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Post by q8 on Dec 7, 2005 20:50:28 GMT
Someone explain something to me please. I notice nowadays there are long rail gaps in the current rail remote from substations. Examples are west of Becontree and east of Dagenham East. I've seen them in video's of other lines too. What is the purpose of these gaps? It can't be sectionalisation as that takes place at substations.I cannot see rhyme or reason for these as when I was on the trains we were told that the fewer gaps the better. Too many gaps made the train equipment work too much with dropping out and notching up being more frequent it wore the RPA out rapidly. This increased costs and maintainance as well. It also increased the amount of rail burn from arcing too.
So why this gaps everywhere policy?
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Deleted
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Post by Deleted on Dec 7, 2005 20:54:38 GMT
Someone explain something to me please. I notice nowadays there are long rail gaps in the current rail remote from substations. Examples are west of Becontree and east of Dagenham East. I've seen them in video's of other lines too. What is the purpose of these gaps? It can't be sectionalisation as that takes place at substations.I cannot see rhyme or reason for these as when I was on the trains we were told that the fewer gaps the better. Too many gaps made the train equipment work too much with dropping out and notching up being more frequent it wore the RPA out rapidly. This increased costs and maintainance as well. It also increased the amount of rail burn from arcing too. So why this gaps everywhere policy? Mebbe it's to do with the expansion of the rail during hot weather? Could be a different composition [metal content] in the rail manufacturing process that has led to the longer gap. |
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Colin
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Post by Colin on Dec 7, 2005 21:00:43 GMT
I take it you are referring to this sort of thing:  |
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Post by c5 on Dec 7, 2005 21:06:45 GMT
You're not thinking of the gaps where section
switches are provided,are you?
I have tried looking on the intranet to see if there are section switches located there, but can only get the not very detailed Protection Maps.
Will keep looking!
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Post by russe on Dec 7, 2005 21:44:40 GMT
Colin's picture is a standard 15m section gap.
Russ
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Post by q8 on Dec 7, 2005 21:58:55 GMT
No what I am reffering to are the same length of gap but nowhere near a substation nor section switches.. They did not have them in my time even at sub gaps so why are they used now?
The one in Colin's pic is what I mean but that is plainly the sub gap at East Ham. There are no subsations at Becontre or Dagenham East yet they have the same length gap in the MIDDLE of a current rail section. Why?
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towerman
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Post by towerman on Dec 7, 2005 21:59:57 GMT
These are the now standard 15m section gaps that were introduced with the opening of the Victoria Line,it's to ensure a car cannot physically bridge two sections.Mind you,there's still some places with the old short gaps.
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Deleted
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Post by Deleted on Dec 7, 2005 22:04:26 GMT
I have tried looking on the intranet to see if there are section switches located there, but can only get the not very detailed Protection Maps. Try searching for Traction Current Diagrams. They are there, as I have downloaded them. |
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solidbond
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Post by solidbond on Dec 7, 2005 22:42:33 GMT
A number of additional gaps have been installed across the network as additional protection during engineering works. They are usually at a place, just beyond a reversing point, whether there is a substation or not, to ensure that if a train went beyond the reversing point, it would not be able to enter the section where engineering work is being carried out.
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Post by russe on Dec 7, 2005 23:53:18 GMT
These are the now standard 15m section gaps that were introduced with the opening of the Victoria Line, What was the standard dimension before the Victoria Line was opened? Russ |
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Post by c5 on Dec 8, 2005 1:47:03 GMT
I have tried looking on the intranet to see if there are section switches located there, but can only get the not very detailed Protection Maps. Try searching for Traction Current Diagrams. They are there, as I have downloaded them. You SAs up north obviously have a lot of time on your hands too   |
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Deleted
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Post by Deleted on Dec 8, 2005 10:15:38 GMT
Are the gaps anywhere near bridges?
