Research On The Influence Of Pantograph Arc On The Catenary Support Insulation Flashover In Sichuan-tibet Railway Tunnel

The construction of Sichuan Tibet railway is a major national demand.The location along the line is high altitude,complex terrain and harsh climate,which puts forward unprecedented requirements for the safe and stable operation of high-speed trains.As one of the three relationships,pantograph catenary relationship directly affects the current collection of trains,and its importance is self-evident.The pantograph catenary arc is inevitably produced due to the impact vibration of pantograph catenary system and the hard point impact between contact wire and pantograph slide plate.Under low pressure environment,the discharge characteristics are significantly different from those under normal pressure,which will have different effects on the ablation damage of pantograph catenary system.Moreover,the arc floats seriously in the low pressure environment,which is easy to develop to the cantilever insulator and cause flashover Collaterals.The research on the discharge characteristics of pantograph catenary offline arc in low pressure environment and its influence on Flashover of support insulator in tunnel can provide guidance for the design of pantograph catenary system and support insulator in Sichuan Tibet railway.In this paper,the magnetohydrodynamic model of pantograph catenary arc under low pressure is established by introducing the air physical parameter information under different low pressure levels.The influence of air pressure drop on the arc shape characteristics,temperature field,gas field characteristics and arc voltage is studied.The results show that:with the decrease of air pressure,the arc diameter increases,the overall temperature presents a downward trend,and the arc temperature drops more slowly at the lower pressure level than at the high pressure level;the vortex structure appears at the junction of arc and air due to the Kelvin Helmholtz instability,and the lower the air pressure,the more obvious the eddy current structure;the lower the air pressure,the more obvious the eddy current structure The pressure decreases with the decrease of air pressure,which enhances the arc maintenance ability.Based on the model of pantograph catenary arc in low pressure environment,considering the cross wind effect of train,the motion and development characteristics of pantograph catenary arc under the combined action of low pressure and strong air flow are studied.The motion characteristics of arc under different air pressure level,different air flow intensity and different contact wire profile are simulated,and the arc motion development characteristics under different conditions are obtained The arc motion was characterized by the arc root position time curve.The results show that: with the decrease of air pressure,the diameter and volume of arc increase,and the development of arc motion is slower than that under normal pressure;under the action of air flow,the overall temperature of arc decreases,the frequency and amplitude of arc voltage fluctuation increase,and the arc root jumps more frequently.The stronger the air flow is,the shorter the stagnation time of arc root is,the worse the stability is,and the easier to extinguish;the proper radius is adopted a larger contact wire or a smaller curvature at the bottom of the contact wire can effectively speed up the arc movement and reduce the arc dwell for a long time,so as to reduce the arc ablation to the electrode.The research results provide theoretical support for arc protection in high altitude area.Based on the conclusion that the pantograph catenary off-line arc has the characteristics of floating arc and motion lag in the low pressure environment,the influence of the pantograph catenary arc development process on the surface electric field distortion of cantilever insulator under the combined action of Sichuan Tibet Railway low pressure cross wind and the difference of the influence under different pressure levels are studied,and the influence of the simulation results on the current environment is analyzed Partial discharge and the risk of developing into flashover accident are evaluated.The results show that: the lower the pressure level of arc,the closer the arc is to the cantilever insulator,and the longer the residence time is;after the arc is generated in the low pressure environment,the electric field on the insulator surface will be seriously distorted in the process of movement and diffusion,which is shown as follows: the potential distribution is not uniform,and the unit gradient drop near the high voltage end is large;the lower the pressure environment The results show that the concentration of electric field intensity is more obvious;the proportion of voltage borne by each shed of insulator is not uniform,and the shed at high voltage end bears most of the voltage.