Analysis And Experimental Research Of Field Winding Inter-turn Short Circuit In Turbine Generator

Field winding inter-turn short circuits is a common fault of the generator, accurate detection and timely diagnosis are effective measures to guarantee the safe operation of generators.The field magnetic motive force (MMF) analysis, mathematical model, simulation analysis and the diagnosis criterion and localization method of field winding inter-turn short circuits in turbine generator are deeply discussed and experimental studied in this dissertation. The major work done and results achieved are as follows:1. The field MMF of the turbine generator with field winding short circuits was analyzed, and a series expression was obtained, which is suitable for the qualitative and quantitative analysis of the turbine generator's field MMF with normal winding and field winding different turn number and different coils short circuits. The series expression not only solves the problem that is difficult represent the field MMF in piecewise function with filed different winding coils short circuits but also considers field MMF harmonic's independent effect. The field MMF distribution and the amplitude variation of the fundamental and harmonic in turbine generator with normal field winding and field winding different turn number and different coils short circuits were obtained, which are identical to the spectrum analysis results of the tested no-load phase voltage.2. The finite element analysis of the field winding different turn number and different coils short circuits considering the saturation and slot effect was completed. The correspondence between the short circuit turn number and flux distribution and the correspondence between the short circuit coil and flux distribution were summarized. Conclusion is consistent with theoretical analysis.3. The multi-loop mathematical model of the turbine generator with field winding inter-turn short circuits under no-load and grid was established. The short circuit field winding of the model is equivalent as the fault loop and the normal loop, the field winding's related inductances were deduced in permeability analysis method, the loop parameter's calculation method was gived, the model is suitable for the simulation of generator with normal winding and field winding inter-turn short circuits.4. Simulation analysis and experimental research of the turbine generator with field winding different turn number and different coils short circuits were achieved. The simulation and experimental waveform comparison shows the validity of mathematical model. The harmonic variation of the phase voltage and field current and the stator's parallel branch circumfluence after field winding different turn number and different coils short circuits were obtained. Simulation of the 300MW turbo-generator with field winding inter-turn short circuits was completed, which shows practicality of mathematical model. 5. The diagnosis criterions that are 2-norm of the branch voltage and parallel branch circumfluence's even harmonics maximum quantity were presented by theory analysis.The change feature of the ratio of the parallel branch circumfluence even harmonics maximum quantity's 2 norm and the phase voltage 3rd harmonic maximum quantity was studied,the one-to-one correspondence between the ratio and field coil was found,The field winding inter-turn short circuits fault localization method was given.The rotor design transformation, installation and commissioning of the 7.5KW turbine generator in dynamic simulation laboratory were completed. The field winding different turn number inter-turn short circuits experiment was carried out.Theoretical analysis, simulation and experimental results are in agreement.