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Discussion Document: Energy Storage and Power Electronics on
the Low Voltage Distribution Network
Problem statement, hypothesis and test deployment programme
1. Introduction
New Thames Valley Vision
The New Thames Valley Vision (NTVV) aims to demonstrate that understanding, anticipating and supporting changes
in consumer behaviour will help DNOs to develop an efficient network for the low carbon economy. This £30 million
project is part of a £500 million programme funded by the Low Carbon Network Fund (LCNF) run by Ofgem, the UK
energy regulator.
Learning Outcomes
The project explores five central learning outcomes:
1 Understanding - What do we need to know about customer behaviour in order to optimise network
investment?
2
Anticipating - How can improved modelling enhance network operational, planning and investment
management systems?
3
Optimising - To what extent can modelling reduce the need for monitoring and enhance the information
provided by monitoring?
4
Supporting Change - How might a DNO implement technologies to support the transition to a Low Carbon
Economy?
5
Supporting Change - Which commercial models attract which customers and how will they be delivered?
Through the deployment of energy storage and power electronics the project will specifically explore questions
centred on learning outcome four, these are:
4.1
How could distributed solutions be configured into the DNO environment?
4.4
How would network storage be used in conjunction with demand response?
Energy Management Trials
In the 2011 project bid submission NTVV identified a number of applications for energy storage and power electronics
that explore their use as ‘network side’ solutions to enable more effective use of the existing network in
accommodating the transition to a low carbon economy. Further details and extracts of the project bid submission are
contained in Appendix 1.
Successful Delivery Reward Criteria
This report is written to develop and clarify the trials of energy storage and power electronics in the New Thames
Valley Vision. In compiling this discussion document, the project is fulfilling Successful Delivery Reward Criteria
(SDRC) 9.4a
CRITERION: Develop problem statement, hypothesis and test deployment programme for coordinated energy
storage and power electronics on the Low Voltage distribution network - building on previous and current battery
installation tests
EVIDENCE:
Produce discussion document and deployment plan for energy storage and power electronics –
include an assessment of the management of network losses and power quality
2. Problem Statement
Changing customer requirements
Network demand will change as individuals, small businesses and larger companies act either on their conscience or
in response to economic stimuli, to reduce their carbon footprint. The action customers take will have many forms
including: energy efficiency measures; the installation of solar thermal or photovoltaic (PV) panels and other smallscale renewable energy devices; and an increased uptake of electric vehicles. The New Thames Valley Vision looks
to support changes in our customers’ energy behaviour as they move towards low carbon technology.
DECC's UK Low Carbon Transition Plan portrays a number of possible paths for the evolution of energy use as the
low carbon economy advances. The document considers the impact of a range of potentially disruptive technologies
capable of changing the scale and nature of energy flows on the network, including:
 Electric cars
 Micro Generation
 Supplier drive demand side management
 Electrification of heat
 Heat pumps
 Electrification of transportation
These, amongst other factors, will have the effect of disrupting the predictability of maximum demands and profiles
that have heuristically evolved over the last few decades. These demand profiles are the centre of our existing
planning methodologies yet within the next few years will be of diminished value as the nature of load flows become
more dynamic.
Better understanding of changing requirements through NTVV
The NTVV is developing new tools and techniques to better understand the changing energy requirements of
customers connected to the Low Voltage network. By aggregating and statistically grouping the modelled profiles of
individual customers on each feeder the project will develop feeder power flow profiles. These will be validated
against monitoring data from this project and other LCNF projects (to the extent that this data is made available) to
identify whether behavioural trends can be drawn.
The project will create an agent-based forecasting model to enable short, medium and long-term demand predictions
with envelopes of uncertainty. It is anticipated that take up of low carbon technology will not be uniform across
customers, and hence neither across LV networks, but more sporadic in clusters. The forecasts will be designed to
account for this non-uniformity. A key feature of both the modelling and forecasting techniques under development is
that they are expected to be applicable to, and have sufficient resolution for DNO purposes, regardless of whether
smart meter data is available from every household and small business in the country.
Technical Standards and Efficiency
Electricity network customers can expect a regular and reliable supply of electricity which is capable of meeting power
requirements within defined characteristics. The design and operation of our low voltage network ensures the network
remains within a number of technical standards concerning voltage and thermal capacity. Each of these criteria has an
impact on design and operation and is impacted as network usage changes. Economic and moral drivers dictate that
networks should operate efficiently, where efficiency seeks to maximise utilisation and minimise loses at the lowest
overall cost. These standards and drivers are described in more detail in Appendix 2
Voltage
The low voltage network is built with fixed transformer tapping ratios at the supplying 11kV/LV distribution substation
with dynamic voltage control at the 11kV busbars of a primary substation only. The dynamic control seeks to maintain
all connected customers within an acceptable voltage range but does not attempt to manage voltage variations for
periods shorter than 1 minute.
Networks are designed to manage voltage with respect to: regulation, harmonic distortion, balance and flicker.
