Transit agencies that use electrical traction (overhead catenary or third rail) generally use the running rails as part of the circuit to return the negative power to substations. Insulated rail joints (IJs) are special devices in the track that separate train control circuits and traction power segments. Some agencies have experienced significant failures of IJs related to arcing of the traction power negative return currents. With higher currents resulting from AC propulsion, IJ failures have become even more problematic and more frequent across many transit properties. In some locations, the same IJs have failed multiple times in a short span of time. These failures result in unplanned delays to passengers and additional expenses related to repairs and damage to the track, train control systems, and traction power systems, and can contribute to stray currents that damage other infrastructure. As such, there is a great research need into IJ failures with possible mitigation guidelines.
IJs are often designed for the freight railroads, with low-voltage/low-amperage train control systems, and may not perform well in a high-voltage/high-amperage (traction power negative return) transit environment. With higher currents resulting from AC propulsion, the failure of current designs needs to be investigated and new guidelines developed, leading to modified existing IJ practices or AC vehicle design. In addition, guidelines are needed as to how to locate and diagnose problematic IJs.
The objectives of this research will include (1) identifying potential causes of IJ failures, especially those under high currents resulting from AC propulsion and (2) developing guidelines for maintenance personnel to diagnose these failures and determine the best mitigation of the root causes.