Influence of rotor capacitance in on-line rotor ground fault location method for synchronous machines with static excitation

This paper presents results about the influence of rotor capacitance in the on-line rotor ground fault location method for synchronous machines with static excitation. The location method is based on the measurement of the voltage in a grounding resistance, connected to the neutral of the excitation transformer. Due to the effect of the rotor capacitance to ground on large synchronous generators, it is observed that waveform of the neutral voltage is perturbed, and it causes an error in the fault location in case of defect in the DC side. Firstly, the influence of the fault resistance value and the fault position is evaluated through computer simulations. Then, the impact of the rotor capacitance in the accuracy of the detection and location method is analyzed in case of ground fault, as well as in healthy operating condition.