Research On Stray Current Distribution Characteristics Under Local Insulation Defect Of Rail-ground

With the increase of the operating time of the urban rail transit system,the insulation between the rail and ground is affected by factors such as the environment and stress damage,causing local insulation defect which resulting in stray current leakage increased.Stray current flowing into underground buried pipelines will affect the pipelines' service life,and it will also bring great hidden dangers to subway traffic safety.Therefore,establishing a stray current evaluation model under the insulation defect between rail and ground,according to the distribution characteristics of stray current and proposing some protective measures are great significance to ensure the safe and reliable operation of urban rail transit system.This article focuses on the stray current leakage caused by local insulation defect,a stray current evaluation model under the local insulation damage of the rail ground is established.Through the above two models,the influencing factors on the stray current distribution were analyzed,and the distribution laws were summarized.The corresponding angle proposes corresponding protective measures to reduce stray current leakage.The main research contents of this paper include:(1)Establishing two types of stray current distribution models of rail-ground and rail-grid-ground.Combined with the boundary conditions of insulation defect,the rail potential,rail current,drainage network potential,and drainage network current distribution formulas are derived.(2)Based on the above model,the factors affecting the local insulation defect of rail-ground is simulated and analyzed with the MATLAB software.The results show that: the location of the insulation defect points and the grounding resistance value will affect the distribution of rail potential,grid potential,grid current and stray current leakage range.The smaller the grounding resistance is,the impact on the return system parameters is greater.When there are two insulation defect points in the section,the defect point which is far away from the "zero" potential point has a significant effect on the parameters of the reflux system.The impact of the number of insulation defect points should be analyzed in conjunction with the distribution of the insulation defect points.(3)According to the composition and spatial distribution of the track bed,a corresponding stray current evaluation model under local insulation defect of rail-ground is established based on CDEGS.Based on the model,a simulation analysis of the influence factors of local insulation defect of rails-groundsis conducted.The results show that: the location of the insulation defect points and the grounding mode will affect the rail potential,the drain network current,the stray current leakage range,and the the corrosion range of the flow network;The second type of insulation defect has a great influence on the reflux system.When there are two second type of insulation defect points,the defect point which is far away from the "zero" potential point has a significant effect on the parameters of the reflux system.(4)A stray current simulation experimental device was set up.The device is used to analyze the influence of insulation defect factors on stray current interference characteristics.The results show that the corrosion risk range and stray current leakage range of buried pipelines are affected by the distribution of insulation defect points and the grounding resistance.There are 50 figures,21 tables,and 85 references in this thesis.