Improving outdoor insulator performances installed at coastal area using silicone rubber coating

Insulator is one of the most important equipments in an electric power system. Ceramic insulators are widely used since long time ago. Under polluted and wet condition, high leakage current may flow on the insulator surface. As the result a dry band arching may take place and in the long time it may degrade the insulator and initiate the insulator flash over leading to the failure of the lines. Several efforts may be taken to improve the insulator performance under polluted condition. They are increasing the number of insulator strings, modification of insulator design to increase the creepage distance and regular washing. This paper reports a proposal to mitigate the outdoor insulator failure using silicone coating. This paper explains the experimental results on the silicone rubber coating on ceramic insulators to improve the performances under coastal pollution. It was found that the coating was significantly suppressed the magnitude of leakage current and drastically reduced the corona intensity. The coating significantly reduced the insulator surface temperature. The coating also significantly increased the flash over voltage of the insulator. Contact angle measurement indicated that silicone rubber coating increased the water repellence as indicated by the drastic increase of contact angle.