l l 1 I i l I i l l NATToNAL coopERArrvE HrcHwAy RESEARcH ri::ååi 317 TRANSIENT PROTECTION, GROUNDING, AND SHIELDING OF ELECTRONIC TRAFFIC CONTROL EQUIPMENT H. W. DENNY and J. p. ROHRBAUGH Georgla Tech Research lnstitute Georgia lnstitute of Technology Atlanta, Georgia RESEARCH SPONSORED BY THE AMERICAN ASSOCIATION OF STATE HIGHWAY AND AREAS OF INTEREST: TRANSPORTATION OFFICIALS IN COOPERATION WITH THE FEDERAL HIGHWAY ADMINISTRATION Maintenance operations and Traffic Control (Highway Transportation) TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL WASHINGTON, D.C, JUNE 1989 NATIONAL COOPERATIVE HIGHWAY RESEARCH NCHRP REPORT 317 PROGRAM Project 10-34 FY'86 Systematic, well-designed research provides the most effec- ISSN 0077-5614 tive approach to the solution of many problems facing high- ISBN 0-309-04ó14-9 way administrators and engineers. Often, highway problems L. C. Catalog Card No. 89-50190 are of local interest and can best be studied by highway de- partments individually or in cooperation with their state universities and others. However, the accelerating growth Price $11.00 of highway transportation develops increasingly complex problems of wide interest to highway authorities. These NOTICE problems are best studied through a coordinated program of The project that is the subject of this report was a part of the National Co- operative Highway Research Program conducted by the Transportation Re- research. cooperative search Board with the approval of the Goveming Board of the National Research Council. Such approval reflects the Governing Board's judgment In recognition of these needs, the highway administrators of thât the program concemed is of national importance and appropriate with the American Association of State Highway and Transpor- respect to both the purposes and resourcc of the National Research Council. tation Offrcials initiated in 1962 an objective national high- The members of the technical committee selected to monitor this project and way research program employing modern scientihc tech- to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the proj- niques. program This is supported on a continuing basis by ecl. The opinions and conclusions expressed or implied are those of the re- funds from participating member states of the Association search agency that performed the research, and, while they have been and it receives the full cooperation and support of the Fed- accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the Nâtional Research Council, eral Highway Administration, United States Department of the American Association of State Highway and Transportation oflicials, or Transportation. the Federal Highway Administration, U.S. Department of Transportation. Eâch report is reviewed accepted publication com- The Transportation Research Board National Re- and for by the technical of the mittee according to procedures established and monitored by the Transpor- search Council was requested by the Association to admin- tation Research Board Executive Committee and the Governing Board of the ister the research program because of the Board's National Research Council. recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as: it maintains an extensive committee structure from which Specia! Notice authorities on any highway transportâtion subject may be The Transportation Research Board, the National Research Council, the Fed- drawn; it possesses avenues of communications and cooper- eral Highway Administration, the American Assæiation of State Highway and Transportation Officials, and the individual states participating in the ation with federal, state, and local governmental agencies, National Cmperative Highway Research Program do not endorse products or universities, and industry; its relationship to the National manufacturers. Trade or manufacturers' names appear herein solely because Research Council is an insurance of objectivity; it maintains they are considered essential to the object of this report. a full-time research correlation staff of specialists in high- way transportation matters to bring the hndings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and trans- portation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association ol State High- way and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted pro- posals. Administration and surveillance of research contracts Published reports of the are the responsibilities of the National Research Council NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM and the Transportation Research Board. are available from: The needs for highway research are many, and the National Cooperative Highway Research Program can make signifi- Transportation Research Board cant contributions to the solution of highway transportation National Research Council problems of mutual concern to many responsible groups. 2l0l Constitution Avenue, N.W. The program, however, is intended to complement rather Washington, D.C. 20418 than to substitute for or duplicate other highway research programs. Pnnted in the United Statð of America i I l .t FOREWORD Transportation engineers and technicians responsible for the design, specification, installation, and maintenance of traffic signal and related types of electronic equipment By Staff will be interested in the fìndings and recommendations of this report. The research Transportation reported herein addresses the problem of damage to trafhc control equipment caused Research Board by electrical noise and transients (voltage spikes and surges) due to lightning, switching, and radiated electromagnetic interference (EMI) from radio and TV stations, radar, and mobile radio transmitters. The research reported herein provides procedures, practices, test methods and specifications for the protection of not only traffrc control equipment but also other types of equipment operated by transportation agencies such as trafflrc counters de- ployed for planning purposes, vehicle classifiers, weigh-in-motion systems, warning devices, and the like, In short, the material in this report can be applied to almost any type of electronic hardware that is exposed to damaging transients. The problem of electrical transient damage to electronic control equipment may be minimized and, in most cases, eliminated by proper application of existing tech- nology; in other words, currently available devices may be able to provide sufhcient protection against equipment malfunction and deter damage. However, there are currently no widely accepted specifications or procedures for the transient protection ,.Transient of traffic control equipment. NCHRP project 10-34, protection, Ground- ing, and Shielding of Electronic Traffic Control Equipment," was initiated in response to this need. Researchers at the Georgia Tech Research Institute, Atlanta, Georgia, conducted the study, drawing on their extensive experience with protection of equip- ment in the flrelds of residential and industrial electrical power, computers and tele- communications, and military and aerospace applications. The researchers began their work with an examination of typical trafhc con- trollers, breaking them down into subparts of equipment cabinet, terminal blocks, internal components, and associated input and output wiring. This was followed by an in-depth review ofprotection devices and grounding, shielding, and bonding tech- niques currently employed in the traffic control field and in related fields. Existing specifications of the Institute of Electrical and Electronics Engineers (IEEE) and the National Electrical Manufacturers Association (NEMA) were reviewed for their ap- plicability and appropriateness for traffrc control equipment. Discussions were held with traffrc system operating personnel in high lightning incidence areas such as Atlanta, Georgia, and rampa and sarasota, Florida. Manufacturers of protection devices were surveyed and descriptive material, costs and performance data were obtained. This report is comprised of six chapters and an appendix which contains rec- ommended modifications to the NEMA standards Publication TSI-1983, Traffic control systems, The main body of the report is a comprehensive state-of-the-art document expected to serve as an in-depth technical reference for years to come. The appendix recommends changes that would be appropriate to allow equipment com- plying with NEMA TSI-1983 to meet a nominal lightning protection requirement. Readers are cautioned that the recommended modiflrcation to NEMA TSI-1983 may not be the most appropriate for their particular case because many localities do not have the lightning problems that others do. Imposing a stringent transient requirement on NEMA equipment would create added expense for many that may be unjustified. Another product ofthe research, expected to be available late in 1989, is a video training tape including both user's and instructors' notes. These materials are intended to provide (non-electrical) engineers