Temperature distribution in RTV silicone rubber coating following dry band arcing

The loss of hydrophobicity of room temperature vulcanizing (RTV) silicone rubber coating on insulators, due to dry band arcing in the presence of contamination and moisture, causes a deleterious effect in the electrical performance of the coating. For example the growth of the leakage current is accelerated resulting in more intense discharges which may lead to flashover and an outage in the system. The arcing causes an increase in the temperature of the surface and then in the bulk of the coating which leads to bond scissions and other chemical changes. In the present paper the temperature distribution on the surface and in the bulk of the coating is determined as a function of the arc duration and the size of the arc on the 100 pph (part per hundred) alumina trihydrate (ATH) filled RTV coating. The significance of the temperature rise in the coating on the loss and recovery of hydrophobicity is discussed