High Impedance Grounding Fault Detection in Resonance Grounding System Based on Nonlinear Distortion of Zero-sequence Current

When the high-impedance grounding fault (HIGF) occurs in the resonant grounding system, the fault current is weak, and the traditional relay protection device cannot identify and remove the fault reliably. A HIGF detection method based on nonlinear distortion characteristics of zero-sequence current is proposed in this paper. When a HIGF occurs, the zero-sequence current waveform is distorted near the zero-crossing point; hence the linear correlation coefficient between the zero-sequence current and the time is small, while the distortion degree is big. For the zero-sequence current caused by other reasons, its waveform is close to a straight line near the zero-crossing point, and the linear correlation coefficient is big and the distortion degree is small. Based on this feature, the identification criterion of HIGF is given. Moreover, the zero-crossing point localization method is proposed to deal with the zero-crossing point deviation caused by attenuation DC component and waveform distortion. Simulation results show that the proposed algorithm has high accuracy and sensitivity.