommodate new customer connections on an LV network with a transformer capacity limitation,
there are a variety of options that would be considered as part of the business as usual approach. The
viability of each option will depend on the details of the network and providing the minimal cost
solution. These costs may include materials (cables, transformer, substation housing), contractor (for
civil works i.e. excavation, reinstatement and traffic management), labour (jointers, field engineers)
and other (legal). Examples of traditional LV connection options are listed below.
Radial Network Options:
 Transfer transformer load – Move the Normal Open Point (NOP) (closer to the overloaded
substation) to reduce the transformer load, i.e. the load shifts to a neighbouring transformer.
Using existing link boxes and LV distribution boards.
N.B. This could apply to any LV main from the substation including the one intended for the
new connection.
 Transfer transformer load – Create NOP (closer to overloaded substation) via the installation
of a new link box.
 Alternative point of connection – Connect new customer on to an LV main being fed from a
different substation (not overloaded). This would often be a dedicated service and would likely
increase the distance of new cable installation and road excavations.
 Increase transformer rating – Replace the overloaded transformer with a higher rated
transformer.
 New substation – Build a new substation i.e. new transformer to feed the new customer.
Interconnected Network Options:
 Alternative point of connection – Connect new customer on to a more optimal LV main within
the interconnected network. This would also increase the distance of the new cable installation
and road excavations.
 Increase transformer rating – Replace the overloaded transformer with a higher rated
transformer.
 New substation - Build a new substation i.e. new transformer to feed the new customer.
If cable capacity is the limitation for making new connections, similar options are considered including
transferring load, connecting to alternative LV mains with capacity or upgrading overloaded cable to a
higher rated cable. Sharing capacity in a radial network via the insertion of links/fuses (in a link box/LV
distribution board) is not typically considered under permanent planning solutions. This is used for
switching under fault scenarios, after which the network should be returned to the configuration as
planned.
PEDs can contribute to the portfolio of already available solutions mentioned above considering their
respective costs and varied applicability. The implementation of PEDs will particularly target cases
where expensive solutions such as a new substation or a combination of alternative point of
connection and increasing the transformer rating are required. This capability is achieved through the
transfer or sharing of capacity between neighbouring substations. The different PEDs available can
cater to meet a variety of network scenarios such as differing connection load requirements (sharing
between two or three substations) or space constraints (choice of pavement or substation
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installations). PEDs additionally provide flexibility in network reconfiguration being that they have
remote operability as well as automated operation and can therefore offer dynamic network
management. In already interconnected networks, PEDs can provide benefits such as reducing and/or
constraining fault level, controlled power transfer (as opposed transfer based on to impedance), load
unbalance/power factor/harmonics correction and capacity sharing across network boundaries.
Substation Lease Requirements
Another factor to recognise for new connections is the condition of the lease for the property
containing a substation. This is evaluated through enquiries to the Operational Property and Consents
department, who are responsible for the protection of existing assets and the acquisition of new
consents as necessary, so as to minimise business risk.
Cable Capacity
For new LV customer connections exceeding 140kVA, the planning department must consider cable
size/type (and associated cyclic ratings) as well as the existing load already connected to the LV
cable. This information will give an indication as to whether the cable being considered has available
capacity to accommodate the new customer connection. This LV cable utilisation data cannot currently
be acquired using RTU data as the current measurements relate to the overall transformer load and
not individual LV cable mains connected to the substation LV distribution board. As mentioned above,
cable size/type information can be found on DINIS (equivalent with data in ENMAC/PowerOn) as well
as NETMAP. Associated cyclic ratings are also available on these applications, however, these are
not an accurate reflection of the cable rating used by the business. Although, high level guidance can
be acquired from ENA Engineering Recommendation P17 – ‘Current Ratings for Distribution Cables’,
the effects of numerous parameters (including ground type, adjacent cables, ducting arrangements)
are not quantified in detail. Moreover, these ratings are based on cyclic load profiles. The UK Power
Networks Engineering Design Standard EDS 02-0049 – ‘Calculation of DINIS Cable Ratings’ provides
cable ratings for summer and winter seasons as well cyclic and continuous load profiles. This standard
includes the representative cables ratings demonstrating the effects of ground type, adjacent cables
and ducting arrangements, although these are not comprehensive. Transfer profiles resulting from
use of PEDs may be similar or very different to typical load profiles and may need continuous cable
ratings to be used.
The existing load connected to LV cables is typically estimated through use of current readings
(measurement devices include tong testers/ammeters e.g. Redskye RSK 2000PA Rogowski Coil).
These current readings are taken instantaneously rather than over extended measurement durations,
this is due to time constraints within the standard license agreement.
When planning the connection of PEDs to the network, power flow studies would be necessary to
ensure that the required transfer/sharing of capacity between substations can be accommodated by
the LV main cable bridging the capacity exchange. Defining a practical magnitude and duration of the
power transfer will ensure that the appropriate LV cables will be able to carry the current without
having an impact on their condition. As mentioned above, a tool would be required to conduct power
flow studies and fault analysis taking into account the dynamic characteristic of the capacity
transfer/sharing and network reconfiguration using PEDs. As part of the FUN-LV project, studies will
be conducted to model PEDs using the software DPlan. As well as using network modelling, the
installation of LV network monitoring in conjunction with PEDs would benefit LV cable loading visibility.
This would allow control systems to actively manage the loading of cables by evaluating time based
cable loading information and cable rating data.
Fault Level Analysis
As well as analysing the additional load of new connections during normal running, fault analyses are
carried out in cases of generation, starter motors and increased transformer ratings within an
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interconnected network. These studies aim to ensure that the fault level (prospective short circuit
current) is within the ratings of protection equipment and that the operation is coordinated
appropriately.
By installing PEDs, capacity sharing/transfer can be achieved without increasing the fault level of that
network (as it would through traditional interconnection). This is due to the functionality of the PED
which does not allow the transfer of fault current, the device will only transfer a specified amount of
current (according to its programmed instructions). This feature is also important in protecting the
device itself as transistors within the inverter bridge have a low thermal inertia. The PED can also be
programmed to stop current transfer altogether if it detects a collapse in voltage, as would occur in a
typical fault.
