Analytical Method for Performance Degradation of Voltage Limiting Type SPD Based on Leakage Current Measurement

摘要

SPD degradation analysis is a key technology of intelligent SPDs. MOV varistor is the core component of voltage limiting type SPD. It is well known that the increase of leakage current is the main factor causing MOV degradation. Therefore, the monitoring of MOV leakage current is the key to judge the operating condition of voltage limiting type SPD. According to the monitored object, it is divided into two categories: the method of full current and the method of resistive current. The full current is simple to implement, since the response sensitivity is low in the initial stage of SPD degradation, which is more common in some low-cost applications; the resistive current measurement method is more complicated to carry out, but can reflect the degradation trend of SPD sensitively and accurately, which is usually applied in some high demand schemes. The measurement methods of resistive current mainly include: active loss, compensation, phase, and harmonic analysis. This paper introduces several methods of leakage current testing, and analyzes the characteristics of various methods. Through a series of experimental data, the measured leakage current data is used to analyze the degradation trend of SPD.