Flashover characteristics of polluted silicone rubber insulators exposed to artificial UV irradiation

This paper presents the results of an experimental investigation on the flashover performance of Silicone Rubber outdoor insulators. The AC flashover voltage of selected samples under dry-clean, clean fog, rain and highly-polluted conditions is measured using ramp-test procedure applied to each insulator mounted in vertical, horizontal and inclined orientations. Conventional design with plain surface and new textured design having uniform hemispherical protuberances have been used and their flashover voltages compared. The effect of UV irradiation on the flashover voltage under controlled temperature and humidity is explored. The results show that under low fog-rate, the flashover voltages of both types of insulators were similar, but had a U-shaped characteristic. For high fog-rate, no significant difference was found between the insulator types, with the flashover voltage increasing with ramp voltage up to a stable value. After UV conditioning, and for polluted insulators under low fog rate and wet tests, vertically-oriented insulators showed a U-shaped characteristic and significant reduction in flashover voltage compared to non-irradiated insulators.