High-Sensitivity Zero-Sequence Pilot Protection for High-Impedance Faults in Low-Resistance Grounded Distribution Networks

Abstract

Reliable detection and rapid isolation of single-phase-to-ground faults (SPGFs) in low-resistance grounded systems (LRGSs) are critical for power utilization safety. However, the conventional zero-sequence (ZS) overcurrent protection method exhibits significant limitations in speed and sensitivity under arcing or high-impedance faults (HIFs). This paper presents a dual-criteria-based pilot protection scheme for HIFs in LRGSs using ZS distribution characteristics. The characteristics of the ZS admittance ratio at the fault point for SPGFs are analyzed, whose minimum value is significantly greater than that at unfaulted points under any situation. The ZS admittance ratio at both ends of the fault section further amplifies the above fault features based on the ZS voltages/currents distribution, which serves as the primary criterion for protection design when protective relays at both terminals are activated. The auxiliary protection logic, a supplementary criterion under HIFs or terminal faults, is triggered by a rise in the single-ended ZS impedance during internal faults. The MATLAB/Simulink simulation and the real-time digital simulator (RTDS) hardware-in-the-loop (HIL) test demonstrate that the proposed scheme achieves a fault resistance tolerance of 4 kΩ within one power-frequency cycle. Moreover, it maintains reliable performance under challenging conditions, including arcing faults and the integration of distributed generators.