Traditional engineering approaches for addressing poor voltage performance seek to: isolate ‘dirty’ loads, reduce
current flow and/or reduce network impedance. Under all three of these approaches the network is not utilised at full
thermal capacity and the connection of new loads or generation may be delayed until additional network assets can be
installed. Clearly the installation of new network assets is a costly, disruptive and carbon-intensive operation.
Thermal Capacity
Electrical assets have finite thermal capacities beyond which their insulation performance deteriorates - excessive
heat will cause an asset to fail. In a low voltage poly-phase cable the thermal capacity is the combined effect of all
phase and neutral conductor limits
The traditional engineering approach for addressing poor thermal performance seeks to: distribute demand/generation
evenly across phases at construction or during operation, if possible; split-up heavily congested networks by
introducing additional interconnection; or overlay sections of reduced capacity. As with the traditional methods for
addressing voltage performance, the above approaches require network reconfiguration and/or new asset installation
which can be costly, disruptive and carbon-intensive operation.
Utilisation
The load-factor for the average low voltage customer1 utilises only 3% of service cable capacity throughout the course
of the year. To scale this up to the distribution network implies that the wider network is similarly under-utilised whilst
simultaneously close to capacity in terms of instantaneous thermal and voltage limits
Since the traditional engineering approach for utilisation is not able to store energy at a local level, there is no scope to
improve the utilisation of the network. With increased deployment of low carbon technologies, the network may be
required to deal with even greater peaks for which the only traditional solution to maintain technical performance
would be the creation of extra capacity and further reduction in utilisation
Loses
The technical2 losses of a distribution network are a function of current flow through shunt and series impedances.
Series losses are result in ‘real’ power lost from the system and constitute the largest contributor, these losses
increase in proportion to the square of current flow. Shunt losses are entirely reactive but affect network performance
by causing increased current flow and impacting voltage regulation. Analysis of the losses in a typical SSEPD GSP
network3 identified that 2.4% of the energy supplied was lost in local low voltage distribution
The traditional approach to technical loss reduction seeks to reduce network impedance through the installation of
additional capacity and by attempting to balance connections across all phases. Both of these options are costly and
disruptive. A proportionately greater improvement could be achieved by reducing peak current flow – however since
traditional networks cannot store energy, this would be entirely at the discretion of the customer.
1
Taking the weighted average of profile-class half-hourly consumption data for the Botley Wood GSP as assessed
over the 2007-2008 period.
2 Technical loses exclude losses as a result of metering or billing inaccuracies and theft
3 For the network connected from Botley Wood GSP as assessed over the 2007-2008 period
3. Solution
Power Electronics and Energy Storage
M
Utilisation
H
H
M
M
H
H
H
H
H
H
H
H
Losses
Flicker
Balance
M
Neutral
M
Phase
1. Balancing load between phases (without
storage)
Power electronics configured to a common DC
busbar to allow dynamic redistribution of current
from one phase to another to either equalise
loading or manage voltages. This would result in
reduced current flow peaks on the most loaded
phase and address thermal constraints but would
also have consequential improvements to
efficiency and voltage regulation.
2. Storage to balance peaks and troughs
Application of storage and forecast energy
consumption to optimise network utilisation within
a specific capacity. Would have an impact on the
directly connected LV circuit and also, in
combination with other units on local substation
and associated HV circuits. Direct benefits to
thermal and efficiency measure with an indirect
improvement in voltage regulation.
3. Balancing load between phases (with
storage)
Combination of (1) and (2) above to allow
optimisation across phases with additional
capacity as enabled by spreading peaks and
troughs across time.
4. Reactive voltage support (without storage)
Use of power electronics to modify current
waveforms to adjust reactive component of load.
Would result in increase to overall demand on
circuit either from the same phase or adjacent
phase. Reactive component use to counteract
reactive volt-drop, mostly as a result of
distribution transformer impedance.
5. Reactive voltage support (with storage)
As above, with the ability to use stored energy to
alter reactive component without increasing
overall instantaneous current on the basis that
the energy store can be charged at some other
convenient time.
6. Improve power quality & harmonics
Use of power electronics to act as active
harmonic filters to identify and generate
mitigating currents to improve power quality and
harmonic limits.
Harmonic
Distortion
Regulation
Applications
The following applications will be trialled to support the technical requirements (identified above). In this table, the
anticipated benefit is marked as ‘high’ where a direct improvement is expected and ‘medium’ where an indirect or
consequential improvement is likely.
Voltage
Thermal
Efficiency
M
M
H
H
M
H
H
M
H
H
CI/CML and
Emergency response
The New Thames Valley Vision will deploy power electronics and storage to allow the existing network to respond
more flexibly. This will maintain the network within the technical standards identified above whilst also maintaining or
improving the efficiency of the network as customers change their energy behaviour as they take up low carbon
technologies.
7. Demand reduction
Use of reserve energy storage capacity to reduce
demand during planned or fault outage to enable
continuity of supply.
8. Frequency response
Use of reserve energy storage capacity to react
to over or under frequency events by absorbing
or releasing power. This would support the
system operator’s duty to maintain frequency and
would help customer maintain electricity during
national frequency events
H
H
Traditional Network Reinforcement
As identified above, the traditional approach to maintaining the technical standards for voltage and thermal limits
results in physical interventions to either increase capacity or reconfigure connections, where possible. Whilst these
solutions remain valid, they do not necessarily encourage good network efficiency and are disruptive, slow to instigate
and have a significant carbon impact.
