Study On Electrical Characteristics And Temperature Distribution During Off-Line Discharge Between Contact Wire And Pantograph

With the development of economy in our country,electrified railway has made rapid progress.The running speed and carrying capacity of trains have been increased obviously.However,the relation between the contact wire and pantograph is more and more severe.The main reason is that when the pantograph and the catenary wire are not in contact,the air in the gap between the pantograph and the contact wire is broken down.On the one hand,the arc can produce harmonics,affecting the current quality of the system.On the other hand,the arc is accompanied by high temperature phenomenon and releases huge heat energy,which increases the electrode surface temperature and causes the pantograph and contact wire to be damaged.Therefore,this thesis mainly focuses on the characteristics of the off-line discharge between the pantograph and contact wire.The main research contents are as follows:(1)A pin-plate discharge model was built on the basis of magnetohydrodynamics.The electrical,magnetic,thermal and flow fields were coupled.The appropriate boundary conditions and circuit parameters were set up and adaptive meshing method was adopted.Then,the correctness of the model was verified.Based on it,the variation laws of characteristic physical quantities such as the electric field strength,temperature and flow field pressure were researched.(2)The off-line discharge model based on magnetohydrodynamics was established and the electrical characteristics were studied.The distributions of the characteristic physical quantities and electrical characteristics of off-line discharge are studied in the process of ascending,descending and descending to ascending motion of the pantograph at a certain speed.The results show that with the ascending of the pantograph the arc temperature,magnetic field,electric field increase and air flow field pressure increases but the velocity decreases.For its descending process it is the opposite.The current waveform is sinusoidal wave and the voltage waveform is distorted.The voltage is higher than its normal value.The electrical characteristics with the pantograph running at different speeds were studied.It is found that the current waveform is not affected but the number of the voltage distortion increases.The distortion time is advanced with the increase of the rise speed of the pantograph.While the distortion time lags behind with the increase of its descending speed.(3)Based on the off-line discharge model established,the temperature distributions of the pantograph and contact wire under the influence of many factors were studied.Firstly,the influence of different values of the thermal conductivity on the temperature inside the electrode was studied.The results show that the maximum temperature inside the electrode is inversely proportional to the thermal conductivity.The temperature in the middle of the electrode is the highest and the outward temperature decreases gradually.Secondly,the effect of the gap on the temperature distribution inside the electrode was studied.It is found that the gap between the pantograph and contact wire is positively related to the maximum temperature of the electrode surface.And the high temperature area of the electrode gradually increases.Finally,the influence of arc polarity on the temperature distribution inside the electrode was explored.It is found that the temperature inside the pantograph has no obvious change,but the temperature inside the contact wire drops and the high temperature area becomes smaller.The research in this thesis has certain reference significance for improving the current quality flowing to the train,reducing the harm of arc to the electrode and improving the service life of the pantograph-catenary system.