Effects of imbalance on single-phase to ground fault characteristics in low-resistance grounded systems

Single-phase to ground faults (SPGFs) are common in low-resistance grounded systems (LRGSs), a type of medium-voltage power distribution network (MVDN). Imbalance is one of the main characteristics of MVDNs. However, there has been little research on the effects of imbalance on SPGF characteristics in LRGSs, especially from the perspective of theoretical analysis. Hence, in this study, a controlled source-based simplified linear model suitable for calculating SPGFs in unbalanced LRGSs is proposed. Based on the model, the effects of unbalanced loads and asymmetrical lines on SPGF are discussed. The analysis results show that "zero-sequence (ZS) parameter intrusion" of loads is absent in LRGSs, and asymmetrical line parameters have a substantial effect on the phase angle between the ZS line current and the ZS bus voltage, which is related to the fault resistance, fault phase and line parameters. Finally, two phase-related detection methods are analyzed, and both methods produce erroneous detection results. Therefore, it is recommended that the effects of imbalance be considered when using detection methods based on the relationship between the voltage and current in LRGSs.