AC CLEAN FOG TESTS ON NON-CERAMIC INSULATING MATERIALS AND A COMPARISON WITH PORCELAIN

AC Clean Fog tests were performed on non-ceramic materials used for ou tdoor high voltage insulators, namely, Room and High Temperature Vulca nizing (RTV and HTV) silicone rubber, and ethylene propylene rubber (E PR), with porcelain used as the reference. The steam input rate was va ried upwards from the value standardized for porcelain insulators. Res ults indicate that higher steam input rates produce a significant redu ction in the flashover voltage of silicone rubber family materials, al though it is always higher than that obtained for EPR and porcelain. F or EPR, the reduction is less and is similar to that established for p orcelain. The mechanisms involved have been examined. The trend in the results is found to be consistent for different formulations and insu lator geometries of the generic polymer (e.g. silicone rubber, EPR) ev aluated. A new, simple method for consistently applying uniform contam ination on silicone rubber (both RTV and HTV) is described, without th e use of extensive physical or chemical treatments, or prior condition ing by dry band arcing.