GWML Electification

[royaloak]

How about lower than standard (for LCs) OLE at Stocks Lane with solid protection beams to prevent larger vehicles coming into contact with the OLE ? No doubt there is a Standard or Directive preventing that too.

As there are 2 alternative routes very close to Stocks Lane that is actually a very good idea, I wonder if that has been thought about?

[royaloak]

Alternatively, in the short term at least, why not just drop the pans and coast through?  In the unlikely event of being stranded all the trains have diesels that can be started up to get them moving again.  An article in Modern Railways suggested the diesels would be used on every run, which sounds like a lot of diesel given that they have to be started up well beforehand to warm them up. 

 

(apologies if I've posted this already - I think it was another forum but may have been somewhere in the preceding pages...)

It will probably be a case of start the engines, lower the pans, coast through, pans up, engines off and away you go, the engines wont need to be revved up at all.

 

The engines do not need to be started to warm them up, sho said they did?

They are preheated up to at least 45c before actually being started, this is done through the TMS system.

 

Oh and they are not called engined, they are called Generating Units, yes seriously.

 

TBH I cant see why they dont just coast through either!

Edited November 8, 2017 by royaloak

[SouthernMafia]

Whilst it definitely seems sensible to close the crossing, could a mitigating factor be the second crossing? In that the wires still can't get from minimum to maximum height within the required distance ? Yes its a few hundred metres extra (if that) but is the angle still going to be too steep ?

If this is the case then closing the first crossing has no merit because the problem will still exist.

[Titan]

Whilst it definitely seems sensible to close the crossing, could a mitigating factor be the second crossing? In that the wires still can't get from minimum to maximum height within the required distance ? Yes its a few hundred metres extra (if that) but is the angle still going to be too steep ?

If this is the case then closing the first crossing has no merit because the problem will still exist.

 

It is quite possible, grading down from maximum height to minimum height at a suitable grade for 125mph takes almost a kilometre.

[Peter Kazmierczak]

​I am opposed to the laying down of rules and conditions to be observed in the construction of bridges lest the progress of improvement tomorrow might be embarrassed or shackled by recording or registering as law the prejudices or errors of today.

 

​From a certain I K Brunel.....

 

He certainly had a nice turn of phrase at times.

[96701]

It will probably be a case of start the engines, lower the pans, coast through, pans up, engines off and away you go, the engines wont need to be revved up at all.

 

The engines do not need to be started to warm them up, sho said they did?

They are preheated up to at least 45c before actually being started, this is done through the TMS system.

 

Oh and they are not called engined, they are called Generating Units, yes seriously.

 

TBH I cant see why they dont just coast through either!

I'll say this again. Trains can coast for miles. Any electric passenger train could set off from Didcot, power off, drop the pans (if necessary - I reckon a long earthed neutral section would fit), coast through the bridge and over the level crossing. The expensive bit would be cabling both high voltage cables under the bridge and over the level crossing.

[Jonboy]

Apart from the fact that installing OHLE under the current bridge is easily done, and it will be done quite soon, its a good plan, as previously stated the problem is the proximity of Stocks Lane LC and the B4017 bridge which means the OHLE has to go from its maximum height over the LC to its lowest height under the bridge and because of the short distance between the two the contact wire would be at too much of an angle causing the pantograph to put too much strain on the wire above about 60mph with the possibility of a dewirement, or in the other direction the pantograph losing contact, which is why there will be a 60mph restriction under the bridge for any trains with pantographs raised.

 

Closing Stocks Lane LC would probably be the best idea as it wouldnt inconvenience too many people as there are 2 alternative routes available, the bridge or Causeway LC.

One alternative route, there is no road access from that part of the village to the bridge. ( there is a private farm track which shows on google maps).

Edited November 9, 2017 by Jonboy

[Titan]

​I am opposed to the laying down of rules and conditions to be observed in the construction of bridges lest the progress of improvement tomorrow might be embarrassed or shackled by recording or registering as law the prejudices or errors of today.

 

​From a certain I K Brunel.....

 

He certainly had a nice turn of phrase at times.

Presumably said on the subject of Maidenhead viaduct! Nothing new then...

[Edwin_m]

I'll say this again. Trains can coast for miles. Any electric passenger train could set off from Didcot, power off, drop the pans (if necessary - I reckon a long earthed neutral section would fit), coast through the bridge and over the level crossing. The expensive bit would be cabling both high voltage cables under the bridge and over the level crossing.

