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First Tier Pro-forma
Project title
Participant DNOs
Project summary
Please provide a narrative which explains the Problem(s) which being addressed by the Project.
Registration Date
Power Transformer Real Time Thermal Rating
UK Power Networks (London Power Networks plc and South Eastern Power Networks)
UK Power Networks (London Power Networks plc and South Eastern Power Networks)
The Power Transformer Real Time Thermal Rating project intends to demonstrate how additional
capacity can be made available from existing assets and defer reinforcement by three years or
more. It is estimated that transformers can be loaded up to 20% above static seasonal rating.
Changes in environmental conditions have a dramatic effect on transformer loading and in urban
areas due to rise in air conditioning installations, current summer or winter firm ratings may not
be fully representative of the situation at particular sites. This seasonal increase in loading is
leading to premature network reinforcement decisions.
This demonstration will be achieved by retrofitting Transformer Management System (TMS) onto
existing assets to provide real-time monitoring of the transformer's health, and continuously
calculate the transformer thermal capacity, thereby safely loading the transformer close to the
maximum top oil temperature less 2 Deg Celsuis allowed by design nameplate.
An increase in capacity will be achieved by carrying out the following:
- Installation of an active TMS, monitoring ambient & top / bottom oil temperatures;
- Installation of additional fans, modification to cooling set-points and enabling pre-cooling;
- Initiate pre-cooling in the event of a loss of one transformer (N-1 scenario);
- Create an "out of firm" condition by altering network normal operational configuration; and
- Use the TMS to ensure design limits are not exceeded and calculate impact on degradation.
A greater understanding, visibility in asset performance is expected to lead to a reduction in
assets replacement, facilitating the connection of additional loads and low carbon technologies.
DNO's are required to plan and develop within P2/6 guidelines and the rating of a transformer and
network operation is governed by thermal considerations. Energised transformers result in losses
in the core and windings which become hot, causing oil temperature to rises. Increased loading
increases the losses and hence the temperature and the highest temperature in the winding must
not exceed the allowable design limit. For the vast majority of the DNOs' installed fleet, it is not
possible to measure this hot spot temperature directly, since fibres have only recently begun to
be embedded in new transformers for particularly sensitive sites. The top oil temperature is
usually measured directly and various methods have been employed to simulate or estimate the
winding hot spot (WHS) temperature. Loading guides define limits to loading based on factors
such as solar radiation, ambient temperature, pre-load and the environment.
These parameters affect the real-time rating of plant and it is anticipated that a significant
increase in ratings can be assigned, if actual operating conditions are used.
Scope and Objectives
Please describe the scope and objectives of the Project should be clearly defined including the benefits which should directly
accrue to the Distribution System.
Success Criteria
Please give details of how the DNO will evaluate whether the Project has been successful.
This section should set out the Method or Methods that will be trialled in order to solve the Problem. The type of Method
should be identified where possible e.g. technical or commercial.
Problem(s) continued
Under transient i.e. N-1 scenarios, the rate of rise of oil and winding temperatures depends on
the difference between rate of energy generation and dissipation, and on the thermal time
constant of the transformer and its components. It therefore becomes more difficult to simulate
or estimate the WHS temperature when load and environmental conditions are changing.
Manufacturer's factory acceptance tests if performed will establish the thermal heat curve for the
transformer can provide a more refined approach to calculating the WHS.
Improved measurements only calculate a shortfall in capacity or the time before a shortfall will
occur. As such, techniques such as pre-cooling, additional cooling, or load transfers need to be in
place to relieve the transformer under N-1 scenarios. No current known LCNF project has active
TMS control fitted to provide enhanced real time output whilst operting close to thermal limits.
The project will retrofit a suitable TMS solution at sites where tight capacity margins prevail
during RIIO-ED1, to trial Power Transformer Real Time Thermal Rating.
The main activities will be:
- Conduct extended heat run tests on at least one new transformer at factory acceptance test to
validate variance between actual WHS measurements using fibres vs calculated WHS
temperatures. This transformer will be representative, but will not be identical to the transformers
on site.
- Real-time monitoring of key parameters at existing transformer sites: top/bottom oil / ambient
temperatures (observing london heat island effect), demand shape (evening peaks/cooling cycle)
& load transfers;
- Installation of additional fans (normal and/or evaporative cooling), real time loading/ageing
calculations based on thermal data; and
- Create “out of firm” conditions and ensure that design limits are not exceeded.
In the event of a predicted out of firm condition arising, consideration will be given to mitigating
actions. These could typically include:
- Calculating rate of winding temperature rise of the remaining transformers in the event of loss
of one circuit and assessing time available at load curve prevailing; and
- Effecting load transfer where available.
The project will trial Power Transformer Real Time Thermal Rating at two primary substations, 1
each in London & South Eastern licence areas of UK Power Networks. The main objectives are to:
- Conduct extended heat run tests on representative transformers in order to clarify the variance
between top oil and measured winding hot spot (WHS) temperature (where fibres are fitted) and
make comparison with calculations;
- Install TMS equipment to gain access to key parameters;
- Conduct tests to establish summer/winter rating with/without evaporative cooling; and
- Develop an approved policy for implementing Power Transformer Real Time Thermal Rating.
