The main function of insulators is to achieve electrical insulation and mechanical fixation, for which various electrical and mechanical performance requirements are stipulated. For example, under the action of specified operating voltage, lightning overvoltage, and internal overvoltage, there should be no breakdown or surface flashover; under the action of specified long-term and short-term mechanical loads, there should be no damage or destruction; after long-term operation under specified mechanical, electrical loads and various environmental conditions, there should be no significant deterioration; the metal fittings of the insulator should not produce any significant corona discharge under the operating voltage to avoid interference with radio or television reception. Since insulators are widely used, their connecting metal fittings are also required to be interchangeable. Furthermore, the technical standards for insulators require various electrical, mechanical, physical, and environmental condition tests according to different models and usage conditions to verify their performance and quality.