Research On The Field Winding Internal Faults Of Large Hydro-generator

When the internal fault of hydro-generator field winding happen, it willproduce enormous destructive power and will cause serious influence ongenerator and even the stable operation of power system. Field winding isdifferent from stator winding, the electrical load is low. Because small-scaleshort-circuit fault impact on generator is not obviously, the detection is difficult.Field current increasing, the asymmetry of the stator current and damper barcurrents increasing is caused by fault. Serious damage is caused at last.In order to reveal the change of the electric parameters of generator withshort-circuit fault, A600MW hydro-generator as example to study. A parametricfinite element model of hydro-generator in finite element software is built.Firstly, the simulation result is compared with electromagnetic design toprove the model correctly and provide the contrasting evidence.Secondly, the generator is solved with field winding short-circuit fault in no-load condition and load condition. The harmonic magnetomotive force with faultis analyzed and the harmonic current is obtained by Fourier decomposition.Harmonic current, power factor, active power, reactive power are calculated andlist shows the variation of generator.Finally, the generator with short-circuit fault is solved in grid-connection.The simulation result is compared with load condition to observe the impactiongird-connection of the operation with fault. The variation and distribution of thecurrent of damper bar with fault is observed. The damper bar harmonic currentis obtained by Fourier decomposition and the distribution law is observed. Theharmonic current with different short-circuit condition is compared to researchtheir distribution.