Train Graphic
Great Western Passengers' Forum [home] and [about]
from GWR - Travel with confidence
Forum in and beyond Coronavirus
DfT Covid Travel Advice
Read about the forum [here].
Register [here] - it's free.
What do I gain from registering? [here]
 today - Railfuture Severnside - CANX
29/09/20 - Tuesday Club - ONLINE
03/10/20 - RailFuture Annual - ONLINE
09/10/20 - Travelwach Southwest
Random Image
Train Running Polls Acronyms/Abbreviations Station Comparator Rail news GWR co. site Site Style 1 2 3 4
Next departures • Bristol Temple MeadsBath SpaChippenhamSwindonDidcot ParkwayReadingLondon PaddingtonMelksham
Exeter St DavidsTauntonWestburyTrowbridgeBristol ParkwayCardiff CentralOxfordCheltenham SpaBirmingham New Street
September 26, 2020, 02:29:56 am *
Welcome, Guest. Please login or register.

Login with username, password and session length
Forgotten your username or password? - get a reminder
Most liked recent subjects
[149] Journeys between places with similar names
[105] lack of rail scenes in modern day films
[66] Low pressure sodium lamps now hard to find.
[66] The new way of running the rails - what would you LIKE in the...
[38] Bristol-Bath Railway Path improvement work
[26] Older types of fluorescent lamp now hard to find.
News: A forum for passengers ... with input from rail professionals welcomed too
 
   Home   Help Search Calendar Login Register  
Pages: 1 ... 57 58 [59] 60 61 ... 70
  Print  
Author Topic: Great Western Main Line electrification - ongoing discussion  (Read 154315 times)
TonyK
Global Moderator
Hero Member
*****
Posts: 5154


The artist formerly known as Four Track, Now!


View Profile
« Reply #870 on: September 22, 2019, 04:57:00 pm »

300 Amps is not an usual peak starting current for intercity type trains

7.5 MW is a lot to ask of diesel engines, especially when it is needed only for a burst to overcome inertia. There are two ways of looking at the effect of having bi-mode IEPs, though. One could say that they are a blessing, because they allow IEPs to penetrate further into the uncharted wilderness that lies outside of the M25. Or one could say that they are an excuse for not finishing the job of electrifying the GWR completely, and therefore kicking the can down the road yet again. As for blaming Network Rail - I am sure they would have been happy to finish the job, had DafT let them.
Logged

Now, please!
Electric train
Hero Member
*****
Posts: 3332


The future is 25000 Volts AC 750V DC has its place


View Profile
« Reply #871 on: September 24, 2019, 06:38:34 pm »

300 Amps is not an usual peak starting current for intercity type trains

7.5 MW is a lot to ask of diesel engines, especially when it is needed only for a burst to overcome inertia. There are two ways of looking at the effect of having bi-mode IEPs, though. One could say that they are a blessing, because they allow IEPs to penetrate further into the uncharted wilderness that lies outside of the M25. Or one could say that they are an excuse for not finishing the job of electrifying the GWR completely, and therefore kicking the can down the road yet again. As for blaming Network Rail - I am sure they would have been happy to finish the job, had DafT let them.

I agree that a rolling stock based diesel will unlikely be viable to produce 7.5MW  This is the advantage of electrification via fixed equipment (OLE / third rail etc)  750V dc is typically limited to 6kA (4.5MW) the dc circuit breakers are typically set to 4 or 6kA a few places they are set to 7kA.  Rolling stock is also programmed to the max for the route even in multiple the overall will not exceed the route max.  The same is done for most ac traction a max current is set for the route, there are some issues with multiple loco's on some freight services where they the FoC has not set the current limit this cause the substation circuit breakers to trip or worse case the wire burns down.

Back to the point, electrification will always provide a quicker acceleration that diesel; the IEP's were originally intended to provide some capability to operate off wired routes, allow for diversions, operate a service when the OLE is not powered and emergency moves; like all things there has been mission creep
Logged

Neither a wise man nor a brave man lies down on the tracks of history to wait for the train of the future to run over him.     
Dwight D. Eisenhower
SandTEngineer
Hero Member
*****
Posts: 3485


View Profile
« Reply #872 on: October 26, 2019, 08:31:39 pm »

It would appear from info elsewhere that the 25kv was switched on in the Severn Tunnel earlier today.  Under test for a period.
Logged
johnneyw
Transport Scholar
Hero Member
******
Posts: 1498


Still want to be a train driver when I grow up


View Profile
« Reply #873 on: October 27, 2019, 10:44:58 am »

It would appear from info elsewhere that the 25kv was switched on in the Severn Tunnel earlier today.  Under test for a period.

