Research On The Relationship Between Current Carrying Capacity And Temperature Rise Of Typical Contact Line

The structural stability of contact wire is the key to ensure the safe operation of electrified railway.When the train is running,the Joule heat generated by traction current will increase the temperature of contact wire,which may cause thread softening and even lead to wire breaking accident.With the development of society,the demand of train for carrying capacity is higher and higher,and the influence of Joule heat on contact line will be greater and greater.Therefore,it is necessary to study the relationship between current carrying capacity and temperature rise of contact wire in order to design appropriate current carrying capacity within the temperature limit of contact wire.In view of the specification120 contact wire and specification 150 contact wire are widely used in ordinary railway and high-speed railway OCS,which have certain representativeness and typicality,this paper takes them as the main research object.According to the working environment of OCS and relevant thermal and electrical knowledge,the main heat affecting the temperature rise of OCS is identified as Joule heat,solar radiation heat,radiation heat transfer and convective heat transfer.The convective heat transfer can be divided into natural convective heat transfer when there is no wind and forced convective heat transfer when there is wind.According to the basic theory,the heat calculation formula of contact line is derived.Among them,the convective heat transfer process of contact line is complex,which can not be solved directly by mathematical analysis.In this paper,the criterion correlation is obtained by fluid structure coupling simulation.The fluid-structure coupling model of contact wire and cylindrical wire is established,which have the same size and material.Comparing the simulation results under natural convection and forced convection,it is found that there is a big difference in heat dissipation effect between them,which further indicates that the contact line shape can not be regarded as a cylinder for carrying capacity calculation.The steady-state temperature and temperature rise curve of contact wire under different current were recorded.The emissivity of the contact line is measured by infrared thermal imager,and the convective heat transfer coefficient of the contact line under each experimental condition is obtained by fluid solid coupling simulation.Based on this,the thermal analysis simulation of the contact line is carried out,and the simulation data is very close to the experimental data,which proves that the convective heat transfer coefficient obtained by fluid solid coupling model is accurate,and lays the foundation for solving the correlation of convective heat transfer criteria.Through the fluid solid coupling simulation,the convective heat transfer of different sizes of contact wire is compared and analyzed,and it is concluded that the size parameters will affect the convective heat transfer law of contact wire.It is necessary to establish their respective fluid solid coupling models,and obtain their respective correlations of convective heat transfer criteria through simulation and calculation,while other heat formulas only need to modify the size related parameters.Finally,according to the law of conservation of energy,the steady-state heat balance equations of indoor(without wind and light)and outdoor(with wind and light)conditions are given,that is,the relationship between the current carrying capacity of contact line and temperature rise.Then,the calculation formula of steady-state(continuous)current carrying capacity of contact wire is deduced,and an example is calculated.Compared with the standard value,it is found that the error is small,which proves that the relationship between current carrying capacity and temperature rise of contact wire studied in this paper has a certain accuracy.