Abstract: In view of the waveform of the fault signal and the signal amplitude are close when the arc suppression coil compensates the line in theant grounding system with a single-phase grounding fault, it is difficult to distinguish the line from the line, which leads to the difficulty of line selection. A method of selection using CEEMD and wavelet packet decomposition and fractal box dimension algorithm is proposed. Firstly, the CEEMD algorithm can effectively reduce the modal alias of the line. Secondly, the wavelet packet algorithm has a good denoising effect on the line decomposition. Finally, the appropriate iteration analysis tree is selected for box dimension calculation to describe the calculation of the line characteristic quantity, and the characteristic value is calculated. In this paper, the fault model is constructed by MATLAB, and simulation of the resonant grounding system can effectively identify the fault line after the single-phase grounding fault, which verifies the effectiveness of the proposed algorithm.