So where are things regarding the previous reports of the corrosion of OHLE in the tunnel?
Logged
grahame
Administrator
Hero Member
*****
Posts: 30655



View Profile WWW Email
« Reply #874 on: October 27, 2019, 11:09:27 am »

It would appear from info elsewhere that the 25kv was switched on in the Severn Tunnel earlier today.  Under test for a period.

So where are things regarding the previous reports of the corrosion of OHLE in the tunnel?

"Corrosion" may not be accurate.   According to top ponchos at GWR and Network Rail, the problem was a deposit of unidentified 'summat' on the insulators - with the 'summat' being conductive.  If the research we were told about quickly identified the 'summat' (and, really, how long should it take?) then cleaning it off and taking steps either to clean regularly of stop it coming back is going to be a darned site quicker / easier / cheaper than replacing something that's corroded.
Logged

Coffee Shop Admin, Vice Chair of Melksham Rail User Group, and on the board of TravelWatch SouthWest.
stuving
Transport Scholar
Hero Member
******
Posts: 4969


View Profile
« Reply #875 on: October 27, 2019, 11:50:54 am »

   According to top ponchos at GWR and Network Rail...

Waterproof ponchos are , of course, essential PPE for any work in the tunnel - and inspecting or cleaning anything overhead calls for a top poncho as well.
Logged
chuffed
Hero Member
*****
Posts: 1365


View Profile
« Reply #876 on: October 27, 2019, 02:09:43 pm »

I thought the reference to 'top poncho' was as, in 'covering up' Grin
Logged
Chris125
Full Member
***
Posts: 48


View Profile
« Reply #877 on: October 27, 2019, 08:25:19 pm »

So where are things regarding the previous reports of the corrosion of OHLE in the tunnel?

F&F's Noel Dolphin has tweeted the following about the wires being switched-on, and what they did to allow this: https://twitter.com/NoelDolphin


"Severn Tunnel is currently live & electrified at 25kv for the first time. For testing in the run up to full switch on later this year"

"Mainly by removing copper contact wire and using aluminium contact wire. Also fixing some of the leaking drip pans after years of arguing internally in NR."

"Never going to be perfect in those conditions. Will always need more maintenance - as it is almost 100% humidity, permanently in some places. However, most corrosion issues minimised now (would not at this point want to say overcome)"
Logged
SandTEngineer
Hero Member
*****
Posts: 3485


View Profile
« Reply #878 on: October 27, 2019, 10:03:10 pm »

Interesting stuff.  Not wishing to digress but this relevant comment elsewhere got to me a bit as I worked in the box there once and remember it going up.......

Quote
Also, a moments silence though for whichever genius designed the termination of the electrification wires at St Pancras in the... 80s???

It's more or less forgotten and I can't even find a photo of it.

....and this one from Roger Ford cheered me up afterwards.....

Quote
In Scotland they spell Decarbonisation as E-L-E-C-T-R-I-F-Y.  So should we all.
« Last Edit: October 27, 2019, 10:17:02 pm by SandTEngineer » Logged
Adrian
Transport Scholar
Sr. Member
******
Posts: 171


View Profile
« Reply #879 on: October 28, 2019, 08:04:38 pm »

So where are things regarding the previous reports of the corrosion of OHLE in the tunnel?

F&F's Noel Dolphin has tweeted the following about the wires being switched-on, and what they did to allow this: https://twitter.com/NoelDolphin


"Severn Tunnel is currently live & electrified at 25kv for the first time. For testing in the run up to full switch on later this year"

"Mainly by removing copper contact wire and using aluminium contact wire. Also fixing some of the leaking drip pans after years of arguing internally in NR."

"Never going to be perfect in those conditions. Will always need more maintenance - as it is almost 100% humidity, permanently in some places. However, most corrosion issues minimised now (would not at this point want to say overcome)"


I thought the Severn Tunnel had something more like a rigid metal bar than a normal contact wire?

Is the idea of using aluminium instead of copper that it's a more reactive metal than steel, and therefore it is the aluminium which will preferentially corrode?  Which I suppose is better if the corrosion is not then be concentrated at the point where the OHLE is fixed to the tunnel.
Logged
stuving
Transport Scholar
Hero Member
******
Posts: 4969


View Profile
« Reply #880 on: October 28, 2019, 10:26:53 pm »

I thought the Severn Tunnel had something more like a rigid metal bar than a normal contact wire?

