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

Experimental results show that the contamination performance of silicone rubber composite insulators is better than porcelain insulators. This is attributed to the hydrophobicity of the silicone rubber. This suggests that the flashover mechanism of these insulators is different. This paper experimentally investigates contamination build-up, diffusion of low molecular weight (LMW) polymer chains, surface wetting, electrical field caused interaction between droplets, generation of conductive regions and filaments, field intensification caused spot discharge and the ultimate flashover of silicone rubber along wetted filaments. The studies resulted in a new flashover mechanism, which provides a better understanding of the superior performance of silicone rubber outdoor insulators. The results will be useful for development of improved laboratory test procedures and to evaluate composite insulators' performance in contaminated conditions. The paper is divided into two parts: Part I describes the overview of flashover mechanism and the diffusion of LMW polymer chains and wetting of the silicone rubber surface in detail.