Because of the wire gradient issue I think they would have to drop pans rather than just coast through on neutral overhead.  In the direction where the wire descends rapidly, keeping the pan up would be putting greater than normal stresses on the wire and possibly the pan too. 

 

I understand the autotransformer feed wire (effectively another 25kV cable) is ducted where it's not possible to run it overhead, and there seems to be no concern about providing long 25kV feeders trackside (eg there will be one from Stalybridge to Manchester) so a ducted cable to link both ends of the disconnected OLE (probably one for each track in fact) shouldn't be an isue. 

[Christopher125]

800002 using the wires at Reading (credit to Dan Warman for this) - looking good for January?

 

Edited November 9, 2017 by Christopher125

[D1059]

One alternative route, there is no road access from that part of the village to the bridge. ( there is a private farm track which shows on google maps).

 

The track from Stocks Lane to the bridge is a public right of way (Byway Open to all Traffic) - albeit unsurfaced and mainly single lane

[jamie92208]

Maybe we should start a new topic on the Steventon Gap.

 

Jamie

[Geoff Endacott]

Steventon Gap would be a good name for a folk group.

 

Geoff Endacott

[Ron Ron Ron]

Steventon Gap would be a good name for a folk group.

 

Geoff Endacott

 

 

The Steventon Gap Band,

or shortened to Gap Band

Oops upside your head (span).......

 

 

.

[96701]

Because of the wire gradient issue I think they would have to drop pans rather than just coast through on neutral overhead.  In the direction where the wire descends rapidly, keeping the pan up would be putting greater than normal stresses on the wire and possibly the pan too. 

 

I understand the autotransformer feed wire (effectively another 25kV cable) is ducted where it's not possible to run it overhead, and there seems to be no concern about providing long 25kV feeders trackside (eg there will be one from Stalybridge to Manchester) so a ducted cable to link both ends of the disconnected OLE (probably one for each track in fact) shouldn't be an isue. 

True, I'd forgotten about the gradient. The problems with cables at level crossings is where the ground changes from normal unstressed to traffic loads. Even a small amount of flexing there can result in cable breaks, but a large enough cable should survive.

[Siberian Snooper]

True, I'd forgotten about the gradient. The problems with cables at level crossings is where the ground changes from normal unstressed to traffic loads. Even a small amount of flexing there can result in cable breaks, but a large enough cable should survive.

Could they not use a solid conductor, as they're through the Severn tunnel, I would have thought that should absorb the stresses of the pantograph on the slope.

[Edwin_m]

Could they not use a solid conductor, as they're through the Severn tunnel, I would have thought that should absorb the stresses of the pantograph on the slope.

 

The problem is the speed at which the pantograph is moved up or down, which depends on the speed of the train and the gradient of the wire relative to the track (which itself may not be level).  When going down this increases the pantograph force on the wire or bar, with extra wear on both.  When going up the upward force on the pantograph may not be enough to keep it in contact with the wire.  A solid conductor would if anything make this slightly worse, as the small amount of flexibility in the wire, which probably reduces the forces on the downward slope a little, would be lost. 

[Edwin_m]

True, I'd forgotten about the gradient. The problems with cables at level crossings is where the ground changes from normal unstressed to traffic loads. Even a small amount of flexing there can result in cable breaks, but a large enough cable should survive.

 

Signal cables are much thinner and don't seem to have this problem, so I'm sure something could be devised to protect a power cable.  If it can't then the cable could go back to being elevated across the crossing. 

[Mike Storey]

Signal cables are much thinner and don't seem to have this problem, so I'm sure something could be devised to protect a power cable.  If it can't then the cable could go back to being elevated across the crossing. 

 

Never been a problem with the gurt great power cables run alongside the SR DC electrified routes. You just have to bury them deep enough.

[Suzie]

I thought that everyone wants to get rid of level crossings (government, Network Rail, TOCs, passengers, local residents, motoring organisations, etc.) - so surely this is a no-brainer to either divert the road(s) or build a bridge? Getting in the way of proper electrification must be an additional reason.

 

The Causeway is half a kilometre from the bridge - is that really too much gradient on the wire?

