Analysis On Discharge Processes Of N₂/SF₆ Under Non-uniform Field

Gas medium has many advantages compared with other media,and SF6 has been widely used in the field of high voltage and insulation due to its high dielectric strength,excellent arc performance,non-combustible and good cooling characteristics.Mixed gas pressure at different point of N2 and SF6 is extremely application prospect medium.In engineering practice,the non-uniform distribution of electric field may be caused by the electrode surface defects or other factors,which will seriously affect the gas insulation properties.Therefore,the research on the discharge characteristics of N2 and SF6 gas under non-uniform field has reference value and guiding significance for engineering applications.The model of gas discharge in 5mm rod-plate gap is established in this dissertation,to deeply investigate the discharge characteristics of N2 and SF6 understand the transport properties of particles during the discharge process and the regularities of electron temperature distribution under non-uniform field.Theoretical calculation and analysis of discharge process is performed,based on the hydrodynamic model and electron energy equation.The model of N2(non-electronegative gas)includes the electron energy equation,the Poisson equation in conjunction with the continuity equations for electrons and positive ions,whereas the model of SF6(electronegative gas)is composed of the electron energy equation,the electrons,positive ions and negative ions continuity equations coupled with the Poisson equation.The numerical calculation of discharge process in N2 and SF6 under non-uniform field at atmospheric is completed by applying the DC voltage,the standard lightning pulse voltage and nanosecond pulse voltage to the plate electrode.The results show that the insulation properties of N2 and SF6 in non-uniform field are decline(compare to those obtained in uniform field,see appendix),especially SF6 gas,the electric field strength of the rod reached 90kV/cm,when the plate electrode applied voltage of 11kV,the applied voltage have a greater effect on the time of the avalanche-to-streamer process and the propagation velocity of streamer,streamer channel shows a large head and small tail shape,the tail of streamer channel is more finer under pulse voltage,the electric field is the main source of energy of the electrons,and it has a greater impact on the distribution of the electron temperature.The tempo-spatial characteristics of the microscopic parameters such as space particle density,electric field strength,and the electron temperature distribution are obtained,the dynamic behaviors and related parameters of charged particles in discharge process also be discovered.Above results can help to better understand the characteristics of the gas discharge in non-uniform field,furthermore,provide the theoretical support for further study of the N2 and SF6 gas mixture discharge mechanism,then optimize and control the gas discharge phenomenon.