Study on factors influencing the impulse withstand capacity of zinc oxide varistors

Abstract

The impulse withstand capacity of zinc oxide (ZnO) varistors is crucial to the reliable performance of arresters, and is influenced by factors such as the impulse current waveform, amplitude, and the number of impulses. This paper studied the effects of these factors on the damage modes and aging degree of ZnO varistors through repetitive impulse testing. The test results indicate that side flashover is the predominant damage mode under different impulse current waveforms (8/20 μs and 15/35 μs), and the probability of pinhole and cracking damage increases with both the current amplitude and the number of impulses per group. The aging degree increases with the shortening of the current waveform, as well as with the increase in both the current amplitude and the number of impulses per group. Side flashover significantly reduces the lifespan of ZnO varistors, and the application of glass glaze remains ineffective in preventing this damage. The evaluation of impulse withstand capacity should consider the effect of current waveforms. These findings provide valuable insights for improving impulse test methods and enhancing the impulse withstand capacity of ZnO varistors.