Research On Influence Of Winding Inter-turn Short Circuit Fault In Large Non-salient-pole Synchronous Generator

The inter-turn short circuit fault of large generator is one of the most common generator faults.To improve the safe and stable operation of generator and power system,it is of great significance to research the influence of inter-turn short circuit fault of generator winding,realize fault early diagnosis and prevent accident enlargement by utilizing the change of electrical quantity before and after the fault.When inter-turn short circuit fault occurs,the influence of dynamic interaction process between generator and grid on large generator should be considered.A model containing control,field,circuit,network modules was established for co-simulation.Factors such as generator structure,magnetic saturation,grid structure parameters and excitation control system were considered.The correctness of the simulation model was verified based on comparison between the simulation and experiment of a 30 k VA generator.The generator was tested by the dynamic physical simulation laboratory with stator winding inter-turn short circuit fault.Then,the nuclear power half-speed turbo-generator is taken as the research object.Its stator winding inter-turn short circuit fault was simulated.The application of the simulation model in large-scale generator was verified to be effective.The results were compared with that calculated by traditional method based on constant voltage excitation.And the comparision shows that the model proposed in this paper can reflect generator characteristics more accurately,which are affected by generator dynamic interaction with the grid.The influence of stator winding inter-turn short circuit fault on generator connected to grid was studied.The stator winding inter-turn short circuit fault in nuclear power half-speed turbo-generator was simulated.Its internal magnetic field,three phase stator currents,harmonic electromagnetic torques were analyzed.The influence of relative fault position on generator internal magnetic field was analyzed.The relative fault position is defined by the distance between fault winding and rotor pole.Stator winding inter-turn short circuit fault with different fault position was simulated.Three phase stator currents and electromagnetic torque were given.At the same time,the function of excitation control system in inter-turn short circuit was analyzed.The relationship between the increment of field voltage and current and fault location and fault degree was obtained.The field winding inter-turn short circuit fault of multipole non-salient-pole generator was studied.The formulas of field winding magnetomotive force(MMF),stator phase branches electromotive force(EMF),circulating current in stator parallel branches were deduced.Relationship between the pole pair number p and these formulas was derived.In addition,influences of fault location and fault degree on stator branch circulating current were analyzed.Then,the nuclear power half-speed turbo-generator was analyzed theoretically.Its theoretical analysis results were verified to be effective by finite element analysis in improving field winding inter-turn short circuit fault theory of multipole non-salient-pole generator.The influence of field winding inter-turn short circuit fault on rotor eddy current loss was studied for nuclear power half speed turbo-generator.Formulas of MMF generated by fractional harmonic circulating current of one stator phase winding,synthesis MMF generated by fractional harmonic circulating currents of all stator phase windings were deduced.Synthesis magnetic filed speed relating to rotor and cause of rotor surface eddy current were analyzed.Eddy currents frequency characteristics were revealed.Eddy current losses of rotor damper after fault were obtained based on calculation method of eddy current loss proposed.By harmonic analysis of eddy current,the theoretical derivation was verified to be correct.Rotor surface eddy current and rotor surface eddy current loss under different fault conditions were calculated.Then,the influence of fault location and fault degree on rotor surface eddy current and eddy current loss were obtained.The research contents of this paper can provides a theoretical reference for inter-turn short circuit fault analysis of large generator,which is of important practical significance to ensure the safe and stable operation of large generators.