Primary Parameter Modeling And Simulation Analysis Of Track Circuit With Ballastless Track

Track circuit is the important signal equipment to ensure safety and efficiency of train operation.It uses two rails as its transmission conductor to transmit train control information,pass traction return current,and check the track occupation.What affects the transmission performance of track circuit is primary parameter of track circuit(including rail impedance and leakage admittance).Compared with ballasted track,ballastless track uses monolithic track bed with reinforced mesh instead of scattered gravel track bed.Because the ballastless track bed contains steel network,the primary parameter of track circuit change greatly,which affects the transmission of train control information.At the same time,the primary parameter is also closely related to track material,structure of track circuit,and its circumstances.And traditional research methods can not describe the change rules of primary parameter of track circuit in detail.Therefore,in this thesis,the electromagnetic field finite element method was used to simulate and analyze the primary parameter of ballastless track circuit,which will provide reliable theoretical support to design,optimization and transmission performance analysis of ballastless track circuit,and have great significance to stable transmission of track circuit signals.Firstly,the thesis introduces the technology of jointless track circuit and ballastless track,and analyzes the distribution of the primary parameter of track circuit.Because the ballastless track contains the reinforcement network,it is impossible to find out the change rules of the primary parameter when using previous four terminal network or six terminal network circuit model method to study the primary parameter of track circuit.Therefore,the electromagnetic field finite element method was proposed in the thesis.According to the structure of ballastless track,a three-dimensional electromagnetic field simulation model of ballastless track with reinforcement network was established.Secondly,if using the electromagnetic field finite element method directly to calculate the three-dimensional electromagnetic field simulation model of the ballastless track,it is difficult to get the simulation result.Things that the material of rail is ferromagnetic,the skin effect exists,and the track bed contains reinforcement network can lead to difficulties such as huge model mesh dissecting and laborious calculation in convergence.To deal with the problem,the three-dimensional rail model was simplified into a two-dimensional rail model and a three-dimensional model only containing a reinforcing mesh,according to the influence of the electromagnetic field distribution on the primary parameter of track circuit.After that,in the light of the symmetry of track line about center line,the simplified three-dimensional model containing a reinforcing mesh was simplified again to half of the former model,based on the odd-even mode method.And the correctness of the simplified model was verified by numerical analysis.Thirdly,considering the influence of the insulation degree between the horizontal and vertical reinforcement mesh in the track board on the primary parameter of track circuit,the influence rules and influence degree of current,the final simplified model of the primary parameter of ballastless track circuit was used to analyze how current,frequency,track structure and circumstances influence the primary parameter of track circuit.Finally,the simulation results of the primary parameter of track circuit verifies the optimization effects of the optimization measures,such as insulation between horizontal and vertical reinforcement,increase in the distance between upper reinforcement mesh and rail bottom,and intermediate partition of horizontal reinforcement.The research provides theoretical basis for design and optimization of ballastless track circuit and a reliable analysis model for transmission performance analysis of ballastless track.