Condition monitoring and deterioration analysis of metal oxide varistor

Abstract

With the growing demand for application of metal-oxide varistor (MOV) in low-voltage electronic circuits for overvoltage protection, it is necessary to ensure its performance to avoid the short-circuit and the line-to-ground fault during operation. In this paper, a precise leakage current analyzer was developed to detect the total leakage current and third harmonic component of MOV for its condition monitoring. The voltage- and temperature-dependent measuring uncertainties were compensated using the multipliers. In addition, the deterioration characteristics of the MOV and the newly developed thermally protected metal-oxide varistor (TMOV) were investigated in the accelerated aging test. From the experimental results, the MOV deteriorated much faster under the lightning current impulse synchronized with power-frequency voltage. The thermally activated fuse of TMOV exploded under two types of impulses, which indicated that the TMOV is much more vulnerable and that it is difficult to diagnose the condition of energized TMOV in advance.