The invention discloses a method for judging a single-phase grounding fault of a small-current grounding
system, which is characterized in that single-phase grounding fault judgment is started according to a sudden change in
electric field intensity and a sudden change in phase current, the fault starting time is accurately determined by using a
morphological gradient method, and accurate synchronization of three-phase current is realized; filtering is performed on
transient current signals so as to determine the
duration time of a transient process, and the characteristic frequency of the
transient current is calculated by using an autocorrelation method; a grounding fault is positioned according to the correlation of
transient current of a fault phase and transient current of a non-fault phase, and detection for a single-phase grounding fault of a small-current grounding
system applied to a
fault indicator is realized. The method disclosed by the invention is not affected by the operating mode, the grounding site, the
grounding resistance or the like, and on-site tuning and debugging are not required compared with a threshold comparison method adopted by the existing
fault indicator, so that the fault judgment accuracy can be greatly improved, a problem of low
false alarm and alarm omission rate of the existing
fault indicator is solved, and the feeder
automation level is greatly improved.