Based on analyzing various single-phase-to-ground faults in the non-solidly grounding system

the system’s zero-sequence voltage and the lines’ zero-sequence current are analyzed by using phrase locus.A new method using phase locus method to determine the fault line is presented

it is simple to realize

and it can gain an easy understanding result

even more

it is free of the CT polarity.The principle can be applied to neutral point non-grounding system and neutral point ineffective grounding system and determine the fault line accurately even when intermittent arc ground faults occur.The phase locus method is more easily achieved than other methods.Simulations of various ground faults under different conditions are performed by using MATLAB.The results show the method is feasible and effective.