Further fault studies will be required, using appropriate software tools, to ensure that the PED
operation complements existing network protection, considering scenarios such as LV distribution
board faults and HV phase-phase and phase-to-earth faults. This reaffirms the necessity of a tool to
conduct power flow studies and fault analysis taking into account the dynamic characteristic of the
capacity transfer/sharing.
Supply Restoration
Within the UK Power Networks distribution planning department, supply restoration is analysed for HV
network planning only. Effective supply restoration planning ensures practical and fast restoration of
as many customers’ supplies as possible following a power outage. On the LV network supply
restoration would involve temporarily reconfiguring the LV network open points (moving/creating NOP
via link boxes and LV distribution boards) whilst the LV fault is repaired. The number of customer
supplies restored depends on how the network can be sectionalised i.e. groups of customers on a LV
cable are separated/isolated between LV open points.
On radial networks, supplies can be restored by isolating the faulty LV leg (e.g. removing links) and
back feeding customers from an adjacent healthy LV feeder (e.g. inserting links/fuses into a NOP). A
well planned network should have sufficient LV network open points available to segregate sections of
network (groups of customers), this will enable a larger group of customers to be isolated from the
faulted section and have their supplies restored from an adjacent healthy LV feeder.
However on an interconnected network customer supplies are already connected in parallel (multiple
substations supplying the same customers), and therefore customers might not lose power supply in
the event of a fault (this is dependent on fault type). Effective planning should minimise the risk of
customer load allocation (number of customers) exceeding the ‘hold up’ capacity of the donor
substations. Hold up capacity in this case referring to the ability of a substation to support the
load/customers on an adjacent network, following a loss of normal supply provision. Further
information on LPN Interconnected Network and Enhanced Meshing is described in the UK Power
Networks Business Plan Annex 9: Smart Grid Strategy.
PEDs can complement supply restoration on interconnected networks through capabilities such as
sharing capacity across network boundaries (primary substation/busbar/group) and supporting
network corners (areas furthest from hold up supply). PEDs being installed on interconnected
networks would be expected to complement the existing hold up arrangements of a network system.
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Guidance Document
Traditional Planning Considerations for Power Electronics Devices
3
Business As Usual Comparison Case Studies – London Sites
The following business as usual comparison case studies illustrate the traditional reinforcement
options at specific FUN-LV trial sites being selected for the installation of PEDs on the LPN network.
These case studies consist of traditional reinforcement scenarios driven by a hypothetical customer
connection request or natural load growth, followed by the proposed FUN-LV trial solution. This
analysis will demonstrate the planning considerations as well as illustrative cost estimates for each
reinforcement solution. There are three LPN case studies in this section, these include an example for
each of the three Methods in the FUN-LV project. Following PED network trials, actual costs will be
used to address the economic feasibility and practicality of meshed networks using these Methods, as
well as the suitability dependent on factors such as location.
Table 1 illustrates a summary of the example business as usual solutions for each case study and the
potential savings gained through use of the proposed FUN-LV trial solution. These savings are
attributed against the total costs for both the customer connection and load growth reinforcement
triggers.
Example
Type of Network
Albert Embankment
Camelford House North
Radial
BAU Solution
FUN-LV
Connection
Load Growth Method
(Customer)
(DNO)
Transformer
Upgrade
Transformer
Upgrade
Total Savings
Connection
Load Growth
(Customer)
(DNO)
1
Approx.
£43,000*
Approx.
£12,000*
£58,000 to
£88,000
plus land costs
Approx.
-£24,000
(negative)
Piccadilly Ritz Hotel
Existing Meshed
New Substation New Substation
(Interconnected)
2
£109,000 to
£139,000
plus land costs
Shaftesbury Avenue 125
Existing Meshed New Substation New Substation
(Interconnected) (in existing site) (in existing site)
3
Approx.
£36,000
* This FUN-LV Method 1 solution uses only one spine circuit and no link box switches, the variant with link box
switches will reduce the above savings by approximately £12,000. The shared capacity for all Method 1 solutions
is dependent upon network impedance.
Table 1 – BAU Comparison Costs Summary
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Guidance Document
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4 LPN Method 1: Albert Embankment Camelford House North
(90008) – Radial Network
4.1
Connection Driven Reinforcement – Planners Log
To represent a connection driven reinforcement scenario a hypothetical request was received from the
customer enquiry system for 200kVA to be provided at 89 Albert Embankment, Lambeth, SE1.
Figure 7 - Google Maps View – Albert Embankment Camelford Hs N
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Figure 8 – LV Geoview – Albert Embankment Camelford House N
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Guidance Document
Traditional Planning Considerations for Power Electronics Devices
Looking at the Geoview LV network, the closest secondary substation is Albert Embankment
Camelford House North (90008) with a transformer rated at 500kVA. Nearby substations include
Albert Embankment-Tintagen House (90007) – 500kVA, Albert Embankment 93 (90005) – 500kVA
and Albert Embankment Camelford House South (90009) – 2 x 500kVA.
Figure 9 – DNV Utilisation– Albert Embankment Camelford House N (90008)
Looking at the utilisation data using DNV for Albert Embankment Camelford House North with a
transformer rated at 500kVA, the maximum demand on Albert Embankment Camelford House North
already exceeds an acceptable level, exceeding 600kVA. This is above 120% of the name plate rating
(600kVA), which is the upper limit that transformers are allowed run at for short periods of time in
radial networks.
In order to reduce the overloading on this transformer it might be possible to transfer load to a
neighbouring substation by moving NOPs. Observing the LV network on Geoview there are multiple
potential NOPs that can be moved, which would involve the neighbouring substations
(90005/90007/90009). However, as the majority of load connected to these other substations are
direct services, transferring these sections of network (by moving NOPs) will not transfer significant
load to alleviate substation 90008. Therefore, the capacity for the new connection can be made
available either by upgrading the transformer at Albert Embankment Camelford House North (90008)
or by connecting to one of the neighbouring substations, the former option is likely to be being more
expensive. In both cases this 200kVA connection request will need to be via a direct service rather
than a passing LV main as any additional load would be likely to exceed the cable rating (200kVA is
approximately 300A at low voltage).
