The Research Of Application Technology Of The Three Gorges Generator Out Of Step Protection And Exciting System

With the power system in China being a modern and large scaled, featured with national interconnected, electricity transmitted from West to East China and between South and North China, the safety and stability of operation of power system and large power equipment has become an important issue worth thorough studying. Especial commissioning of the Three Gorges Project Units and the construction of large-scale hydropower projects in west China, as well as the big leap in single unit capacity, operation stability of the generation units affects the safety of the whole power system more and more. From the perspective of the safety and stability of power system, the paper is intended to deeply study out of step protection and excitation technology applied in the large generator according to the Three Gorges Project, and the new step protection strategy, the selection of de-excitation resistance and optimization excitation regulation parameters are emphasized.According to the analysis of operation stability of the Three Gorges Project Units, the paper firstly indicates the basic request of step protection and out-of-step prediction protection of large units. It analyses the step protection criterion and out-of-step prediction theory thereof. Based on aforementioned analysis, the paper introduces an ameliorative step protection scheme with the startup element of self–adaptive power angle measurement, on which the main criterion is implemented by the mature three-reactance relay indicating generator edge's measuring reactance track, and a startup element of self–adaptive power angle measurement and a element of trip occasion control are added to improve the adaptability and reliability of the protection scheme. The paper elaborates related theory and implementation of the protection by taking an example of a real generator.The paper discusses the selection of de-excitation resistance in terms of the prerequisite for correct conversion. Then it analyses energy absorbing capacity of de-excitation resistance of synchronizing generator at two most severe conditions of forced excitation at no load by mistake and sudden short circuit at stator leads.The Paper further discusses the optimization of excitation regulation parameters and its application on the Three Gorges Units. Based on analysis of necessity of optimization of working parameters of excitation system and procedures of achieving optimization, simulation has been run on the two different types the Three Gorges Units to propose a set of optimal parameters. Simulation results show that major operation index have been optimized and better operational stability achieved. With the successful application of the optimal scheme on the Three Gorges Units, it has been proved worthwhile optimizing excitation system parameters according to in-situ conditions.