FEA Modelling of Current Transformers with Composite Insulators in Various Rigid Busbar Configurations
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.