Fault Line Detection Method for Flexible Grounding System Based on Changes of Phase Difference Between Zero Sequence Current and Voltage

At present, the definite time limit zero sequence overcurrent protection is mostly used in the flexible grounding system, but it is easy to be refused when high resistance grounding fault occurs. A line detection method is proposed in order to solve this problem. This paper analyzes the features of electrical quantity changes before and after the input of the parallel resistance, i.e., the phase difference between zero sequence current of the non-fault line and zero sequence voltage of the bus bar remain constant, but for the fault line, this phase difference changes. Besides, it is found that the transition resistance only affects the phase change of zero sequence voltage of the bus, but has no effect on the phase difference between the zero sequence current of each line and the zero sequence voltage of the bus. The proposed method makes use of the change features of electrical quantity, and the fault line can be determined without using the electrical quantity of the other feeders. The simulation results show that the method is not affected by the transition resistance, and can still accurately select the fault line when the high resistance grounding fault occurs. © 2021, Power System Technology Press. All right reserved.