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2 Introduction 1.1 Problem Statement In some metro rail networks, an electrified third rail is installed on the electric railways to provide traction power for the rail cars. To isolate the third rail from the ground and to pre- vent them from finding a short circuit path to the negative return, insulators are used. The insulators are usually covered with contaminants that originate from the trainsâ operation and other resources that accumulate over time and lead to fires, smoke, leakage currents, and even failure of the insulators. The problem is exacerbated when incidents occur in tunnels. Insulator failures can lead to delays in one component of the transit system and impact the whole railway. Passengers lose trust in the ability of the metro system to get them to their destination safely and on time, and they look for other modes of transportation. Thus, it is important to investigate the causes of insulator failures in third rail transit systems. The primary objective of this study was to investigate the present practices and lessons learned related to third rail insulator systems in the United States. To accomplish these objec- tives, the following sub-objectives were developed: 1. Investigate the characteristics of third rail infrastructure specifications that are imple- mented by various U.S. transit agencies (e.g., materials, mounting configurations, contact types, or environmental aspects). 2. Identify the types of failures and their corresponding causes (e.g., environmental, mechanical, operational, and electrical). 3. Determine the rate of third rail failures in transit agencies. 4. Examine the impacts of failures on the operations of transit agencies (e.g., costs or customer loss). 1.2 Technical Approach This study included four major steps. First, the existing literature related to third rail insu- lators was collected and studied. The database included peer-reviewed articles, conference papers, manuals, books, and reports published by academicians, experts, and professionals who study third rail systems. Second, a content analysis of the collected documents was performed, which led to identification of third rail characteristics, arrangements, mechanisms, advantages and disadvantages, challenges and failure causes, and material types. Third, a survey collecting data on respondent information, agency information and size, general informa- tion about third rail insulators, cost of insulator failures, and causes of insulator failures was developed and distributed among experts active in transit agencies with third rail systems. Finally, five transit agencies were selected and an in-depth study of their third rail issues was performed and analyzed. C H A P T E R 1
Introduction 3 1.3 Organization of the Report The content of this research study is explained and organized in five chapters as follows: Chapter 1: Introduction. This chapter presents the problem statement, objectives, and technical approach of the current study. Chapter 2: Literature Review. This chapter documents a summary of existing literature on third rail systems and their corresponding issues and potential solutions. Chapter 3: Survey. This chapter provides information on the development and distribution of the survey and presents the identified results. Chapter 4: Case Examples. This chapter provides a detailed description of the conditions of third rail insulators for five transit agencies that implement third rails in their system. Chapter 5: Conclusions and Future Research. This chapter summarizes the findings of this study. Following the five chapters are references and appendices. Appendix A contains a copy of the invitation email. Appendix B contains a survey of TCRP Synthesis J-7. Appendix C contains a case example questionnaire. Appendix D contains a case example interview guide. Finally, Appendix E displays graphical results of the survey.