To benchmark and asses the effectiveness of power electronics with energy storage, the NTVV will consider the
implications of the main alternative, which is to do nothing new.
As the 2011 project bid submission identified, the most challenging part of replacing distribution assets would be at
low voltage level, with the upheaval and cost of replacing individual service cables, substations and associated plant.
The replacement value for the complete renewal of these assets just for SSEPD's two licences would be circa £3
billion.
Operational Management
Other than reinforcement, networks can seek to apply operational measures to manage changing network
performance. It typically takes around 3 to 4 months from recognition of the need to reinforce an LV feeder to
completing that reinforcement. During this time customers' generation is likely to be tripping out on G83 protection (if
there is an excess of generation connected) or LV network fuses are likely to blow (if there is an excess of HP or EV
connected). This would not be remedied by the deployment of automatic replacement fuses such as the Bidoyng.
Increasing Requirements for Customer Equipment Performance
All equipment which connects to the Distribution Network must meet certain standards such that it does not
unreasonably affect other customers connected to that network. This may be of particular relevance to harmonic
performance. As an alternative to network reinforcement there may be relative merits in insisting on higher harmonic
standards from appliances installed by customer.
Benchmarking Costs
From SSET 1008 LV Connected Batteries project, we have learnt that Energy Storage and Power Electronics can be
expensive assets to deploy. Whilst we expect the cost of units to decrease as the technology matures and as greater
economies of scale are realised, at present it does not seem feasible that units designed to address just one technical
requirement would justify their deployment.
However, raw cost aside, Energy Storage and Power Electronics demonstrate the potential to exceed the
performance of traditional reinforcement with respect to speed of deployment, level of disruption, coordinated
improvements in technical standards and improved network efficiency.
The costs of energy storage and power electronics are broadly split as follows:
 Energy storage 80% of the cost
 Power electronics 20% of the cost
Therefore the challenge in driving economy is to combine multiple functionality into a single unit such that the same
installed assets are able to simultaneously address a variety of technical standards. Likewise, improvement which
can be realised using the electronics alone should be explored and delivered in such a way that allows storage to be
added as and when economic.
4. Hypothesis
From a consideration of the Problem Statement in section 2 and the Solutions identified in section 0 as supported by
the findings to date in SSET 1008 LV Connected Batteries project has drawn the following hypothesis:
Economic and flexible support for LV networks will be provided by power electronics with energy storage running
smart control algorithms which make use of forecasted demand to provide a coordinated response to addresses the
technical standards of voltage and thermal performance in the most efficient manner possible.
5. Test Deployment Programme
To assess the hypothesis of section 4 the NTVV has developed the test plan detailed in this document. The following
summary illustrates the linkages between the hypothesis and the test plan.
Summary
Hypothesis statement
“… for LV networks…”
“Economic and flexible support…”
“… most efficient manner possible…
“… the technical standards of voltage and
thermal performance…”
“… coordinated response…”
Test Plan
Location
The fundamental aim of NTVV is to better understand and anticipate
customer behaviour, which will help to reduce the uncertainty about
future demands on distribution networks. The Thames Valley is
considered to be an ideal location for such a project due to the
'ordinariness' of the network. The distribution system has no unique
features; is of average age and reliability; has no significant low
carbon initiatives in the area and no eco-towns. In short, it is typical of
much of the UK. We believe therefore that the findings from NTVV will
be applicable to much of the country and thus the learning useful to all
DNOs.
Assessment criteria
Distribution networks are built to serve the needs of their customers
and as customers move to lower carbon technologies, the networks
will need to adapt so that the same reliable levels of service can be
maintained. Through the assessment of Energy Storage and Power
Electronics alongside traditional reinforcement the NTVV will assess
the comparative benefits of:
1. Cost
2. Speed of deployment
3. Level of disruption
4. Impact on technical standards (per standard and in combination)
5. Impact on efficiency
Network impact
The project will trial energy storage and power electronics units with
the ability to operate the flowing functions in combination:
1. Balancing load between phases (without storage)
2. Storage to balance peaks and troughs
3. Balancing load between phases (with storage)
4. Reactive voltage support (without storage)
5. Reactive voltage support (with storage)
6. Improve power quality & harmonics
7. Demand reduction
8. Frequency response
As identified in section 0 these functions will provide varying degrees
of support to:
 Voltage – regulation, harmonic distortion, balance and flicker
 Thermal Limits – phase and neutral
 Efficiency – Utilisation and Losses
 CI/CML and Emergency response
A central theme of the hypothesis and test plan is to assess the ability
or otherwise of control algorithms to optimally dispatch these different
requirements.
“… smart control algorithms which make use
of forecasted demand…”
“… coordinated response…”
Control environment
The NTVV is developing algorithms to analysis and forecasts future
energy consumption on the low voltage network in Bracknell. The
Energy Storage and Power Electronics test plan will take advantage of
this data and will assess its application in the practical control of field
dispatched units.
