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Author Topic: Great Western Main Line electrification - ongoing discussion  (Read 239662 times)
Mark A
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« Reply #1125 on: May 31, 2022, 02:59:42 pm »

"Bath Newseum" has put together an article prompted by one of his correspondents, who makes the point that the deferment of the electrification has also stalled maintenance on various structures in Bath, including the bridge on which I should fess up to being taken to, to enjoy the exhaust from the procession of large, blackened and smoky locos that passed beneath with the various trains at that time. The experience greatly enhanced by the bridge's relatively open parapets and also the gaps in the timber deck of the structure, so, thanks for those, IKB (Isambard Kingdom Brunel).

https://bathnewseum.com/2022/05/31/brunels-other-little-bridge/

Mark

(Another structure to have suffered thus being the little footbridge at Hampton Row - though not as a result of electrification - around 1995, getting rusty, it was scheduled to receive extensive maintenance, promptly cancelled on privatisation, since when it's had nothing.)

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onthecushions
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« Reply #1126 on: July 07, 2022, 05:18:10 pm »


Back on my trips to Oxford for the first time since 2019, I noticed vegetation clearance either side of the bridge over the Thames, North of Didcot, together with a Balfour Beatty van close by. They trimmed the grass very neatly!

Could this be a portent of a renewal of interest in completing the wiring to Oxford, perhaps? Other wirings, such as to Wigston and Stalybridge have commenced without announcement.

The capped piles, unwired masts and TTC's and the deserted Radley ATS (Automatic Train Supervision), still stand unused.

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ellendune
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« Reply #1127 on: July 07, 2022, 06:18:36 pm »

Can't see electrification going to Oxford at least until Botley Road Bridge has been rebuilt and the additional platform and western entrance to the station completed.   
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« Reply #1128 on: July 07, 2022, 07:01:05 pm »

It is posible that the Region has funding in this control period, even if there was no funding in CP6 (Control Period 6 - The five year period between 2019 and 2024) plans the Region may have an underspend on other projects, to fund design completion / verification or even some enabling works ready for CP7. 

Can't see electrification going to Oxford at least until Botley Road Bridge has been rebuilt and the additional platform and western entrance to the station completed.  

The work South of this can commence so that it will be ready when those projects are electrification ready
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« Reply #1129 on: July 08, 2022, 06:13:19 am »

plenty of money for East Coast main line,south west of England starved.

https://www.railjournal.com/analysis/east-coast-main-line-etcs-installation-receives-1bn-funding-boost/?utm_source=&utm_medium=email&utm_campaign=33630
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grahame
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« Reply #1130 on: July 08, 2022, 06:24:25 am »


It's the nature of things for investments to come in chunks ... not so long ago there was huge investment in the GWR (Great Western Railway) main line with the intent of electrifying from London to places like Oxford, Bristol Temple Meads, and perhaps Swansea.
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« Reply #1131 on: July 08, 2022, 08:19:23 am »


The re-signalling of the ECML (East Coast Main Line) has been in development for a number of years, projects like the dive under at Peterborough, Kings Cross remodelling even the Hitchin flyover are all part of the bigger plan.   The ECML was re-signalled South of Hitchin in the early 1970's for the Electrification the rest of the ECML re-signalling follow fairly quickly after that, so it is at the end of its life.   There are lot of issues with the existing signalling equipment, wire insulation degradation, silver migration in relays and general obsolescence   
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onthecushions
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« Reply #1132 on: July 08, 2022, 03:12:43 pm »

The work South of this can commence so that it will be ready when those projects are electrification ready

...and even a wiring stub as far as Appleford or Radley would be usable by the 80x's, going fast to Oxford and the Cotswold Line.

Bring it on...

