A Current Orthogonality Method to Extract Resistive Leakage Current of MOSA

A new resistive current extraction method based on orthogonality between the capacitive current and the resistive current (COM) is presented. Orthogonality of the resistive and capacitive current of metal-oxide surge arrester (MOSA) in the low current region is proven. The resistive and capacitive current of MOSA can be obtained accurately, regardless of the harmonic voltage. Several algorithms include the point-on-wave method, the capacitive current compensation method, the harmonic analysis method, and the proposed method are used to extract the resistive current based on simulated voltage and leakage current signal, and to study the influence of MOSA model parameters, capacitance, integral harmonics, and noninteger harmonics of voltage signal, the signal frequency deviation, and the offset in sampling time between current and voltage channels on calculation accuracy. The result indicates that the proposed method has no error if the voltage and current are noiseless, but gives rise to a small error even if the signals have noise. The proposed method is more accurate than other methods. The real voltage and leakage current signals of a 10-kV MOSA are acquired by experiment, and the result indicates that the proposed method is effective and the most stable.