Studies On The Heat Distribution And Current Conduction Of Pantograph-Catenary Electric Contact And Their Influence Laws

As the electrified railway approaching to a high-speed and heavy-duty future, the requirements for the current capacity of catenary and the current collecting amount of pantograph are becoming higher and higher, leading to some increasingly prominent problems of the pantograph-catenary (PAC) electric contact. The combination of all the problems including maximum allowable current, contact resistance and resistivity, thermal effect, electrical abrasion, etc. constitute to the core problem of pantograph-catenary electric contact.Starting with both perspectives of the favorable PAC electric contact and the pantograph arcing, this paper aims to study the thermal flow, current conduction and influence rules. The corresponding research route is as'Analyzing the generating heat flow on PAC surface->Transmitting heat caused by pantograph arcing-> PAC thermal flow in steady state and transient state-> Establishing a spatial chain-arc model and extending an electrical black-box model for pantograph arcing->Evaluating overvoltage of locomotive body by introducing the extended habedank's equation-based arc model into actual traction power supply line. The main work of this paper is as follows.Firstly, aiming at the high-temperature thermal erosion problem caused by the PAC sliding electric contact, a detailed PAC surface heat flow analysis and computational model between pantograph and contact line are proposed. The results point out that the PAC surface heat sources include the surface temperature-rise generated by friction, the surface temperature-rise generated by contact resistance and the surface temperature-rise generated by arc. Meanwhile, the three thermal erosion processes and influencing factors are deduced and calculated in detail. As an example, the simulation results based on the Beijing-Tianjin railway line show that the frictional heat, Joule heat and arc heat generally exist at the same time and influence one other. Also, the influence rules of pantograph contact pressure, wind speed, driving speed, current change on the contact wire and slide surface heat flux are obtained.Next, aiming at the PAC detachment arc phenomenon that frequently occurs, the theoretical study for PAC temperature field under the pantograph arcing is performed. Combining the nonlinear finite element theory with the ANSYS software, this paper established the finite element model for the pantograph slides and contact wire. And the influence of pantograph arcing on PAC temperature distribution is analyzed. The intensive analysis on instantaneous PAC temperature distribution difference under different PAC materials and different material matching selection of PAC system are given. The measures for weakening arc's infringement on PAC are discussed, and the optimal material matching selection for PAC system is evaluated from the temperature field perspective.Then, the steady state and transient state heat distribution models when the pantograph with double conducting slide plate is lifting or lowering are proposed respectively. The heat flow differences of single/double sliding electric contact are investigated. The temperature changing processes for heat conduction under favorable PAC electric contact and pantograph lifting or lowering from contact wire are analyzed. Meanwhile, the linear initial and boundary conditions of heat flow model are proposed. Also, based on the non-contact infrared thermography, the experimental temperature-rise data of contact wire under PAC sliding contact and current collecting/breaking process during pantograph rising/dropping with different carrying current, contact pressure and electrical contact effect are obtained. Then, by comparing with the experimental results, the feasibility and effectiveness of the steady-state temperature-rise model of contact wire considering pantograph's double slides* electrical contact and transient-state temperature-rise model of contact wire considering pantograph rising and dropping process are respectively verified.Besides, aiming at the pantograph arcing in the process of locomotive lifting or lowering pantograph, the spatial physical model of the pantograph arcing is established combining the chain-arc dynamic characteristics. By considering the thermal buoyancy, air resistance, electromagnetic force and wind load, the arc current element force model between pantograph and catenary is built. Among these, the arc current element velocity at contact line end is corrected, and the jumping rule of arc root at contact line end is determined. Through the comparison of different forces, the influences of arc motion under constant carry current but different wind loads are emphatically analyzed. The calculation results indicate that the proposed chain-arc model is effective and capable of simulating the spatial motion and length variation characteristics of arc in the process of locomotive lifting or lowering pantograph.Furthermore, to study the electrical characteristics of pantograph arcing, an extended Habedank's equation-based model is bulit. Based on intensive investigation on the formation mechanism and influence factors of pantograph arcing, the relationship among the voltage gradient, power dissipation and arc length are confirmed. By establishing and introducing the PAC FEM to obtain the maximum detachment interval law between pantograph and contact wire, an extended habedank's equation-based EMTP model of pantograph arcing considering pantograph-catenarv interactions and train speeds is acquired. Based on the electrical rail line of China Beijing-Yizhuang, the extended Habedank's equation-based EMTP model is embedded to study deeply. On the basis of model's parameter determinations, the influences of internal parameters and external loads on extended model's characteristics are compared and analyzed. The comparison results illustrate that the extended model is valid and feasible for determining and revealing the pantograph arcing characteristics and influences in electrical rail line as well as the PAC contact-loss problems.Finally, based on the extended Habedank's black-box arc model, this paper further studied the influence of arcing on running locomotive's safety. Aiming at the arc influence on vehicle roof, considering the situation that massive high-speed railway lines which are actually laid on viaduct will be affected by electrical coupling, this paper carried out numerical solution and comparative analysis for train-roof over-voltages during locomotive passes electric phase separation with the electrical coupling influence of viaduct. Also, aiming at arc influence on vehicle bodies, corresponding analysis on voltage fluctuations of each locomotive's bodies and locomotive body discharge to ground during detachment arc occurs was mainly compared and studied.