In order to suppress the arc of the single-phase-to-earth fault in neutral point non-effectively grounded system

the operation which switches the fault phase to the earth has been widely used. The prerequisite of this method is to identify fault phase correctly in one cycle. However

the traditional fault phase identification method based on steady process is prone to failure in the case of grounding fault via intermittent arc. This paper analyzes the defects of the conventional methods

establishes the equivalent model of distribution network

and derives the transient time domain expression of the three-phase voltages after the arc extinguishing. The multi-scale wavelet transformation is used to extract the transient high-frequency components of three-phase voltages. A novel method is proposed to identify the fault phase by calculating the amplitude and phase characteristics of the high-frequency components and the conventional methods are combined with this novel method. The simulation results prove the effectiveness of the proposed identification method.