Through the analysis of MOA AC V-I characteristics

it is found that with voltage increasing

the harmonic contents of resistive current is increasing bigger than that of first-harmonic

and the increasing of the magnitude of first-harmonic is well-proportioned. Some simulation of the effect of voltage fluctuation on MOA leakage current is made according to MOA AC V-I characteristics

which shows that resistive current and its harmonic contents change linearly with voltage fluctuating; and the first-harmonic of resistive current varies little

the third-harmonic of it does big. So the first-harmonic detection of resistive current is critical in the MOA leakage current detection.