Study On DC Arc Characteristics In Hydrogen Arc Extinguishing Medium With Controllable Magnetic Field

With the rapid rise of new energy in China,DC power supply and distribution systems such as electric vehicles,all-electric aircraft,rail transit,photovoltaic power generation have developed rapidly.Demands for DC switches are also increasing.Using hydrogen medium to improve DC arc interruption ability is a potential arc extinguishing technology,which has been widely studied.Relying on hydrogen medium combined with effective magnetic blowing can cool the high heat generated by high current,restrain arc contraction,keep diffusion state to improve arc voltage and reduce contact edge ablation,so as to realize rapid arc energy dissipation.However,the thermodynamic and dynamic mechanism of energy dissipation process is not perfect and in-depth,which needs to be solved urgently.In the process of DC arc short circuit interruption in hydrogen medium,the intrinsic characteristics of hydrogen and plasma arc interact in a complex non-linear system.Magnetohydrodynamic force effect under the synergy of volume force and multi-physical field of magnetic field is an important factor for the rapid dissipation of arc energy,and then affects the interruption ability.Therefore,it is necessary to study the characteristics of DC arc in effective magnetic blowing hydrogen medium in order to guide the equipment manufacturing of switchgear with large interruption capacity.In this paper,the Eindhoven micro-arc model is used to establish the micro-arc plasma model with different proportions of hydrogen and nitrogen,taking into account Dalton's partial pressure law,quasi-neutral charge condition,mass action law and stoichiometric equilibrium condition.The non-linear equations of various particle number densities under the above conditions are obtained.The non-linear equations are programmed and calculated by Newton iteration method.The physical parameters of hydrogen-nitrogen arc with different proportions,including conductivity,thermal conductivity,density and viscosity,are obtained.It provides data support for macro arc simulation.In this paper,the finite element method is used to simulate the DC discharge module in COMSOL software,and the first boundary condition is adopted.In hydrogen medium,the arc ignition process of arc under different magnetic field types and different magnetic induction intensities is simulated by MHD.The results show that under the action of transverse magnetic field,with the increase of magnetic induction intensity,the overvoltage at both ends of the contact increases gradually,and the arcing time of the arc decreases significantly.Under the action of longitudinal magnetic field,with the increase of magnetic induction intensity,the voltage curve perturbation at both ends of the contact increases.In addition,the dynamic process of typical H₂-N₂ arc breaking experiment and the breaking ability under specific conditions are simulated and analyzed in this paper.It provides some reference for the design of DC contactor.In this paper,a closed prototype of bridge contact structure is used for the experiment.The electro-piezoelectric rheological changes and arc ignition time of DC arc under different magnetic field intensity,different proportion of hydrogen and nitrogen mixed medium,different breaking speed and different current were measured.The results show that the arcing time of hydrogen medium is shorter than that of other medium,but the molecular weight of hydrogen is smaller than that of nitrogen,the particle movement speed is faster,the interception overvoltage is higher,and the arc disturbance and even the arc re-breakdown are prone to occur.When H₂-N₂ mixed medium is 3:2,the phenomenon of arc re-breakdown can be effectively reduced.