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« Reply #1133 on: August 06, 2022, 01:43:22 pm »

Modern Railways has got its sticky journalistic fingers on an internal NR» (Network Rail - home page) planning document: the Regional Traction Decarbonisation Strategy for Wales and Western Region (dated February 2022). There is a long article (currently public) on the details, ending with this summary:
Quote

SIX TRANCHES TO DECARBONISE THE WESTERN

Tranche 0: Acton to Willesden; Bristol Temple Meads to Bristol Parkway (Filton bank); Chippenham East to Bristol Temple Meads; Didcot to Oxford (and potentially on to Hanborough)

Tranche 1: Newbury to Cogload; Bristol to Exeter; Westbury to Thingley, Bathampton and Warminster; Somerset quarries; Oxford to Banbury

Tranche 2: Bromsgrove to Westerleigh (including Worcester); Swindon to Standish Junction; Gloucester to Severn Tunnel Junction; Norton Junction to Hanborough; Severn Beach and Hallen Marsh lines; Westerleigh and Tytherington quarry

Tranche 3: Thames Valley passenger branch lines – Greenford, Windsor, Marlow and Henley-on-Thames; freight branches – Brentford and Colnbrook

Tranche 4: Exeter to Plymouth and Paignton; Barnstaple, Exmouth and Okehampton branches; West of England main line

Tranche 5: Plymouth to Penzance; Cornish passenger branches: Gunnislake, Looe, Newquay, Falmouth and St Ives; freight branches: Moorswater, Fowey and Parkandillack

Look! Electric Melksham! Though no doubt some ungrateful souls would rather have two more rails on the ground than any number of wires in the sky.
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Worcester_Passenger
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« Reply #1134 on: August 07, 2022, 03:13:15 am »

The re-signalling of the ECML (East Coast Main Line) has been in development for a number of years, projects like the dive under at Peterborough, Kings Cross remodelling even the Hitchin flyover are all part of the bigger plan.   The ECML was re-signalled South of Hitchin in the early 1970's for the Electrification the rest of the ECML re-signalling follow fairly quickly after that, so it is at the end of its life.   There are lot of issues with the existing signalling equipment, wire insulation degradation, silver migration in relays and general obsolescence  

What's "silver migration in relays"?
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onthecushions
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« Reply #1135 on: August 07, 2022, 07:25:27 am »


When an electrical circuit with inductance (a coil for instance), is broken, the current drops suddenly. The inductance therefore tries to oppose this by producing a large inverse voltage. This is sufficient to cause a spark across opening contacts. At such high energies small particles of the (silver alloy) metal surface are transferred with the spark. You can see this also in a traditional car ignition system. Over years of frequent operation even highly rated railway relay contacts therefore start to lose their initial shape, producing some resistance between them when closed.

ISTR (I seem to recall/remember) that railway policy was to replace them every 21 years but condition monitoring was not used, so heavily used ones were not changed any more often than lightly used ones. Modern practice is to use more solid state devices and to use strategies such as "Zero volt/current switching" in ac circuits.

Our esteemed ET member could give a clearer more precise description.

OTC

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TonyK
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« Reply #1136 on: August 07, 2022, 10:34:10 am »

Modern Railways has got its sticky journalistic fingers on an internal NR» (Network Rail - home page) planning document: the Regional Traction Decarbonisation Strategy for Wales and Western Region (dated February 2022). There is a long article (currently public) on the details, ending with this summary:
Quote

SIX TRANCHES TO DECARBONISE THE WESTERN

Tranche 0: Acton to Willesden; Bristol Temple Meads to Bristol Parkway (Filton bank); Chippenham East to Bristol Temple Meads; Didcot to Oxford (and potentially on to Hanborough)

Tranche 1: Newbury to Cogload; Bristol to Exeter; Westbury to Thingley, Bathampton and Warminster; Somerset quarries; Oxford to Banbury

Tranche 2: Bromsgrove to Westerleigh (including Worcester); Swindon to Standish Junction; Gloucester to Severn Tunnel Junction; Norton Junction to Hanborough; Severn Beach and Hallen Marsh lines; Westerleigh and Tytherington quarry

Tranche 3: Thames Valley passenger branch lines – Greenford, Windsor, Marlow and Henley-on-Thames; freight branches – Brentford and Colnbrook

Tranche 4: Exeter to Plymouth and Paignton; Barnstaple, Exmouth and Okehampton branches; West of England main line

Tranche 5: Plymouth to Penzance; Cornish passenger branches: Gunnislake, Looe, Newquay, Falmouth and St Ives; freight branches: Moorswater, Fowey and Parkandillack

Look! Electric Melksham! Though no doubt some ungrateful souls would rather have two more rails on the ground than any number of wires in the sky.

