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| Route Releasing over point zone 25/03/2011 at 12:30 #2646 | |
indian_railways_fan
72 posts |
In the simulations,route releasing over point zones is accomplished by the picking of the track relay of a single common point track circuit.While normally this should not create any problems,there is a possibility of track circuit ''bobbing'' which may actually cause the point locking to release prematurely.Protection against such an occurrence is probably provided in the interlocking circuits.Would someone explain these arrangements? Recently I have studied the system on the Indian Railways which are a mix of British and German practices.In this system,the point zone has at least two track circuits which must be proved to have occupied and then released to actually release the route group as also the locking on the concerned points. Simsig no doubt implements the arrangement on the real panels and consequently what is approved practice on Network Rail. Khalid, India. Log in to reply |
| Route Releasing over point zone 25/03/2011 at 12:30 #14234 | |
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indian_railways_fan
72 posts |
In the simulations,route releasing over point zones is accomplished by the picking of the track relay of a single common point track circuit.While normally this should not create any problems,there is a possibility of track circuit ''bobbing'' which may actually cause the point locking to release prematurely.Protection against such an occurrence is probably provided in the interlocking circuits.Would someone explain these arrangements? Recently I have studied the system on the Indian Railways which are a mix of British and German practices.In this system,the point zone has at least two track circuits which must be proved to have occupied and then released to actually release the route group as also the locking on the concerned points. Simsig no doubt implements the arrangement on the real panels and consequently what is approved practice on Network Rail. Khalid, India. Log in to reply |
| Route Releasing over point zone 25/03/2011 at 13:30 #14239 | |
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TomOF
452 posts |
I hope this kind of answers your query:- I can't speak for Relays but in SSI terms you're looking for 1) the previous subroute(s) free AND 2) the track circuit free AND 3) ( the track circuit occupied for a few seconds OR the next track circuit occupied) there are a few variations on those themes but that's basically it. in some cases in areas where poor ground conditions are likely to cause interference with the track circuit sometimes extra timing might be inserted. Log in to reply |
| Route Releasing over point zone 26/03/2011 at 09:33 #14291 | |
GeoffM
6288 posts |
To clarify slightly: 1. Preceding subroutes not locked 2. This track clear 3. (This track clear for time OR next track occupied) For subroutes immediately after signals: 1. This track clear 2. Relevant routes from signal not set There is no distinction in the UK between tracks over pointwork and those on plain line. The "track clear for time" (usually 15 seconds) is an anti-bobbing protection, eg for a train going over rusty rails intermittently not showing the track occupied. Of course, if the train stopped without being detected, the subroutes would drop away. For subroutes immediately after signals, the signal itself has logic built in which proves the train moving through the section before the route will release, hence why the tests there are so simple. There is no way to emergency release subroutes under an occupied track. Compare this to Norway where there is such a release, but they also have sequential proving of track occupancy for each track, so if a train did fall off, the subroutes would remain locked. Relay and SSI logic is not exactly the same but similar enough in principle (no timed test for relays). For axle counter areas, since rusty/contaminated rails don't affect train detection, again the timer test can be dropped. Interestingly though, that may be revisited since some axle counters can report a short, fast train clearing one track before the SAME axle counter head reports it occupied into the next track. SOmething to do with communications paths and evaluators. SimSig Boss Log in to reply |
| Route Releasing over point zone 26/03/2011 at 13:29 #14307 | |
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indian_railways_fan
72 posts |
GeoffM said:To clarify slightly: A similar arrangement is available on the Indian Railways.But this is for movement of points under track relay down(or occupied) condition.The button for this is provided on the panel but is kept sealed with a rotating disc.The seal must be broken and the disc rotated out from under the button to operate it.In addition this operation is also recorded by a non-resettable counter and the count must be entered into the relevant register along with a valid reason.This provision is only for emergencies in case of a track circuit failure over the point zone. An emergency full-route/subroute release button is also provided in case the route "hangs" after the passage of a train.This normally happens when a small wheel-base vehicle like a shunting engine passes over the section and fails to operate the track circuits in proper sequence. The operating manual of the Indian Railways gives details of panel operation Khalid. India. Log in to reply |