Numerical Simulation Of Positive And Negative Point-Plane Corona Discharge Mechanism In Air

With the wide application of uhvdc transmission,the insulation performance of hv equipment is required to be higher.When high voltage equipment insulation defects such as burrs forming easily point discharge,corona discharge is early discharge point discharge form,is a harbinger of high voltage equipment insulation damaged,therefore,timely grasp the positive and negative corona discharge mechanism,identification of corona discharge characteristics for effective prevention of sudden failure,guarantee the safe operation of the dc power system is of great significance.Studies show that positive polarity corona discharge and negative polarity corona discharge in the discharge form has a bigger difference,with the increase of voltage,normal polarity corona discharge,in turn,will be the starting time corona,glow corona,streamer corona,lingers breakdown discharge,negative corona discharge in terry cher pulse and pulse discharge.In this paper,the fluid dynamics model of COMSOL finite element simulation software was used to establish a two-dimensional axisymmetric pine-plate corona discharge simulation model.The initial streamer corona,glow corona,streamer corona,positive polarity streamer breakdown,tritscher pulse and pulsation-free discharge were simulated respectively.The research results of this paper show that:(1)in the process of positive corona discharge,the secondary electrons generated by the bombardment of cathode by positive ions are the necessary conditions for the recurrence of positive corona secondary pulse.(2)in the process of starting time and glow corona discharge,the current rapid increase stage is due to electron avalanche formation,current rapid decline stage is due to pinpoint areas electronic number decreases,is due to end of the electron avalanche discharge shock stage,shock stage discharge time consuming in theory is equal to the positive ion clouds through the needle-plate clearance time.(3)streaming breakdown discharge can be divided into four discharge stages: rapid rise stage,linear increase stage,electric breakdown stage and large current discharge stage.The surge of current is caused by the surge of current caused by the formation of electron avalanche.The linear current increasing stage is the process of the flow forming stable self-sustaining discharge in the gap and developing towards the plate electrode along the axis.The continuous high current in the large current discharge phase may be related to the secondary electrons generated by the positive ions colliding with the cathode in the ion channel.(4)in the process of terry cher pulse discharge,rapid rise stage is due to electron avalanche formation,a sharp decline stage is due to the declining electric field caused by negative ion clouds make needlepoint area discharge shock stage is mainly due to the electric field inside the accumulation of negative ions make gap continue to reduce,leads to the formation of a new electronic slides cannot be caused by,only when the anion group away from the electrode,electrode near field after recovery,a new current pulse will recur.(5)compared with the process of tritscher pulse discharge,in the process of accumulation of anions without pulse corona discharge in the area of needle electrode,the accumulation of anions is still insufficient to inhibit the formation of electron avalanche at the tip due to the strong electric field at the tip,and the ionization reaction continues to produce a large number of electrons,forming dc discharge.