Handover acceptance test, overhaul test refers to the installation department, overhaul department of the new cast equipment, overhaul equipment in accordance with the product technical conditions and national and industry standards for the test. New installations in the operation of the handover acceptance test, used to check the product for defects, transportation damage, etc.; overhaul of the equipment used to check the overhaul of the test quality is qualified. Preventive test refers to the equipment put into operation, according to a certain period of time by the operation department, the test department for the test, the purpose is to check the operation of the equipment without insulation defects and other defects. Compared with the factory test and handover acceptance test, it mainly focuses on insulation test, the test project is less. According to the nature and requirements of the test, the electrical test is divided into two categories of insulation test and characteristic test.