Jump to content


Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.

Photo
* * * * - 6 votes

GWML Electification

Electrification GWML Crossrail



  • Please log in to reply
3583 replies to this topic

#3576 Great Western

Great Western

    Member


  • Members
  • PipPip
  • 664 posts

Posted 14 August 2017 - 14:46

From what I've seen of the plans to transfer signalling control from, Bristol Panel (in part) to TVSC there is very very little new in terms of signals or points. Pretty much as now just additional mid way platform signals in place of the St Andrews Crosses, current issues surround how it's going to be manned at TVSC, single or double and if the latter arrangement how.
  • Informative/Useful x 1

Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.

#3577 caradoc

caradoc

    Member


  • Members
  • PipPip
  • 1,097 posts

Posted 14 August 2017 - 16:17

Just to note that the Oxford - Worcester has NOT been redoubled. What has actually occurred is the addition of a long dynamic passing loop to facilitate a more frequent service. As with the Salisbury - Exeter line quite a lot remains single track still with no firm plans to add any more.

 

Swindon - Kemble by contrast saw the entire section restored to double track throughout.

 

Sorry phil-b259 but that is somewhat incorrect; Charlbury/Ascott (3.75 miles approx) and Moreton-in-Marsh/Evesham (15 miles approx) have been redoubled. A bit more than a dynamic passing loop !



#3578 The Stationmaster

The Stationmaster

    Member


  • Members
  • PipPip
  • 29,499 posts

Posted 15 August 2017 - 11:28

Sorry phil-b259 but that is somewhat incorrect; Charlbury/Ascott (3.75 miles approx) and Moreton-in-Marsh/Evesham (15 miles approx) have been redoubled. A bit more than a dynamic passing loop !

 

Judging by all the various timetable/infrastructure studies I did on the western end of the Cotswold Line  Moreton to Evesham is really a dynamic loop in most respects.  If it were really going double the logical extension would go a good way west of Evesham as well (where there are potentially greater timetabling and perturbation recovery benefits) but that takes section would take things into a far higher cost bracket because of various complexities such as Norton Jcn.

 

With today's speeds you are probably looking at around 10 miles to get a decent dynamic loop capability.


Edited by The Stationmaster, 15 August 2017 - 11:28 .

  • Informative/Useful x 2

#3579 The Stationmaster

The Stationmaster

    Member


  • Members
  • PipPip
  • 29,499 posts

Posted 15 August 2017 - 11:31

From what I've seen of the plans to transfer signalling control from, Bristol Panel (in part) to TVSC there is very very little new in terms of signals or points. Pretty much as now just additional mid way platform signals in place of the St Andrews Crosses, current issues surround how it's going to be manned at TVSC, single or double and if the latter arrangement how.

But is it a transfer of control (as was done initially at Reading) or a complete transfer with new remote interlocking (as came later with Reading)?   Whichever it happens to be change of control is a long way short of the drastic layout alterations and total re-signalling with axle counters and a new interlocking (at TVSC) that would be required for electrification.



#3580 phil-b259

phil-b259

    Member


  • Members
  • PipPip
  • 4,179 posts
  • LocationBurgess Hill, UK

Posted 15 August 2017 - 23:09

But is it a transfer of control (as was done initially at Reading) or a complete transfer with new remote interlocking (as came later with Reading)?   Whichever it happens to be change of control is a long way short of the drastic layout alterations and total re-signalling with axle counters and a new interlocking (at TVSC) that would be required for electrification.

 

One advantage of transferring control to a new computer based interlocking is the relative ease with which it can be updated (i.e. downloading fresh software to it rather than making lots of hard wired alterations to relays). Thus if NR was looking to go for a more sagged / phased approch with respect to the track layout at Bristol, then it could be attractive to re-control the Bristol area first with a WestLock / Smartloc interfaced solution, then carry out the rest of the work in smaller byte sized chunks. This also produces an easy win in getting rid of annoying interlocking faults due to high resistance contacts - but does of course rely on robust data links if you don't want a repeat performance of the debacle that prevented your attendance at Taunton this year.

