Study On The Influence Of Magnetic Field Distribution On The Characteristics Of DC Vacuum Arc Pre-arc Plasma

In recent years,the DC transmission has been developing rapidly.As the key device of DC transmission system,the switching device has the function of turning up and closing off the transmission line.Compared with other switching devices,the vacuum switch has the advantages of environment-friendly,good maintainability and excellent breaking ability,which has been widely used in the transmission and distribution system.As a kind of electrical equipment with contacts,vacuum switch is bound to produce arc in the process of breaking,and there is no natural zero crossing point of DC,so breaking is more difficult.Magnetic field is an important means to control the arc of vacuum switch,so it is of great significance to study the influence of magnetic field on the characteristics of vacuum arc.In this paper,the influence of different distribution of magnetic field on the characteristics of vacuum arc is studied by numerical simulation.Firstly,based on the drift diffusion equation of gas dynamics,the transport equation of heavy matter and the Poisson equation of coupled electric field,the finite element simulation software COMSOL Multiphysics,a two-dimensional micro simulation model of DC vacuum arc is established,and the micro characteristic parameters of plasma in front of DC vacuum arc are studied and analyzed.Then,the influence of uniform magnetic field with different magnetic intensity on the micro characteristic parameters of plasma in front of DC vacuum arc is analyzed from two aspects of transverse uniform magnetic field and longitudinal uniform magnetic field influence.In the established simulation model,coupled with the magnetic field module,the influence of saddle shaped non-uniform magnetic field on the micro characteristic parameters of arc front plasma during the breaking process of DC vacuum circuit breaker is studied.Finally,the simulation results of uniform magnetic field and non-uniform magnetic field are compared,and the influence of different magnetic field distribution on the micro characteristic parameters of arc front plasma is analyzed.The research results provide a reference for DC vacuum circuit breaker to use magnetic field to control arc and improve the ability of arc extinguishing.