Railway Points Monitoring


Tycon Automation Ltd were tasked to improve on the maintenance strategy and design an active approach to early failure diagnosis by a major UK rail contractor. With the key focus on two areas of rail system monitoring. These were:

Track points changeover – measurement of existing forward and reverse motor current. The track points mechanically change state in, typically, 2 – 3 seconds, and as such the motor current must be accurately captured during this period.

Track section monitor – measurement of existing monitor point voltage. The resultant output from this equipment, the monitor point voltage, is an electrical signal which indicates whether a train is present on the respective portion of rail track:

  • Train present / track occupied: Monitor point voltage is low (0.2 – 4.0V)
  • Train not present / track clear: Monitor point voltage is high (6.2 – 7.0V)

A Mitsubishi Q series PLC system was conceived utilising the new Q series UDE CPU range. With its integrated Ethernet port this CPU allowed seamless communication with a third party SCADA system.

The new Q series high speed data logging module QD81DL96 was specified to allow a sample resolution of 20msec to be achieved. From a trigger value the QD81DL96 provided one second (50x20msec samples) prior to trigger and seven seconds after (350x20msec samples). This give a total span of 450 samples of 20msec provided enough resolution to satisfy the brief. Once captured this data was then transferred via FTP to the third party SCADA system to back populate its trend database.

The bottom of the two traces shows the ideal trace so that any degradation can be checked and analysed. The operator can also select the top trace to become the ideal trace via a pushbutton selection.

The search facility included also allows the user to drill into any date and time frame and select from forward or reverse events that are all uniquely time and date stamped.