Measurement of the resistive current of MOA based on an improved equivalent model

摘要

Most of the methods available for the resistive current of metal oxide surge arrester are based on a simplified equivalent model, which consists of a nonlinear resistance in parallel with a constant capacitance, and there always exists a phase discrepancy between the resistive current and the applied voltage, it may be caused by the nonlinearity of the equivalent capacitance. In this paper, an improved equivalent model consisting of a nonlinear conductance and a nonlinear capacitance in parallel is presented. A new time-domain resistive current method is then proposed. The time-domain equations of every current component on the applied voltage are deduced based on the improved model. The circuit parameters in these time-domain equations are calculated by least square and then are substituted into the time-domain equations to obtain the resistive current and the capacitive current. The capacitive current compensation method and the proposed method are used to obtain the resistive current and to study the influence of the nonlinearity of the conductance and capacitance on calculation accuracy. The simulation results show that the proposed method have little error when the applied voltage and the total leakage current are noiseless. The resistive current obtained by the proposed method is in phase with the applied voltage, there no exists a phase discrepancy between them. Besides, the proposed method is hardly affected by the nonlinearity of the equivalent model.