The third rail supplies electrical power to the trains operating on the rail line. It is elevated and runs parallel to the rest of the track. A part of the train known as the Current Collection Device (CCD) is in constant contact with the third rail through a component called the CCD shoe. If you imagine the third rail to be similar to the wall socket at home, the CCD is the plug. However, in the context of a train, the “plug” is sliding along a very long “socket”. As such, the alignment of the elevated third rail has to be very precise in order to power the trains at all times.
The Linear Variable Displacement Transducer (LVDT) helps monitor the alignment of the third rail. The LVDT measures the movement of the CCD shoe and through this data, the system can chart the precise height of every inch of the third rail.
Engineers compare the latest graphs with earlier ones to identify locations where the height of the third rail was recorded as too low, or where the height has changed too much from the last measurement. With this info, the Permanent Way maintenance team can quickly zoom in, inspect and rectify any potential Third Rail faults relating to misalignment.
With the LVDT technology, the frequency of third rail inspection is increased and real time detection is possible, even during service hours. The degradation trend of the third rail can also be tracked.
The LVDT is the first of a few other condition monitoring devices we will be sharing on this blog. Check back again soon to find out more about the technologies we use to make maintenance of the track as efficient as possible.