Rotor Ground Capacitance Coupled Harmonic Fault Detection Boundary in Large Synchronous Generators

Abstract

Focusing on the impact of rotor-to-ground capacitance on passive ground fault detection in large-scale synchronous generators, this paper proposes an error analysis method using an amplitude deviation factor. Based on the classical equivalent circuit model of the excitation system, the proposed method explicitly incorporates the rotor-to-ground capacitance parameters. It systematically reveals the non-linear mechanism by which ground capacitance affects the harmonic voltage amplitudes of faults on both the DC and the AC sides. This study addresses the limitations of existing research, which is primarily confined to small and medium capacity machines and often neglects the ground capacitance. Verified by computer simulations and field data from large-scale units, the results demonstrate that the proposed method effectively clarifies the detection boundaries and improves fault detection accuracy in high-capacitance scenarios.