Flashover mechanism of silicone rubber insulators used for outdoor insulation-II

Flashover mechanisms of silicone rubber used for outdoor insulation is presented and experimentally proven. A hydrophobic surface of silicone rubber wets and accumulates contaminants differently compared to conventional porcelain and glass insulators. This suggests that the flashover mechanism of silicone rubber insulators is different than porcelain and glass. This part of the paper experimentally investigates ohmic heating, electrical field caused interaction between water droplets, generation of conductive regions and filaments, field intensification caused spot discharges and the ultimate flashover of silicone rubber along wetted filaments. These studies have resulted in a new flashover mechanism which provides a better understanding of silicone rubber outdoor insulators and their excellent contamination performance. These results will be used for the development of a better laboratory test procedure to evaluate composite insulators´ performance in contaminated conditions