Rotor ground-fault diagnosis methods for synchronous condensers based on amplitude and phase-angle of voltage

Abstract

A single ground fault of the rotor windings in a synchronous condenser can cause serious damage if the fault is not eliminated in time. This paper proposes a new rotor ground-fault diagnosis method for synchronous condensers based on the amplitude of the 150 Hz component of the voltage across a grounding resistance (GR) placed in the neutral of an excitation transformer. It can be seen that the amplitude of the 150 Hz component of the voltage across the GR increases with a decrease of the ground-fault resistance (GFR). This method is an improvement of existing algorithms for rotor ground-fault detection that requires less analyzing and can achieve online detection of the severity of a rotor ground fault at any point of the excitation winding. In addition, the influence of different excitation voltages on the algorithm based on phase-angle is analyzed considering actual working characteristics. Moreover, a model is built in the MATLAB/Simulink platform using the real parameters of a TTS-300-2 synchronous condenser to verify the effectiveness of the proposed method. Finally, a dual diagnostic criterion is given according to the results of simulations. The research conclusions can have a great significance on the healthy running of synchronous condensers and they can help to drastically reduce both cost and repair time.