disc insulators (hereinafter referred to as insulators) for high-voltage overhead transmission and distribution lines in the insulation and fixed wire. Generally assembled into insulator strings for different voltage levels on the line. Insulators according to their use of the environment and the region, divided into two types of ordinary and pollution-resistant. Ordinary insulators for general areas, such as the appropriate increase in the number of insulators can improve the performance of pollution flashover. Insulated insulators are divided into bell-type and double-umbrella type according to their umbrella structure. The stain-resistant insulator is suitable for industrial dust, chemical industry, salt, coastal and foggy areas. Good use of the scope, need to be completed by pre-trial to determine.