Guidebook for Detecting and Mitigating Low-Level DC Leakage and Fault Currents in Transit Systems (2020)

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2020 T R A N S I T C O O P E R A T I V E R E S E A R C H P R O G R A M TCRP RESEARCH REPORT 211 Research sponsored by the Federal Transit Administration in cooperation with the Transit Development Corporation Subject Areas Energy • Public Transportation • Safety and Human Factors Guidebook for Detecting and Mitigating Low-Level DC Leakage and Fault Currents in Transit Systems Yilmaz Sozer The UniversiTy of Akron Akron, OH

TCRP RESEARCH REPORT 211 Project D-17 ISSN 2572-3782 ISBN 978-0-309-48164-9 © 2020 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FTA, GHSA, NHTSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the Transit Cooperative Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report. TRANSIT COOPERATIVE RESEARCH PROGRAM The nation’s growth and the need to meet mobility, environmental, and energy objectives place demands on public transit systems. Cur- rent systems, some of which are old and in need of upgrading, must expand service area, increase service frequency, and improve efficiency to serve these demands. Research is necessary to solve operating prob- lems, adapt appropriate new technologies from other industries, and introduce innovations into the transit industry. The Transit Coopera- tive Research Program (TCRP) serves as one of the principal means by which the transit industry can develop innovative near-term solutions to meet demands placed on it. The need for TCRP was originally identified in TRB Special Report 213—Research for Public Transit: New Directions, published in 1987 and based on a study sponsored by the Urban Mass Transportation Administration—now the Federal Transit Administration (FTA). A report by the American Public Transportation Association (APTA), Transportation 2000, also recognized the need for local, problem- solving research. TCRP, modeled after the successful National Coop- erative Highway Research Program (NCHRP), undertakes research and other technical activities in response to the needs of transit ser- vice providers. The scope of TCRP includes various transit research fields including planning, service configuration, equipment, facilities, operations, human resources, maintenance, policy, and administrative practices. TCRP was established under FTA sponsorship in July 1992. Proposed by the U.S. Department of Transportation, TCRP was authorized as part of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). On May 13, 1992, a memorandum agreement outlining TCRP operating procedures was executed by the three cooperating organi- zations: FTA; the National Academies of Sciences, Engineering, and Medicine, acting through the Transportation Research Board (TRB); and the Transit Development Corporation, Inc. (TDC), a nonprofit educational and research organization established by APTA. TDC is responsible for forming the independent governing board, designated as the TCRP Oversight and Project Selection (TOPS) Commission. Research problem statements for TCRP are solicited periodically but may be submitted to TRB by anyone at any time. It is the responsibility of the TOPS Commission to formulate the research program by identi- fying the highest priority projects. As part of the evaluation, the TOPS Commission defines funding levels and expected products. Once selected, each project is assigned to an expert panel appointed by TRB. The panels prepare project statements (requests for propos- als), select contractors, and provide technical guidance and counsel throughout the life of the project. The process for developing research problem statements and selecting research agencies has been used by TRB in managing cooperative research programs since 1962. As in other TRB activities, TCRP project panels serve voluntarily without compensation. Because research cannot have the desired effect if products fail to reach the intended audience, special emphasis is placed on disseminat- ing TCRP results to the intended users of the research: transit agen- cies, service providers, and suppliers. TRB provides a series of research reports, syntheses of transit practice, and other supporting material developed by TCRP research. APTA will arrange for workshops, train- ing aids, field visits, and other activities to ensure that results are imple- mented by urban and rural transit industry practitioners. TCRP provides a forum where transit agencies can cooperatively address common operational problems. TCRP results support and complement other ongoing transit research and training programs. Published research reports of the TRANSIT COOPERATIVE RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to https://www.nationalacademies.org and then searching for TRB Printed in the United States of America

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.

C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR TCRP RESEARCH REPORT 211 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Gwen Chisholm Smith, Manager, Transit Cooperative Research Program Stephan A. Parker, Senior Program Officer Stephanie L. Campbell, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Kami Cabral, Editor TCRP PROJECT D-17 PANEL Field of Engineering of Fixed Facilities Robert A. Schmitt, Metropolitan Transportation Authority—New York City Transit, New York, NY (Chair) John Pliny Aurelius, East Haven, CT Steven D. Bezner, Rockville, MD Melvin Clark, LTK Engineering Services Pamela J. McCombe, HNTB David T. Montvydas, Southeastern Pennsylvania Transportation Authority (SEPTA), Philadelphia, PA Edward J. Rowe, LTK Engineering Services Terrell Williams, FTA Liaison Louis F. Sanders, APTA Liaison Stephen J. Andrle, TRB Liaison