To facilitate this, the NTVV will deploy battery units which pass all
relevant metrology from power electronics and energy storage along
with other network information back to central system. The central
control scheme then simulate various control level of control authority
including ‘simulation’ of local control within the unit and also agent
based communication between units
Staged Deployment Plan
1. Refine specification, design and tender
Oct-12 to Jun-13
a. Define functional and non-functional requirements of power electronics and energy storage units – to include
1. Balancing load between phases (without storage), 2. Storage to balance peaks and troughs, 3. Balancing
load between phases (with storage), 4. Reactive voltage support (without storage), 5. Reactive voltage
support (with storage), 6. Improve power quality & harmonics, 7. Demand reduction and 8. Frequency
response
b. Define functional and non-functional requirements of control scheme: What functions require external control
(i.e. can frequency response be a locally defined set-point)? Where is control best placed – locally, centrally
does this vary by function? Finite capacity, on what basis should inverter and storage capacity be deployed to
best support each of the identified functions?
c. Define optimisation problem: if the variables are known (into the future) then what potential is there for these
to be optimised but how is uncertainty managed; what non-network variable also need to be considered (i.e.
maintenance of battery lifespan)
d. Define physical dimensional limits for deployed units – draw on Tier 1 Battery Storage findings and support
with site surveys and consultation with Highway authority.
e. Tender of power electronics and energy storage units
f. Tender communication provider
2. Development of smart control algorithms
Jan-13 to Mar-14
a. Smart control algorithms will be developed for individual storage devices to achieve specific applications
(peak demand, voltage regulation etc.) using the aggregated forecast for the location of the storage devices.
b. The algorithm will take into account the storage devices specifications (battery size, charge and discharge
rate etc.) and constraints that will maximise the life of the storage devices.
c. Distributed control algorithms, such as multiple agent systems, will be developed for deployment to the grid.
These algorithms will ensure that storage devices are able to work together in order to achieve specific
applications (peak demand, voltage regulation etc.)
d. Control Methods will be implemented and simulated using the aggregated forecast and actual smart meter
data.
3. Construction of power electronics and energy storage units
Jul-13 to Dec-13
4. Installation of power electronics and energy storage units
a. Type test units away from site to assess safe performance
b. Complete civil works
c. Commission units to networks
Jan-14 to Jun-14
5. Installation of communication infrastructure
Jan-14 to Jun-14
a. Commission to control system
b. Commission to power electronics and energy storage units over communication to control system
March 2014 - SDRC 9.4c Install 25 LV connected batteries
6. Test functional deployment without smart control algorithms (under supervision)
a. Assess performance of unit for each of the separate network functions
b. Assess performance of unit for combinations of separate network function
Apr-14 to Sep-14
November 2014 - SDRC 9.8a(4) Report into LV Network Storage
7. Deploy smart control algorithms to simulated network
Apr-14 to Dec-14
8. Test functional deployment with smart control algorithms (under supervision)
a. Assess performance of unit for each of the separate network functions
b. Assess performance of unit for combinations of separate network function
Jan-15 to Mar-15
March 2015 - SDRC 9.4d - Produce learnings from energy storage and power electronic deployment to assess the
hypothesis.
9. Operate units under smart control without supervision
Apr-15 to Sep-15
10. Reduce the amount of forecast and ‘live’ information available to units
Oct-15 to Mar-16
a. Reduce the degree of information available to algorithms – noting that algorithms will be hosted centrally
though simulating varying degrees of local control. This approach maintains central control in the event of
poor algorithm performance
11. Operate units with reduced central control
a. Develop agent based control algorithms
b. Simulate algorithms
c. Deploy simulation of agent based control using central control scheme
Oct-15 to Jun-16
12. Analysis
Jul-16 to Sep-16
a. Review schemes performance against traditional reinforcement methods and/or increased requirements of
customer equipment performance
b. Assess benefits with respect to 1. Cost, 2. Speed of deployment, 3. Level of disruption, 4. Impact on technical
standards (per standard and in combination) and 5. Impact on efficiency
13. Identify future applications - desk top analysis of applicable findings in relation to other aspects of controllable
demand
Oct-16 to Dec-17
a. Automatic Demand Repose
b. Thermal hot storage to manage PV (i.e. EMMA units)
c. Thermal cold storage in conjunction with Building Management Systems
Appendix 4 contains a Gantt chart of this programme
Building on previous learning
SSEPD has gained and is developing a broad experience of energy storage and in particular battery systems. The
NTVV will build on the learning across a range of project with a focus on the Tier 1 project ‘SSET 1008 LV Connected
Batteries.’ From this previous learning, we are able to build on:




Full safety case and risk assessment which focuses on the installation and operation issues relating to energy
storage with a particular emphasis on Lithium-Ion technology. The document makes reference to the potential
hazards, the mitigations in place and the relevant standards and directives the devices must comply with.
The commissioning process has been detailed and recorded from the basic start up tests from the
manufacturer right through to the G59/2 testing.
