High-Impedance Fault Pilot Protection Method Based on Zero Sequence Current Comparison in Low-Resistance Grounding Distribution System

China's urban distribution network lines are increasingly being cabled, and more and more large and medium-sized cities are using low resistance neutral grounding mode. When the zero-sequence current is lower than the activation value of conventional zero sequential current protection, faults in single-phase low-resistance grounding systems may not be protected. In order to address this problem, a zero-sequence network analysis is used in this paper to determine the features of one-phase ground faults in low resistance grounding systems. As a result of the results, it appears that the transition resistance does not have a significant influence on ration of zero serial current flow across the busbars on either side of the trouble spots. Regardless of the trouble spots, the ratio is always greater than 15, so it is chosen as a protection criterion to construct a pilot protection method for high resistance earth fault in a low resistance earthing system based on zero serial current ratios. Finally, PSCAD simulations are used to verify the correctness of the method and the capacity to withstand transitional impedance above 1kΩ was demonstrated.