Influence of power system´s harmonic voltage on leakage current of MOA

Surge arresters are important over voltage protection equipment in a substation. It is necessary to monitor the resistive leakage current of MOAs (metal oxide surge arresters) on line so that we can prevent faults from developing in time to avoid economic loss. It is reasonable to adopt the resistive leakage currents basic component, i/sub r/, and thrice component, i/sub 3r/, as metal oxide surge arrester indicators. These indicators can detect the aging phenomenon of a metal oxide surge arrester in time. However, the existence of harmonic voltages in the power system influences the indicator accuracy. We analyze this effect and put forward an improved compensation method to separate the resistive leakage current under the existence of harmonic voltage. Finally, according to these methods, we develop an on-line MOA resistive current monitoring system based on the bus-module.