A Flexible Power Source-Based Method for Stator Ground Fault Detection in Large Generators

To address the issues of low sensitivity, high misjudgment rate, and insufficient adaptability in stator grounding fault detection in large generators with neutral-point non-effectively grounded systems, this paper proposes a stator ground fault detection method for large generators based on an externally applied flexible power source. Firstly, by flexibly regulating the neutral-point voltage, a fault-phase identification criterion is established. A phase selection method based on the admittance angle phase shift is introduced, where a 120° phase difference between the admittance angles of the faulty and non-faulty phases under neutral-point potential offset is utilized to construct a phase selection interval. This approach overcomes the failure of traditional voltage magnitude-based criteria in the presence of high-resistance grounding faults at the generator terminals. Secondly, during shutdown, a novel method is employed in which a low-frequency signal is injected using a flexible current source. Based on the current difference between the two ends of the fault branch and combined with a bisection-based measurement strategy, the method achieves rapid identification of the fault branch and precise location of the faulted stator bar. The proposed method is validated in the PSCAD simulation environment, and the results demonstrate that it can accurately identify the faulted phase and locate the fault, thereby improving the reliability of fault location.