ECML Damaged OHL

[Bald Rick]

Stick it up in the air and clamp it to gantries.
Overhead electrification for men!

Precisely what is happening through the Thameslink core at Easter.

 

[A-driver]

Can't link to it as on my phone but on FCCs twitter feed there is a statement from NR apologising for both radlett and barford stating initial investigations suggest 'component Failiure'. So looks like it was NR and not the rolling stock. I believe there is still some suggestion that the rolling stock was part responsible for hitchin though from rumours I've heard but nothing official.

 

[HSTEd]

Stick it up in the air and clamp it to gantries.
Overhead electrification for men!

Furrer and Frey have a product that can do this.

It can, and has been, installed on open route, and is rated for up to 250kph operation.

That would be the ultimate reliability overhead I think.... and it would also allow fewer substations because it is a rather good electrical conductor, being a giant piece of aluminium.

 

[EM2]

Precisely what is happening through the Thameslink core at Easter.

There are a number of tunnels that have a solid conductor, I believe?
Makes me wonder why it's not used on open line too.

 

[philjo]

The catenary wire zig zags so it doesn't cut a groove in the pantograph.
Perhaps if solid conductors are used a large chunk of the pantograph is worn down? If the conductor is wide enough it probably isn't a problem but that would add to the cost of the conductor bar.

 

[Zoidberg]

The catenary wire zig zags so it doesn't cut a groove in the pantograph.
Perhaps if solid conductors are used a large chunk of the pantograph is worn down? If the conductor is wide enough it probably isn't a problem but that would add to the cost of the conductor bar.

If it's necessary to ensure that the pick-up area of a pantograph is fully swept, then it ought to be possible for a solid conductor to be so arranged. Although "solid", the conductor will not be rigid.

 

[jopsuk]

A tensioned wire is a fair bit lighter than a rigid solid bar... much much less metal.

 

[bangor-toad]

The physics of what goes on with the 25kV conductor aren't obvious.

There's something called the "Skin Effect" which means that 50Hz electrical current only flows in the outer edges of the metal. For copper that's about 8mm.

If you look at almost all UK OHLE wiring it's fairly thin. I've never been up close to some (and hopefully never will!) but it doesn't look much more than about 16mm diameter to me.

There's no point increasing the size for better electrical conduction. Maybe the conductor size is increased for rigidity but that's the only additional benefit of using an overhead rail.

Cheers,
Jason

 

[HSTEd]

The physics of what goes on with the 25kV conductor aren't obvious.

There's something called the "Skin Effect" which means that 50Hz electrical current only flows in the outer edges of the metal. For copper that's about 8mm.

If you look at almost all UK OHLE wiring it's fairly thin. I've never been up close to some (and hopefully never will!) but it doesn't look much more than about 16mm diameter to me.

There's no point increasing the size for better electrical conduction. Maybe the conductor size is increased for rigidity but that's the only additional benefit of using an overhead rail.

Cheers,
Jason

Actually the conductor rail produced by Furrer and Frey is not a solid piece of metal.

It is effectively a box girder with a copper contact conductor clamped into the bottom of it.

The sides of this "girder" are sufficiently thin that skin effect can be neglected.

 

[Clip]

The problem didn't just arise with Twitter. I remember several years ago when there were major delays at Kings Cross with large crowds there. There was an announcement that the train at Platform xx is now available for boarding. Everyone headed towards there, only to be met by a member of staff who insisted that this was not the case but then gave up trying to stop the flow, faced with the number of insistent passengers. When everyone got to the train it was indeed getting ready to depart.

Similarly at Darlington several years ago the London-bound side of the station was closed due to a passenger on the line. he platform staff continued to insist all the way through that there was no information on when the next train would be, even though the display screens were clearly showing information that was being updated on a regular basis.

I never said it started with twitter. Your example is a perfect illustration of the difficulties faced by front line staff getting info as and when they need it.

 

[FGW_DID]

I think a few people are somewhat over reacting on here!

Seems to happen on the majority of threads on here

 

[JGR]

I think we've found a solution!!

I wonder if, one day, we'll be able to power trains by inductive charging/power; such as the trials being carried out by Qualcomm to charge cars (http://www.slashgear.com/qualcomm-h...largest-wireless-car-charging-trial-07255855/)

Obviously there's a difference between charging and actually moving, and a train consumes rather a lot of power, but I still wonder if we'll be able to do it in the next 10, 20 or 30 years. That would mean no need for wires that can fall down, or third rail that can get iced up.. just the whole track as one big power grid - yet people could walk on.

[Then we'll discover it causes cancer or something and...!]

These schemes are not really appropriate for transferring energy: cheaply, at high power, or at high efficiency.

Filling the 4ft with sufficiently beefy induction coils would be absurdly expensive and you'd need to use selective powering to achieve even a low efficiency. It'd probably be cheaper to just use nuclear-powered locomotives :P.

The physics of what goes on with the 25kV conductor aren't obvious.

There's something called the "Skin Effect" which means that 50Hz electrical current only flows in the outer edges of the metal. For copper that's about 8mm.

If you look at almost all UK OHLE wiring it's fairly thin. I've never been up close to some (and hopefully never will!) but it doesn't look much more than about 16mm diameter to me.

There's no point increasing the size for better electrical conduction. Maybe the conductor size is increased for rigidity but that's the only additional benefit of using an overhead rail.

Cheers,
Jason

The skin effect is usually easy to manage at frequencies as low as 50Hz.
Given that the voltage is reasonably high at 25kV, you only need a hundred odd A per train, very roughly.
16mm diameter copper wire would get you on the order of 0.1Ω/km, which is more than good enough for that.
(I've seen a figure of 150mm^2 cross-sectional area quoted, which works out as roughly 14mm diameter).

I would imagine that mechanical/tensioning issues would be more significant.

 

[yorksrob]

Filling the 4ft with sufficiently beefy induction coils would be absurdly expensive and you'd need to use selective powering to achieve even a low efficiency. It'd probably be cheaper to just use nuclear-powered locomotives :P.

Just replace the firebox on a kettle with a fuel rod and Bob's your uncle

 

[thelem]

I wonder if, one day, we'll be able to power trains by inductive charging/power

That's not too far off maglev - the problem there being that the track is very expensive and you can't run maglev trains on a traditional network.

 

[dysonsphere]

That's not too far off maglev - the problem there being that the track is very expensive and you can't run maglev trains on a traditional network.

On that subject I remember reading a report on maglev and one of the biggest problems was arranging points and routing It was fine on A to B with no entry exit tracks but in the real world that is not much use. Does anyony know if this has been solved yet.

 

[jon0844]

No, it's not like maglev surely? It just provides power. Normal tracks and signalling (and points) would remain.

I know we're not there now but spoke of the future, where trains might have their own power source (batteries or some other fuel cells) and merely need charging on the move and when stopped, stabled etc.

Think we have some way to go for now though!

 

[HSTEd]

On that subject I remember reading a report on maglev and one of the biggest problems was arranging points and routing It was fine on A to B with no entry exit tracks but in the real world that is not much use. Does anyony know if this has been solved yet.

The transrapid system can supposedly switch vehicles at ~100mph or so, and this has apparently been demonstrated in service in Shanghai.

And I would hope the Japanese have solved this problem as they are now committed to constructing the Chūō Shinkansen using Maglev technology.