Study Of Faulty Synchronization And Sudden Short-circuit Of Terminal For Half-speed Turbo Generator In Nuclear Power Station

Faulty synchronization and sudden short-circuit of terminal have serious harmto the generating unit and power network. The strong impact current andelectromagnetic force produced by fault may damage the winding insulation andstator end structure. The impact upon shaft of tremendous pulsation torque willreduce the operating life of unit. Dynamic problem of machine and network is moreprominent for turbo generator with slender shaft system and large single machinecapacity. Short-circuit of terminal and some serious faulty synchronization need to becalculated in order to optimize design of shaft for large synchronous generator.On the basis of the equivalent system of single machine-infinite bus for largesynchronous generator, the field-circuit-mechanical system-network coupled time-step finite element model for dynamic analysis of machine and network was set up.The generator was modeled with2D transient time-step finite element modelconsidering the magnetic saturation and eddy current and so on. The mechanicalsystem was modeled with multi-mass spring system considering torque transmittedby every mass, damping torque and speed variation of different mass. The maintransformer and transmission line were modeled respectively with electromagnetictransient mathematical model and the effects of transmission system parameters canbe taken into account. The coupling of2D transient electromagnetic field, externalcircuit, multi-mass spring mechanical system and power network was successfullyrealized.In this dissertation, faulty synchronization at120°and180°for a1250MW half-speed turbo generator were simulated with the field-circuit-mechanical system-network coupled model and PARK equation method. The main variables of electricand mechanical system were obtained, and variation rule of electromagnetic phenomenon was obtained as well. The analysis with coupled model set up in thisdissertation are more accurate for considering speed variation of every mass,magnetic saturation and eddy current and so on. Based on the dynamic simulationexperimental system in State Key Laboratory of Hydropower Equipment, the faultysynchronization at120o was simulated with field-circuit-mechanical system-networkcoupled model and simulation results were compared with experimental results. Thecomparison shows that the coupled model is correct.Different sudden short-circuit of terminal for1250MW half-speed turbogenerator were simulated with the field-circuit coupled model and PARK equationmethod, and the results obtained with two methods were compared. The statorcurrent, excitation current and electromagnetic torque are obtained. The actualaccident of sudden short-circuit of terminal in a power plant are simulated withabove two methods, the simulation results are compared with the recorded results. Itis shown that the results obtained with field-circuit coupled time-step finite elementmodel are closer to the recorded value.