Research On Electromagnetic Problem Of Hydro-generator Stator Winding Internal Faults

When the internal faults of hydro-generator Stator Winding has happened, itwill produce enormous destructive power. That will cause serious influence onthe generator itself and even the stable operation of power system. Therefore,hydro-generator must be configured effective main protection scheme, in order totimely detect the internal fault of hydro-generator. Usually generator mainprotection must action after the internal fault happened0.02s, however thetransient process of the generator is not over yet, so that need to accuratelycalculate hydro-generator stator winding internal fault transient process.The method of FEM coupled with electric circuit was applied in thisdissertation and the model of SF600-42/1308large hydro-generator-transformer-Infinite grid was built. Firstly, in the no-load condition, sudden three-phase shortcircuit fault currents of this generator were calculated, and the results wereverified by classical analytic formula method. That proved the method and modelcorrectly of this dissertation.The second, still keeped generator for no-load condition, the fault branchcurrent、short circuit ring current、field current and non-fault branch currentwere calculated of turn to turn short-circuit、branch to branch short-circuit faultin the same phase and branch to branch short-circuit fault in the different phase.After that, this dissertation analyzed the harmonics content of current waveformand revealed the characteristics of each branch current after the internal faults.The fundamental amplitude of branch currents were compared of correspondingmulti-loop method analytical results, which verified the accuracy ofmathematical model analyzed internal faults proposed in this dissertation.Furthermore, this dissertation also analyzed laws governing the fault currents ofabove three kinds of internal faults changing with the short-circuit turns ratio (difference), and the position of internal faults and the moment of internal faultsoccurring influenced on fault branch currents were studyed. It can be thetheoretical support for well configuring main protect of hydro-generator.Finally, based on turn-to-turn short circuit, the damper windings eddycurrent waveforms were calculated at the rated load condition. Meanwhile, thereason of eddy current caused was analyzed, and revealing the characteristics ofthe eddy current waveform. And the damper winding pitch、 the radius ofdamping bar and the connection mode of damping system that affected theamount of internal fault currents were studied in this dissertation, which providereferences for further study the eddy current of damper winding after an internalfault.