Study On Key Factors Contributed To The Overrun Alerts By Stray Current Monitoring System And Corresponding Countermeasures

Urban mass transit brings a series of problems while providing convenient services to people.Among them,the problem of the stray current generated during the operation of subway trains is particularly serious.This will not only shorten the service life of metal pipeline,but also reduce the strength and durability of the reinforced concrete main structure of the subway tunnel.As the subway is a systematic and complex underground project,it is difficult to reinforce or renovate its main structure after commencement of operation.Therefore,it is of great practical significance to study the key factors influencing the distribution of stray current and the monitoring system for the subway lines in operation.This thesis is mainly consisted of the following aspects:(1)Based on actual on-site measured data,select targeted power supply interval and establish a "rail-discharge network-earth" stray current distribution model of bilateral power supply to verify the effectiveness of the monitoring system;(2)Through the collection,comparison and analysis of a large number of stray current monitoring system data,identify the key factors affecting the stray current distribution of subway operating lines;(3)Based on the result of above data analysis,recommend potentially feasible protection measures for the subway lines in operation against possible stray currentFinally,through the analysis,it can be obtained that:(1)Preliminary analysis on the models and on information provided by system alerts indicate that the monitoring system appears to be effective in reflecting the leakage situation of stray current with relative accuracy.(2)Based on the study of the distribution,quantity,position and other information related to and provided by system alerts,it appears that the transition resistance between the rail and the discharge network may be the key factor affecting stray current leakage in the subway operating line.(3)Based on analysis of the monitoring system,this paper discusses and compares the protective measures for limiting stray current from three aspects : "plug stray current as the main part","discharging stray current as the auxiliary part" and "strengthening stray current monitoring",and conducts the feasibility analysis thereof.