A line selection method for single phase ground fault in coal mine power supply system based on wavelet packet

In view of problems of low accuracy and poor reliability of line selection methods for single phase ground fault in existing coal mine power supply system, a line selection method for single phase ground fault in coal mine power supply system based on wavelet packet was proposed. At first, transient zero modal current of each line is decomposed by wavelet packet, the lowest frequency band containing steady power frequency is eliminated, and sum of wavelet packet energy of each frequency band is calculated and sorted. And then, characteristic frequency band of each line is selected based on principle of the maximum energy, the line with opposite polarity is identified as fault line by comparing polarities of the modulus maximum of the wavelet packets decomposition coefficients of characteristic frequency band of lines. The double criteria for fault line selection of single phase ground fault can be formed by the different characteristics of transient zero modal currents between fault line and non-fault line, which overcomes the problem that single criteria may not select fault line correctly. The simulation experiments results prove correctness and effectiveness of the method.