Intelligent Infrastructure Track Circuit Monitoring A guide from LNW(N)

1. Intelligent InfrastructureTrack Circuit MonitoringA guide from LNW(N) John Walsh (v1.0) v1.0

2. Data Logger Central Server Current Sensor Track relay Typical DC Track Circuit Installation v1.0

3. Typical AC Quick Release Track Circuit Installation ~ Data Logger Central Server Current Sensor Transformer - Rectifier Track relay v1.0

4. ~ Control Current Data Logger VT1 Integrator Central Server Current Sensor Current Sensor ~ Local Current VT1 Vane-type Track relay Typical AC 50Hz VaneTrack Circuit Installation v1.0

5. TI21 Digital Transmitter Data Logger Central Server Serial Link Track relay TI21 Digital Receiver Typical Digital TI21 (aka EBI Track 200)Track Circuit Installation v1.0

6. Dividing the current level into bands Relay coil current (mA) • These 4 levels are set by the Delivery Unit and therefore define the 5 bands. • No Alarm or Alert events so long as current level sits in either ‘Occupied’ or ‘Clear’ bands (‘deadband’ timings allows transit from one level to another without event). Time v1.0

7. Moving out of Clear / Occupied bands Relay coil current (mA) • Current moving into the following bands: Excess Low Clear High Occupied • Generates an ‘event’, but it normally II is set take more than 1 event to produce an Alarm or Alert (how many is again set by the Delivery Unit) Time v1.0

8. Setting the Count levels Count before Hi (Alert) generated Actual event count Count before Hi Hi (Alarm) generated However all counts reset at midnight! v1.0

9. Moving out of the ‘Clear’ band There are 3 cases: • Excess Current • If Excess Current threshold is exceeded • Low Clear Current • Current falls below Low Clear Current threshold greater than set time • Unstable Clear Current • If current falls into the Low Clear threshold for a short duration (less than set time) v1.0

10. Excess current • Here the current is higher than the Excess Current Limit ( shown by red line) • No count made on this event – Alert generated (Recorded as priority 3) • Possible causes – track circuit set for what was poor ballast resistance which has since improved, adjacent (un-staggered) track feed assisting this track etc. v1.0

11. Low Clear Current v1.0

12. Low Clear Current Low Clear Deadband set to 2 seconds Low Clear Level is set to 230mA v1.0

13. Low Clear Current Low Clear Level count Midnight count reset Low Clear Level • This event is only generated when transition is made from known good level in Clear band. • Track circuit current remains in Low Clear band for a duration greater than Low Current-Clear deadband (here it is set to 2s) • Track circuit current is above Occupied Level but below Low Clear Level. • Possible causes: deteriorating rail insulation pads (pads and nylons), high resistance tail cables or connections or IBJ failure, salt in level crossing etc v1.0

14. Unstable Clear Current Count v1.0

15. Unstable Clear Current Count v1.0

16. Unstable Clear Current Count Falling belowLow Clear Currentthreshold Unstable Clear Currentcount • This event is only generated when transition is made from known good level in Clear band but returns back within deadband time • Track circuit current falls below the Low Clear Current threshold • Causes could be due to intermittent connection (loose track circuit pin, damaged tail cable, loose back nut etc) v1.0

17. Unstable Clear Current Count Low Clear Currentthreshold Occupied Level • Another example, a genuine track circuit occupation is not counted. • Also it is normal (at the moment!) for the count to sometimes lag the event (for all events) • Count increases for each incursion into Low Clear band for duration < Low Current – Clear deadband (s) AND recovers in this time • This clearly shows the current is unstable - moving rapidly and erratically. v1.0

18. Moving out of the ‘Occupied’ band There are 2 cases of moving out of this band • High Occupied Current • Exceeds High Occupied Current for a set time • Poor Shunt • Exceeds High Occupied Current level for a less than set time (also known as ‘unstable occupied’) v1.0

19. High Occupied Current v1.0

20. High Occupied Current High Occupied Level is set so that it is no higher than 50% of minimum drop away value (OCC Level) High Current – Occupied Deadband set to 2 seconds v1.0

21. High Occupied Current Occupied Current Greater than 2 seconds duration in High Occupied band High Occupied Currentcount High Occupied Currentlimit • Track circuit current rises above the High Occupied Current Limit (termed WSF level in II) for duration greater than High Current - Occupied deadband time – i.e. it has stayed in the High Occupied band for too long. • Possible causes are: wheel or rail contamination, failure of an un-staggered block joint (adjacent track feeding the relay). • In this case it was staff working – possibly with trolley or RRV that shunted the track sufficiently for it not to be classed as a Poor Shunt (next) v1.0

22. Poor Shunt High Occupied Limit (WSF Level) Track Occupied Current Greater than 2 seconds High Occupied Current event Less than 2 seconds Poor Shunt event Poor Shuntcount High OccupiedCurrent count • IF current rises above High Occupied Current for duration less than High Current – Occupied deadband time AND returns back into Occupied band. • Wheel or rail contamination briefly preventing the train from properly shunting the track circuit. v1.0

23. Track circuit flicks • 2 cases: • Track flick: Clear-Occupied-Clear • Track flick: Occupied-Clear-Occupied v1.0

24. Flick: Clear-Occupied-Clear Clear Occupied Clear Flick count v1.0

25. Flick: Clear-Occupied-Clear Clear-Occupied-Clear Flicks, to register the duration must be: greater than Lower Limit (s) but less than Upper Limit (s) Duration Count of Clear-Occupied-Clear v1.0

26. Flicks • Flicks are basically genuine track clear and occupy events but the duration doesn’t tally with normal operation • For example if a track circuit occupies for a time less than the fastest and shortest train (with a sensible tolerance) what has caused it? This is counted as a “Clear – Occupied – Clear Flick”. • Conversely if the track circuit clears whilst is it occupied (“Occupied – Clear – Occupied Flick”) you would certainly want to know about that as it could potentially be a WSF, but there could more subtle reasons especially at the instant the train rolls on and off the track circuit. v1.0

27. Processes • This presentation has focussed on the analysis of track circuits only. • Success of RCM also depends heavily on our judgment, knowledge, experience and good communication between all parties. • Be careful not to make the system redundant or insensitive by masking Alarms out or setting wide tolerances. • Relevant procedures: • NR/L3/MTC/II0219 [Issue 1] Management of Alerts and Alarms from Remote Condition Monitoring (9 pages) • NR/L3/OCS/043/3.11 [Issue 2] Response to Remote Condition Monitoring Alarms (3 pages) • NR/L2/SIG/19811 [ Issue: 3 ] FMS For Network Rail Fault Management (Formerly NR/SP/SIG/19811) v1.0

28. Questions v1.0 28