Electric stress analysis of a 11kV RTV silicone rubber coated porcelain insulator

Abstract

In this contribution, electric stress analysis have been performed on a 11kV RTV (Room Temperature Vulcanized) coated porcelain insulator under dry and wet pollution conditions. Porcelain insulators coated with RTV silicone rubber are used widely in power transmission and distribution systems to improve the pollution performance of a normal porcelain insulator. Hence, they can be used in extremely polluted environments. Considering the aforesaid fact, in the present work, electric stress analysis is performed on a coated insulator surface so as to investigate the electric field and potential distribution on the surface of a coated insulator under clean as well as polluted conditions. The length of the pollution layer along the insulator surface is varied so as to observe the effect of non uniform pollution. The conductivity of the pollution layer is also varied to have an idea about electric stress during varying contamination levels . Moreover, since RTV coating is hydrophobic in nature, discrete water droplets are formed on the surface of the insulator. But, silicone rubber surface may loose hydrophobicity during extreme humidification which changes the contact angle of water droplets on the surface. Hence, performance of coating under wet conditions in presence of water droplets with varying contact angles are also investigated considering different level of hydrophobicity class. Moreover, the power dissipation along the surface insulator is also computed for different pollution levels.