Edited November 10, 2017 by Suzie

[jamie92208]

I 

 

I thought that everyone wants to get rid of level crossings (government, Network Rail, TOCs, passengers, local residents, motoring organisations, etc.) - so surely this is a no-brainer to either divert the road(s) or build a bridge? Getting in the way of proper electrification must be an additional reason.

 

The Causeway is half a kilometre from the bridge - is that really too much gradient on the wire?

 

can't remember the exact figures but there is apparently a tried and tested formula for designing such gradients.  Roger Ford explained it and IIRC the workable distance depends on the square of the speed.

 

Jamie

[Titan]

 

 

The Causeway is half a kilometre from the bridge - is that really too much gradient on the wire?

 

 

I can't remember the exact figures but there is apparently a tried and tested formula for designing such gradients.  Roger Ford explained it and IIRC the workable distance depends on the square of the speed.

 

Jamie

 

 

The formula is quite simple, maximum gradient of the wire is 1 in (5 x line speed).  So for 125mph that is 1 in 625.  At a level crossing design wire height should be 5.8 meters. Under a low bridge it can be down to 4.3m, a difference of 1.5m. at 1 in 625 that will take 937.5m. You also need a transition at each end because you can't go from level wire straight in to maximum gradient, so adding a couple of spans at each end for that will take the whole distance to over a kilometre.

Edited November 11, 2017 by Titan

[jim.snowdon]

Never been a problem with the gurt great power cables run alongside the SR DC electrified routes. You just have to bury them deep enough.

The Southern's 33kV cables are either laid in surface or elevated trough route. They are buried only when they have to be, such as through platforms.

 

Jim

[jim.snowdon]

The formula is quite simple, maximum gradient of the wire is 1 in (5 x line speed).  So for 125mph that is 1 in 625.  At a level crossing design wire height should be 5.8 meters. Under a low bridge it can be down to 4.3m, a difference of 1.5m. at 1 in 625 that will take 937.5m. You also need a transition at each end because you can't go from level wire straight in to maximum gradient, so adding a couple of spans at each end for that will take the whole distance to over a kilometre.

Quite right. A key factor in all of this is the ability of the pantograph to follow the changes in the contact wire height. Although pantographs are built to be as light as practicable they still possess quite a bit of inertia, which effectively governs the rate at which it can rise and fall. The effect is that if the wire rises too rapidly, the pantograph head will lose contact as it can't follow the wire. If power is being taken at the time, an arc will develop between the pan head and the wire, which, when repeated is good for neither. When the wire descends too rapidly, although the pan will follow, the contact force increases, resulting in increased wear, and if the change back to level wire isn't properly transitioned, the pan will overshoot, which will cause more arcing. Compared to conductor rail, overhead wiring is rather more delicate.

 

The issues of wire height is part of the reason for the wiring on the older parts of the Great Eastern being new auto-tensioned equipment. With the original equipment, the wire was fixed at each end, with the result that the amount of sag between supports varied between winter and summer. What was tolerable for the speeds when the GE was originally electrified became an issue with today's higher speeds, with speed restrictions having to be imposed when the temperature got too high. (There are also other issues with snaking if the wire tension drops too far.) It is also why the wire height on the high speed lines is built and maintained to a much higher standard. Even then, it is also common practice to build high speed pantographs as two stage devices, effectively a mini-pantograph mounted on top of the main pantograph. The top stage, being small, can respond to the small variations, whilst the main pantograph takes care of getting the reach.

 

Jim

[royaloak]

I'll say this again. Trains can coast for miles. Any electric passenger train could set off from Didcot, power off, drop the pans (if necessary - I reckon a long earthed neutral section would fit), coast through the bridge and over the level crossing. The expensive bit would be cabling both high voltage cables under the bridge and over the level crossing.

Try reading my posts again, you are not even close with your solution to the problem.

 

Actually to save you the effort of actually reading what has been posted previously-

 

The problem is the proximity of Stocks Lane LC and the B4017 bridge which means the OHLE has to be at quite a steep angle to get from full height over the LC down to minimum height under the bridge, this would cause excessive forces from the pantograph onto the OHLE with the possibility of a dewirement, hence the imposition of a 60 mph restriction for all trains with pans raised once it is electrified.

 

Can you please explain how coasting through would solve the actual issue and not what people are assuming is the issue?

 

Electric trains are not routinely allowed to drop their pans and coast.

Edited November 11, 2017 by royaloak