Investigation of Spinel Phase Content on the Performance of ZnO Varistors by Simulation

Uneven current distribution inside ZnO varistors is a key factor affecting the current carrying performance and fault failure of ZnO varistors. However, it is difficult to directly observe the internal current distribution in the process of ZnO varistors subjected to external current and voltage. In this paper, the finite element method and Voronoi network are combined to construct a reasonable model to simulate the electrical-thermal-force multiphysics field of ZnO varistors under the impulse. The effects of spinel phase content in the microstructure of ZnO varistors on the current distribution of ZnO varistors and the effects of temperature and stress under the impulse are analyzed. The results show that when the spinel content is around 1%, the concentrated current distribution, the local temperature rise and thermal stress are within a more reasonable range, which is favorable to the current carrying performance of ZnO varistors. The results of this simulation calculation provide guidance for the performance optimization of ZnO varistors.