Fault line selection research for resonant grounding system based on HHT detection and injection method

This paper aims at the transient fault line selection method maybe invalid when the single-phase ground fault occurs at the moment of phase voltage through zero. Author proposed a method by using transient method and injecting signal method's complementary advantages. HHT has a clear physical meaning for dealing with nonlinear, nonstationary signals, so author decomposed the transient current signal using HHT's EMD and made denoise by wavelet before decomposition. When the phase voltage through zero, author decomposed the fault and nonfault signals using EMD, and used the fault line's high-frequency component's polar was opposite to the nonfault line at singularity dot to select the fault line; however, when the phase voltage through zero, the transient current signal is weak, this time author used the method of injecting into the low-frequency signal and detecting it to select the fault line. At last, author simulated the distrubition system including three lines and one cable-line mixed line using Matlab/simulink, and comfirmed combined method is valid to various single-phase ground fault.