If the arbitrariness of the asymmetrical voltage direction is ignored

it is impossible to accurately describe the trajectory of neutral point displacement voltage varying with the transition resistance when a single-phase grounding fault occurs in the distribution network. Considering the conductance of ground leakage and the direction of asymmetrical voltage

an accurate model of single-phase grounding fault is established. In the incomplete compensation state

the trajectory of neutral point displacement voltage varing with transition resistance is a circular arc; in the full compensation state

the trajectory of neutral point displacement voltage varied with transition resistance is a straight-line segment. According to the analysis: the amplitude of fault phase voltage decreases after grounding

the fault phase voltage after grounding is ahead of the phase voltage before fault in the under-compensated state

the fault phase voltage after grounding lags behind the phase voltage before fault in the over-compensated state

the voltage of the fault phase before and after grounding remains unchanged in the fully compensated state. By comparing the relative change of amplitude and phase of three-phase voltage before and after fault

the grounding fault phase can be identified. Finally

the analysis are verified by MATLAB/Simulink simulations.