Research On Setting Calculation And Technical Improvement Of Relay Protection For Large Nuclear Power Plant

With the improvement of China’s economic and social needs for clean and efficient energy and the development of nuclear power technology,the proportion of large nuclear power generating units that have been put into operation has increased substantially since 2011.The importance of large nuclear power units in the power grid is becoming increasingly prominent,and relay protection is an important guarantee for the stable and safe operation of nuclear power plants.At the same time,the many problems encountered in the development of nuclear power units have also made many nuclear power plant relay protection operation technology face many challenges.In view of the particularity of the operation of nuclear power units,the thesis carried out in-depth research on the setting calculation and software development of relay protection for large nuclear power units,as well as the protection and principles reflecting the operating characteristics of nuclear power plants.Combining with the characteristics and operation requirements of the electrical system of nuclear power plants,the relay protection configuration scheme and unified setting principles of large nuclear power plants are proposed.Aiming at the characteristics of nuclear power generating units with two grounding points during normal operation,a setting calculation scheme for stator grounding protection suitable for the operation of nuclear power plants is proposed.According to the operating characteristics of nuclear power plants,the protection setting schemes for nuclear island motors and conventional island motors are proposed.Furthermore,the application of these schemes in the setting calculation of relay protection in a large nuclear power plant is introduced in this paper.The special protection of nuclear power plant and its principle improvement technology were studied.Aiming at the engineering problem of transformer disconnection,which is of concern to nuclear power plants,the electrical characteristics of transformer disconnection faults on the high-voltage side of the transformer and their impact on plant power operation of nuclear power plants are analyzed through theoretical derivation.And the high-voltage side open-phase protection scheme of the transformer that meets the safety requirements of nuclear power operation is proposed.Aiming at the problem that the current stator grounding protection principle and action criterion cannot fully reflect the degree of fault,a grounding current calculation scheme reflecting the fault degree of nuclear power generators is proposed.By constructing a quasi-distributed parameter model,the effectiveness of the scheme is verified by model simulation.Unified and standardized relay protection setting calculation schemes and automatic,learnable setting calculation software are important means to improve the operation level of relay protection in large nuclear power plants.On the basis of summarizing the characteristics of large-scale nuclear power plant relay protection setting calculation and the work needs of nuclear power plant technicians,the software for nuclear power plant relay protection setting calculation was developed through MATLAB GUI.At the end of the thesis,the main research results obtained are summarized,and the future research work is prospected.