Study On Overheat Protection Of Overhead Contact System

With the continuous development of China's high-speed railway,the train transforms from low speed,low load to high speed,high load.High-speed railway has grown rapidly,while higher requirements are put forward for the safe operation of railway system.Overhead contact system is an important part of high-speed railway,and there is no backup.Its operation performance directly affects the stability of traction power supply system.Once the high-speed railway or heavy load railway runs for a long time,the heat accumulation caused by large load current will lead to the decrease of contact wire's mechanical strength and current-carrying capacity,which will reduce the reliability of the overhead contact system and may develop into a fault in serious cases.Therefore,under the background of the increasing density of railway load,the study on the overheat protection of overhead contact system will have important economic significance and social value.Based on the analysis of the power supply system of high-speed railway,the currentreceiving process of locomotive and the structure of overhead contact system are studied.For the problem of the overheat of overhead contact system,considering the technology of the temperature monitoring and the special relationship between pantograph and catenary,in this paper,the temperature of the contact wire is monitored by measuring the temperature of the catenary wire.Firstly,direct feeding system and AT feeding system are studied respectively according to the different feeding system.Based on Carson theory,the wire parameters of these two feeding systems can be calculated respectively.According to the spatial position of the wires in the overhead contact system,the Simulink simulation software is adopted to construct the direct power supply mode and AT power supply mode,and analyze the current distribution.Through the result of current distribution,can get the current ratio value of the catenary wire of JTMH120 and the contact wire of CTM120,which provides data reference for the study of temperature relationship between them.Then,analyze the influence caused by the overheating of the overhead contact system,the temperature rise process of wire and the influencing factors in the process of temperature rise.The heat balance equation in IEEE(Institute of Electrical and Electronics Engineers)standard is selected to calculate the temperature rise of overhead contact system,and analyze the similarities and differences between CIGRE(International Council on Large Electric systems)standard and IEEE standard in the calculation of wire temperature.Then verify the calculation results with the relevant railway standards,and obtain the temperature relationship between the catenary wire and the contact wire based on the results of current distribution study,which provides theoretical support for the overheat protection scheme.The finite element mode of the overhead contact system is constructed by the Fluent simulation software,and the numerical analysis is completed based on mass conservation equation,momentum conservation equation and energy conservation equation.After studying the distribution of the temperature field of the catenary wire,the contact wire and the surrounding environment of them,the results are verified with the conclusions of the theoretical analysis.Then,analyze the effects of wind speed,solar radiation intensity,humidity and ambient temperature on the temperature rise of the wires.Finally,the framework of the overheating protection scheme of overhead contact system is proposed,which provides reference for solving the overheating problem of the overhead contact system.