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Reference Number NIA_UKPN0001
Title Power Transformer Real Time Thermal Rating
Status Completed
Energy Categories OTHER POWER and STORAGE TECHNOLOGIES(Electricity transmission and distribution) 100%;
Research Types Applied Research and Development 100%
Science and Technology Fields ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 100%
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Project Contact
No email address given
Eastern Power Networks plc
Award Type Network Innovation Allowance
Funding Source Ofgem
Start Date 01 June 2014
End Date 01 July 2018
Duration 49 months
Total Grant Value £1,522,000
Industrial Sectors Power
Region London
Programme Network Innovation Allowance
Investigators Principal Investigator Project Contact , Eastern Power Networks plc (99.998%)
  Other Investigator Project Contact , UK Power Networks (0.001%)
Project Contact , South Eastern Power Networks plc (0.001%)
Web Site
Objectives 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 by 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, historic conditions of load and ambient temperature may not be fully representative of the situation at particular sites. This seasonal increase in loading may lead to cautious network reinforcement decisions. This demonstration will be achieved by retrofitting 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 Celsius 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. The main remaining risks for the project will be not being able to gain network outages to install the second 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 and further mitigated by robust planning. 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.
Abstract The project was started as a LCNF Tier 1 project and was forecast from the outset to transition to NIA. DNOs 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 up to 20% increase in ratings can be assigned, if actual operating conditions are used and additional evaporative cooling is introduced. 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 within the transformer 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 and 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. The project will retrofit a suitable Transformer Management System (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, 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 an "out of firm" condition 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.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above
Publications (none)
Final Report (none)
Added to Database 17/09/18