Short duration current impulse waveform effects on the degradation and energy absorption capability of zinc oxide varistors

•Resistive peak and harmonic components of leakage current increase with MOV aging.•MOV samples withstood less energy and fewer impulses on longer waveforms.•Shorter current impulses result in higher increases in the leakage current of MOVs.•There is a correlation between single impulse withstand capability and aging of MOVs.•The performances of different MOV manufacturers can be compared. Surge arresters are subjected to different types of overvoltages, and the ZnO varistors, which are their active element, must be able to not only absorb the energy from these overvoltages but also present degradation levels that do not compromise their functionality after the event. The lack of correlations between surge waveforms, associated energy absorbed by a varistor and its degradation has motivated the investigation proposed in this research, in which varistors from different manufacturers had their energy absorption capabilities evaluated at different short duration current impulse waveforms (4/10 µs, 8/20 µs, and 30/75 µs). Energy absorption capability was analyzed using two methods: the up-and-down method (to verify the single discharge energy absorption capability) and degradation by successive impulses of different energy levels (2.45 kJ, 3.45 kJ, and 4.45 kJ) with leakage current analysis between impulses. The results demonstrate that, although shorter waveforms result in more intense leakage current variations, longer waveforms resulted in worse energy absorption capabilities, despite the lower peak current value. This suggests that, for the samples studied, the time under overvoltage is more critical than the peak current value for their impulse withstand capabilities.