Comparison with the influence of different types of impulse currents on the degradation of Zinc-oxide varistors

Abstract

To compare different types of impulse currents on the degradation of Zinc-oxide varistors, 2 milliseconds square wave and 10/1000 microseconds impact current with the same impact energy were respectively applied to the same type of ZnO varistor samples. The three characteristic parameters' trends of samples with a diameter of 20 millimeters after multiple pulses are different, and the sample after 940 times impacts by 2 milliseconds square wave with an amplitude of 160 amperes remained intact, while the one exploded after 499 times impacts by 10/1000 microseconds impact current with an amplitude of 260 amperes. And the microstructure of samples with a diameter of 10 millimeters after the single pulse by using scanning electron microscopy (SEM) are observed. We find that with the same impact energy, the damage degree of 10/1000 microseconds impact current on ZnO varistor is relatively greater than that of 2 milliseconds square wave, which is more likely to cause the deterioration and aging of ZnO varistors.