The basic harmonic resistive current ir and the third resistive current i3r generated by the basic voltage can reflect the MOA’s operation state.The capacitive current in the full current can be effectively removed through the improved capacitive current compensation method

but the resistive current generated by the harmonic voltage still exists in the full current.So the extraction accuracy of ir and i3r is influenced

especially for the larger error of i3r.In order to resolve this problem

the modified method of the improved capacitive current compensation method is proposed in this paper.The resistive current generated by the harmonic voltage is partially compensated by the use of one equivalent linear resistor

which can reduce the error generated by the harmonic voltage and improve the extraction accuracy of i3r.The simulation analysis result shows that the error of i3r is reduced by half through the modified method and the effectiveness of the proposal algorithm is verified.Therefore

the accuracy of MOA fault diagnosis based on ir and i3r is improved.