A detailed test plan to cover initial safety and operational tests moving into detailed functionality testing over a
12 months period
Communications integration in relation to the radio communications between the batteries and a control hub
and from the hub back to the SSEPD control system in the control room at Portsmouth.
Appendix 3 explores the key findings to date that are relevant to the NTVV.
Indicative Energy Storage and Power Electronics Units
Whilst the plan allows for detailed design and refinement followed by a period of tender, the following indicative
designs have been developed:
Technology
Deploying energy storage on the low voltage network requires a high energy density medium to provide high power
without necessitating a large amount of space. This requirement means the most likely technology is a lithium
chemistry based battery.
Form-factor
It is proposed to design a modular and scalable solution which will allow the power electronics to be deployed with or
without the associated storage, with additional storage added later if required. We will work with the local authority to
ensure the physical dimensions can be accommodated within the built environment.
Power Electronics
Inverter electronics can be configured with 4, 6 or 12 gates – where 4 gates provide single phase operation, 6 gates
allow balanced three-phase operation and 12 gates would allow independent operation of three-phases. It is
proposed to use three phase with 12 gate inverters to allow the full range of functions as identified in section 3.
Subject to tender, we propose to deploy only three phase units but with the functionality to operate with only one
phase live. This would be a departure from the original 2011 bid submission which indicated an even mix of single
and three phase units. A final decision of the mix will be informed by detailed specification and tender in the context of
the project hypothesis.
Sizing
Lithium technology can be expensive to procure, with the DC element of the system making up approx 80% of the
cost of a single hour capacity unit. We will draw on the SSET 1008 project is to prevent the storage units being over
sized. To ensure compatibility and ongoing operation and maintenance, it is proposed to size units to match standard
distribution network infrastructure and hence inverters are expected to have a 20kW peak output to match the sizes of
a typical 100A service connection.
Appendix 1
Summary and extracts from 2011 bid submission
Thematic Summary
In the 2011 project bid submission, NTVV identified the following applications and delivery factors for power electronic
converters and energy storage as ‘network side’ to support the transition to a Low Carbon Economy.
Applications
(a) Without energy storage
 Control voltage along a circuit - Static VAr Compensation (SVC)/four quadrant operation
 Balance phases
 Reduce losses to gain maximum network benefit from embedded generation
 Improve power quality and harmonics management
(b) With energy storage
The primary objectives of this element of the project are to:
 Reduce peak demand on the LV network (demand and generation)
o The battery units will be used to peak lop both demand and generation under theoretical cable
limits thereby demonstrating the effectiveness of the technology without affecting the security of
supply
 Negate the need for traditional network reinforcement
The secondary objectives of this element of the project are to:
 Quantify the effect on the high voltage network of reducing the peak demand at low voltage level
 Stop network constraints limiting the connection of LCT to customers on the low voltage network
 Understand the economic case for energy storage as an alternative to traditional reinforcement (reactive)
and as tactical buffer in advance of predicted LCN installation (pro-active)
 Appreciate the technical implications of installing a large array of inter-connected energy storage units
 Understand how storage could continue to provide power to customers during fault conditions (possibly
under constraints) until restoration can occur
(c) Additional project applications
 In the initial stage of NTVV we intend to use the smaller domestic storage facilities to
o simulate the effect of low carbon technologies
o 'stress-test' the facilities' ability to help balance networks.
Delivery

To demonstrate robust understanding of how a DNO can effectively deploy and operate this technology to
support customer choice. This will build on learning acquired from three single-phase units installed as
part of the ‘LV Connected Batteries’ IFI project
Test metrics
By March 2014 - Install 25 LV connected batteries
 >30 power electronic converters on the LV network, may/not be associated with electrical energy storage
 15 single-phase (10kW/10kWh)
 16 three-phase (25kW/25kWh)
Extracts from Project Submission and Appendix
NTVV will evaluate solutions including: … low voltage (LV) static voltage control; street level energy storage; and a
range of communications solutions [Project Submission: Page 1, Section 1.3]
Objectives … [number] 3... Demonstrating mitigation strategies... b. Where and how power electronics (with and
without energy storage) can be used to manage power factor, thermal constraints and voltage to facilitate the
connection of renewables on the LV network [Project Submission: Page 2, Section 2]
Methods... 4... Tactically deploy power electronics and electrical energy storage on the low voltage networks... Finally,
we will deploy power electronics and electrical energy storage on low voltage networks as a tactical 'buffer'. This will
demonstrate the extent to which these technologies could manage power factor, harmonics and voltages to provide a
fast and flexible alternative ensuring customers have the freedom to deploy low carbon technologies without waiting
for time-consuming reinforcement (or their alternatives) to take place. All of the technical solutions outlined above will
be fully integrated into the distribution network control room. [Project Submission: Page 3, Section 2]
…Although better understanding of customers and of network feeders can reduce the need for premature
reinforcement, when LCT connections have used up the true available headroom it will be necessary to reinforce. In
some cases this may be reactive… Chalvey LCNF T1 monitoring project has highlighted that a precursor of thermal
and voltage constraints will often be power quality issues of power factor and harmonics... We will demonstrate how