Other secondary substations in close proximity to supply the new direct service would be Albert
Embankment-Tintagen House (90007) – 500kVA or Albert Embankment Camelford House South
(90009) – 2 x 500kVA.
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Guidance Document
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Figure 10 – DNV Utilisation– Albert Embankment-Tintagen House (90007) and
Albert Embankment Camelford House South (90009)
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Guidance Document
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Customer
Location
Selected
Substation
Available Duct
Route
(empty circle)
Figure 11 – NETMAP Webview– Albert Embankment Camelford House North
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Guidance Document
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Looking at the utilisation data from DNV for Albert Embankment-Tintagen House (90007) and Albert
Embankment Camelford House South (90009). The maximum demand on Albert EmbankmentTintagen House (90007) is approximately 330kVA in 2013, therefore there is less than 200kVA spare
capacity (500kVA transformer). The maximum demand on Albert Embankment Camelford House
South (90009) is below 300kVA, therefore there is more than 700kVA spare capacity (2 x 500kVA
transformers). Additionally, observing the scaled NETMAP view in Figure 11, the cable route from
Albert Embankment Camelford House South (90009) is shorter and would therefore require less
excavation than from Albert Embankment-Tintagen House (90007). The approximate length for this
direct service would be 80m. It is also apparent that there is an old duct route between the two
substations, however, it is unlikely that this could be utilised for the length of the direct service.
Due to items stated above, it would be proposed to the customer that the transformer in Albert
Embankment Camelford House North (90008) is replaced with a 1MVA rated transformer and a direct
service is installed for the customer at 89 Albert Embankment to cater for the 200kVA request. This is
provided that an additional service/fuse-way can be feasibly connected to the existing LV distribution
board or by extending the board. This arrangement would provide an additional 200kVA spare
capacity to the network as well as providing the customer with 200kVA under the minimum cost
scheme.
4.2
Load Growth Driven Reinforcement
This area of network is configured as a radial system and therefore the transformer could be allowed
to run at 120% of its capacity (600kVA) for short periods of time. From the utilisation data shown in
Figure 9, the maximum demand is already above 600kVA and is therefore exceeding this limit. The
transformer could be upgraded by replacing the original 500kVA rated transformer to one with either
an 800kVA or 1MVA rating.
Reinforcement Options:
 Transfer transformer Load – Move/create NOP (closer to the overloaded substation). As the
majority of load connected in this area of network is direct services, transferring these sections
(by moving NOPs) will not transfer significant load to alleviate substation 90008
 Increase transformer rating – Installing an additional 500kVA transformer would increase the
120% rating to 1.2MVA. This would involve retaining the existing old 500kVA (potential asset
condition issues) and therefore more space is required to hold both transformers.
 Increase transformer rating – Installing an 800kVA transformer replacement would increase
the 120% rating to 960kVA.
 Increase transformer rating – Installing a 1MVA transformer replacement would increase the
120% rating to 1.2MVA.
 New substation – Build a new substation and transfer network load/direct services from old
substation onto a new installed network substation.
The proposed planning solution in this case would be to replace the original 500kVA transformer with
an 800kVA transformer (costs for an 800kVA transformer are comparable to that of a 500kVA
transformer). This option should provide adequate capacity for the existing connections at Albert
Embankment Camelford House North (90008) as well as spare capacity to cater for new connections
and future load growth. The new transformer will utilise a comparable footprint to the original. Based
on load estimates for this substation, the latter options of installing a 1MVA transformer or a new
substation are likely to be unnecessary.
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Guidance Document
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4.3
Proposed FUN-LV Method 1
In this area there is spare capacity of 170kVA at Albert Embankment-Tintagen House (90007) and
700kVA at Albert Embankment Camelford House (90009), over capacity of 100kVA at 90008 and
therefore a total surplus of 770kVA. This spare capacity can be utilised for sharing capacity through
meshed networks if load profiles are complementary. As part of the FUN-LV project, this site was
selected for the installation of Method 1 comprising of LV circuit breakers at both substations with no
link box switches required. These LV circuit breakers allow automated operation and may enable a
capacity transfer of up to 200kVA between Albert Embankment Camelford House North (90008) and
Albert Embankment Camelford House South (90009).
Figure 12 – Proposed PED Solution – Albert Embankment Camelford House North
In the configuration proposed, the LV circuit breakers will replace fuses on the LV distribution board
connecting both substations. The circuit will be run in a meshed arrangement by closing the existing
NOP currently at Albert Embankment Camelford House South (90009) and will allow the remote
operation of LV circuit breakers at both ends. Figure 13 demonstrates arrangements for the existing
network configuration and proposed FUN-LV Method 1 in this example, which does not require use of
a remote controllable link box.
Figure 13 – Method 1 Variant – no link box switches
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Guidance Document
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Another variant of FUN-LV Method 1 being used at other trial sites includes the installation of a remote
controllable link box (containing switches). The diagram in Figure 14 demonstrates arrangements for
the existing network configuration and proposed FUN-LV Method 1 for this type of trial site. In this
arrangement there are additional equipment costs as well as civil works associated with replacing and
jointing the new link box. The benefits of this variant include additional flexibility to configure the LV
network as necessary for example it can be run as two shorter radial circuits, one long radial circuit,
one parallel circuit or sectionalised in the event of a fault. The photo in Figure 15 shows one set of
three LV circuit breakers installed on an LV distribution board.
Figure 14 – Method 1 Variant – with link box switches
Figure 15 –Method 1 LV Circuit Breakers
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Guidance Document
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FUN-LV Method Comparison and Considerations
Costs – In comparison with the business as usual solutions, the PED costs (approx. £14,000) are less
than both the connection driven reinforcement (customer – approx. £49,000, DNO – approx. £8,000)
and the load growth driven reinforcement (approx. £26,000).
Longevity – Current estimates for the lifetime of the PED equipment is under 10 years, therefore it is
providing a temporary solution by delaying traditional reinforcement. A typical transformer life time
would be 40 years.
