The purpose is to check the defects and avoid accidents.
Arrester may have defects that are not detected during manufacturing, such as moisture brought in in advance when the air is wet or when it is assembled and delivered in the season; It is damaged during transportation, the internal porcelain bowl is broken, the parallel resistance is broken, the external porcelain bushing is bruised or damped during transportation, the end of the porcelain bushing is uneven, the rolling is not tight, the sealing rubber gasket is aging and hardening, the porcelain bushing cracks, and the parallel resistance and valve pieces are aging during operation. These deterioration can be found through preventive tests, so as to prevent accidents such as maloperation and explosion of arrester during operation.
Arrester is a protective device widely used in the power system. It is connected between the cable and the earth and is usually connected in parallel with the protected equipment. The arrester can effectively protect the electrical system and various equipment. Once abnormal voltage occurs, the arrester will act to protect. When the electrical equipment operates under normal working voltage, the arrester will not work. For the ground, it is regarded as breaking current to guide the earth, so as to limit the voltage amplitude and protect the electrical system and equipment insulation. When the over-voltage disappears, the arrester will quickly return to its original state, enabling the electrical equipment to work normally.