The key to the detection of MOA resistive current is the detection of the phase difference between fundamental component of voltage and fundamental component of leakage current.Based on the analysis of conventional phase difference detection method

a new algorithm of phase difference detection is presented according to Fourier series decomposition method and the characteristic that inner product of two orthogonal vectors in a linear space is zero.The algorithm calculates the phase of fundamental component of voltage and the phase of fundamental component of leakage current

respectively

and then calculates their difference.Furthermore

the calculation principle and discrete calculation formula of the algorithm is introduced.Higher-order harmonic and white noise can be suppressed and filtered simultaneously by the orthogonal calculations in the algorithm.Correctness and validity of the algorithm are verified through simulation and MOA resistive current test.This algorithm is simple to implement without determininge the crossing zero point

and can remove the interference of harmonic voltage in calculation with a high precision.