Mar 2013
Electricity Transmission
Polymeric Insulation Evaluation
Mar 2013
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
Traditionally ceramic insulation has been used for all substation devices required to provide High Voltage (HV) conductor to ground insulation clearance. Examples are Current Transformers (CTs), Voltage Transformers (VTs), Bushings and Post Insulators which use a special shed profile to optimise on size, strength, ‘creepage’ and provide weather and pollution resilience. This technology is well proven, reliable with a predictable life and has been used for over 50 years. However these devices can fail catastrophically and unexpectedly and cause serious injury and collateral damage to other plant and equipment. In addition they are heavy and susceptible to damage during manufacture, transport and installation phases and require larger civil foundations and structures to support them than those made from lighter materials.

Polymeric insulation is now a viable alternative to ceramic insulation and there is growing adoption and experience in other utilities. However there are a number of choices on the market, particularly relating to material, shed profile and manufacturing processes. There is also uncertainty over the mechanical strength, proven life, maintenance needs and performance over time.

This project will engage NAREC (NDSL) to carry out a technical survey, evaluate and report on the choices available and provide recommendations for optimum selection. This will enable National Grid to risk manage the introduction of polymeric insulation into main projects. This work will also include a market study to examine the worldwide experience of major utilities in the use or trial of polymeric insulators on post type current transformers in substation applications.

This R&D Project aims to gain an understanding of the technical performance and market experience of the material compounds available, preferred manufacturing process and optimum choice of shed profiles for polymeric insulation systems. This will enable clear policy and specifications to be established for the future application of polymeric insulation in substation applications such as Instrument Transformers. This will form part of the risk management process for the introduction of this new technology into replacement and new build substation projects