Electrical appliances refer to all electrical devices that consume electricity. From a professional perspective, they mainly include electrical devices, equipment, and components used for connecting or disconnecting circuits, changing circuit parameters, and achieving control, regulation, switching, detection, and protection of circuits or electrical equipment. From the perspective of ordinary people, they mainly refer to some commonly used electrical devices in households that provide convenience for daily life, such as televisions, air conditioners, refrigerators, washing machines, various small appliances, etc.

The metal parts or live parts in electrical appliances are mutually insulated. Under the conditions of excluding "applying voltage" and "no obstacles", the current formed on the surface of the insulating parts through the medium is the leakage current. The existence of leakage current is one of the important indicators to evaluate the insulation performance of an electrical appliance. From a safety perspective, people have higher requirements for the performance of electrical appliances, especially household appliances. It is unacceptable for electrical appliances to have current leakage, which would pose a threat to the personal safety of users.