A Novel On-lineMonitoring Device ofStray Current inDC RailTransit Systems

At present, therail transit system adopts DC electric traction. Thecurrent required bythevehicles flows outfromthe traction substation, andthenpassthrough theOCS (Overhead Contact System) andtherunning rails. At last, thetraction current will return tothetraction substation. A proportion ofthe traction current will leaktoearth, suchleakage current iscalled straycurrent. Generally, thestraycurrent canbecalculated indirectly byusingthefollowing parameters: therunning rail longitudinal resistance, runningrail-to-carth resistance and running rail-to-carth voltage. Itisnecessary todevelop on-line monitoring device ofstray current inmetro. Inthis paperanovel straycurrent on-line monitoring device basedon embedded microcomputer system isdeveloped. According tothenewmethod presented inthispaper, theon-line monitoring device willbe installed alongtherail, and connected eachotherwith communication cabletoforma real-time monitoring system. Comparing withthetraditional methodthatinstalling the monitoring device attheequal distance along therail, this novel methodcouldnotonlyreduce thesystemcomplexity andfunds budget, butalso enhance themonitoring accuracy andprecision.