It is difficult to diagnose the stator ground fault caused by a faulty terminal capacitor with the help of detecting insulation resistance. The corresponding mechanism is analyzed first based on the equivalent circuit of stator ground fault. Three-phase reference composed of stator voltages is adopted to make a comparative analysis on the phase characteristics of zero sequence voltage

which can be used to discriminate the stator ground fault caused by a faulty terminal capacitor or grounding transient resistance. And a practical method is proposed based on the foregoing characteristics. In this approach

the position of zero sequence voltage in the three-phase reference can be judged by voltage waveforms from the wave-recording device. Furthermore

the winding capacitance to ground and grounding resistance of the neutral point should be utilized to realize rapid diagnosis. Finally

the effectiveness of the proposed approach is verified through a relevant fault example.