Two-point out-of-phase grounding protection method for low resistance grounding system based on zero sequence impedance

The existing protection system for low-resistance grounding systems is susceptible to malfunctions, leading to potential electric shock and electrical fires when single-phase-to-ground faults (SPGFs) occur between two points on a single circuit line. To address this issue, this study first establishes a mathematical model for SPGFs between two points on a single circuit based on ideal transformer theory and multi-port network theory. The paper analyzes voltage and current characteristics during such faults and identifies characteristic changes in the zero-sequence impedance angle. Building upon this analysis, we propose a protection criterion grounded in the zero-sequence impedance angle and present a method for safeguarding against SPGFs in low-resistance grounding systems. Subsequently, a simulation model is constructed using the Power Systems Computer Aided Design (PSCAD) software, and comprehensive simulations are conducted for three scenarios: low resistance, high resistance, and intermittent arc grounding. Simulation data demonstrate that the proposed method remains unaffected by transition resistance or fault location. It effectively detects SPGFs between two points on a single line, thereby confirming the precision and efficacy of this proposed approach. In conclusion, the author asserts that this method is both accurate and highly effective.