TCRP Research Report 211 documents low-level leakage current detection methods using two approaches. The first approach involves injecting a high frequency signal into a segment of the power line nonintrusively and determining the high frequency impedance of the selected line segment. Segmentation of the line is achieved by applying a virtual blocker at each end of the chosen segment. The high frequency impedance of that segment is thus linked to the condition of the cable and the level of the leakage current in the segment. The second approach measures the radio frequency (RF) emissions from the power network and relates the condition of the network to the frequency content of those emissions. This guidebook provides specifications for the sensors for the two approaches as well as outlines their capabilities and appropriate operating conditions. The sensors developed can be classified into two categories: (1) nonintrusive injection- based and (2) RF emission-based sensors. The frequency, voltage, and current limitations are specified for the injection-based sensors. The data processing and linkage to failures along with the frequency of operation are provided for the RF emission-based sensors. The report will be of interest to those responsible for detecting and mitigating low-level DC leakage and fault currents in transit systems. Improving the reliability of railway electric systems and preventing electrical outages resulting from insulator flashover and insulation failure are difficult because of aging infra- structure and the lack of tools for continuous monitoring. Leakage currents resulting from insulator failure or contact of nonconductive surfaces, such as animals or trees, with the conductor fall below the detectable level of conventional relays. Because these faults are often caused by energized conductors within public reach, they pose a threat to personal safety and property security. More often than is desirable, the service that electric rail- way systems provide to travelers is interrupted because of electric power disruptions. To minimize service disruptions, there is a need to design and develop a smart sensor network system to perform predictive electric system monitoring and to keep faults from occurring. The objectives of TCRP Project D-17 were to develop (a) one or more prototype methods, tools, or techniques for detecting and monitoring low-level DC leakage and fault currents (i.e., magnitude of current and location of fault) in electrified transit systems and (b) a guide to detecting and mitigating low-level DC leakage and fault currents in transit systems. Electrical faults of interest include, but are not limited to, those originating from sub surface conductors as well as third rail and overhead contact systems. The research team for TCRP Project D-17 developed prototypes for overhead contact systems. TCRP Project D-19 (Phase II of TCRP Project D-17) will develop prototypes for third rail systems in an effort to eliminate electrical fires in tunnels and on rights of way. F O R E W O R D By Stephan A. Parker Staff Officer Transportation Research Board

Led by principal investigator Yilmaz Sozer, the research team for TCRP Project D-17 began by conducting a literature survey of the existing technologies and standards for leakage current modeling and prediction in transit railway systems. Standards reviewed included the following: • Institute of Electrical and Electronics Engineers (IEEE) Standard 80; • National Electrical Safety Code (NESC) or American National Standards Association (ANSI) Standard C2 published by IEEE; • National Electrical Code (NEC) or NFPA 70, part of the National Fire Codes series published by the National Fire Protection Association (NFPA); • NFPA 130, Standard for Fixed Guideway Transit and Passenger Rail Systems; • American Railway Engineering and Maintenance-of-Way Association (AREMA) Chapter 12, Rail Transit; • AREMA Chapter 11, Commuter and Intercity Rail Systems; • AREMA Chapter 17, High Speed Rail Systems; and • AREMA Chapter 33, Electrical Energy Utilization. The research team developed a model and a simulation of the electric transit system and tested the feasibility of the proposed nonintrusive injection method in determining the level of the leakage current. For the RF emission-based approach, Exacter, Inc.’s, alternating current (AC) emission measurement system was modified for direct current (DC) systems. The research team finalized the development of the active clamp injector units and deployed them on a transit railway segment for testing purposes. Similarly, Exacter RF emission units were modified based on the tests and deployed for testing on a transit car. This guidebook is available on the TRB website (www.trb.org) by searching for “TCRP Research Report 211”.

1 Chapter 1 Introduction 2 Chapter 2 Nonintrusive Injection-Based Techniques 4 2.1 Segmentation of the DC Electric Network 5 2.2 Frequency Range Allowed to Be Injected into the Line 5 2.3 Signal Level That Can Be Injected into the Line 6 2.4 Environmental Conditions for the Sensor 7 2.5 Power Consumption for the Sensors and Communication Channels for the Sensors 7 2.6 Decisionmaking 7 2.7 Wireless Communications 8 Chapter 3 RF Emission-Based Sensors 8 3.1 Data Structure and Interface for the Sensor Data 8 3.2 Data Event 9 3.3 Data Security 10 3.4 Sensor Location 10 3.5 Failure Signatures 11 3.6 Group Maintenance Reports 15 Acronyms, Abbreviations, Definitions, and Initialisms 16 Bibliography and Other Resources 18 Appendix Developing the Guidebook for Detecting and Mitigating Low-Level DC Leakage and Fault Currents in Transit Systems C O N T E N T S