Security/Quality of Supply – The PED capability includes an automated response in the event of a
fault as well as remote switching. In this example as there is no link box between the two sets of
Remote Controllable Circuit Breakers there is no decrease response time in the event of restoring a
fault on this circuit. Traditionally fuses would have operated to clear the fault.
Equipment Size – The LV circuit breakers are equivalent to the dimensions of a fuse carrier with a
deeper housing unit.
PED Location – The LV circuit breakers would be installed on the LV distribution board, the power
data bus below the fuse carriers and the gateway is attached to a wall within the substation.
Planners Time – The PED solution would require additional LV load flow studies and fault level
studies to ensure that sufficient capacity is being shared. However, the majority of planning for this
radial network is comparable to traditional solutions . In addition the Remote Controllable Circuit
Breakers have an inhibit function preventing it from attempting to clear a fault which is close to the
substation. The inhibit zone is a function of circuit impedance and is determined to be the point where
the fault current is calculated to be less than the break rating of the power electronics thyristor of 6kA.
Installation Time – The Method 1 equipment would be delivered and installed within 1 day, whereas
BAU solutions (transformer replacement) could require 3-4 days.
Planning Permissions/Consent – As Method 1 equipment is internal to the existing substation no
planning permissions would be required.
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Guidance Document
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5 LPN Method 2: Piccadilly Ritz Hotel (31529) – Interconnected
Network
5.1
Connection Driven Reinforcement – Planners Log
To represent a connection driven reinforcement scenario a hypothetical request was received from the
customer connection gateway for a further 240kVA to be provided at Piccadilly Ritz Hotel, 150
Piccadilly, London, W1J.
Figure 16 - Google Maps View – Piccadilly Ritz Hotel
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Location
1.0 MVA
Guidance Document
800 kVA
Traditional Planning Considerations for Power Electronics Devices
1.0 MVA
Figure 17– LV Geoview- Piccadilly Ritz Hotel
Looking at the Geoview LV network, the closest secondary substation is Piccadilly Ritz Hotel (31529)
with a transformer rated at 1MVA. Nearby substations include Arlington Street 1-3 (35852) – 1MVA,
Arlington St 20 (31463) – 800kVA, Piccadilly Green Pk Stn (36746) - 1MVA, and Berkley Street 40-50
(36300) – 2 x 800kVA.
Figure 18 – DNV Utilisation – Piccadilly Ritz Hotel
Looking at the utilisation data in Figure 18 (over the past 2-3 years or to the coldest winter) from DNV
for the closest secondary substation, Piccadilly Ritz Hotel Substation (31529) with a transformer rated
at 1MVA. The maximum demand on Piccadilly Ritz Hotel Substation (supplying LV network mains and
direct services) already exceeds an acceptable level, in 2013 the maximum demand rose above
1MVA. On interconnected networks, the typical practice is for the maximum demand substations to be
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Guidance Document
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kept within 80% of their name plate rating to allow for hold up (which would be 800kVA in this case).
As 1MVA is the largest capacity transformer UK Power Networks uses at a secondary level, it is not
possible to upgrade to a higher rated transformer. Therefore it is not possible to accommodate the
240kVA new connection on to Piccadilly Ritz Hotel substation.
As an alternative point of connection, it might be possible to connect via a direct service or an existing
LV main from one of the surrounding substations. N.B. Connections of ~250kVA and above should
typically be connected via a direct 3 phase service, as connecting to an LV main with existing load
would be likely to overload the cable (even those highly rated). Connections to Berkley Street 40-50
(36300) would not be entertained since this would require a major crossing (large associated costs)
and the substation lies across a primary substation boundary, supplying a customer from different
primary substation/group/busbar is not permissible since it creates circulating currents. Similarly,
Piccadilly Green Pk Station (36746) would not be utilised as it is customer dedicated substation and
lies across a group/busbar Boundary. Two secondary substations within the same primary substation
and group/busbar boundary would be Arlington Street 1-3 (35852) and Arlington St 20 (31463).
Although there maybe capacity from one of these two substations to supply a direct service, this would
not be the proposed point of connection as it would introduce further multiple services to the same
building therefore impact on implementing safe isolation of supplies on the premises. There should be
minimal (ideally one) points of isolation, other arrangements may lead to misperception and
inadvertent live equipment posing a danger of electrocution.
Due to the concerns stated above, it would be proposed to the customer that a dedicated substation is
installed for the Piccadilly Ritz Hotel to cater for the additional 240kVA and that existing 3 phase
services (currently fed from the network substation 31529) are also transferred to this new substation.
This would satisfy having a single source of supply for the 3 phase services into the building (safe
isolation) as well as alleviate the load on Piccadilly Ritz Hotel network substation (31529). An
appropriate HV point of connection for this dedicated substation might utilise one of the nearby HV
feeders, such as W5 or NW1 on the Leicester Square Main Substation.
A Parasitic Load Tripping Unit (PLTU) would be installed for the customer’s dedicated substation to
ensure that the customers’ dedicated load is isolated from the network in the event of a HV Phase to
Earth fault. This does have an implication on lowering the customers’ security of supply in comparison
to a network substation connection.
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Guidance Document
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Figure 19 – HV Geoview – Piccadilly Ritz Hotel
Observing the HV cables on Geoview (Figure 19) shows a variety of HV feeders in close proximity of
Piccadilly Ritz Hotel. To connect to the NW1 HV feeder group would require a main road crossing
(incurring a significant cost), whereas, the W5 feeder has sections on the same side of the road as the
building requiring the new connection. The importance of managing fault level in the interconnected
area means that some HV feeders would be discounted from providing additional large connections. It
is possible that a more expensive connection involving an alternative HV feeder would be proposed in
such circumstances. Further HV analysis is required to ensure that the additional dedicated substation
would integrate suitably with the existing network arrangements under both normal running conditions
and in compliance with ENA Engineering Recommendation P2/6 – “Security of Supply” for n-1
conditions (loss of a single circuit).
