Mar 2013
Electricity Transmission
FEA Modelling of Current Transformers with Composite Insulators in Various Rigid Busbar Configurations
Mar 2013
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
High Voltage Technology
The structural performance of post type Current Transformers (CTs) fitted with composite supporting rigid tubular busbars cannot be practically demonstrated by direct testing methods alone. Finite Element Analysis (FEA) offers a reliable method of determining the behaviour of materials under various conditions and scenarios that can be envisaged in typical busbar configurations. The data collected from the FEA modelling study is anticipated to lead to the introduction of composite insulators on post type current transformers as a safe alternative to current transformers fitted with ceramic insulation.
The recent catastrophic failures of GEC FMJL post type current transformers represent significant safety hazards to NG personnel and third parties. Failures have resulted in complete disintegration of the ceramic insulator and widespread dispersal of porcelain fragments over large areas of the site. Sites affected currently have Risk Managed Hazard Zones (RMHZ) of up to 75 metres around each FMJL unit which is preventing system access to carry out essential capital infrastructure and replacement work.

As an alternative to porcelain, composite insulators can be supplied as an option by most of the post type CT manufacturers. These are typically of silicon rubber material which has the advantages of being lightweight, superior in terms of pollution performance and more importantly are inherently safer then porcelain insofar that they will not shatter or fragment.

This project will investigate the impact of replacing current transformers with porcelain insulators for composite insulated current transformers and how these composite insulators will behave in typical busbar arrangements under static and dynamic load conditions.