Analysis Of Transient Negative-sequence Component Of The Large Half-speed Turbine Generator At Internal Phases Short Circuit

In order to solve the key technology of AP1000type million-kilowatt-class half-speed turbine generator design, in combination with the sub-topics of major projects of national science and technology," Large-scale advanced pressurized water reactor and high temperature gas cooled nuclear power plant" topic "Electromagnetic programs and structural design technology research of large-scale nuclear power half-speed turbine generator"—key technology research of large half-speed turbine generator (No.2009ZX06004-013-04-01),transient negative sequence component calculation of the large half-speed turbine generator is analyzed.The basic principle of negative-sequence current and the harm of negative-sequence to generator are analyzed in this thesis. From the definition of transient negative-sequence capability and characteristics of the rotor transient fever, the inner link of short-circuit current and rotor instantaneous heating in fault is analyzed. Due to the shortage of traditional transient negative-sequence formula, the synthetic magnetic field which the non-periodic components of three phase current generate when short circuit occurs is introduced into the calculation. The non-periodic component of rotated relative to the rotor is added into the improved formula of transient negative-sequence.According to the winding configuration mode, possible position of the internal short-circuit is analyzed. Two shorted branches is selected, internal short-circuit is simulated on the basic principle of field-circuit coupling. Then harmonic content of three phase steady current is analyzed. The negative-sequence current is calculated. Unbalanced and steady negative-sequence capability current which happens in two short-circuit branch in the different location is achieved. The current in frequency domain can not be analyzed at the same time because of the limitations of the Fourier transform algorithm. The wavelet transform method is used to analyze a short-circuit transient current in this thesis, the portion of non-periodic component and periodic component fundamental wave of the transient current are achieved, the high-order harmonic component and decreased periodic component is removed.the transient parameter of the internal short-circuit generator is calculated on the principle of transformed current waveform. Furthermore, the transient negative-sequence component of the generator is calculated in two branches internal short-circuit, which provides a theoretical basis for the protection of large-scale generators.