Influence of Micro-structure Disorder in the Numerical Modeling of Metal Oxide Varistor on Current Distribution

Abstract

Metal Oxide Varistors (MOVs) are important components to construct arresters which suppress overvoltage and divert surge in the power system. By building the numerical model of the microstructure of MOVs, their characteristics can be better studied and interpreted. Due to different production processes, the uniformity of varistor micro-structure will also be different. In order to simulate the uniformity of varistor micro-structures, Voronoi networks with different disorder degrees are established in this paper. The boundary condition of the grain boundary layers is simplified by the fitting method. By endowing the numerical model with material properties and current—voltage ($I - V$) characteristics of the varistor sample, the influence of the different disorder of the varistor micro-structure on the current distribution is analyzed based on the finite element method simulation. The results show that the uniform micro-structure can make the current uniformly distribute inside MOVs, which can effectively prevent the rapid thermal breakdown of MOVs due to the local current concentration.