Research on the Degradation Process of Metal Oxide Varistor based on Macroscopic Capacitance

Metal Oxide Varistor (MOV) is extensively used in overvoltage protection due to its excellent nonlinear voltage-current characteristics. Serving as the core component of arresters and surge protection devices, MOV is subjected to prolonged operation and repeated lightning strikes, inevitably leading to degradation. Various parameters such as the varistor voltage and the leakage current are commonly employed to investigate this degradation process. However, due to the apparent inflection point effect, these two parameters cannot reflect the degradation degree of MOV correctly. In this paper, macroscopic capacitance is introduced as a novel metric to analyze the degradation process of MOV under surge current, supported by extensive experimental data. A new parameter, denoted as "K", which represents the product of varistor voltage and capacitance is proposed to assess the degradation degree of MOV. By integrating K with varistor voltage and leakage current, a more reliable evaluation of MOV degradation can be achieved.