Comparative tests on RTV silicone rubber coated porcelain suspension insulators in a salt-fog chamber

The development of leakage current on vertical and horizontal strings of RTV coated porcelain suspension insulators in a salt-fog chamber are presented in this paper. Strings comprising of three-units, fully coated, and bottom surface coated, are investigated for leakage current development over a 1000 hour test period. The bottom surface coated insulator strings are used to examine the merits of half-coated insulators in comparison to fully coated insulator strings. Two coating formulations, containing ground quartz in one system, and alumina trihydrate in the other, both at the same filler level, are studied to determine whether filler type affects the development of leakage current, flashover, and their ability to prevent erosion under dry-band arcing.