power conversion power electronics can be used to manage these issues with and without energy storage modules at
the LV network… supported by Imperial College… [Deploying] statistically relevant quantities. This will provide a
robust understanding of how a DNO can effectively deploy and operate this technology to support customer choice. A
total of 15 single-phase (10kW/10kWh) domestic storage units and 16 three-phase (25kW/25kWh) street storage units
are planned in the NTVV project. Energy storage units will be used to peak lop both demand and generation to keep
supplies within cable limits. The devices also have the capability of four quadrant operation, meaning it is possible to
provide voltage support to keep the supply within the given standards. [Project Submission: Page 7, Section 2]
In the initial stage of NTVV we intend to use the smaller domestic storage facilities to simulate the effect of low carbon
technologies - 'stress-testing' the LV network." [Project Submission: Page 7, Section 2]
Supporting change through deployable solutions… On the network side we will deploy LV connected electrical energy
storage and power electronics, in statistically relevant quantities. This will provide a robust understanding of how a
DNO can effectively deploy and operate this technology to support customer choice. Integration is key - both the
customer side and network side solutions will be linked to the DNO's control room to provide a robust end-to-end
control system. [Project Submission: Page 4, Section 2]
Generic activities of DMS
o GE's DMS will act as the coordination hub for network management which will integrate with various intelligent
distributed energy resources to be deployed in the LV network, leading with demand resource and battery storage
resources
o The ability to calculate where and when additional resources can be used to re-enforce the current network during
peak demand times
o The ability to charge LV storage units during off-peak times in order to make them available during peak times
without impacting current demand
o The availability of power analysis information based on load profiles for estimation of current system demand
o The availability of power analysis information based on substation monitoring information available from the
monitoring solution detailed previously
o The ability to link into the Honeywell ADR as an aggregator of demand response across an estate of buildings to
create a despatchable demand resource
o Systematic evaluation of telecommunications solutions in NTVV and other available projects
[Project Submission: Page, Section 2]
… potential to enable the network to continue to provide power to customers during fault conditions (possibly under
constraints) until restoration can occur, reducing customer interruptions (CI) and customer minutes lost (CML).
Additionally they potentially could be used to avoid significant network reconfiguration under fault conditions… Energy
storage could provide local power to support the local network… Building Management Systems could have an
'emergency' setting where all but essential load is switched off, enabling the network to continue to operate at
significantly reduced capacity for a time… Rapid deployment of storage in the event that several EVs or HPs connect
into a given street will enable customers to use these technologies without causing overloads of local network assets
and avoiding local loss of supply due to the operation of circuit protection. [Project Submission: Page 21, Section 4(c)]
Learning Outcomes and associated project trials description
LO-4: Supporting Change - How might a DNO implement technologies to support the transition to a low carbon
economy?
[Project Submission: Page 24, Section 4]
Focusing on the technical solutions for managing the effects low carbon technology is likely to have on a distribution
network. All network mitigation techniques rely upon the deployment of appropriate solutions such as the
conventional network assets; novel network assets; or novel customer side solutions. NTVV will focus on the
integrated application of two key solutions, one on the network side and one on the customer side, in a range of
scenarios. On the network side, electrical energy storage will be deployed in statistically relevant quantities and
managed at key locations and working with Honeywell on the customer side NTVV aims deploy 30 demand
management systems.
LO-4.1 How could distributed solutions be configured into the DNO environment
[Project Submission: Appendix page 11 (page 64) onwards]
The distributed technology solutions we are concentrating on for NTVV are:
 Use of power electronic converters (with and without electrical energy storage): a network-side solution that
can be applied to LV networks, and in some instances rolled out to customers’ premises
 Building management systems (BMS): a customer-side solution for large and (potentially) light commercial
customers. This will also include the use of two variants of thermal storage.
Use of power electronic converters
The power electronic converters typically used with electrical energy storage provide a platform to provide reactive
power injection to the LV network, allowing the network to be used more effectively without reinforcement. Acting as a
form of Static VAr Compensation (SVC), they have the ability to:
 Reduce losses to gain maximum network benefit from embedded generation
 Improve power quality and harmonics management
 Control voltage along a circuit
 Potentially balance phases
 Add energy storage
We intend to deploy over 30 power electronic converters in NTVV. These will all be installed on the LV network, and
may or may not be associated with the connection of the electrical energy storage described below.
Use of energy storage
NTVV will deploy LV-connected electrical energy storage, in statistically relevant quantities. This will provide a robust
understanding of how a DNO can effectively deploy and operate this technology to support customer choice.
A total of 15 single-phase (10kW/10kWh) domestic storage units and 16 three-phase (25kW/25kWh) street storage
units are planned in the NTVV project. This will build on learning acquired from three single-phase units installed as
part of the ‘LV Connected Batteries’ IFI project (Appendix G) where such storage is connected at the midpoint of a LV
feeder circuit supplying SSE’s ‘Low Carbon Homes’ project. The primary objective of the IFI project is to prove the
functionality of the battery units, to gain experience of the technology and hence de-risk the larger deployment for
NTVV.
