Research On Faults Features And Electromagnetic Performance Related To Stator Internal Short-Circuit In Nuclear Power Turbo-generator

With upcoming China’s third generation nuclear power technology transition,which owns large capacity and high performance,its nucleus equipment’s capacity that is to say nuclear power turbo-generator is growing.The machine halt due to the large synchronous generator set faults could induce big numbers of economic loss,consequently,the safe operation of large nuclear power turbo-generator has draw increasing attention.The stator internal short circuit fault is not only a common but also a tremendously destructive fault,therefore fault diagnosis method and protection are always the research hotpots for scholars.The fault features and alteration law of phisical quantities after the internal short circuit fault of large synchronous generators is the foundation for fault diagnosis and protection of traditional synchronous generators.Moreover,it provides valuable information for fault diagnosis and protection of other special electrical machines,as well.Therefore,it is very significance to research on fault features and electromagnetic performance.Put forward the method of analyzing electromagnetic torque characteristics during the instantaneous process after the internal short-circuit fault of synchronous generator.Additionally,taking the influence of eccentric vibration into account,fluctuation characteristics and amplitude frequency characteristics of electromagnetic torque during the instantaneous process after the fault have been emphatically studied.The two-dimensional field multi-loop coupling mathematical model of synchronous generator is built up,moreover,the dynamic model test about stator phase current at half rated load condition after stator winding inter-turn short circuit fault is used,which can effectively prove the validation of the simulation model.At the same time,combining Maxwell tensor method,the electromagnetic torque before and after synchronous generator stator internal short circuit fault is achieved.And based on spectrum analysis,the electromagnetic torque before and after the fault is analyzing.In the end the amplitude law of electromagnetic torque component at each frequency with different short circuit turns and positions is discussed.In order to study the influence of internal short-circuit fault on rotor eddy losses,a two-dimensional field multi-loop coupling model of nuclear power turbo-generator is built.The air gap flux density before and after synchronous generator fault is computed,which impacts rotor surface loss,afterwards employing fast Fourier principle to do harmonic analysis on air gap flux density,the transient variation of each harmonic air gap flux density and the variation characteristics of mean value of each harmonic amplitude of air gap flux density under different fault conditions after the fault is further investigated.Provided with eddy current loss calculation method,transient eddy current loss and average eddy current loss in a period of rotor surface small teeth and wedges before and after nuclear turbo-generator stator internal short-circuit fault are computed and analyzed.Additionally,the inflence of stator internal short-circuit fault of nuclear power nuclear power turbo-generator on the distributions of eddy losses is obtained by computing the average eddy current loss of rotor surface small teeth,big teeth and wedge under different fault conditions.In order to study the influence of internal short-circuit fault on the variety and distribution of dynamic electromgnetic force of nuclear power turbo-generator.Based on the electromagnetic field calculation result,the local electromagnetic force after synchronous generator stator internal short-circuit fault is computing by combining Maxwell tensor method and Lorenz force principle.It reveals the rotor surface radial force and tangential force,the stator and rotor electromagnetic force of groove tooth wall,and the stator winding and rotor winding of radial force and tangential force after nuclear turbo-generator fault.Meanwhile,the relative concentrated area of electromagnetic force after the faults are obtained by analyzing the stator and rotor of electromagnetic force distribution characteristics,which provides the theoretical basis for the further development of the failure.In order to obtain more effective fault features,an new method of the graphical auxiliary diagnosis of stator internal short-circuit fault of synchrongous generator.Based on Lissajous sine wave information blending theory,the amplitude and phase information of three phase currents and voltages of the synchronous generator have been synthesized.Afterwards establishing the stator three phase electrical quantity Lissajous mathematical model.As the fault features of monitoring and diagnosis,the Lissajous graph parameters can effectively represent the stator internal short-circuit fault.That is proved by the theoretical analysis and the dynamic model experiment when the stator internal short-circuit fault occur.Also,it gives new ideas and methods for monitoring and diagnosis at stator winding short circuit fault in synchronous generator.