Research on electrothermal characteristics of metal oxide varistor based on multi-physical fields

The electrothermal characteristics of metal oxide varistor (MOV), closely related to its microstructure, are important for studying its failure mechanism. This paper proposes an improved MOV microstructure model based on the Voronoi network for simulating the electrothermal behaviour of MOV. With the proposed model, not only the simulation accuracy under constant electrical stress can be improved, but also the simulation of MOV under time-dependent electrical stress (a.c. or impulse) can be realized. The simulation results are in good agreement with the experimental data. In addition, according to the electrothermal characteristics of MOV microstructure and the failure phenomenon of MOV in the experiments, the failure mechanism of MOV under different electrical stresses is analysed and discussed. It is found that the serious local heating caused by current concentration and thermal stress caused by huge temperature gradient are the main reasons for the MOV failure. This paper provides an effective method for the study of MOV electrothermal characteristics and theoretical reference for the performance improvement of MOV.