The battery units will be used to peak lop both demand and generation under theoretical cable limits thereby
demonstrating the effectiveness of the technology without affecting the security of supply. The devices also have the
capability of four quadrant operation (provides comprehensive balancing of the network) meaning it is possible to
provide voltage support to keep the supply within the given standards. In the initial stage of NTVV we intend to use
the smaller domestic storage facilities to simulate the effect of low carbon technologies - 'stress-testing' the LV
network.
The primary objectives of this element of the project are to:
 Reduce peak demand on the LV network
 Negate the need for traditional network reinforcement
The secondary objectives of this element of the project are to:
 Quantify the effect on the high voltage network of reducing the peak demand at low voltage level
 Stop network constraints limiting the connection of low carbon technologies to customers on the LV network
 Understand the economic case for energy storage over traditional reinforcement
 Appreciate the technical implications of installing a large array of inter-connected energy storage units
Further to locating electrical energy storage on LV feeders, we aim to introduce micro storage facilities – small
batteries - on the low voltage network to simulate the effect of low carbon technologies and 'stress-test' the facilities'
ability to help balance networks.
Appendix 2
Distribution technical standards and drivers
Technical Standards
Electricity network customers can expect a regular and reliable supply of electricity which is capable of meeting power
requirements within defined characteristics. The design and operation of our low voltage network ensures the network
remains within a number of technical standards concerning voltage and thermal capacity. Each of these criteria has an
impact on design and operation and is affected as network usage changes. These standards are described in more
detail in Appendix 2
Voltage
The low voltage network is built with fixed transformer tapping ratios at the supplying 11kV/LV distribution substation
with dynamic voltage at the 11kV busbars of a primary substation only. Dynamic control, in combination with fixed
ratios further down the network, seeks to maintain all connected customers within an acceptable voltage range but
does not attempt to manage voltage variations for periods shorter than 1 minute.
Networks are designed to give performance within the following criteria:
 Regulation – defined under the Electricity Supply, Quality and Continuity Regulations as 216.2-253V (i.e.
230V +10%/-6%)
 Harmonic Distortion - Engineering Recommendation G5/4 covers the planning levels for harmonic distortion
and the connection of non-linear equipment to transmission and distribution systems. The phenomena
considered in this standard include voltage distortion and voltage notching. Other aspects of voltage distortion
are covered in P29 and P28.
 Balance – Engineering Recommendation P29 contains the planning limits for voltage unbalance. A voltage
unbalance of greater than 1 or 2% can cause unacceptable degradation of equipment if it remains for a
prolonged period.
 Flicker – Engineering Recommendation P28 covers planning limits for voltage fluctuations caused by
industrial, commercial or domestic equipment. Voltage fluctuations are typically caused by motor start-up, arcwelders, blast furnaces and rolling mills. ‘Flicker’ is the visual phenomenon seen (in a fluorescent light bulb)
when voltage fluctuations become particularly bad.
The traditional engineering approach for addressing poor voltage performance seeks to:
1. Isolate ‘dirty’ loads – segregation of network loads where the characteristics of the load and supplying network
would result in poor performance.
2. Reduce current flow – operate the network at reduced utilisation to ensure voltages remain within limits
3. Reduce network impedance – increase assets deployed or connect to alternative network locations to reduce
the impact on voltage as a result of the connected load/generation.
In all three of these cases the network is not utilised at full thermal capacity and the connection of new loads or
generation may be delayed until additional network assets can be installed. Clearly the installation of new network
assets is a costly, disruptive and carbon-intensive operation.
Thermal Capacity
Electrical assets have finite thermal capacities beyond which their insulation performance deteriorates - excessive
heat will cause an asset to fail. In a low voltage poly phase ‘mains’ cable the thermal capacity is the combined effect
of phase and neutral conductor limits:
 Phase conductors carry the current required to service the connected demand or generation. Individual
connections may be connected to one or more of the phase conductors on a poly phase cable however the
distribution of load or generation across the phases is not necessarily even which may result in one phase
carrying significantly more current than the other two.
 Neutral conductors carry the summation of all associated phase currents. In a three-phase network, balanced
demand or generation will have no resultant neutral current. However, unbalanced loads will result in a
neutral current which in combination with significantly leading and lagging reactive connections on different
phases and/or third harmonics (on a three phase system) could result in the neutral conductors carrying
significantly more than the phase conductors.
The traditional engineering approach for addressing poor thermal performance seeks to:
1. Distribute demand/generation evenly across phases at construction
2. Re-distribute demand/generation evenly across phases during operation, if possible
3. Split-up heavily congested networks by introducing additional interconnection
4. Overlay sections of reduced capacity
As with the traditional methods for addressing voltage performance, the above approaches require network
reconfiguration and/or new asset installation which can be costly, disruptive and carbon-intensive operation.
Efficiency
Economic and moral drivers dictate that networks should operate efficiently, where efficiency seeks to maximise
utilisation and minimise loses at the lowest overall cost.
Utilisation
The following graph illustrates the load-duration characteristics of domestic customers by profile class (profile classes
are the average usage patterns for broad groups of customer type) with a weighted average representative of the
typical mix of customers within an SSEPD GSP 4. The load-factor for the weighted average profile is only 2.9%, which
means if the network is designed to just supply their customer’s maximum demand, then during through the course of
the year only 2.9% of the cables capacity would be utilised.
