Electrical Arc Modeling And Application To The Supercon-Ducting Magnet And Power Supply System In Tokamak

Tokamak device is considered as one of the effective ways to achieve controlled fusion.The superconducting magnet and power supply system,which have a strong coupling magnetic field and complex circuit,are the fundamental part of the tokamak device.In such a complex system,the safety and protection of the device may be influ-enced by the arc discharge phenomenon.As the difficulty in arc modeling and integra-tion,it poses a strong challenge to the simulation and analysis of arc and external circuit response.This thesis presents the research of arc modeling and application to the su-perconducting magnet and power supply system.Firstly,the basic theory of arc and commonly used arc models are introduced.The empirical model(Kronhardt model),gas arc model(Holmes model),and fuse arc model(Wright model)are chosen as they are suitable for tokamak.Then the mechanism,der-ivation process,and solving approach of the three models are introduced in detail.In addition,the issues in the application are discussed.In the third chapter,the research and simulation on arc fault analysis in ITER to-roidal field(TF)coil system are presented.Firstly,the potential arc faults are analyzed,and the Kronhardt model and Holmes are optimized.The time-domain calculation method is employed to evaluate the arc burning speed and arc length based on electrode theory.After the issues on convergence and time-varying arc models are solved,the built-in arc model is set up.Then the ITER TF internal coil circuit model and tempera-ture-based fast discharge unit(FDU)model are developed.The distributed parameters of FDU are obtained.To take into account the impact of voltage,the temperature-related resistor model is employed,and thus simplified FDU model is achieved.Finally,with appropriate built-in arc models,the response of inner multi-arc fault and the external double arc faults are simulated and analyzed.As the whole commutation process of fuse-based quench protection circuit is dif-ficult to model,the analytical model of the commutation process and its application based on arc model is discussed in the fourth chapter.The improved Wright model is embedded in circuit simulation,and the entire commutation response of the CFETR central solenoid model coil(CSMC)quench protection circuit is simulated.Then the impacts of the external load inductance,quartz sand filling rate on the commutation and arc extinction are analyzed.According to the characteristics of coil coupling for EAST poloidal field(PF)quench protection,the multi-coupling commutation simulation pro-gram based on parallel computing is developed.The influences of pre-arc and arc time to the coil current variety under mutual induction are analyzed.Finally,experiments are set up to investigate the fuse arc and fault arc of the su-perconductor.The performance of the CSMC quench protection system is tested and the improvement suggestions of the fuse are proposed.The multi-coupling commuta-tion model is verified by the engineering test data of the EAST PF quench protection circuit.The phenomenon of current rises abnormally in the experiment is explained,and the magnet hot spot temperature I2t is recalculated.The experiment platform for arc combustion of tokamak superconducting conductors is set up.The arc experiments of the copper conductor sample and realistic superconductor sample are carried out.The analysis of experimental data shows that the time-domain calculation method for arc length is validated,and it has certain reference significance to improve the modeling of superconducting fault arc mechanism in the future.