Examples of Stray Current Interference

Running a passenger train on an electrified traction system of a DC source can sometimes lead to stray DC current. The metallic structures and installations across tunnels and railways will often lead to the current moving out from the imperfect insulation in the third rail or connecting rail. Because the return circuit with the earth may be closer, the currents flowing across the running rails may often leak into the ground when it easier to make the connection. Buried metallic structures and low electrical resistance paths can cause straight DC current easily. 

When a stray currently is a metallic structure damaging corrosion can occur as well as the chance for parking and fire. Having proper communication systems to signal this interference can be important to reducing endangerment and accidents. 

The design of a monitoring system is just one aspect of managing straight DC current. Another objective is to limit the intensity of the current that leaks into the ground and this means making sure that the current flow can lead back to the traction power substation. Adequate insulation for the running rails as well as a low running rail resistance can be important to preventing the chance that stray current occurs. 

Extra provisions can also be added in including insulated sleepers and redesigning for adequate clearance between the support structure and the tracks. Making these modifications to handle stray DC current can reduce the overall risk of running a locomotive and the series of events that can regularly trip warning equipment or disrupt operations. 

If you need assistance with managing straight DC currents are monitoring and improvements to your electrical design, contact our team today. We can assess issues with stray DC current on your systems and create appropriate solutions. 

This post was written by Justin Tidd, Director at Swartz Engineering. For nearly a half a century, Swartz Engineering has been at the forefront of industry safety. They are a family-owned company specializing in power distribution for the electrical industry. They are the leading manufacturer of Type 76 DC relays. It is the most widely accepted protective overcurrent device used in the transit industry today.