AC/DC Stray Current and Mitigation

Stray currents in a rail transit environment may consist of direct current components associated with the operation of DC electric traction systems and alternating current components associated with the operation of AC electric traction systems and electric utility systems.

The impact on the infrastructure will be different for the unidirectional flow of iron ions from a structural steel element due to DC stray currents than for the flow of iron ions from a structural steel element on one half-cycle and the reversal of current into the structural steel element on the other half-cycle due to AC stray currents. The consideration of this issue will yield functional and economic benefits in designing stray current mitigation measures that are commensurate with the electrical environment.