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Neutral Sections
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edwin_m
Veteran Member
You also see isolation switches on 25kV. The actual switch is at OLE level but has a rod up from near ground level, where there is a handle to rotate it and operate the switch. I think either these or DC hook switches can only be operated when the whole section in question is isolated, but after they are opened the remainder of the section can be re-energised.
pdeaves
Established Member
A list of neutral sections can be found here: http://www.railwaycodes.org.uk/electrification/neutral.shtm
WatcherZero
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The 350 are ****ing deafening especially if you are stood under the breakers. The Pendolino from what I remember it just sounds like a door being slammed in the distance so a let better sound insulated.
Trog
Established Member
I think there used to be a section of wooden conductor rail on the North London Line where the line crossed an under bridge with a girder situated such that if they had just gapped the con rail the hot shoes would have dropped onto the girder. Probably the nearest DC equivalent to the AC neutral sections, in that you had an insulating section of contact material even if the cause of the short it was preventing was different.
Mordac
Established Member
A very offputting one (or rather two in close succession when you're turning from the WCML to the Edinburgh branch), because the train has to slow down to a crawl as line speed falls to something like 20mph, and the State Hospital is right next door.
A very offputting one (or rather two in close succession when you're turning from the WCML to the Edinburgh branch), because the train has to slow down to a crawl as line speed falls to something like 20mph, and the State Hospital is right next door.
I've seen mention of it a few times on here, hence why it came to mind
driver9000
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A very offputting one (or rather two in close succession when you're turning from the WCML to the Edinburgh branch), because the train has to slow down to a crawl as line speed falls to something like 20mph, and the State Hospital is right next door.
15mph on the curve itself and 30mph passing the hospital towards Carnwath Moss and Auchengray, it rises to 95mph once clear of the curve at Carstairs East. The SPTs are apparently a special speaker phone type in the area but having never stopped at those signals I can't confirm what phones are installed these days.
Flying_Turtle
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Well, ATP Ebicab and its derivative, the french KVB, as also ermts have beacons for that purpose (even for voltage change and eth switch off/on).
The question of phases in AC feeding is way more complex. Even if you have monophasic feeding you need to have the exact same sincronized frequency it is not enough to be 50 hz (the current changes direction 50 times a minute), it has to be sincronized.
In the old days you had the countries electric networks divided in feeding areas usually related to a single power station.
With the advent of very reliable comunications you now manage to have multiple power stations sincronized which allows you to have all the country in single network.
This is the historical reason why neutral sections exist beyond the simple fact of power losses with distances,at least on monophasic substation feeding systems. Also, if they didn t exist the railway would have to surrender the control of the ohl to the national grid to avoid short circuits
sciisfun
Member
You don't need it for that reason, but you still have to have them, Imagine if there was an incident at Brighton, you would have to, in theory, switch off every section of 3rd rail that it connects to to ensure that the rail is isolated, all the way into London, all the lines that share junctions with it, thats a lot of track just to be sure! and most of London ground to a halt! (Extreme I know, but without isolating sections if there is a possibility it can be live, You must assume it is live!)
You are confusing a neutral section with an electrical section break. The first is specifically to keep different phase pairs apart, and has a neutral (earth) section in its centre. The latter, which is a feature of both AC and DC systems, is a simple air gap or insulator to keep different circuits separated. On overhead systems the latter is achieved by cutting insulation into the OLE overlap and then connecting a switch around it.
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PeterY
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I'm also learning a lot from this thread.
How long are the neutral sections?
How long are the neutral sections?
Flying_Turtle
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The UK ones are very short (under 10 yds) and hard grounded, But in many countries like France & Portugal and 25 kv high speed lines they can be up to 50 yds, having emergency feeders.
Japan uses rolling neutral sections on their high speed lines so trains never have to open the main switch
sciisfun
Member
AHH, ok that makes sense
Whistler40145
Established Member
With the implementation of the Autotransformer system on the WCML, does this effect the Neutral Sections?