Is the idea of using aluminium instead of copper that it's a more reactive metal than steel, and therefore it is the aluminium which will preferentially corrode?  Which I suppose is better if the corrosion is not then be concentrated at the point where the OHLE is fixed to the tunnel.

In the F+F ROCS system (which I presume is what's been used), the actual contact with the pantograph is made by a wire. This is clamped in the base of the rigid "rail" - actually a hollow aluminum section. That can be replaced when it wears, like any other contact wire. It also provides for the transition to the standard suspended OLE.

For "damp" sites, they offer plastic covers for the rail and a special grease to waterproof the copper wire/rail contact and prevent corrosion. It seems that the Severn Tunnel is wetter and nastier than that level of "damp". Using aluminum wire will remove the electrochemical corrosion (due to potential differences between dissimilar metals) - how completely will no doubt depend on the alloy used.
Logged
MVR S&T
Sr. Member
****
Posts: 254


View Profile
« Reply #881 on: October 28, 2019, 10:51:28 pm »

Could stainless steel/plastics not be used? I have had lots of problem with Aluminium alloys in damp eletrical boxes.
Logged
ellendune
Transport Scholar
Hero Member
******
Posts: 3676


View Profile
« Reply #882 on: October 28, 2019, 10:56:54 pm »

Could stainless steel/plastics not be used? I have had lots of problem with Aluminium alloys in damp eletrical boxes.

If I have understood correctly it is the conductor wire that has been changed.  Stainless steel is a poor conductor compared to copper or aluminium so could not be used for the conductor wire. Aluminium is a very good conductor. 
Logged
onthecushions
Transport Scholar
Hero Member
******
Posts: 811


View Profile
« Reply #883 on: October 29, 2019, 02:40:31 pm »


Aluminium and its alloys have an unusual behaviour in corrosion.

It has a low hydrogen electrode potential and a heat of combustion about 30% higher than sodium metal (which catches fire in water - pinching the oxygen from the hydrogen!). However it is so reactive that it coats itself immediately with a layer of impervious Aluminuim oxide - called a passive film. Thus Aluminium (Al) panels do not need painting, unless the film is damaged and interrupted such as by scratching or more likely by chemicals such as the chloride ion in saline environments. Thus marine Al rapidly turns to white powder.

We shall see whether the metal survives but tunnels are severe environments for most metals - Merseyrail has had many problems just with steel track, albeit sharply curved. The Seven Tunnel will become a lot cleaner and the heavy gradients better addressed if the OLE works well.

Fingers crossed.

OTC
Logged
CyclingSid
Data Manager
Hero Member
******
Posts: 997


Hockley viaduct


View Profile
« Reply #884 on: October 29, 2019, 06:28:48 pm »

Aluminium has a higher resistance than copper. Hopefully nothing more than the fact that the electricity meter will turn more for each train.

Worked for a company who made electrical furnances and the like, hundreds of volts and hundreds of amps. Some bright spark (pun intended) in purchasing thought it a good deal to get some cheap cable, which happened to be aluminium. All sorts of problems ensued, especially for the person in purchasing.
Logged
Do you have something you would like to add to this thread, or would you like to raise a new question at the Coffee Shop? Please [register] (it is free) if you have not done so before, or login (at the top of this page) if you already have an account - we would love to read what you have to say!

You can find out more about how this forum works [here] - that will link you to a copy of the forum agreement that you can read before you join, and tell you very much more about how we operate. We are an independent forum, provided and run by customers of Great Western Railway, for customers of Great Western Railway and we welcome railway professionals as members too, in either a personal or official capacity. Views expressed in posts are not necessarily the views of the operators of the forum.

As well as posting messages onto existing threads, and starting new subjects, members can communicate with each other through personal messages if they wish. And once members have made a certain number of posts, they will automatically be admitted to the "frequent posters club", where subjects not-for-public-domain are discussed; anything from the occasional rant to meetups we may be having ...

 
Pages: 1 ... 57 58 [59] 60 61 ... 70
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.2 | SMF © 2006-2007, Simple Machines LLC Valid XHTML 1.0! Valid CSS!
This forum is provided by a customer of Great Western Railway (formerly First Great Western), and the views expressed are those of the individual posters concerned. Visit www.gwr.com for the official Great Western Railway website. Please contact the administrators of this site if you feel that the content provided by one of our posters contravenes our posting rules (email link). Forum hosted by Well House Consultants

Jump to top of pageJump to Forum Home Page