5.2
Load Growth Driven Reinforcement
In the scenario that an area of network is at risk of exceeding its intended capacity then a planning
solution should also be provided to reinforce that network. Incremental load growth might have arisen
due to the large volume of small service connections (small single phase supplies are not passed
through the LPN distribution planning process) or natural load growth from existing connections due to
increased use of energy intensive appliances.
This area of network is known for having a high load density and as demonstrated above the
maximum demand on Piccadilly Ritz Hotel already exceeds its 1MVA capacity (over 1MVA in 2013).
The transformer could be allowed to run at 120% of its capacity (1.2MVA) for short periods or time,
however, this only applies to radial networks or in normal running conditions. The transformer should
not be loaded above 80% (800kVA) in an interconnected network to allow for LV hold up in the event
of a circuit loss (n-1 condition). The transformer cannot be upgraded as 1MVA is the highest rated
transformer used on the secondary networks.
Reinforcement Options:
 Radialise the whole network – This would mean that transformers would not be limited to the
80% rating for hold up as it is with interconnected networks and instead could run up to 120%.
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


Radialise this section of network (radial embedded) – This would degrade other sites within
this interconnected network i.e. there will not be sufficient capacity in the area to hold up under
LV and HV faults.
New substation on existing feeder – This would allow network load to be transferred from the
old substation (keeping only direct services) onto a new installed network substation.
Connecting this to the existing feeder would raise the fault level (~46kA) above the acceptable
limit and to reduce this would require splitting some network interconnection. Splitting up the
‘network clunch’ would cause issues with the surrounding network due to loss of hold up
capacity.
New substation on different feeder – This would allow network load to be transferred from the
old substation (keeping only direct services) onto a new installed network substation. Some
interconnection would be split such that the ‘network clunch’ fault level is acceptable. By
connecting this new substation to the new feeder the ‘hold-up’ capacity in the area can be
retained, this would involve reconfiguring the interconnection.
The screenshot in Figure 20 demonstrates the network under consideration in the DINIS tool. In
proposing a reinforcement solution for the area, a fault level study would be conducted using the fault
study package to ensure acceptable limits of operation and effective network protection.
The proposed planning solution in this case would be to install a new network substation in close
proximity to the Piccadilly Ritz Hotel (31529) substation but connecting to an alternative HV feeder.
The LV network cables currently fed from the LV distribution board at Piccadilly Ritz Hotel (31529) will
be transferred to the new network substation, therefore shedding load from the original transformer
(only left with dedicated 3 phase services). This option will better support the surrounding network
whilst satisfying concerns with keeping an acceptable fault level and having adequate hold up capacity
across the interconnected network area.
Ideally this new substation would be built using the existing substation space in Piccadilly Ritz Hotel
(31529), however, there is not sufficient space to accommodate the equipment for a double substation
and therefore an independent substation would be required.
Figure 20 – DINIS Network View – Piccadilly Ritz Hotel
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5.3
Proposed FUN-LV Method 2
As part of the FUN-LV project, this site was selected for the installation of a dual terminal PED
(labelled ‘Method 2’). The device will be installed as a piece of street furniture in the pavement section
adjacent to Green Park Tube Station. This dual terminal PED will enable a capacity transfer of up to
240kVA between Piccadilly Ritz Hotel (31529) and adjacent interconnected networks.
Power Electronics Device
Figure 21 – Proposed PED Solution – Piccadilly Ritz Hotel
In the configuration proposed, the device would be jointed onto the LV main that connects Piccadilly
Ritz Hotel (31529) and Link Box 30145. In addition to this jointing the trial will require that the NOP is
closed (via insertion of 1 set of links) so that power can be transferred between Berkley Street 40-50
(36300)/Stratton St Stratton House (31550) and Piccadilly Ritz Hotel (31529). The diagram in Figure
23 shows the proposed design for the free standing cabinet Method 2 device and the schematic
shown in Figure 22 illustrates the general arrangement of the connection to an LV network.
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1000mm
800mm
1400mm
1270mm
200mm
Figure 23 – Method 2 Free Standing Cabinet
Figure 22 – Method 2 general arrangement
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FUN-LV Method Comparison and Considerations
Costs – In comparison with the business as usual solutions, the PED Costs (approx. £48,000) are
less than both the connection driven reinforcement (customer – approx. £152,000-£182,000 PLUS
land cost value, DNO – approx. £5,000) and the load growth driven reinforcement (approx. £106,000£136,000 PLUS land cost value).
Longevity – Current estimates for the lifetime of the PED equipment is under 10 years, therefore it is
providing a temporary solution by delaying traditional reinforcement. A typical transformer life time
would be 40 years.
Security/Quality of Supply – Through capacity equalisation, the network is less overloaded and
therefore at less risk of faulting. The PED is designed to improve quality of supply by providing
voltage support, power factor correction, harmonic content and phase imbalance improvement.
Additionally, the PED would allow a customer to connect to a network substation rather than providing
the connection via a dedicated substation which would require a Parasitic Load Tripping Unit (PLTU).
The PLTU device disconnects HV customers and large LV three phase customers and therefore
reduces security of supply.
Fault Level – The dual terminal PED can constrain the fault level, whereas the business as usual
solution (new substation on interconnected network) will require splitting interconnected feeders to not
further increase fault level.
Equipment Size – The dual terminal PED has dimensions as shown in Figure 23.
PED Location – The dual terminal PED would be installed as a piece of street furniture in the
pavement section adjacent to Green Park Tube Station.
Planners time – The PED solution would require LV load flow studies and fault level studies to ensure
that sufficient capacity is being shared and fault level studies to ensure effective network protection.
However, the BAU solution planning for this interconnected area would require a large amount of time
to redesign the network as it has various constraints on accommodating further capacity. The new
substation may require a new feeder to be installed from the 11kV switchboard at the main substation
and currently there are no available panels at Leicester Square. The PED can provide a temporary
solution at this local scale allowing time to understand what areas of load are growing in order to
sensibly design a wider network area reinforcement solution.
Installation time – The dual terminal PED would be delivered and installed within 2-3 days, whereas
the BAU solutions (new substation) would require upwards of several weeks depending on the
substation construction and alternative feeder.
