Condition monitoring of railway electric point machines

An electric point machne is a motor-driven device whch operates railway track switches (points). Failure of such a device causes delay to trains and, on privatised railways, is likely to incur a financial penalty for the infrastructure owner. The most probable types of fault occurring with a typical point machine design are described. Using analyses of the results of laboratory and field tests, techniques for condition monitoring are reviewed. A net energy technique is proposed and is shown to produce discrimination and repeatability. The technique uses non-invasive sensors and may have a pay-back period of under one year for a large installation.