Technical Reports

Conductive Interference in Rapid Transit Signaling Systems, Volume I: Theory and Data

  • 01
  • Nov
  • 1985
AUTHOR: F. Ross Holmstrom
SUBJECT: Signal and Train Control
KEYWORDS: Circuits, Impedance, Propulsion Systems, Signaling Equipment, Substations
ABSTRACT: The purpose of this report is to summarize the results of a comprehensive program that has been pursued to delineate all aspects of conductive interference (Cl) in rail transit systems and to help avoid its effects in new rail transit systems. The report documents the efforts to achieve an understanding of the nature and characteristics of Cl required to remedy specific situations. This program has been under taken as a cooperative venture of U.S. manufacturers of rail transit propulsion and signaling equipment, rail transit system operators, and members of the research and consulting community. In rail transit applications, Cl is defined as electromagnetic interference (EMI) affecting signaling or automatic train control (ATC) systems, caused by spurious currents flowing in the running rails ahead of or behind the train. A prime cause of Cl, and the one dealt with in this report, is the induction of unwanted currents in the running rails by AC harmonic currents present in the third rail. These EMI currents can cause interfering voltages in wayside track circuits and car-borne ATC receivers. The AC harmonic currents in the third rail can be produced by rectification substations and solid-state propulsion control systems on board rail transit vehicles. The report provides an overview of rapid transit propulsion systems, including rectification substations. The major part of the Cl program has dealt with Cl arising from these sources. The authors point out, that as a result of this program, rail transit Cl due to car propulsion systems and rectifier substations interfering with track signaling, is well understood, predictable, and measurable. The report indicates that the techniques of data gathering, measurement, and analysis developed in this program and presented in this report should serve as a basis for mitigating the effects of Cl in future rail transit systems.