Influence of generator load conditions on voltage 3rd harmonics in generator stator winding

Summary form only given. The influence of changes in load conditions of the generator-transformer unit on the operating conditions of the 100% ground-fault protection of the generator stator winding based on the 3rd harmonic voltages were analyzed. The analyzed stator ground-fault protection system is by ratio of the voltages 3rd harmonic in generator neutral and at the generator terminals. The 3rd harmonic voltages were determined on the base of the experimental tests (measurements) run in real conditions at changes in active and reactive load conditions of the generator. It was found that mainly the generator active load influences the voltage feeding the measuring element of ground-fault protection. Therefore determining operating conditions of ground-fault protection the influence of the generator active and reactive load should be deeply considered. This can ensure the proper operation of the ground-fault protection based on the voltage 3rd harmonics in the whole range of the changes in generator load. Considering of the influence of changes in generator load on the 3rd harmonic voltages (feeding measuring element of the protection system) will allow eliminating irregular generator tripping as a result of unselective operation of these protections.