Line selection method for grounding fault in resonant grounding distribution systems

To solve the problem of low accuracy of line selection when grounding fault occurs in a small current grounding system, a new method for single-phase grounding fault line selection in resonant grounding system is proposed. By analyzing the characteristics of zero-sequence current and zero-sequence impedance of different lines, it is found that the zero-sequence impedance of the healthy line is always capacitive, and the zero-sequence current is the pure capacitive current. But the zero-sequence current of the faulty line contains the inductive component of the arc-suppression coil in the low frequency band, and the amplitude is greater than that in the high frequency band. Firstly, the low-pass filter is used to extract the signal component of the bus zero-sequence voltage and the zero-sequence current of each feeder in the low frequency band, and the bus zero-sequence voltage is derived. Then it compares the difference between the product of the zero-sequence current and the pure capacitive current of any two lines. The one which has largest difference is the fault line. Simulations of single-phase ground fault under different working conditions have been done. The results show that the method is accurate and adaptive. © 2019, Power System Protection and Control Press. All right reserved.