Observation Of Vacuum Arc Morphology And Microscopic Particle Dynamics

With the global problems of energy shortage and environmental pollution becoming increasingly prominent,renewable energy DC transmission has become the main direction of power system development.Due to the advantages of good environment,vacuum circuit breaker has gradually become the main breaking device in the field of medium voltage distribution.The shape and distribution of vacuum arc during arcing process will affect the transport characteristics of plasma,and it is also the initial condition of the recovery process of dielectric strength after arcing,which directly determines whether the circuit breaker can successfully break the fault current,and is an important factor in the design of circuit breaker parameters.Compared with the power frequency arc,the plasma often has no time to diffuse under the fast zero crossing condition,which puts forward more stringent requirements for the dielectric recovery after arc.Controlling the rapid homogenization of micro particles in the process of vacuum arc combustion can improve the breaking reliability of the circuit breaker.Therefore,the research on the morphology of vacuum arc and the dynamic distribution of micro particles under different conditions of initial diffusion process is carried out.In order to study the dynamic changes of vacuum arc microparticles in the initial diffusion process,the experimental parameters are designed and the diagnostic platform of vacuum arc microparticles is built.Combined with the macro shape of vacuum arc,the image processing and the calculation program of microparticles are used to calculate the spatial distribution of plasma parameters under different conditions.The experimental results show that in the initial diffusion stage,the electron density gradually decays in the radial direction,and decreases in the axial direction according to the arc column,cathode area and anode area;the electron temperature has an upward trend in the radial direction,the electron temperature in the central region is below 1e V,and the axial direction is opposite to the electron density distribution.With the increase of arcing time,the range of high electron density in the arc column region gradually "expands",and the maximum electron density appears prior to the peak current,and the electron temperature is "insensitive" to arcing time.With the increase of current amplitude,the electron density increases significantly and the electron temperature decreases correspondingly;The results show that the arcing time is short and the diffusion speed is slow at medium and high frequency.Compared with power frequency,the electron temperature and density are higher,and the radial distribution fluctuation is stronger;The results show that the amplitude of electron density of longitudinal six slot contact is lower,and the radial attenuation is more regular.The electron density of the central area of the contact with ferromagnetic material is higher,and the electron density of the flat contact fluctuates significantly in the radial direction.The electron temperature of the three contact structures decreases in the order of ferromagnetic,flat and longitudinal.The energy power and the area of action are the two main factors that affect the level of electron density.The results of this research can provide a basis for the control of the micro particle transport process in the arc burning stage of vacuum arc.It is important to control the initial plasma density in the recovery stage of the dielectric after arc,which is of great significance to improve the reliability of vacuum circuit breaker.