Study on Lightning Thermal Damage Characteristics of ZnO Varistor under Operating Duty

Aiming at the problem of thermal collapse and fire burning of ZnO varistors in power system applications often caused by lightning, the experimental study on thermal damage characteristics of ZnO varistors under multi-pulse lightning operating duty was carried out, and the thermal damage characteristics and damage mechanism of ZnO varistors under multi-pulse were analyzed from two aspects including failure mode and temperature rise characteristics. The research shows that: during the multi-pulse lightning impulse, the heat lost by ZnO varistors is far less than the heat injected by multi-pulses, and the huge energy exerted by successive pulses causes disturbance. When the operating duty power frequency current is superimposed, the shock energy is absorbed and thermal damage is caused. Moreover, the temperature rise exceeds the allowable limit of ZnO varistors, which leads to the thermal balance out of control and finally results in fire and combustion. The research results are helpful to further reveal the lightning damage mechanism of ZnO varistors, and have important reference value for the research and development of multi-pulse surge protectors in power systems.