The primary function of insulators is to achieve electrical insulation and mechanical fixation, for which various electrical and mechanical performance requirements are stipulated. For instance, under specified operating voltages, lightning overvoltages, and internal overvoltages, no breakdown or surface flashover should occur; under specified long-term and short-term mechanical loads, no destruction or damage should be produced; after long-term operation under specified mechanical, electrical loads, and various environmental conditions, no significant degradation should be observed; and the metal fittings of insulators should not produce noticeable corona discharge under operating voltages to avoid interference with radio or television reception. Since insulators are widely used devices, their connecting fittings are also required to be interchangeable. Furthermore, technical standards for insulators dictate that various electrical, mechanical, physical, and environmental condition tests must be conducted on the insulators, based on different models and usage conditions, to verify their performance and quality.