GRALISTAIR
Established Member
me three.
http://file.scirp.org/pdf/EPE_2013102916203267.pdf
This is a paper which I found fascinating.
https://en.wikipedia.org/wiki/Overh...orbrug_Meppel_-_Buitenvaart,_Jaagpad_-_04.JPG
This one is on the continent with a total gap over a bridge.
https://www.youtube.com/watch?v=q55EfuVYNW0
This is a cool neutral section/air gap in Australia.
We have seen some of this before but very useful to have the information pulled together in one thread IMHO.
two types in the UK; traditional inline insulator type, made historically by BICC and now by Arthur Flury, are very short as already mentioned. On GW electrification we are pioneering the use of the Carrier Wire type on NR infrastructure; these use a series of OLE overlaps back to back with cut in insulation. They are typically 200m long but don't suffer from the same reliability issues and maintenance burden that the inline ones do.
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--- old post above --- --- new post below ---
It means there are fewer of them, since the higher power means the feeder stations are further apart, but an AT railway is still fed single phase so still needed.
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Philip Phlopp
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No, just the same (though obviously changing feeding arrangements can require changes to the location where neutral sections are provided).
The neutral section is the boundary for each feeding station, it doesn't matter if the feeder itself is a conventional 25kV or a 25-0-25kV AT feeder.
Impressive... Locos must have a control on the pan to drop it a little way below contact wire heightme three.
http://file.scirp.org/pdf/EPE_2013102916203267.pdf
This is a paper which I found fascinating.
https://en.wikipedia.org/wiki/Overh...orbrug_Meppel_-_Buitenvaart,_Jaagpad_-_04.JPG
This one is on the continent with a total gap over a bridge.
https://www.youtube.com/watch?v=q55EfuVYNW0
This is a cool neutral section/air gap in Australia.
We have seen some of this before but very useful to have the information pulled together in one thread IMHO.
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Whistler40145
Established Member
Thanks for your replies.
I didn't think it was like that. I think the pantograph is designed so that its knuckle can't get completely straight, but reaches a limit while still bent. On the approach to the gap, the contact wire rises gradually, and the pantograph rises to follow it, but the contact wire eventually gets too high for the pantograph to follow.
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Philip Phlopp
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You would need overheight protection though (unless they're not bothering with it).
I'd agree with the idea that it's dropping and maintaining a lower height through the air gap.
Rick1984
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I've noticed a similar gap on a lifting bridge near Den Holder, also in Netherlands.
Can be seen here:
https://goo.gl/maps/UYQevBmEmVk
Interesting to see a classic Dutch bridge used on a railine
Can be seen here:
https://goo.gl/maps/UYQevBmEmVk
Interesting to see a classic Dutch bridge used on a railine
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SodTheDrummer
Member
Are the Aussies particularly bothered with all that health & safety nonsense?
25Kv - meh! Use that to open me tinny with mate*
*I realise I might be stereotyping slightly here..
Philip Phlopp
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There's a video on t'internet. From memory, it's a pan down/pan up gap.
--- old post above --- --- new post below ---
Are the Aussies particularly bothered with all that health & safety nonsense?
25Kv - meh! Use that to open me tinny with mate*
*I realise I might be stereotyping slightly here..
It's not health and safety, it's one mechanism which exists to prevent the pantograph obliterating the OLE if something goes quite badly wrong.
SodTheDrummer
Member
Fair point! Excuse my flippancy!
Seriously though, out of interest has this type of thing ever been considered over here or would it ever be?
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Flying_Turtle
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I believe modern stock has that kind of protection
We have an ADD (automatic dropping device ?). When the Pan loses the wires it will push upwards but when it reaches a specific height and the wires aren't there. It will automatically drop the pantograph.
If your on DC (on our units) and you try to put the pan up it will try and find the wire but again reach the pan over height limit and drop the pantograph.
SodTheDrummer
Member
Cool, thanks - but I was meaning the 'air gap' principle i.e. has that idea ever been considered here or would it even be feasible/suitable/appropriate/cheap enough etc? I'm guessing not as I'm not aware of any of these in the UK...
Whistler40145
Established Member
AFAIK the contact wire at a Neutral Section has a section of Glass Fibre inserted.
I presume this makes the short section dead?
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I presume this makes the short section dead?
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