In view of the difficulty of single-phase earthing fault line selection in the neutral non-earthing faulty phase of bus and access to the small resistance of the neutral point so to select the faulty line. The zerosequence network model of various stages is set up during the fault transfer stage and before and after switching the shunt resistor. The variation characteristics of respective zero-sequence current amplitude for sound and faulty lines are analyzed. The variation of zero-sequence current amplitude of each feeder is significant sequence current of the sound line significantly decreases after the opening of the bus switch

while the zerosequence current of the faulty line increases. A fault line selection criterion of non-earthing systems is constructed by using the zero-sequence current variation characteristics of the faulty and sound lines. The good adaptability of the method for single-phase earthing faults in non-earthing systems is verified by a large number of simulation calculation

which helps to improve the accuracy of fault line selection further.