Abstract: Abstract: Low resistance grounding system, it is difficult to be identified when high resistance grounding fault occurs. In view of this problem, the electrical characteristics of single-phase grounding fault are analyzed, the active component of zero sequence current of faulty line and non-faulty line compare respectively with that of neutral point, which shows that the ratio differs a lot and the difference has a little relation with the transition resistance. Based on this, high resistance grounding fault can be identified and quickly isolated in the early stage of high-resistance grounding fault. The simulation model is built on PSCAD, and the simulation results verify that the scheme is reliable.