The invention discloses a neutral point non-effective
earthing system single-phase earthing fault identification method which includes the steps that a zero sequence
voltage instantaneous value and a instantaneous saltation value are taken as the startup criteria of an
identification scheme; when any of the above values is out of the limit, an identification process is started, a saltation moment is determined according to a
signal saltation point, and the effective values of the zero sequence voltages and the three-phase voltages in cycles before and after the
signal saltation point and the variations of the effective values are calculated; and a single-phase earthing fault is judged to have happened only when the variation of the zero sequence
voltage and the variations of all phases of
voltage all satisfy all the criteria. The method takes
voltage variation for identification, and the saltation of the state of the
system can be reflected; a low threshold value scheme is adopted in the method, so the
system can be started sensitively under a
high impedance fault; and the
multiple criteria scheme of zero sequence voltage and three-phase voltage are adopted, so the method has high reliability. The method is simple and easy to realize.