A Grounding Fault Protection Method for Low Resistance Grounded Distribution Networks Based on Capacity Current

When a single-phase grounding fault occurs in a low resistance grounded distribution network, the threshold for zero-sequence overcurrent protection is often set based on the principle of avoiding the maximum capacity current of the non-fault line. Due to the high threshold value, the protection will refuse to operate under high resistance grounding conditions. This paper proposes a grounding fault protection method for low resistance grounded distribution networks based on capacity current compensation on the basis of the existing zero-sequence overcurrent protection. This method serves as a backup protection for the existing overcurrent protection. When the low resistance grounding fault occurs, the existing protection operates. When the high resistance grounding fault occurs, the existing protection refuses to operate. The zero-sequence current of each outgoing line is compensated using the bus voltage and line capacity parameters, and the ratio after and before compensation is calculated. By comparing this ratio with the protection threshold in this paper, reliable operation of the protection in case of high resistance grounding faults can be achieved. After theoretical derivation and model simulation, this method can cope with stable grounding faults and the ability to handle fault resistance can reach about 4000.