Introduction: L2 towers are designed to operate at 275kV but have been uprated to operate at 400kV, in order to do this the insulator strings are shorter than L6 towers in order to maintain clearances and the creepage is little above the minimum required by the current NG Technical Specification 3.4.1. ECL units offer an increased creepage distance without increasing the string length. NG does not currently have an extra creepage length insulator approved to the Technical Specification. Policy Statement PS (T) 80 states that ‘In coastal areas and/or areas of high pollution ceramic ECL insulators shall be deployed’. In the past this policy has not been adhered to and the only solution has been to use insulators that have been dipped in a coating which bonds to the surface of the unit to assist the run off of rain and pollution through natural washing, It is unlikely that this application will be suitable for prolonged use in dry wind blown areas such as coastal zones.

NG currently has approximately 530 L2 structures that are within 5km of the coast or estuaries.

Objectives: To design and develop a fully type registered suspension and tension extra creepage length insulator to conform to TS 3.4.17. This will offer an alternative insulator for areas of high industrial or salt pollution on L2/U routes where the nominal size of insulator is 190kN.