Detecting and Mitigating Low-Level DC Leakage and Fault Currents in Transit Systems

Low-level electrical fault currents are phenomena found in direct current (DC) traction systems used in public transit systems and electrified rail systems worldwide. These low-level currents are typically caused by small and sporadic failures of insulation within the electrification system, which often make them difficult to locate, measure, and control. The apparent effects of these faults can go unnoticed for long periods of time as a result of their slow and progressive nature; however, if these faults are left undetected, evidence exists to show that extensive damage to infrastructure of transit systems and infrastructure of adjacent private/public utilities may result. Recently, a transit system suffered damage to its electrification system because of low-level faults in the central core area. The failure resulted in damage valued at more than a million dollars that impacted rush hour revenue service at the time of occurrence. The failure further necessitated service reductions for several days in the central core transit system area while emergency repairs were performed. Similar problems have occurred at other transit agencies. Low-level DC leakage and fault currents may also create safety hazards to transit employees, patrons, and the general public as contact to any metallic structure (such as fences, light poles, and handrails) is potentially lethal because structures may become energized to dangerous voltages. At present, awareness of such hazards is dependent on acute conditions observed (e.g., boom, flame, smoke, steaming or glowing poles, steaming manholes, smoking insulators; train doors that do not open) or felt (e.g., sluggish train operation; shock or tingle on contact; hot water in cable hole), as well as chronic conditions observed (e.g., rail deterioration, rail web entirely destroyed, burnt surge arresters). Currently, there are no known technologies available to easily detect low-level DC leakage and fault currents. To detect low-level DC leakage and fault currents (at the agency level), it is necessary to conduct extensive field research, which is costly, labor intensive, and difficult to accomplish, particularly in areas remote from traction power substations. With current operating budget restrictions prevalent throughout the industry, this type of testing is not feasible. Research is needed to identify possible workable solutions; develop prototypes for detection and monitoring systems; and, produce a guide to mitigating low-level DC leakage and fault currents. The objectives of this research are to develop (a) one or more prototype methods, tools, or techniques for detecting/monitoring low-level DC leakage and fault currents (i.e., magnitude of current and location of fault) in electrified transit systems and (b) a guide to detecting and mitigating low-level DC leakage and fault currents in transit systems. Electrical faults of interest include, but are not limited to, those originating from subsurface conductors as well as third rail and overhead contact systems.


  • English


  • Status: Completed
  • Funding: $250000
  • Contract Numbers:

    Project D-17

  • Sponsor Organizations:

    Transit Cooperative Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC    20001

    Federal Transit Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Performing Organizations:

    University of Akron

  • Principal Investigators:

    Sozer, Yilmaz

  • Start Date: 20141024
  • Expected Completion Date: 20170930
  • Actual Completion Date: 20170930

Subject/Index Terms

Filing Info

  • Accession Number: 01712954
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project D-17
  • Files: TRB, RIP
  • Created Date: Jul 29 2019 3:26PM