A Single-Phase-to-Ground Fault Detection Method Based on the Ratio Fluctuation Coefficient of the Zero-Sequence Current and Voltage Differential in a Distribution Network

Abstract

Because the traditional zero-sequence overcurrent protection method is not effective in detecting single-phase-to-ground faults (SPGF) in a low-resistance grounded system (LRGS), this paper analyzes the fault characteristics of a 10-kV LRGS in detail. From the perspective of the time domain, the relationship between zero-sequence current and zero-sequence voltage is deduced, and the characteristics corresponding to faulty lines and nonfaulty lines are analyzed. The analysis reveals that the ratio fluctuation coefficients of the zero-sequence current to the differential zero-sequence voltage corresponding to faulty lines and nonfaulty lines have notably different characteristics; consequently, a high-sensitivity SPGF detection method is proposed. This method considers the existence of unbalanced loads and asymmetric parameters in the distribution network, can effectively identify high-impedance faults as high as 5000 $\Omega $ and nonlinear arc grounding faults, and can resist noise interference with a signal-to-noise ratio of 20 dB. Finally, many simulations and comparisons based on PSCAD/EMTDC verify that the proposed detection method has better applicability than the existing methods in detecting high-impedance SPGFs.

Keywords

• Low-resistance grounded system
• single-phase-to-ground fault
• fault characteristics
• fault detection
• fluctuation coefficient