Research On Characteristic Parameters Of Traction Backflow In Integrated Grounding System Of High-Speed Railway

The integrated grounding system of high-speed railway has an important inhibitory effect on the rail potential,and is the key guarantee for the safe operation of the traction power supply system.With the speed increase of high-speed railway trains and the development of digital transportation in China,the danger of rail potential rise to railway staff and equipment along the line has become more and more prominent,and higher requirements have been placed on the return performance of the integrated grounding system.It needs to be tested and evaluated.However,the relevant standards of the current railway industry do not clearly stipulate the return parameters in the detection and evaluation,and the actual site mostly relies on engineering experience to determine the parameters and thresholds.The comprehensive grounding system engineering acceptance and operation and maintenance lack basis,which brings great inconvenience to the safety assessment of high-speed railway.Therefore,this paper will trace the origin and establish the characteristic parameters of traction backflow based on the correlation between traction backflow and rail potential,which will provide theoretical guidance for the application of backflow parameters in the integrated grounding system,which is of great significance to actively promote the construction of high-speed railway standardization system.In this paper,according to the direction of the traction return path,the research on the return flow characteristics is divided into the diversion characteristics and the dispersion characteristics.On the basis of analyzing the influence of shunt abnormality on system safety,the shunt coefficient is defined and selected as the characterization parameter of shunt characteristics,and a long direct conductor model is established to modify the parameter calculation method.The current dissipation mechanism of the integrated grounding system is analyzed,and the effective dissipation length is defined based on the mapping relationship between the integrated ground wire dissipation rate and the rail voltage,and it is selected as the characterization parameter of the dissipation characteristics.Based on the voltage calculation,the calculation method of this parameter is established.Secondly,based on the theory of multi-conductor transmission line,a 10-conductor chain circuit model of the fully parallel AT traction power supply system is established.Both the upstream and downstream include T busbar(contact line and load-bearing cable),F busbar(forward feeder),and R busbar(dual rail),PW wire and integrated ground wire.In the process of establishment,the horizontal connection spacing of rails,PW lines and comprehensive ground lines is used as the standard for dividing the sub-network,and the conductors are combined and simplified by equivalent value according to the requirements of backflow analysis.After the combination,the calculation accuracy of the model will not be affected.The model is well suited for backflow analysis.The integrated ground wire adopts the buried bare conductor model,which is convenient for analyzing its current distribution.Finally,based on MATLAB/Simulink,the current distribution characteristics of the return conductor of the integrated grounding system under normal operation are analyzed,and the variation law of the shunt coefficient of each return conductor in different AT power supply circuits is revealed.The dispersion mechanism clarifies the effective dispersion length of the integrated grounding system.The comparative calculation and error analysis were carried out using the established characterization parameter calculation method,and its applicability was verified.The influence of the system structure design on the return flow characteristic parameters is explained;according to the requirements of the detection link on the operating conditions,the influence of the load distribution and fault conditions on the return flow characteristic of the system is analyzed.