The following will be considered when assessing whether the project has been successful:
- Tests to compare fibre measurements and calculations have been carried out.
- Transformer management systems have been installed at the trial sites and performing correctly
- An understanding of whether an improved rating can be assigned to primary transformers has
been developed.
The DNO should highlight any material, known risks that could impact the Project’s costs and/or programmes.
Scale of project
Please justify the scale of the Project. In particular, the DNO should explain why there would be less potential for new learning
if the Project were a smaller scale.
Geographical area
Details of where the Trial(s) will take place. If the Project is a collaboration, the DNO area(a) in which the Trial(s) take place
should be identified.
Potential for new learning
Detail what the parties hope to learn and how the learning will be disseminated.
This should be between 5-8 to be eligible for Tier 1 Funds.
Predicted start and end dates.
DNOs should provide an estimate of the expected project starting and completion dates.
Start Date: End Date:
Project partners and external funders
Please give details of actual or potential Project Partners and External Funding Support as appropriate
The project partner will be Wilson Transformer Company for the supply, installation and
commissioning of TMS equipment.
The main learning that will be shared with other DNOs is expected to include:
- An improved understanding of transformer thermal behaviour and asset utilisation.
- What is a safe enhanced transformer rating;
- The required minimum specification for TMS equipment and
- What policies need to be developed to implement Power Transformer Real Time Thermal Rating.
The main risks for the project will be not being able to gain network outages to install the TMS
equipment, the ability to carry out load transfers, and operating under N-1 conditions (close to
transformer nameplate rating). The risks during the trial will be mitigated at primary substation
by using load banks (which can be quickly disconnected) to supplement transformer loading.
Actual network load will be used to load the transformer to remain within seasonal capacity,
managing the operational risk, mitigated by robust planning.
Project funding estimated at £1.046m will be spent within regulatory year 2014/15. UK Power
Networks are aware that a separate application to the Network Innovation Allowance will be
required early in regulatory year 2015/16 for estimated £335,995 for the remainder of the funds.
The trial will be carried out at 2 Primary substations and will monitor 6 primary transformers.
- Four Transformers will be monitored at Lithos Road 66/11kV substation; and
- Two Transformers will be monitored at Weybridge Town Primary 33/11kV substation.
These two selected configurations would be representative of typical primary substation
installations within LPN (urban) / SPN (rural) and how the trials could be repeated at other
primary sites following successfull testing with minimum retrofit equipment.
Some elements of remote monitoring of the equipment will be managed from the control centre
at Fore Hamlet, Ipswich.
Work has been carried out to review and select appropriate trial sites. We currently expect to
proceed with the trial in the following areas, subject to detailed design and also subject to any
outage restrictions:
Area (1): London Power Networks - North West London - Lithos Road 66/11kV SS.
Area (2): South Eastern Power Networks - Surrey - Weybridge Town 33/11kV SS.
This project will comprise 2 Primary substations having 6 transformers in total. 4 transformers at
Lithos Road 66/11kV substation LPN area and 2 transformers at Weybridge Primary 33/11kV
substation SPN area.
Please tick if the project conforms to the default IPR arrangements set out in
the LCN Fund Governance Document?
The DNO should indicate if the Project does not conform to the default IPR conditions. A justification for alternative arrangements and why the Project
should still be approved must be provided, in accordance with paragraph 2.18 of the Governance Document.
Please tick if you do not consent to the First tier pro-forma being published in
If you do not consent please identify any information in the completed First Tier LCN
Project Registration that you do not wish to be published.
The DNO must demonstrate that it (or its Project Partners) will face commercial harm from its disclosure and that
information is considered eligible for exemption under the Freedom of Information Act 2000 or the Environmental
Information Regulations 2004.
All information submitted within the First Tier LCN Project Registration Pro-forma will be made available on the Ofgem
website, unless Ofgem has agreed otherwise as part of the Registration process set out above.
Estimated Project funding
An indication of the revenue allowed for within the DPCR5
settlement that is likely to be saved as a result of the project.
An indication of the total Allowable First Tier Project
Expenditure that the DNO expects to reclaim the for the
whole project.
Revenue allowed for in
the DPCR5 Settlement (£)
Indicative total Allowable
First Tier Project
Expenditure (£)
Please tick if the project involves making payments to related undertakings
The DNO must set out all payments that it proposes to make to itself or any Related Undertaking. Further, if a payment is to
be made to any Related Undertaking that is a Distribution System User, the DNO must demonstrate that it has offered the
same terms to similar Distribution System Users on the part of the network that is within the Project boundary and has used
reasonable endeavours to identify such Users.
The project will be completed during the RIIO ED1 period and will therfore be registered as a NIA
project. £1,382,000 is the total expenditure which we expect will be incurred during the full
duration of the project (including both LCNF Tier 1 and NIA expenditure)
An estimated split of the expenditure is shown below:
LCNF Tier 1: £1,046,005
NIA: £335,995
The project will comply with the default NIA IPR arrangements.
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