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