Dielectric spectroscopies of ZnO varistors with high voltage gradient under surge aging condition

ZnO varistors have been widely used in power systems as metal oxide arresters (MOA) against overvoltage surges due to their excellent nonlinear current-voltage (I-V) characteristics and surge energy absorption capabilities. The MOA applied in power system with rated voltage usually has remarkable huge size, which results in great difficulty for MOA design and manufacture. Thus, ZnO varistors with higher voltage gradient have been developed, which can sufficiently shorten the height of MOA and solve above problems. However, the aging performances of ZnO varistors with high voltage gradient have not been revealed yet. In this paper, we studied the aging characteristics of ZnO varistor samples by comparing their dielectric spectroscopies before and after surge aging experiments, which were carried out under 8/20 mus surge currents. The experimental results indicate that ZnO varistors with high voltage gradient behave distinct aging performances.