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TitleModelling geomagnetic interference on railway signalling track circuits
AuthorBoteler, D HORCID logo
SourceSpace Weather 2020 p. 1-18, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200464
PublisherAmerican Geophysical Union
Mediapaper; on-line; digital
File formatpdf; html
SubjectsScience and Technology; Transport; geomagnetism; models
Illustrationsdiagrams; graphs
ProgramPublic Safety Geoscience Assessing space weather hazards
Released2020 11 17
AbstractMisoperation of railway signalling during geomagnetic disturbances has occurred in a number of countries. Railway signals are activated by track circuits that detect the presence of a train in a particular rail section, but geomagnetically induced electric fields can interfere with the track circuit operation, causing the wrong signal to be displayed. This paper develops a new model for track circuit operation that includes the induced geoelectric fields produced by geomagnetic field variations. Rails are modelled as transmission lines with series impedance given by the rail resistance and parallel admittance determined by the current leakage from the rail through the ballast to ground. The transmission line model is then converted into an equivalent-pi circuit for each rail and these are combined with the track circuit power and relay components to form a nodal admittance network for the track circuit. This is used to examine the effect of induced geoelectric fields on track circuit operation. First, an individual track circuit is examined and it is shown how the length, between insulating rail joints, of the individual rails influences the geomagnetic interference voltage produced across the track circuit relay. Then a series of track circuits is considered: a general solution is developed and then the conditions are identified that allow this to be reduced to a simpler solution considering each track circuit individually. This modelling provides insight into the conditions that produce signalling problems and provides the tools to assess the geomagnetic hazard to railway signalling.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. This paper examines the process of electromagnetic induction in track circuits used to control railway signals. A new method is presented for modelling the geomagnetic interference to the track circuits. This can be used to understand the geomagnetic conditions that produce voltages in track circuits that can interfere with operation of the railway signals.

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