Experienced gained from 132 kV EPDM composite insulators in a coastal environment

A number of EPDM insulators have been taken from service on a 132 kV system after eight years in a harsh environment and have been examined. Fortuitously three different insulator designs are available and compared. Two of the insulators were installed in a vertical orientation and one in the horizontal. The insulators are characterized visually, electrically and for hydrophobicity. They have been found to be fit for purpose, but show extensive superficial ageing, in particular blackening, of the polymer surfaces. No severe degradation has been identified. In particular there is evidence of discharge activity around the prominent longitudinal mould lines on all the insulators.