Performances of silicone and ceramic materials used for outdoor insulation in field test

Cylindrical silicone rubbers and ceramic intended for outdoor insulation were tested in field at Chubu University for about two years. We employed as samples three types of silicone rubbers and one type of ceramic. Leakage current on all the samples were characterized and separated into the three categories, which were sinusoidal, local arc, and their transition components. The contamination severity of the test site was mild. The ceramic samples allowed a larger leakage current than the silicones, in which its cumulative charge was -160 C in about two years. The cumulative charges of the silicone samples were less than 12 C. The level of the cumulative charge and the composition of the above three components were dependent on the type of silicones.