A Simplified Decoupling Method for Phase-to-Phase Interference to the Resistance Leakage Current of Metal Oxide Varistors

Metal oxide varistor (MOV) is widely used to protect power equipment from overvoltage impact in substation. The MOV can be degraded during the operation and it is important to monitor its status. Resistive current is calculated from leakage current and has much higher sensitivity to evaluate the status of MOV. However, there are some inevitable interferences which influence the calculation accuracy of resistive current. The phase-to-phase interference is one of these influence factors and induced by the coupled capacity of adjacent MOVs, which makes the phase position of leakage current lagging or leading the real phaser. This phenomenon can make the calculation of resistive current much smaller or larger than the real value, which should be corrected. In this work, a simplified decoupling method was proposed to remove the phase-to-phase interference to leakage current induced by adjacent MOVs. Field experiments were conducted in a 500 kV substation. The proposed method was verified by applying to the field data and comparing with measurements with other monitoring devices.