Lightning and its effects on railroad signal circuits

PDFTech ReportDOT-TSC-FRA-75-21FRA-OR&D-76-129RR602LightningTrack circuitsRailroad signalsInterferenceAtmospheric interferenceUnited StatesJohn A. Volpe National Transportation Systems Center (U.S.)Holmstrom, F. RossUniversity of Massachusetts at LowellJohn A. Volpe National Transportation Systems Center (U.S.)United States. Federal Railroad Administration. Office of Research and DevelopmentAGR-INFRASTRUCTURE-RailroadsNTL-RAIL TRANSPORTATION-Rail SafetyVolpe National Transportation Systems Center, Technical Reference CenterThis study discusses the occurrence of lightning, its effects on railroad signal equipment, and protection of such equipment from lightning damage, with special attention to known protective techniques which are employed in a variety of situations in the power, communications, and railroad industries. A brief review is offered of the causes of lightning and other surges, followed by an extensive treatment of the means by which lightning and power-line transients induce surges and over-voltages in signalling circuits. Specific topics include the effects of the direct stroke current, the collapsing electric field when the stroke occurs, inductive coupling, and the effects of ground currents in the earth. A survey of protective devices and techniques currently in use for specific types of equipment is presented, including categorization of arrestors by type and application. Preferred lightning protection practices in railroad signalling are examined and related to practices in other fields. The problem of lightning protection is addressed from an overall systems viewpoint, encompassing development and testing of protective systems and design of systems, so that they can more easily be protected. Recommendations for future research are made