Research on leakage current characteristic of metal oxide varistor

Abstract

MOA (Metal Oxide Arrester) has been widely used in the world because of its excellent nonlinearity, long-lasting anti-aging properties and excellent overvoltage protection performance. The performance degradation of the MOV occurs in the long-running process because of environmental reasons, so the online monitoring system for the MOA has a great significance for the stable operation of the power system. With the improvement of MOA manufacturing technology and the adjustment of the resistance sheet formula, the state parameter's characteristics of MOA had changed obviously. The traditional MOA state detection method could not guarantee the validity and correctness of the test. MOV (Metal Oxide Varistor) is the core component of MOA. The state change of MOV can partly reflect the changes of MOA. In this paper, six typical ultrahigh pressure MOV from two manufacturers are experimented separately to obtain resistive fundamental harmonic leakage current, resistive third harmonic current and continuous current of the MOV under different conditions. We extract the most obvious changes in the current component as a reference that can detect the fault type of MOA. In this paper, we study the three factors: Electric load rate, temperature and damp. The experimental results show that: (1)When the continuous operating voltage changes, the resistive third harmonic currents of the MOV is the highest of the three leakage currents.(2) The change of continuous current caused by damp is related to the surface condition of MOV, if the surface of MOV is in good condition, the continuous current does not change significantly; if the surface of the MOV damaged, the continuous current resistive component of MOV will change significantly (3) In the MOV temperature test, the MOV heated from 20 degrees Celsius gradually to 80 degrees Celsius, we tested the resistive fundamental harmonic leakage current, the resistive third harmonic current and the continuous current of the MOV. With the change of the temperature, the resistive third harmonic current and the continuous current change not obviously. At the same time, the resistive fundamental harmonic leakage current changed obviously, So the resistive fundamental harmonic leakage current can reflect the temperature change of the MOV.