Study On The Stray Current Distribution Characteristics Of Urban Rail Transit Under The Combined Action Of Multiple Soil Factors

Compared with other modes of transportation,urban rail transit system has certain advantages in terms of transportation speed,volume,energy conservation and environmental protection,so it is playing an increasingly important role in transportation.However,DC power supply is usually used in the operation of urban rail transit,and because the track and the earth can not be completely insulated,in the process of the traction current flowing back to the traction substation through the track,there will always be part of the traction current flowing into the earth through the track,which is called stray current.When the stray current acts for a long time,it will cause great harm to the buried metal structure,signal equipment and workers.Firstly this thesis describes the operation principle and composition of power supply system of urban rail transit,and then introduces the current research status of stray current of power supply system of urban rail transit at home and abroad,including the formation principle of stray current,electrochemical corrosion of metal structure and the monitoring and protection of stray current.In order to clarify the influence of soil factors on the distribution of stray currents,this thesis uses MATLAB software to simulate and analyze the stray currents,and use Simulink module to establish the structure model of running rail-ground and running rail-drainage network-ground,and analyze the distribution law of stray current during the operation of the power supply system in a given interval,and the influence of the drain network and external resistance on the magnitude of the stray current.The experimental test platform corresponding to the simulation model was built.Through the experimental test data,the influence of various soil factors on the stray current distribution law is analyzed,and which soil factor have the greatest influence on the stray current under the simultaneous action of various soil factors.Finally,through the fuzzy comprehensive evaluation of the experimental data,the final evaluation matrix of stray current in the sample soil can be obtained.The results show that the value of stray current will decrease under the action of the resistance outside the zone,but the inhibition degree of stray current is less than that of the drain network,so the reasonable connection of the drain network in the engineering can effectively suppress the generation of stray current.The results of soil samples from Dong Gang Station and Qi Lihe Station of Lanzhou Rail Transit Line 1 show that soil p H value has the greatest influence on the distribution of stray current relative to soil moisture,temperature,porosity and salt content.According to the evaluation matrix B,the membership degree of stray current in the "good" state in the sampled soil accounts for the largest proportion of all possible states,with a value of 46.31%,indicating that the sampled soil is not conducive to the formation of stray current,so it has little impact on operation safety.