Planning Permissions/Consent – The dual terminal PED would require permission from the council
to install the device enclosed within a kiosk, whereas the business as usual solution (new substation)
would require the customer/DNO to acquire the land/space to accommodate a new substation and
road closures for cable overlays.
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Guidance Document
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6 LPN Method 3: Shaftesbury Ave 125 (24410) – Interconnected
Network
6.1
Connection Driven Reinforcement – Planners Log
To represent a connection driven reinforcement scenario a hypothetical request was received from the
customer connection gateway for a further 400kVA to be provided at 125 Shaftesbury Avenue,
London, WC2.
Figure 24 - Google Maps View – Shaftesbury Ave 125
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Customer
Location
Figure 25 – LV Geoview – Shaftesbury Ave 125
Looking at the Geoview LV network, the closest secondary substation is Shaftesbury Ave 125 (24410)
with a transformer rated at 750kVA. Nearby substations include Stacey Street (24409) – 750kVA,
Shaftesbury Ave 164 (24143) – 500kVA, Charing X Rd 82 (31023) – 750kVA, and Tower Street 22
(24146) – 800kVA.
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Figure 26 – DNV Utilisation– Shaftesbury Ave 125
Looking at the utilisation data from DNV for Shaftesbury Ave 125 with a transformer rated at 750kVA.
The maximum demand on Shaftesbury Ave 125 already exceeds an acceptable level, in 2013 the MD
rose above 800kVA. This is above 80% of the name plate rating (600kVA), which would allow for hold
up. Although the transformer could be upgraded to a 1MVA capacity this would not sufficiently
accommodate the 400kVA new connection.
As an alternative point of connection, it might be possible to connect via a direct service from a
separate substation with sufficient spare capacity. However, due to the large load requirement a
particular highly rated cable type would be required, this being a single core cable (either 4 core or 8
core double run). However, this cable type is not designed to be laid in ducts or underground and
typically would be used for connections in the closest proximity to the substation (same building via
accessible culverts). Therefore, none of the other surrounding substations (Charing X Rd, Stacey
Street, Tower Street 22 and Shaftsbury Ave 164) are close enough to transfer a direct service of this
size.
Another option would be to install a new network substation at 125 Shaftsbury Avenue. If a customer
dedicated 500kVA substation was installed this would not provide any spare capacity should the
network require it in future whereas an 800kVA network substation could supply the new 400kVA
connection with 240kVA for spare network capacity (640kVA at 80%). Additionally using an 800kVA
transformer does not significantly alter the overall project cost or space required. In this scenario it
was supposed that the customer requesting the new connection was not associated with the existing
direct services attached to Shaftsbury Ave 125 and therefore these could not be transferred to plan a
dedicated substation. Being a network substation, the costs would be apportioned between the DNO
and the customer on a pro rata basis, in this case 50/50 (400kVA of 800kVA). An appropriate HV point
of connection for this network substation might utilise one of the nearby HV feeders, such as E4 or E5
on the Fisher Street B Main Substation. If a network substation is feasible then the Parasitic Load
Tripping Unit (PLTU) would not be required and therefore there is not an added detriment to the
security of the customers supply. In order to support/be supported via the interconnected network, the
new 800kVA network substation would require 3 LV cables to be transferred from Shaftesbury Ave
125 (24410) on to its LV distribution board.
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Figure 27 – HV Geoview – Shaftesbury Ave 125
Observing the HV cables on Geoview shows that using a different HV feeder would require a HV cable
to be looped from across the main road and this would likely require extensive excavation across the
road (old ducting would not accommodate new HV cable). Due to the high fault level on this network
an alternative feeder would be required for the HV point of connection and this would incur higher
costs.
Further HV analysis is required to ensure that the additional substation would integrate suitably with
the existing network arrangements under both normal running conditions and in compliance with
Engineering Recommendation P2/6 for n-1 conditions (loss of a single circuit).
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6.2
Load Growth Driven reinforcement
This area of network is known for having a high load density and as demonstrated above the
maximum demand on Shaftesbury Ave 125 already exceeds its 750kVA capacity (over 800kVA in
2013). The transformer could be allowed to run at 120% of its capacity (900kVA) for short periods of
time, however, this only applies to radial networks or in normal running conditions. The transformer
should not be loaded above 80% (600kVA) in an interconnected network to allow for LV hold up in the
event of a circuit loss (n-1 condition). The transformer could be upgraded by replacing the original
750kVA rated transformer to one with a 1MVA rating.
Reinforcement Options:
 Increase transformer rating – Installing a 1MVA transformer replacement would increase the
80% rating to 800kVA, however, the maximum demand has already exceeded 800kVA in
2013.
 New substation on existing feeder – This would allow network load to be transferred from the
Shaftesbury Ave 125 onto the new network substation. In order to coordinate with the modern
ACB protection, an 800kVA transformer should be installed.
 New substation on different feeder – This would allow network load to be transferred from the
Shaftesbury Ave 125 onto the new network substation. An alternative HV feeder would require
a HV cable to be looped across the main road.
This screenshot demonstrates the network under consideration in the DINIS tool. In proposing a
reinforcement solution for the area, a fault level study would be conducted using the Fault Study
Package (FSP) to ensure acceptable limits of operation and effective network protection.
Figure 28 – DINIS Network View – Shaftesbury Ave 125
The proposed planning solution in this case would be to install a new network substation within the
existing Shaftesbury Ave 125 (24410) substation space and connecting to an alternative HV feeder.
Three LV network cables will be transferred onto the new substation to shed load from the original
transformer and support the interconnected network.
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6.3
Proposed FUN-LV Method 3
As part of the FUN-LV project, this site was selected for the installation of a multi-terminal PED
(labelled ‘Method 3’). This multi-terminal PED will enable a capacity transfer of up to 400kVA between
Shaftesbury Ave 125 (24410) and adjacent interconnected networks.
Figure 29 – Proposed PED Solution – Shaftesbury Ave 125
In the configuration proposed, the device would be installed within Shaftesbury Ave 125 (24410)
substation and connected to the adjacent interconnected network via fuse ways on the LV distribution
board. In addition, this trial will require that the NOPs at LB 222111 and LB 222116 are closed (via
insertion of 1 set of links) and cross-jointing is carried out to at LB 222116 (as shown in Figure 29).
