Study On Distribution Of Metro Stray Current

In recent years,China's subway construction in the proportion of public investment in the country is getting higher and higher.Many cities are in full swing in the subway construction.1500V and 750V DC power supply is used in the subway power supply system in china by using the rail return.In the course of the rail return,a part of the current does not pass through the rail to form stray current.Stray current is very harmful to the structural steel of the subway construction and brings about serious corrosion to the city underground pipeline.Not only does it pose a major threat to the construction and pipeline safety,but it also causes a lot of economic losses.Therefore,it is of great significance for the future construction and passenger safety to analyze the distribution of stray current and predict the distribution of track potential and stray current.At present,most of the research on stray current is based on the study of its continuous model and discrete model.However,the track used in the subway is ballastless track,and stray current flows through the sleeper into the earth.Therefore,the continuous model is not consistent with the actual situation.Although the discrete model takes it into account,it is just the deduction and simulation of unilateral power supply and the bilateral power supply of the single vehicle,so it is not in accord with the actual situation,either.In this paper,the actual situation of the subway operation is considered,and the traction substation and the trains are considered as the injection current source,and the formation of stray current and rail potential is considered as the result of the interaction between them.Based on Kirchhoff s current law and superposition theorem,the calculation model of subway stray current is established.Three different network structures including the "rail-earth","rail-drainage net-earth",and "rail-drainage net-buried metal-earth" are used.Then the mathematical models for calculating the rail potential and stray current of the three different grid structures are calculated respectively.Based on the simulation of Matlab,the variation rules of track potential,track current and stray current are analyzed according to the simulation results,which verify the correctness of the model.At the same time,the calculation of the total area of reinforcement and the calculation of DC resistance of the auxiliary drainage net is introduced in this paper.The four-layer network structure "rail-drainage net-auxiliary drainage net-earth" has been adopted.When the auxiliary drainage net takes different longitudinal resistance values,respective simulation analysis is carried out on stray current and rail potential distribution of the new subway lines and operating lines in the absence of discharge,as well as stray current and rail potential distribution of the new subway lines and operating lines during discharge.The analysis results show that when the auxiliary drainage net longitudinal resistance varies within a certain range,it has no influence on stray current and rail potential distribution of the new lines and the operating lines in the case of no discharge and discharge.