A novel 20Hz power injection protection scheme for stator ground fault of pumped storage generator

Based on the analysis of the start-up of pumped storage generator under motor circumstance, it is found out that the conventional 20 Hz injection component is influenced by the low frequency component when ground faults take place in the stator windings for static frequency converter (SFC) start-up generator. The conventional relay is just simply blocked in case mal-operation during 20 Hz working condition. To overcome the disadvantage, a novel scheme is proposed to improve grounding- resistance(R) calculation accuracy and enhance ability to limit impact of 20 Hz component from generator. The simulation results proved its effectiveness and practicability of the scheme.