Investigation results of silicone rubber insulators under wet and contaminated conditions

Generally nonceramic insulators are considered to have contamination withstand voltage characteristics superior to porcelain or glass insulators owing to the higher hydrophobicity of the surface, especially just after production. But it was reported that in the field the flashover probability of nonceramic insulators was higher than that of porcelain insulators, in spite of having equal or larger leakage distances compared to porcelain insulators. In general, nonceramic insulators show excellent water repellency at first, but gradually lose it with time. But in case of silicone rubber insulators, it is said that owing to the migration of low molecular silicone from the bulk of silicone rubber to the surface of the insulator, the water repellency can be maintained for a long period. The artificial contamination test methods developed for porcelain or glass insulators are sometimes applied to evaluating the contamination withstand voltage characteristics of nonceramic insulators. But including the contaminating methods of these insulators, there is no established insulator artificial contamination test method to evaluate the withstand voltage characteristics of contaminated nonceramic insulators in a laboratory. In this report, the influences of both wetting conditions and amount of nonsoluble contaminants on the withstand voltage of contaminated silicone rubber insulators were investigated