Abstract：In order to resolve the selective protection for Powerformer with more than one generator directly connecting a bus, the characteristics of the stator winding phase-to-ground zero-sequence current (zero-sequence fundamental component and third-harmonic fault component) are analyzed in this paper. Through comparing the direction of zero-sequence currents, magnitude of zero-sequence currents, and fault point energy dissipation, the stator grounding faults can be detected occurred in generator stator winding or not. Simulation results show that the fundamental component and the third-harmonic fault component of leakage current are combined to realize 100% coverage of fault detection for the stator windings of powerformer. What’s more, the protection can distinguish the single-phase earthed fault occurred in stator winding or outside of generator, and can detect stator ground faults in which generator with high sensitivity and selectivity.
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2013, Vol. 14 