This will allow power to be transferred between Stacey Street (24409)/Shaftesbury Ave 151-165
(21388), Charing X Rd 82 (31023)/Tower Street 22 (24146) and Shaftesbury Ave 125 (24410). The
schematic shown in Figure 30 illustrates the general arrangement for the connection of the multiterminal device to an LV network. A photo of the device is presented in Figure 31, this shows the
internal build of a single power electronics panel and control panel.
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Figure 30 – Method 3 general arrangement
Figure 31 – Method 3 Control Panel and Power Electronics Panel (1 of 3)
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FUN-LV Method Comparison and Considerations
Costs – In comparison with the business as usual solutions, the PED Costs (approx. £124,000) are
less than the connection driven reinforcement (customer – approx. £150,000, DNO – approx. £10,000)
and more than the load growth driven reinforcement (approx. £100,000).
Longevity – Current estimates for the lifetime of this equipment is under 10 years, therefore it is
providing a temporary solution by delaying traditional reinforcement.
Security/Quality of Supply – Through capacity equalisation, the network is less overloaded and
therefore at less risk of faulting.
Fault Level – The multi-terminal PED can constrain the fault level, whereas the business as usual
solution (new substation on interconnected network) will require splitting interconnected feeders to not
further increase fault level.
Equipment Size – The multi-terminal PED has dimensions 1.8H x 2.4W x 0.6D metres. The setup will
include Litton connectors (disk clamps for busbar) attaching to fuse ways on the LV distribution board
at one end and the PED on the other, it may also include HVAC equipment.
PED Location – The multi-terminal PED would be installed within the substation Shaftesbury Ave 125
(24410).
Planners time – The PED solution would require LV load flow studies and fault level studies to ensure
that sufficient capacity is being shared and fault level studies to ensure effective network protection.
However, the business as usual solution planning for this interconnected area would require a large
amount of time to redesign the network as it has various constraints on accommodating further
capacity. The new substation may require a new feeder to be installed from the 11kV switchboard at
the main substation. The PED can provide a temporary solution at this local scale allowing time to
understand what areas of load are growing in order to sensibly design a wider network area
reinforcement solution.
Installation time – The multi-terminal PED would be delivered and installed within 5-6 days (including
3 additional days for cross jointing), whereas the business as usual solution (new substation) would
require upwards of several weeks depending on the substation construction and alternative feeder.
Planning Permissions/Consent – The multi-terminal PED would not require planning permission as
it will be installed within the existing substation, whereas the business as usual solution (new
substation) would require the customer/DNO to acquire the land/space to accommodate a new
substation and road closures for cable overlays.
Ventilation – The multi-terminal PED may additional HVAC equipment to keep the environment within
an acceptable temperature range. This will require suitable venting arrangements within the substation
and additional space.
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7
Trial Site Case Studies – Brighton Sites
The following trial site case studies cover specific FUN-LV trial sites being selected for the installation
of PEDs in Brighton (SPN). These case studies illustrate the traditional planning considerations for
accommodating PEDs at these selected sites. There are three SPN case studies in this section, these
include an example for each of the three Methods in the FUN-LV project.
8
SPN Method 1: Regent Hill (523461) – Radial Network
8.1
Example FUN-LV Method 1
As part of the FUN-LV project, this site was considered for the installation of a simple PE method
comprising of LV circuit breakers at both substations with no link box switches required (referred to as
‘Method 1a’). These LV circuit breakers allow automated operation and will enable a capacity transfer
of up to 200kVA between 523461 Regent Hill and 523686 M&S Regents Hill. The primary benefit of
this arrangement is to reduce the load on substation 523461 Regent Hill.
Figure 32 shows the proposed routes of interconnection to balance the loading across the two
substations.
Figure 32 – Traditional Planning for PED Solution – Regent Hill
Substation
Current kVA
Balanced kVA
Increase kVA
Regent Hill
400
300
-100
M&S Regent Hill
500
600
100
Table 2 – Example Load Transfers – Regent Hill
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The example load transfers listed in Table 2 are based on the of proportional loading of the
transformers i.e. 100kVA may be transferred on LV network from 523461 Regent Hill to 523686 M&S
Regent Hill. Load flow studies would be required to model the power transfer for Method 1 trials.
Table 3 lists the cables and ratings used in this LV network. These traditional cable ratings are based
on the assumption of a cyclic load pattern. In the FUN-LV trials the transfer profiles are expected to
differ from this typical load pattern, however, the user will be able to input cable ratings into the PED
control algorithm ensuring that the loading does not incur an adverse impact on the cable. The PED
will not make a transfer that is greater than this threshold, for greater than a certain amount of time
(i.e. will allow for an acceptable overload and then limit transfer and alert control).
Cable
Summer Direct Rating
Amps
kVA
0.3
445
320
0.1
250
180
unknown
?
?
Table 3 – Cable Ratings – Regent Hill
This network involves one section of unknown cable construction, and one length of .1 which could
potentially act as throttles to load transfer.
The fuses at 523686 M&S Regent Hill act as the open point on this interconnection, 523461 Regent
Hill has an approximate 61kVA load on this feeder, this would form part of the 100kVA potential
required loading on this interconnection.
For business as usual, the .1 cable, dark blue, is of suitable capacity, with an 80kVA potential for
additional load transfer. The unknown cable, light blue, forming the first section out of 523686 M&S
Regent Hill, is believed to be .3 construction meaning this is also of suitable capacity. This would need
to be positively confirmed on site rather than assumed.
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9
SPN Method 2: Duke Street (523338) – Radial Network
9.1
Example FUN-LV Method 2
As part of the FUN-LV project, this site was considered for the installation of a dual terminal PED
(labelled ‘Method 2’). The device will be installed as a piece of street furniture in the pavement section
adjacent to link box 4K1565. This dual terminal PED will enable a capacity transfer of up to 240kVA
between 523338 Duke Street and 523653 Churchill Square East. The primary benefit of this
arrangement is to reduce the load on substation 523338 Duke Street.
