A digital technique for stator winding protection of synchronous generators

This paper describes a digital technique for detecting internal faults in stator windings of synchronous generators. The technique uses positive- and negative-sequence models of the synchronous generator, and voltages and currents measured at the generator terminals. It does not need information concerning the machine parameters and is applicable to all types of generators, irrespective of their size. Fault discrimination characteristics and a digital algorithm based on the proposed technique are described. The performance of the proposed technique was evaluated using fault data generated by simulations using an electromagnetic transient program, EMTDC. Fault data were also acquired by subjecting a laboratory generator to internal and external faults. Results of the studies using simulated and experimental data are included in the paper. The results indicate that the proposed technique can detect faults including open circuits and faults that short-circuit windings of one phase.