Insulator pollution and wetting processes at a severe coastal site

Abstract: High voltage insulators that are exposed to a coastal environment become conductive due to the formation of a conductive layer on the insulator surface. This layer could be due to a salt spray near the coast or due to the deposition of a dry pollution layer with subsequent wetting due to rain, dew or fog. The pollution collection depends on the type of material of the surface of the insulator and the condition of the surface. The pollution collection of identically shaped insulators made of different materials was monitored for a period of twelve months. The pollution deposition was monitored on the sample insulators and compared to that of non-energised insulators. The pollution sources, pollution deposition and wetting mechanisms were investigated. It was found that wind is the main carrier of pollution and that the wind causes directional deposition of pollution. More pollution was visible on the non-energised units than on the energised units, although the surface conductance measurements indicated the contrary. A hypothesis is presented for the phenomenon