CONTROL OF STRAY CURRENT ON THE MARTA RAIL SYSTEM

Stray Current is current flowing through a path other than the intended circuit. Stray Current Corrosion is probably the most critical corrosion problem within direct-current powered transit systems. The Metropolitan Atlanta Transit Authority (MARTA) uses direct current traction power. This propulsion system has an underground traction power circuit. The transit car has steel wheels and operates on standard guage track constructed with 115 lb. rails (the running rails). 750 volts DC traction power is supplied to the car through a pick-up shoe in contact with a third rail located to the side of the track. The negative return from the car is through the car wheel to the running rails. With this system, the running rails are the primary source of stray current. Therefore, it is necessary to accomplish two main goals which will effectively reduce stray current levels to an acceptable minimum; first the electrical resistance of the negative return pathway through the running rails mist be minimized; secondly, the electrical isolation of the running rails from ground must be maximized. Because MARTA is an underground traction powered system, the substation, components of the third rail, and trackway systems must be isolated. Also, it is mandatory to effectively isolate other facilities such as train control, wayside equipment and signal systems. With isolation installed properly, stray curent from the running rails produced by the train operation at one location must return again to the running rails elsewhere in the system rather than through the ground mat to reach the ground bus. The major aspects of corrosion control are: track-to-earth resistance testing; bonding, which makes the system continuous; necessary measures provided during the design and construction stage; cathodic protection on elevators and pipes; and Constant Stray Current monitoring of the system. Corrosion control monitoring is a very important program when maintaining a transit system build for the future.

• Corporate Authors:

  American Public Transportation Association

  1201 New York Avenue, NW
  Washington, DC    20005
• Authors:
  • Terry-Nixon
• Conference:
  • Proceedings of the 1996 Rapid Transit Conference of the American Public Transit Association
  • Location: Atlanta, Georgia
  • Date: 1996-6-2 to 1996-6-6
• Publication Date: 1996

Language

• English

Media Info

• Features: Figures; References;
• Pagination: p. 154-158

Subject/Index Terms

• TRT Terms: Cathodic protection; Corrosion; Corrosion protection; Electric power transmission; Propulsion; Railroad tracks; Rapid transit; Stray currents; Structural design; Traction; Underground structures; Vehicle power plants
• Identifier Terms: Metropolitan Atlanta Rapid Transit Authority
• Uncontrolled Terms: Propulsion systems; Track design
• Old TRIS Terms: Power systems; Underground
• Subject Areas: Bridges and other structures; Energy; Operations and Traffic Management; Public Transportation; Railroads; Vehicles and Equipment;

Filing Info

• Accession Number: 00750134
• Record Type: Publication
• Report/Paper Numbers: Volume 4
• Files: TRIS
• Created Date: Jun 24 1998 12:00AM