BACKGROUND

Transit agencies use electrical traction (overhead catenary or third rail) for the propulsion of trains, which is typically designed using high AC or DC voltages. The running rails are used as part of the system to return negative power to substations. Insulated rail joints are track work components installed in the rails to provide a train control circuit and traction power segment separation between blocks. Insulated joints are implemented in the design of both freight and transit railroads, which operate in vastly different system environments. Freight railroads are typically designed to use low-voltage/low-amperage train control systems with diesel power while transit is typically designed to use train control systems that function in high voltage/high amperage (traction power negative return) systems. 

Some transit agencies have experienced significant failures of insulated joints related to arcing of the traction power negative return currents. With higher currents resulting from AC propulsion, insulated joint failures have become more problematic and more frequent across many transit systems. In some locations, the same insulated joints have failed multiple times in a short span of time. These failures result in unplanned delays to passengers; 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.  

Research is needed on insulated joint failures in high voltage/high current transit environments. Insulated joint failure of in-service designs needs to be investigated in order to develop new guidelines to locate and diagnose problematic insulated joints and recommendations leading to modified insulated joint practices, with possible recommendations for control of the heavy negative returns from AC propulsion rail cars.

OBJECTIVES

The objectives of this project are (1) to identify potential causes of insulated joint electrical failures, particularly those under high currents resulting from AC propulsion; (2) to identify and document the electrical conditions under which various types of joint failures occur; (3) to develop guidelines for maintenance personnel to diagnose insulated joint electrical failures and determine the best mitigation of the root causes; and (4) to recommend additional research needed to address root causes of insulated joint electrical failures.

RESEARCH PLAN

The research plan will describe appropriate deliverables that include the following (which also represent key project milestones):

1. An Amplified Research Plan that responds to comments provided by the project panel at the contractor selection meeting.
2. An Interim Report and panel meeting. The Interim Report should include the analyses and results of completed tasks, an update of the remaining tasks, and a detailed outline of the final research product(s). The Interim Report and panel meeting should occur after the expenditure of no more than 40 percent of the project budget.

FINAL DELIVERABLES

The final deliverables will include but not be limited to:

• Guidelines for maintenance personnel to diagnose insulated joint electrical failures and determine the best mitigation of the root causes;
• A stand-alone technical memorandum titled “Implementation of Research Findings and Products”;
• A report with the following:
  • Documentation of the research activities;
  • Key findings; and
  • Other topics identified during the project.

STATUS: A research agency has been selected for the project. Research in progress.