Study And Application On Huge Hydro Generator Internal Fault Transient Simulation And Optimized Main Protection Scheme

The persistent rapid development of economy puts forward higher demand for construction and production of power system in China. In order to exploit the abundant water resources, state has programmed to construct numbers of huge hydro power station in several five-year plans followed. At the same time, the rated capacity of these generators becoming larger, for example, the capacity of generators in the Three Gorges, Longtan and Xiluodu power station are 700MW, generators in Xiangjiaba are 750MW, and generators in Baihetan power station may amount to 800MW or so. The secure working of these huge hydro power stations is important for the stabilization of the whole power system, so it is important to implement effective main protection on these generators. And the research about main protection scheme and electric characteristics under internal short circuit fault condition has become momentous project.To research the electric characteristics of internal short circuit faults in generator, the real generator short circuit testing or digital simulation can be employed. But internal short circuit fault may cause severe damage on generator, so it is impossible to use huge generator to carry through these research, and digital simulation become the primary approach. But transient electromagnetism relationship of internal short circuit fault is complex, so how to construct the transient simulation model, which suits for main protection scheme research is a difficult problem.When internal short circuit fault happened, the stator structure becomes asymmetrical and the gap magnetism contains amount of harmonics, moreover, the arrangement of stator coil is intricate, so the model must take the effects of gap harmonics and spot of short circuit coil into consider. By taking each stator coil and rotor damper loop as independent unit to construct simulation model can calculate these aspects well, but huge hydro generators contain large mount of dampers, so model expression may result to a high dimension differential equation group. To resolve these differential equations is time-elapsing. To solve the problem, some scholars use algebra method to calculate faulty steady characteristics to analyze the protection scheme. But the transient process is not finished at the moment of main protection operation, so the research work must be based on transient electric characteristics.In order to use transient simulation model to design main protection scheme, the model must be simplified. The dissertation proposed a simplified transient simulation model based on principle of each pole with two dampers. The simplified model suits for internal fault simulation and main protection scheme analyze, and its validation is validated. In this dissertation, the model is used for main protection scheme research of huge hydro generator for the first time.Dynamic model testing is another method to research power system faults. The dissertation introduces the first dynamic model generator based on the parameters of real huge hydro generator in China. The model generator is constructed according to the structure of ALSTOM generator in Three Gorges power station, and it provides a flat to analyze electric characteristics of generator internal fault and the abnormal condition in power station. By comparing dynamic model faults testing and digital simulation results, the validation of simplified model is proved again.The dissertation investigates the software design for internal faults simulation and main protection scheme research. Internal fault aggregation, fault simulation, and protection scheme analysis software are developed on Windows VC++ flat.As to newly-built hydro power stations in China, the comfirming of optimized main protection scheme for their generators must be based on the systemic transient simulation analysis. The dissertation analyzed transient electric characteristics of all the possible short circuit faults that may be happened in DFEM and ALSTOM 700MW hydro generator in Three Gorges, 600MW generator in Pubugou and 250MW generator in Zhexi power station, and simulated the protection effection under different neutral side stator branches connection types and main protection schemes, and confirmed the optimized main protection scheme for each generator. The research results in these projects have been adopted in the practical design and engineering application process, and these productions can be served as references for raleted research and engineering application in the construction of other hydro power stations.At the end of this dissertation, the research results are summarized and the further investigative directions are pointed out.