Keeping train operators toeing the line

Equipment at present being installed by Railtrack, which owns almost all of Britain’s railway infrastructure, is designed to reduce costly repairs and delays to trains. Around £3.1 million is being spent on computerised monitoring equipment being erected at key locations on overhead electric lines in England and Scotland to prevent damage to the lines.

Called Panchex, the system designed and developed by BRR, part of AEA Technology, automatically measures the amount of uplift exerted by a train’s pantograph as it passes the monitoring equipment. The pantograph, mounted on the train’s roof, makes contact with the high voltage overhead cables and incorporates a joint system which allows the top to move up and down while maintaining an almost constant contact with the cable.

Monitoring the amount of movement allows the system to alert Railtrack and the train operator if a pantograph is likely to damage overhead line equipment. Faulty or badly-adjusted pantographs can be quickly removed from service and sent for repair or adjustment by the train operator.

To help improve potential fault detection and train operation the system incorporates conductive plastic position sensors supplied by Variohm Components. Robust and fully sealed Novotechnik Series LWG transducers were specified, which produce a signal corresponding to the upward force exerted by the pantograph. The signal is amplified and the output monitored by computer. Deviations of the order of 12mm are the critical factor. This information allows corrective action to be taken before damage occurs.

Accurate measurement of the twin-bearing actuating rod transducer is assured with a resistance element of conductive plastic, sprayed on a glass-fibre reinforced substrate.

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