Flashover of high voltage insulators used in transmission system and substations is treated as a major problem that can affect the transfer of large amount of electrical energy over long distances. Contamination in coastal, industrial, desert and agricultural areas under environmental conditions of fog, light rain and dew is the main cause of high voltage insulator flashovers. Flashover in most cases leads to lengthy service outage; hence it has a considerable impact on power system reliability. As such, several methods have been used in order to improve the performance of high voltage insulators under polluted conditions. Among these methods are creepage extender, Coating and regular washing of insulators.