Insulating Dielectrics: Esters & Alternative Liquids

Completed

Other Power and Storage Technologies(Electricity transmission and distribution)

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering)

Not Cross-cutting

Project Contact
National Grid Electricity Transmission

Network Innovation Allowance

Ofgem

01 September 2022

28 February 2025

ENA months

£700,000

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

This project seeks to understand the thermal performance of alternative liquids, both currently in service and for potential designs, in high voltage power transformers, to inform loading guidance. Coupled thermal and Computational Fluid Dynamics (CFDs) simulations would be used to calculate oil flow within transformers. The governing equations underlying mineral oil loading guides will also be analysed to assess whether they can be modified for alternative liquids. In conjunction with these simulations, experimental investigations would also be undertaken to understand material properties and their suitability for high voltage power transformers. State-of-the-art characterisation techniques will be used to understand the oxidation behaviour of alternative liquids, with a focus on the influences on chemical and biological degradation, and compatibility with other insulation materials found in transformers at high temperatures. Since the oxidation behaviour and reaction to humidity have been identified in literature as limiting factors for biodegradable insulation fluids, these measurements will be performed in regular intervals when subjecting candidate liquids to extreme conditions and voltages. The results from this project will inform the use of novel insulation fluids in HV transformers, and outline how properties and stability of the next-generation of naturally-derived fluids might be improved.Data Quality Statement (DQS):The project will be delivered under the NIA framework in line with OFGEM, ENA and NGGT / NGET internal policy. Data produced as part of this project will be subject to quality assurance to ensure that the information produced with each deliverable is accurate to the best of our knowledge and sources of information are appropriately documented. All deliverables and project outputs will be stored on our internal Sharepoint platform ensuring access control, backup and version management. Relevant project documentation and reports will also be made available on the ENA Smarter Networks Portal and dissemination material will be shared with the relevant stakeholders. Measurement Quality Statement (MQS): The methodology used in this project will be subject to our suppliers own quality assurance regime. Quality assurance processes and the source of data, measurement processes and equipment as well as data processing will be clearly documented and verifiable. The measurements, designs and economic assessments will also be clearly documented in the relevant deliverables and final project report and will be made available for review.Risk AssessmentTRL Steps = 1Cost = 2Suppliers = 1Data Assumption = 2Assessed risk score 6 – Low. The project will be delivered in the following six workstreams which will in totality investigate thermal performance of synthetic esters, natural esters and a bio-based insulating oil compatible with mineral oil:WS1: State of the Art Review and Analysis WS2: Modelling of thermal conditions in operational transformers that use alternative liquids WS3: Identification of Natural Ester Liquid degradation processes WS4: Development of thermal network models for Business as Usual activities WS5: Performance and degradation of alternative insulation fluids WS6: Recommendations for asset management, ratings & operations This project will deliver greater understanding of the thermal performance of mineral oil alternatives that may be used in power transformers. Specifically, the following objectivesare planned:Practical solutions to enable calculation of rating enhancements for synthetic ester-filled transformersEvaluation of the benefits and barriers of natural estersQuantification of the uprating opportunity and other benefits for retro-filling transformers with bio-based oil.

Ester-based insulation fluids offer several benefits for the operation of transformers. They have improved fire safety, reduce the risk of moisture build-up in paper insulation, they are biodegradable, and some are from sustainable sources. They also offer the possibility of improved thermal performance, due to their typically lower viscosity. However, such liquids are typically more expensive than mineral oil, and have only been used in high voltage power transformers relatively recently, so operational experience with them is limited. This project will work to improving the understanding of the impact of alternative liquids on transformers through simulations and experimental investigations. Particular attention will be given to the thermal performance of such liquids, and the possibility of improved ratings.

14/10/22