The influence of soil characteristics on coupling between DC traction systems and buried utilities

The production of stray currents by DC Light Rail Systems leads to the corrosion of the supporting and third party infrastructure in close proximity to the rail system. This paper focuses on the impact of earthing topologies on the level of corrosion that will be observed on buried structures in the proximity of a transit system. The work describes a modeling technique that can be applied to predict the level of stray current (and hence corrosion damage) in a DC traction system where the soil resistivity varies along the route of the transit system, vertically as well as horizontally. The modeling technique used involves the accurate computation of the shunt and series parameters for use in a resistive type model using a commercially available software package. The results demonstrate the importance that soil resistivity has on the corrosion risk to traction system and third party infrastructure. Such information could ultimately be used to vary the stray current control design across a transit system to provide a match with the external environment and ensure a consistent corrosion lifetime for structures across the whole route. © 2007 by NACE International.