Third Rail Insulator Failures: Current State of the Practice (2020)

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1 Rail transit systems are important and critical components of transportation networks, particularly in large metropolitan areas. Third rail systems provide traction power to electrified rail systems in many parts of the world, including the United States, and encounter problems such as failures that need to be investigated and remediated. In this study, causes of third rail systems’ failures were investigated. The existing litera- ture was comprehensively reviewed and characteristics of third rail systems were studied in detail. The causes of the third rail systems’ failures were classified into four categories: environmental, mechanical, electrical, and operational. Based on the reviewed literature, a multi-section survey was developed that included (1) respondent information, (2) agency information and size, (3) general information about third rail insulators, (4) cost of insu lator failures, and (5) causes of insulator failures. The results from the survey demonstrated that the transit agencies average 10 insu- lator failures and less than 10 hours of delays annually. An average of 1,000 passenger hours were lost annually because of insulator failure by each of the eight surveyed transit systems. Porcelain insulators were reported as the most expensive insulators, with an average cost of US$256 per unit, and epoxy insulators were reported as the least expensive, with an average cost of US$108 per unit. Dirt buildup was found to be the most frequent cause of insulator failures, and the penetration of saltwater into the conduit the least frequent cause of failure. Based on the collected survey responses, five case examples were selected from different transit agencies with third rail systems. The goal of the case example collection and analysis was to perform an in-depth study of third rail characteristics and failures. The results of the analysis revealed that • Local environmental conditions can cause degradation of third rail insulators over time, • The operational cost per insulator failure is higher than the average price of an insu- lator unit, • The lessons learned need to be documented more frequently, and • Performing regular maintenance and inspections is an effective approach to reducing the number of failures in transit systems. In sum, this synthesis study documented the current maintenance practices and/or renewal of third rail insulators, lessons learned from third rail insulator failures, and the agencies’ mitigation strategies. The research findings serve as an appropriate source of information on third rails in transit systems for practitioners and future researchers. S U M M A R Y Third Rail Insulator Failures: Current State of the Practice