Performance of RTV silicone rubber insulator coatings

The results of the performance of room-temperature vulcanizing (RTV) silicone rubber insulator coatings in a salt-fog chamber are presented. The coatings were evaluated at 900-μS/cm conductivity for the water forming the salt-fog. The loss of hydrophobicity was studied from monitoring the leakage current on the coatings. The effect of scale formed during dry band arcing was evaluated with respect to the performance of RTV coatings. The development of leakage current on the RTV coatings without scale is associated with a temporary loss of surface hydrophobicity. However, with scale deposited during dry band arcing the leakage current development is not only dependent on the temporary loss of hydrophobicity, but also strongly dependent on the amount of scale. The flashover voltage of the RTV coatings was determined subsequent to varying the time of the application of the electric stress in the salt fog. The performance of RTV coatings was studied as a function of the alumina trihydrate (ATH) filler level. Leakage current and contact angle measurements were used as indicators of the effectiveness of the RTV coatings. RTV coatings enable insulation systems to attain increased flashover performance by about 30% over uncoated insulators