Research On Rail Potential Of Urban Rail Transit Based On AC Power Supply System

At present,most of the city rail transit adopt DC traction mode,the voltage level is lower and it's difficult to guard against the problem of stray current.However,the power frequency single-phase AC power supply mode has the advantage of higher voltage level and overcome the problem of electrochemical corrosion.Furthermore,with the great breakthrough in traction power supply technology and AC drive technology for locomotives,it will be possible to apply AC traction power supply technology in urban rail transit.The problem of rail potential has always been the focus of high speed railway,intercity railway and urban rail transit,because the rise of the rail potential not only affects the normal operation of the locomotive,but also poses a threat to the safety of the body and the various electrical equipment.Therefore,it is necessary to research the rail potential of urban rail transit under AC power supply mode.First of all,the dynamic distribution of rail potential of metro with AC traction power supply system is studied in this paper.Based on the distribution of network current in AC traction power supply system,the static traction reflux model of single machine and multi locomotive is established,and analytical formula for the static distribution of the potential of a single and multi-locomotive rail is derived.Taking the locomotive running position as the demarcation point,the dynamic adaptive mapping between the locomotive current value and the operating condition is completed according to the traction calculation of the locomotive.Based on MATLAB simulation,the rail potential distribution and the influence of partial reflux system parameters on rail potential distribution are analyzed under different working conditions.Secondly,for city rail transit in the underground tunnel,two kinds of three-dimensional finite element model subway tunnel models with ground wire and without ground wire grounding wire are built based on the finite element software ANSYS in this paper,analyzing the subway tunnel's potential distribution law under the AC power supply system to determine the AC voltage protection scope,and at the same time,the influence of soil resistivity on different locations,the different backflow lengths of locomotives and the length of traction substation on the potential distribution of subway tunnels are analyzed.Finally,the methods of decreasing the running current of locomotives,reducing rail leakage impedance,shortening the distance between substations,improving the soil resistivity,laying the ground line,grounding the pillar and using the rail potential limiting devices to reduce the rail potential are specifically analyzed.The cross section area of the grounding line is calculated and checked,and the selection range of the cross section area of the ground wire is determined.