Transcript Intelligent Infrastructure Track Circuit Monitoring
Intelligent Infrastructure Track Circuit Monitoring
A guide from LNW(N) John Walsh (v1.0) Date 24.02.201224/02/2012
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Typical DC Track Circuit Installation
Data Logger Central Server Current Sensor Track relay 2 Date 24.02.2012
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Typical AC Quick Release Track Circuit Installation
~ Data Logger Central Server Transformer - Rectifier Current Sensor Track relay Date 24.02.2012
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Typical AC 50Hz Vane Track Circuit Installation
~ Control Current VT1 Integrator Data Logger Central Server Current Sensor VT1 Vane-type Track relay Current Sensor ~ Local Current Date 24.02.2012
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Typical Digital TI21
(aka EBI Track 200)
Track Circuit Installation
TI21 Digital Transmitter Data Logger Central Server Track relay TI21 Digital Receiver Date 24.02.2012
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Dividing the current level into bands
Relay coil current (mA) Time • 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). Date 24.02.2012
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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 Date 24.02.2012
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Setting the Count levels
Actual event count Count before Hi (Alert) generated However all counts reset at midnight!
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Count before Hi Hi (Alarm) generated
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Moving out of the ‘Clear’ band
There are 3 cases: 1. Excess Current – If Excess Current threshold is exceeded 2. Low Clear Current – Current falls below Low Clear Current threshold greater than set time 3. Unstable Clear Current – If current falls into the Low Clear threshold for a short duration (less than set time) Date 24.02.2012
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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.
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Low Clear Current
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Low Clear Current
Low Clear Deadband set to 2 seconds Low Clear Level is set to 230mA Date 24.02.2012
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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 Date 24.02.2012
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Unstable Clear Current Count
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Unstable Clear Current Count
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Unstable Clear Current Count
Falling below Low Clear Current threshold Unstable Clear Current count • 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) Date 24.02.2012
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Unstable Clear Current Count
Low Clear Current threshold
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 v1.0
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Moving out of the ‘Occupied’ band
There are 2 cases of moving out of this band 1.High Occupied Current – Exceeds High Occupied Current for a set time 2.Poor Shunt – Exceeds High Occupied Current level for a less than set time (also known as ‘unstable occupied’) Date 24.02.2012
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High Occupied Current
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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 Date 24.02.2012
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High Occupied Current
Greater than 2 seconds duration in High Occupied band
Occupied Current High Occupied
Current limit
High Occupied
Current count • • Track circuit current rises above the
level
High Occupied Current
in II) for duration greater than
High Current - Occupied
Limit (termed
WSF
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)
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Poor Shunt
Track Occupied Current
Greater than 2 seconds High Occupied Current event
High Occupied Limit
(WSF Level) Less than 2 seconds Poor Shunt event
Poor Shunt count High Occupied Current 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.
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Track circuit flicks
• 2 cases: – Track flick: Clear-Occupied-Clear – Track flick: Occupied-Clear-Occupied Date 24.02.2012
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Flick: Clear-Occupied-Clear
Clear Occupied Clear Flick count Date 24.02.2012
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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 Date 24.02.2012
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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.
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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) Date 24.02.2012
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Questions
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