Analysis of Metro Station Grounding Fault Protection Design

［Objective］ Grounding fault protection has long been neglected due to the complexity of verification and calculation, leading to safety hazards in engineering design. Therefore, it is necessary to conduct an in-depth analysis of grounding fault protection in metro stations to ensure engineering safety. ［Method］ Considering the potential impact of external errors, the concept of grounding fault current multiple is introduced and compared with the trip range of circuit breaker tripping devices, so as to facilitate efficient sensitivity verification for grounding fault protection. Detailed calculations and analysis of actual data from metro stations are conducted, and the results are summarized to define the circuit range requiring sensitivity verification and determine the corresponding grounding fault protection configuration strategy. ［Result & Conclusion］ It is recommended that electronic trip units be used for substation feeder circuit breakers. By appropriately setting the short-time delay current value, the dual functionality for short-time delay protection and grounding fault protection can typically be achieved. For distribution box feeder returning circuits, grounding fault protection sensitivity verification should be performed based on specific conditions. Although the impact of incoming cables is relatively small, it still needs to be appropriately considered. The rated current of circuit breakers should be selected according to actual needs and should not be excessively high. The tripping curve must be reasonably chosen to ensure the performance. When using circuit breakers with grounding fault protection functions, special attention must be given to the coordination between upstream and downstream protection devices. Additionally, when circuit breakers are used for grounding fault protection in metro distribution systems, the maximum allowable length of copper core cables is provided for reference to relevant designers.