The influence of surface ageing features of insulators on wet flashover performance

This paper presents an investigation into how aged surfaces can reduce the wet flashover performance of composite insulators under extreme weather conditions. Surface ageing features of composite insulators returned from service reveal a non-uniform distribution of roughness that creates interfaces between smooth and rough surface areas. The resulting surfaces have radically different hydrophobicities. This interface can, under "suitable" wet and windy weather conditions, impact the way in which water moves on the surface of the insulator and may act as a guide for water to accumulate and create water streams that can bridge the sheds. Such water streams will consequently cause a reduction of the leakage current distance and adversely impact the flashover performance of the insulator. Measurements of wet-flashover of aged insulators and experimental model systems are presented.