Alas, the article has hidden behind a paywall. Presumably Tranche 0 should be first?
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Now, please!
Red Squirrel
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« Reply #1137 on: August 07, 2022, 01:04:47 pm »

Alas, the article has hidden behind a paywall. Presumably Tranche 0 should be first?

To quote my son, who tends to be rather direct: Yes, that's how numbers work!

I can access the MR (Midland Railway) article intermittently - sometimes the paywall blocks it, sometimes it doesn't. Might be worth having another go, maybe on a different browser or platform? Sadly the article doesn't link to the NR» (Network Rail - home page) report, the Wales and Western Region Regional Traction Decarbonisation Strategy dated February 2022. It would be interesting to see this!

The article refers to Tranch 0 as the 'Hendy tail' - schemes removed from GWEP (Great Western Electrification Program) following the review of the CP5 (Control Period 5 - the five year period between 2014 and 2019) enhancements by Network Rail Chair Sir Peter Hendy:

Quote
The strategy notes that electrification from Chippenham to Bristol can utilise spare capacity in the feeder station at Thingley and could cut journey times by up to 2.5 minutes. On Filton bank (Bristol Parkway to Temple Meads), the potential for South Wales to Bristol EMUs (Electric Multiple Unit) is noted, as are the environmental benefits of decarbonisation in an urbanised area.

Labelling this 'Tranch 0' does sort of imply that it should have happened already. MR says the NR report describes these schemes as ‘mature’, with power supply in place and signalling immunised in readiness for electrification.

Is the shaving of 2.5 mins off journey times really a key selling point though? I would have thought the environmental benefits would be an easier sell...

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onthecushions
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« Reply #1138 on: August 07, 2022, 02:42:54 pm »


This link has worked without paywall:

https://www.modernrailways.com/article/decarbonising-western

OTC

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broadgage
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« Reply #1139 on: August 07, 2022, 02:45:27 pm »


When an electrical circuit with inductance (a coil for instance), is broken, the current drops suddenly. The inductance therefore tries to oppose this by producing a large inverse voltage. This is sufficient to cause a spark across opening contacts. At such high energies small particles of the (silver alloy) metal surface are transferred with the spark. You can see this also in a traditional car ignition system. Over years of frequent operation even highly rated railway relay contacts therefore start to lose their initial shape, producing some resistance between them when closed.

ISTR (I seem to recall/remember) that railway policy was to replace them every 21 years but condition monitoring was not used, so heavily used ones were not changed any more often than lightly used ones. Modern practice is to use more solid state devices and to use strategies such as "Zero volt/current switching" in ac circuits.

Our esteemed ET member could give a clearer more precise description.

OTC



Not certain that this is correct. Contact wear in relays is undoubtedly a problem as described above, it may be reduced in various ways.
SILVER MIGRATION is however a different phenomena. It is an electrolytic process whereby in the presence of traces of moisture, silver is dissolved to form ions, which then migrate under under an electric field, and form metallic silver in some place other than the original location of the original silver contact.
This can result in maloperation, and in extreme cases even in a wrong side failure of signaling.

Silver migration is the result of a DC (Direct Current) voltage, it wont occur on AC circuits.
It may be reduced by physically larger equipment with greater clearances, and by excluding damp.
It may be eliminated by not using silver contacts.

Contact wear from sparking has been known about since the very beginning of the electrical age, well over 100 years ago.

Silver migration was not recognised until the 1950s, and not fully understood until some years after that.

Railway signaling schemes that use miniature relays are vulnerable.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
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