Figure 33 shows the proposed routes of interconnection to balance the loading across the two
substations.
Substation
Current kVA Balanced kVA Increase kVA
Duke Street
505
293
-212
Churchill Square East
375
587
212
Table 4 –Example Load Transfers – Duke Street
It is possible to balance loading as desired, the example listed in Table 4 demonstrates transfers
based on proportional loading of transformers i.e. 212kVA may be transferred on LV network from
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Figure 33 – Traditional Planning for PED Solution – Duke Street
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Traditional Planning Considerations for Power Electronics Devices
523338 Duke Street to 523653 Churchill Square East. The dual terminal PED used in the Method 2
trials can transfer up to 240kVA.
Table 5 lists the cables and ratings used in this LV network. These traditional cable ratings are based
on the assumption of a cyclic load pattern. In the FUN-LV trials the transfer profiles are expected to
differ from this typical load pattern, however, the user will be able to input cable ratings into the PED
control algorithm ensuring that the loading does not incur an adverse impact on the cable. The PED
will not make a transfer that is greater than this threshold, for greater than a certain amount of time
(i.e. will allow for an acceptable overload and then limit transfer and alert control).
Cable
Summer Direct Rating
Amps
kVA
300H
468
337
.3
445
320
.15
290
209
.1
250
180
unknown
?
?
Table 5 – Cable Ratings – Duke Street
This network involves two sections of adjoining unknown cable construction, one length of .15 cable
construction and one length .1 which could potentially act as throttles to load transfer.
Two link boxes exist on the cable route identified via Boyces’ Street, 4K1565 and 4K1564. Both of
these have the links removed such that the cable section between them is currently fed from a third
substation 523751 77 West Street, this section of cable is also loaded feeding all the customers
located along Boyce’s Street.
Combined with this section being comprised of the unknown and .1 cable sections it is taken that a
new cable would need to be laid along Boyce’s Street, with an additional link box to be able to enable
the required load transfer network arrangement. Existing open points would remain where they are.
Power electronics would be installed across the new link box.
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Figure 34 – New Cable Installation Boyces’ Street
The .15 cable between 523338 Duke Street and link box 4K1565 has a quoted capacity just under the
required load transfer for business as usual. This indicates that the cable may become stressed and
subject to failure if the maximum load transfer is sustained for any length of time. This would need to
be monitored carefully, more detailed load profiling completed or pro-actively overlaid to eliminate the
possibility.
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10 SPN Method 3: New Road (523230) – Radial Network
10.1 Example FUN-LV Method 3
As part of the FUN-LV project, this site was considered for the installation of multi-terminal PED
(labelled ‘Method 3’). This multi-terminal PED will enable a capacity transfer of up to 400kVA between
523637 Prudential North Street and adjacent networks (522941 Vokins and 523230 New Road). The
primary benefit of this arrangement is to reduce the load on substation 523230 New Road.
Figure 32 shows the proposed routes of interconnection to balance the loading across the three
substations.
Figure 35 – Traditional Planning for PED Solution – New Road
Substation
Current kVA
Balanced kVA
Increase kVA
Vokins
275
529
254
Prudential
725
661
-64
New Road
850
661
-189
Table 6 – Example Load Transfers – New Road
It is possible to balance loading as desired, the example listed in Table 4 demonstrates transfers
based on proportional loading of transformers i.e. 189kVA may be transferred on LV network from
523230 New Road to 523637 Prudential North Street, and 254kVA must be transferred on LV network
from 523637 Prudential North Street to 522941 Vokins. The multi-terminal PED used in the Method 3
trials can transfer up to 400kVA.
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Table 7 lists the cables and ratings used in this LV network. These traditional cable ratings are based
on the assumption of a cyclic load pattern. In the FUN-LV trials the transfer profiles are expected to
differ from this typical load pattern, however, the user will be able to input cable ratings into the PED
control algorithm ensuring that the loading does not incur an adverse impact on the cable. The PED
will not make a transfer that is greater than this threshold, for greater than a certain amount of time
(i.e. will allow for an acceptable overload and then limit transfer and alert control).
Cable
Summer Direct Rating
Amps
kVA
.3a
351
253
.3
445
320
300H
468
337
unknown
?
?
Table 7 – Cable Ratings – New Road
This network involves three sections of unknown cable construction, and one length .3a which
potentially acts as a throttle to load transfer.
523230 New Road  523637 Prudential North Street
The fuses at 523230 New Road act as the open point on this interconnection, 523637 Prudential North
Street has an approximate 100kVA load on this feeder, meaning a potential required loading of
289kVA on this interconnection.
This would require the two unknown cable sections, light blue on the plan, to be investigated to
determine if an upgrade to 300H is required.
A more in depth analysis of the .3a cable, dark blue on the plan, would be required to determine the
necessity for it to be upgraded to 300H construction. This replacement is dependent on the distribution
of existing load on this cable. Using existing planning tools it is difficult to determine given the clarity of
MPAN information available.
523637 Prudential North Street  522941 Vokins
The fuses at 523637 Prudential North Street act as the open point on this interconnection, 522941
Vokins has a currently unknown loading on this interconnection.
It is known that there is a load of 102kVA – 150kVA located at unit 5 of 32-36 North Street, however it
is unknown if this is serviced via the 300H or six single core 600a cables at 522941 Vokins. Either way
the suggested implication is that approximately half the existing load on the substation must be on the
300H cable, if not more.
This means that even ignoring the unknown cable section, light blue on plan which would require
investigating, the 300H cable forming the first section of this feeder would be overloaded in balancing
the existing load on these three feeders, requiring a capacity in the order of 390kVA (136kVA half load
+ 254kVA transfer), this is more than 50kVA over the rating of the cable.
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In order to be able to accept the transfer required to balance the existing loading of these three
substations, one of the following would need to be implemented:
1) Transferring off the existing feeder load onto another adjacent LV feeder, this would require
moving it to another substation which may potentially have other knock on effects.
2) The establishing of an additional interconnection between these substations, availability of
spare ways at the substations/ducting/cable trays unknown at this time.
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