Switching Surge Performance of Contaminated Insulators

The "wet contaminant" test method, originally developed for use with alternating voltage, is extended for use with switching surges. In order to evaluate insulators under conditions where dry bands would form, it was found necessary to first energize the contaminated insulators with alternating voltage before applying the surges. Included in the investigation are the effect of front time and tail time on the critical flashover voltages, and a comparison of the switching surge performance of five insulator types under various levels of contamination.