Grounding Protection of flexible grounding systems Based on Polarization of Faulty Phase Voltage

Abstract

At present, the grounding protection of flexible grounding systems mostly follows the common protection methods of the low-resistance grounding system, and there are problems of insufficient adaptability and utilization of fault information. In the paper, We analyze the fault characteristics of flexible grounding systems after grounding faults, find that when a high-impedance grounding fault happened, after the low-resistance is connected to the Petersen Coil, the phase characteristics between the zero-sequence of voltage and current of flexible grounding system is similar to that of low-resistance grounding system when grounding faults happened, at this time the faulty phase voltage amplitude is far more than the zero sequence voltage and the phases of the two are opposite. Based on this, a flexible grounding system grounding fault location method using the phase relation between zero sequence current of lines and faulty phase voltage is proposed. By taking advantage of the mature phase selection technology of the resonant grounding system, selecting the faulty phase in the compensation stage of the Petersen Coil. When the low-resistance is in parallel, the faulty phase voltage is used to compare the phase with the zero sequence current of lines, which solves the problem that the zero sequence voltage is weak and difficult to measure when the high impedance grounding fault occurs. Simulation experiments and field tests show that this method can improve the reliability of high-impedance grounding protection, and the method can be used as a backup protection for zero sequence overcurrent protection to meet field requirements.