Calculation And Analysis Of The Distribution Of Rail Tracion Return Current And Rail Potential In Long And Large Tunnel

In recent years, the construction of the high-speed railway lines is in full swing. In comparison with the general speed railway, the phenomenon of high rail potential is visible at the high-speed railway because of the high locomotive power, the high rate of traffic flow, the high speed of the locomotive and the high value of the impedance per unit length between the rails and earth, which does damage to the safety of staff and the signal equipment along the railway. What’s more, about60%of the electric railway is built in the mountainous district and the train has to run through the long and large tunnels, which means that there exits obvious differences when comparing the surroundings of traction power supply systemin tunnels and in general circumstances. The paper does research on the distribution of the traction return current and the rail potential in long and large tunnels.First of all,based on the parameters of the traction power supply system of the Guanjiao tunnel,which is built on the railway line of QingHai—ibet from XiNing to Ge’ermu, the paper calculates and compares the relative error of two formulas of calculating the self-impedance and mutual impedance, which are the Carson formula based on the semi-infinite planar earth model and the Tylavskyformula based on the circular tunnel with peripheral infinite earth model,and does research on the influence of the earth resistivityand frequencyon the results.Secondly,the paper builds the model of the traction power supply system inside and outside the Guanjiao tunnel on general modules provided by MATLAB/SIMULINK, then simulates and compares the distribution of the traction return current and the rail potential in different conditions inside and outside the tunnel using the Carson formula and the Tylavskyformula. The paper calculates the short-circuit impedance of the traction network in the condition of conduct wire-rail short circuit and conduct wire-return wire short circuit. What’s more, the paper takes consideration of the influence of the partial capacitance on the above results. At last, the paper talks over the integrated grounding system inside the tunnels, and does research on the influence of the factors on the rail potential such as the impedance per unit length between the rails and earth, the integrated grounding wire, the cross lines connecting the upper and lower rails, and draws the appropriate conclusions.