An Approximate Single-Line-to-Ground Faulted Feeder Identification Method for 35 kV Resonant-Grounded Distribution Networks Based on Cross-State Apparent Admittance

Single-line-to-ground (SLG) faults are the most frequent fault type in medium-voltage distribution networks. In 35 kV networks equipped with Y/Y/Δ transformers, the zero-sequence coupling with the transmission grid and inherent line asymmetry make reliable SLG faulted feeder identification highly challenging, especially under high fault resistance. To address these issues, this paper proposes an approximate cross-state apparent admittance method for identifying SLG faulted feeders in 35 kV asymmetric distribution networks. First, the pre-fault and post-fault zero-sequence current responses are analytically derived, accounting for the structural asymmetry of feeder phase-to-ground parameters and the neutral grounding branch. Then, a cross-state apparent admittance formulation is established using synchronized zero-sequence voltage and current phasors. Considering that the proposed criterion relies on the phase relationship of cross-state apparent admittances, its practical implementation requires a high-accuracy synchronized voltage and current measurement loop. Measurement-class CTs/PTs or equivalent high-precision acquisition channels are therefore recommended to ensure sufficient phase-angle accuracy for the admittance-plane criterion. For healthy feeders, the apparent admittance is represented by the inherent zero-sequence line-to-ground admittance under the adopted bus-voltage measurement configuration. For the faulted feeder, the nonlinear coupling term associated with the fault resistance is rigorously eliminated through system-level Kirchhoff’s current law analysis, yielding a fault-resistance-independent analytical expression. A quadrant-based identification criterion is subsequently developed in the complex admittance plane. Finally, a simulation model based on the real architecture and parameters of an actual 35 kV substation is established in PSCAD/EMTDC. The simulation case studies demonstrate that the proposed method can identify the faulted feeder under the tested severe-asymmetry and high-impedance fault conditions up to 10 kΩ, provided that sufficiently accurate synchronized zero-sequence voltage and current phasors are available. In the simulation model, the zero-sequence voltage is measured at the bus or neutral grounding branch, and the feeder zero-sequence currents are measured at the outgoing feeder branches.