Low-level electrical fault currents are a phenomenon found in DC traction systems used in public transit systems worldwide. These low-level currents are typically caused by small and sporadic failures of insulation within the electrification system, which make them difficult to locate, measure, and control. The effects of these faults go unnoticed for long periods of time because of their slow and progressive nature; however, evidence shows that if these faults go undetected, they can cause extensive damage to infrastructure of transit systems and that of adjacent private/public utilities. The main concern of private/public utilities is the significant corrosion of subsurface utilities caused by the compounding effects of low-level faults. They may also create a safety hazard to transit patrons and the general public as contact with any metallic structures, such as fences, is potentially lethal because they become energized to dangerous voltages. Furthermore, smoke generated by burning cable insulation in tunnels and confined areas creates safety hazards for transit patrons.
Under TCRP Project D-17, a lab breadboard model was developed and testing was conducted at the Greater Cleveland Regional Transit Authority (GCRTA). This research showed positive results in detecting low-level faults in DC transit systems.
Moreover, work is needed to detect low-level fault conditions. To detect these conditions, it will be necessary to conduct extensive testing.
The objective of this research is to develop a prototype system that can detect low-level faults in electrified transit systems powered by third rails.
STATUS: Research in progress.
