While planning or building a brand-new DC transit system with all its new concrete and steel
infrastructure, and an expected design life of 75 to 100 years, someone unexpectantly mentions these corrosive words – STRAY CURRENT. Concern sets in: What is stray current, how is it impacting us, and what do we do especially when we have pre-stressed and post tensioned elements in our infrastructure? There are stray current prevention and protection methods available, that when systematically applied throughout the life of your infrastructure, will alleviate these concerns.

Prevention of stray current impacts start at the design stage, continue through the construction phase, and become an integral part of a long-range preventative maintenance. Stray current protection is all about building in layers of protection, starting with two key elements: electrical isolation and electrical continuity. The challenge lies in where to isolate and where to apply continuity bonding, and then what testing needs to be performed to verify all is in order. A stray current design guideline along with stray current testing plans need to be developed and implemented. Based on recent experiences on several DC transit projects; this paper will explore the noted key elements of any stray current design and
appropriate testing plans required for a successful DC transit system build and long system operating life.