Investigation of electrical properties of ZnO varistors stressed by current pulses

ZnO varistors produced by current technology have excellent non-linear voltage dependent characteristics. Therefore, they are suitable for use as a surge protection device of electric and electronic equipment. The operating life and the stability of installed arrester is affected by several factors, such as overvoltages having different duration and amplitude and increased ambient temperature. Moreover, the above factors act simultaneously and mutually influence each other. The article deals with the changes of electrical properties of low-voltage ZnO based varistor caused by injection of current pulses with a defined shape and energy. Comparison of changes in electrical properties is based on the observation of shift in dependence of the DC voltage and the corresponding current. Moreover, changes of nonlinearity coefficient and the absorbed energy have been observed. It was found that repeated injection of current pulses results in a significant change in electrical characteristics of the ZnO varistor. Total destruction of the varistor is demonstrated.