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Post by stanmorek on Dec 8, 2005 10:22:34 GMT
I agree with SB's theory. Gaps have certainly been cut through traction current rails on the District with 15m gaps as a minimum.These gaps are reconnected with HV cabling and disconnected during isolations for weekend possessions. Additional protection measures in place are short circuiting devices placed across all roads (the dead side) at the possession limits and sub-station feeds. A number of additional gaps have been installed across the network as additional protection during engineering works. They are usually at a place, just beyond a reversing point, whether there is a substation or not, to ensure that if a train went beyond the reversing point, it would not be able to enter the section where engineering work is being carried out. |
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Post by q8 on Dec 8, 2005 13:24:42 GMT
OK fair enough. These gaps have been put in for safety reasons during possesions. But it makes me wonder why the assocaited sections switches are and gaps are always put in where trains are leaving and therefore accelarating AWAY from a platform and need the power. I would have thought that he obvious place for gaps and switches was the APPROACH to a platform where trains are coasting or braking.
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Post by Harsig on Dec 8, 2005 15:08:21 GMT
OK fair enough. These gaps have been put in for safety reasons during possesions. But it makes me wonder why the assocaited sections switches are and gaps are always put in where trains are leaving and therefore accelarating AWAY from a platform and need the power. I would have thought that he obvious place for gaps and switches was the APPROACH to a platform where trains are coasting or braking. Which of course would mean that any train approaching the gap would have to stop short of the platform if traction current on the far side was discharged for any reason. For some reason passengers seem to think it is a God given right that when they alight from a train they can do so at a platform and they tend to get upset if this not possible ;D |
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TMBA
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Post by TMBA on Dec 8, 2005 16:00:34 GMT
Have you noticed the gap on the westbound approaching Chiswick Park WB? The home signal is situated so that if you stop right on top of it you gap yourself  so obviously you stop short - so if that signal was to fail would you be gapped assuming the batteries are low whilst reseting your trip? or if the battery fuse is defective could you end up with a dead cab whilst reseting. |
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Colin
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Post by Colin on Dec 8, 2005 17:48:01 GMT
Have you noticed the gap on the westbound approaching Chiswick Park WB? The home signal is situated so that if you stop right on top of it you gap yourself so obviously you stop short - so if that signal was to fail would you be gapped assuming the batteries are low whilst reseting your trip? or if the battery fuse is defective could you end up with a dead cab whilst reseting. I can't picture the area right now, but approaching Earls Court eastbound from West Kensington/Olympia is similar, by the sounds of it (EC4). If only the leading cab is off current, the train is not considered gapped - a train is gapped when all pickup shoes are off current. The cab would only be dead if the batteries are dead, or, as you say the battery fuse is blown. Of course that would be a problem, but not a major one, as the train would only have to be moved (using the correct proceedure) a few feet. Of course any driver worth his salt (especially at this time of year) will always make sure the leading cab has traction current - cos it powers the cab heaters!! |
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TMBA
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Post by TMBA on Dec 9, 2005 15:50:29 GMT
Had a good look today - there is a gap on the westbound and a gap on the eastbound just before Chiswick station, I didn't notice the picc but I assume the gaps on the district are to protect the bridge just east of Chiswick Park
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Post by stanmorek on Dec 9, 2005 21:26:53 GMT
Sounds like you're describing Chiswick Sub-Gap, an actual current section gap. A possession gap is to the west of Chiswick Park. However, the westbound District is CWR track and the standards require expansion switches to either side of an underbridge. Had a good look today - there is a gap on the westbound and a gap on the eastbound just before Chiswick station, I didn't notice the picc but I assume the gaps on the district are to protect the bridge just east of Chiswick Park |
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Post by stanmorek on Jan 16, 2006 3:37:11 GMT
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so obviously you stop short - so if that signal was to fail would you be gapped assuming the batteries are low whilst reseting your trip? or if the battery fuse is defective could you end up with a dead cab whilst reseting.