 

(Not that any of what I wrote will be unknown to a man of your experience Mike )



#3581 jim.snowdon

jim.snowdon

    Member


  • Members
  • PipPip
  • 715 posts

Posted 15 August 2017 - 23:44

One advantage of transferring control to a new computer based interlocking is the relative ease with which it can be updated (i.e. downloading fresh software to it rather than making lots of hard wired alterations to relays). Thus if NR was looking to go for a more sagged / phased approch with respect to the track layout at Bristol, then it could be attractive to re-control the Bristol area first with a WestLock / Smartloc interfaced solution, then carry out the rest of the work in smaller byte sized chunks. This also produces an easy win in getting rid of annoying interlocking faults due to high resistance contacts - but does of course rely on robust data links if you don't want a repeat performance of the debacle that prevented your attendance at Taunton this year.
 
(Not that any of what I wrote will be unknown to a man of your experience Mike )


It is, in theory, but putting all of the interlocking in one place can make even simple changes very expensive. Computer based interlocking has its value compared to relay interlockings, but it has always seemed more sensible to my mind to keep the interlocking in site-based chunks and use non-vital communications to drive all the remote interlockings from one operations centre. Part of the thinking is that operational control systems, including the signalling and train control, should be designed for failure, not optimistic reliability, as sooner or later failures will occur and the important task is keeping the railway going, not having everything stopped pending arrival of the S&T technician.

Jim
  • Like x 2

#3582 Edwin_m

Edwin_m

    Member


  • Members
  • PipPip
  • 6,325 posts

Posted 16 August 2017 - 07:32

It is, in theory, but putting all of the interlocking in one place can make even simple changes very expensive. Computer based interlocking has its value compared to relay interlockings, but it has always seemed more sensible to my mind to keep the interlocking in site-based chunks and use non-vital communications to drive all the remote interlockings from one operations centre. Part of the thinking is that operational control systems, including the signalling and train control, should be designed for failure, not optimistic reliability, as sooner or later failures will occur and the important task is keeping the railway going, not having everything stopped pending arrival of the S&T technician.

Jim

However remote relay based interlockings have more recently not been provided with local control panels so effectively the TDM link back to the control centre is another source of unreliability.  And at least with the interlockings in the control centre there is probably a technician on site, not having to drive out to a remote interlocking many miles away. 



#3583 The Stationmaster

The Stationmaster

    Member


  • Members
  • PipPip
  • 29,499 posts

Posted 16 August 2017 - 23:46

However remote relay based interlockings have more recently not been provided with local control panels so effectively the TDM link back to the control centre is another source of unreliability.  And at least with the interlockings in the control centre there is probably a technician on site, not having to drive out to a remote interlocking many miles away. 

 

But then the point of remote failure can move away from the interlocking and you're no better off - as happened on the GWML in April when an electronic unit failed in a remote location cupboard disabling several miles of signalling ion the mainline between Didcot and Swindon and the spare part came with a man from Doncaster.

 

Distributed interlockings as mentioned by Jim have the potential advantage that if one fails the others don't or local failures at one could be used to create a through routes situation and keep trains moving.  WR RRIs had numerous remote interlockings supervised by TDM but the Region had very few emergency local control panels (I can only immediately think of one off hand) but interlockings could go into through routes with supervisory links down and they were still working as interlockings.  The idea of putting all the eggs in a York, Didcot or Cardiff basket comes with certain penalties when that basket hits problems and its entire control area is on stop.


  • Informative/Useful x 1

#3584 jim.snowdon

jim.snowdon

    Member


  • Members
  • PipPip
  • 715 posts

Posted 17 August 2017 - 08:09

It isn't all that long ago that an equipment cabinet at Hayes & Harlington failed and stopped the entire GWML for a substantial period. At that point (and everywhere east of Didcot) is four tracked and operates as two parallel railways, which makes it sensible to signal it that way, so that a single failure at least leaves the other two tracks operable. It's the principle of making systems failure tolerant, something that aircraft designers understand very well, whereas the railway approach seems more aligned to armour-plated design, ie making equipment so robust that, all being well, it will not fail. Parkinson's Law dictates that everything will fail sooner or later, usually when you least expect it. What seems to be disappearing from today's railway is the traditional principle of keeping traffic moving, with the result that when failures do occur, as they do, everything stops whilst someone from the diminishing band of maintenance technicians is despatched from far away to locate and fix the problem.

Jim
  • Agree x 4







Also tagged with one or more of these keywords: Electrification, GWML, Crossrail

Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.