Electrothermal characteristics of zinc oxide varistors with different aging states after multiple lightning strikes based on Voronoi network finite element model

Abstract

Multiple lightning strikes significantly degrade the electrical and thermal properties of zinc oxide (ZnO) varistors, affecting their protection capability. In order to quantitatively analyze the hazard of multiple lightning strikes on ZnO varistors, simulations at the microscopic level are required to account for the changes in macroscopic parameters. Unlike other published research, this paper presents an analytical approach to simulate the micro-level performance of ZnO varistors in different aging states. The details of the model construction, experimental platform, and computational results are thoroughly investigated. First, a Voronoi network finite element model for ZnO varistors is developed, and the required model parameters are presented. Next, an experimental testing platform is used to physically simulate multiple lightning strikes and perform parametric testing. Finally, the microscopic electrical and thermal properties of ZnO varistors under different aging states and pulse numbers are analyzed and compared. The results show that with an equivalent amount of energy per impact, triple-strike aging causes severe degradation for ZnO varistors. Compared to single-strike aging, triple-impact aging results in a 15.21 times higher quality coefficient and a 7.67 times higher 10 min temperature rise ratio.