6
5
kW
4
3
2
1
0
Duration
Weighted Average
PC01
PC02
PC03
PC04
The above analysis is limited in that customer load usage tends to be more peaky and more sporadic than the typical
half-hourly average profile class data shown above and, as such, the network which supplies a number of customers
must be built with a significant amount of capacity to meet short duration peaks.
Since traditional engineering approach for utilisation is not able to store energy at a local level, there is no scope to
improve the utilisation of the network. With increased deployment of low carbon technologies with, the network will be
required to deal with even greater peaks – for which the solution to maintain technical performance would be the
creation of extra capacity
Loses
The ‘technical’ losses in a distribution network are a function of current flow through shunt and series impedances.
Technical loses exclude losses as a result of metering or billing inaccuracies and theft. Series losses are result in
‘real’ power lost from the system and constitute the largest contributor, these losses increase in proportion to the
square of current flow. Shunt losses are entirely reactive but effect network performance through causing increased
current flow and affecting voltage regulation.
2
S losses 
Vi
2
 Io Z series
Z shunt
Zseries
Ii
Io
Zshunt
Vi
Vo
Is
Si
So
network 5
Analysis of the losses in a typical SSEPD GSP
local low voltage distribution network as follows:
4
5
identified that 2.4% of the energy supplied was lost in the
For customers connected from Botley Wood GSP as assessed over the 2007-2008 period
For the network connected from Botley Wood GSP as assessed over the 2007-2008 period
HV/LV Transformer
LV Feeder
LV Service
Meter
0.6%
1.5%
0.0%
0.3%
The traditional approach to technical loss reduction seeks to reduce network impedance through the installation of
capacity and by ensuring connections are as balanced across all phases as possible. Both of these options are costly
and disruption. A proportionately greater improvement could be achieved by reducing peak current flow – however
since traditional networks cannot store energy, this would be entirely at the discretion of the customers’ needs.
Appendix 3
Learning from other LCNF projects including SSET 1008
SSEPD has gained and is developing a broad experience of energy storage and in particular battery systems. The
NTVV will build on the learning across a range of project with a focus on the Tier 1 project ‘SSET 1008 LV Connected
Batteries.’ This section explores the key findings to date that are relevant to the NTVV.
Under SSET 1008, the batteries are deployed as three single phase unit installed as one each phase. This
configuration allows units to operate completely independently, e.g. the black phase may be charging, brown phase
could be discharging and the grey phase in float mode.
Figure 1.1 shows the electrical connections the batteries as located in relation the distribution substation and the LV
feeder circuit.
Figure 1.1 – Network schematic illustrating battery connection point
Figure 1.2 – Battery site layout
Figure 1.2 illustrates the site layout under the SSET 1008 trial. The devices are then fed back to a distribution board
to allow isolation / switching of the units individually. As can been seen, each battery unit has an interposing
transformer convert the battery from 2 x 120V line voltages with a centre tapped neutral to a 240V supply with a live
and neutral leg. The interposing transformers and distribution board will not be necessary in the NTVV since, the
NTVV will have the opportunity to specify and deploy units designed for the native UK market.
Figure 1.3 – DC element of system
Figure 1.4 – AC part of the system
The DC part of the system is contained underground within a fibreglass vault as can be seen in figure 1.3. The AC
part of the system along with the inverter / rectifier sits on top of the DC element. The communications and control
equipment are also located within the top of the device.
After the physical installation of the devices the units were put through a detailed commissioning programme in order
to prove functional operation and comply with the requirements under G59/2. All three units passed the
commissioning as required.
The communications between the devices and the control hub have now been proven to function as required and will
be further documented within the test plan prior to the functional testing.
At present the civil works are being completed at the site, once this has been concluded the batteries will go into a
detailed test programme. The testing will begin with basic charging and discharging, at various power levels. As
confidence in the devices increases the testing will become more complex and push the limits of thermal and voltage
control on the network. The testing is expected to begin early July 2012 and run for 2 years.
Through delivering SSET 1008, we are able to de-risk the Tier 2 deployment and the following documents have been
highlighted to aid the larger rollout:




Full safety case and risk assessment completed by external party EA Technology. The work focuses on the
installation and operation issues relating to energy storage with a particular emphasis on Lithium-Ion
technology. The document makes reference to the potential hazards, the mitigations in place and the relevant
standards and directives the devices must comply with.
Commissioning evidence. The complete commissioning process has been detailed and recorded from the
basic start up tests from the manufacturer right through to the G59/2 testing.
Detailed test plan prepared in conjunction with EA Technology. The plan covers initial safety and operational
tests moving into the detailed functionality testing over the next 12 months.
Communications integration. Significant work has been completed in relation to the radio communications
between the batteries and the control hub and from the hub back to the SEPD Enmac system at the control
room in Portsmouth. This work has been documented with screenshots, flow diagrams etc.
Appendix 4
Programme Gantt Chart