Abstract: The characteristics of system parameters were given when a single-phase-to-ground fault occurs in a neural ineffectively grounded system, and the principles and methods of present fault feeder detection devices were analyzed. The fault feeder detection method was investigated based on the ‘S injection' principle, and three methods were proposed to improve the accuracy of fault feeder detection, i.e., magnitude comparison of burst current, signal phase detection and double frequencies injection.

Key words: neural ineffectively ground, S injection, single-phase-to-ground fault, feeder detection