Neutral sections

Discussion in 'Infrastructure & Stations' started by aal7, 11 Jun 2015.

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  1. aal7

    aal7 Member

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    Last week I was on this train:

    http://www.realtimetrains.co.uk/train/P70469/2015/06/04/advanced

    As you will see, it lost 77 minutes between Wembley and Harrow. This was caused by (what seemed like) an emergency stop which finished in a neutral zone. The train had no power, couldn't move, and had to be rescued.

    We were told what had happened but not why it had happened.

    It's not something I've come across before so I'm interested in the details of neutral zones, how long they are, how fast a train needs to be going to get through one etc. I'm assuming that drivers would normally avoid stopping in them like the plague, so something odd must have happened here. What could have caused it?

    Please note that I am not complaining or "having a go" at anyone, just genuinely interested by something I was previously unaware of.
     
    Last edited: 11 Jun 2015
  2. TDK

    TDK Established Member

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    For a train to stop with it's pan under a neutral zone is very rare as they are only possible 20' in length. A neutral zone I believe is where the contact wire has a neutral section between substations. Trains are advised to shut off power when passing them and the zones are indicated with line side signs however if a train has an emergency stop and unfortunately stopped over the neutral zone the probability of this is very high I would say one in 1000 at least so it was a stroke of bad luck.
     
  3. najaB

    najaB Veteran Member

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    As you probably figured out by now, neutral sections are the gaps between segments of the OHLE. They allow stretches of the line to be de-energised for engineering work, etc. as well as separating sections of line that are powered from different substations.

    They aren't very long (20 to 30 feet at a guess) so it's extremely bad luck that the train should stop with its pantograph in the neutral - it's similar to a third-rail train stopping with the shoe in a gap.

    As to how fast you need to be going, I would think that any appreciable velocity would get you across the gap - 5mph upwards? In fact, I think it would take some skill to get stuck in one deliberately! If the train has multiple pantographs it my guess is that it should be possible to raise one of the others in order to move the train out of the gap.
     
  4. Domh245

    Domh245 Established Member

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    A Neutral section is marked out by lineside boards, as well as Automatic Power Control (APC) magnets by the track (which operate the vacuum circuit breakers (VCB) - which effectively separates the train from the overhead to prevent arcing when passing through the section, and make the loud thunk noise). The neutral section is about 155 feet long in total. There is a 100ft run on from the first set of APC magnets to the ceramic insulators. There is 5ft of ceramic insulator, 5ft of dead wire, and another 5ft of ceramic insulator, with a 40ft runoff. If a train is stopped in a neutral section, it will be able to do a few things. If it has stopped with the pantograph in the 100ft before the dead section, the VCBs can be reset and it can be reversed out (after liasing with signaller) and the driver can have another go at it. If it is stopped in the 40ft runoff area, the VCBs can be reset and then the train driven off, resetting the VCBs again once passing the magnets.

    If it has stopped in the 15ft dead section, the driver can either hope for the train to roll out of the dead section on a gradient, or they will have to get assistance.
     
  5. edwin_m

    edwin_m Veteran Member

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    They are generally referred to as neutral sections. As stated they are relatively short, and positioned to minimise the risk of trains getting stuck in one (so not near signals or stations). They are needed because different parts of the 25kV overhead line are fed from different phases of the national grid, and if two phases were ever connected electrically there would be a massive short circuit. The neutral section has to be long enough so there is no possibility of a passing pantograph creating an arc between the different phases either side of it.

    Trains can roll a surprisingly long way, so I think moving at walking pace would be enough to get through a neutral section as long as the brakes weren't applied. I guess if there is a risk of stopping in one the driver would either release the brakes and roll through, or apply the brakes harder to stop before it. However neither is an option on an emergency stop.
     
  6. mbreckers

    mbreckers Member

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    There's a neutral section immediately after the signal at Platform 2 at Newton-On-Ayr station.
     
  7. aal7

    aal7 Member

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    Thanks for all the info. I was in a 350/1, which I think only has one pantograph. We were told that a rescue train would be required. Whether one arrived or not (I never saw it on the opentraintimes map or felt it couple up), we eventually reversed/were dragged backwards out of the neutral zone for quite some distance (a couple of miles I reckon) before proceeding forwards towards our destination. We all held our breath as we passed through the site where we'd been stopped for over an hour!
     
  8. A-driver

    A-driver Established Member

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    As far as I'm aware (and am not usually pedantic) it's a neutral SECTION. I believe a neutral ZONE has something to do with Klingons and romulans in Star Trek!

    If an emergency brake is applied the driver can't then release the brakes until it stops so if it stops in a NS then there is little a driver can do about it.

    How fast you need to pass them depends on the gradient. There are a few leading up to or after red signals where you can do 15mph through as the gradient is on your side.

    A few years ago a train was cautioned through the NS at Caldwell, near Hitchin, at 15mph with an 8 car (so 2 pans) and got stranded as it couldn't make it through.
     
  9. Quakkerillo

    Quakkerillo Member

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    Pfft, rescue train. Just do it the Dutch way and give it a push! No health and safety issues at all! ;)
    http://i48.tinypic.com/xmsnpw.jpg

    (Train stopped with its pantagraph just on the bridge bit without OHLE.)
     
  10. najaB

    najaB Veteran Member

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    H&S, what are you on about? They are clearly wearing high-viz.
     
  11. edwin_m

    edwin_m Veteran Member

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    No UK EMU has more than one pantograph as far as I'm aware except Pendolinos and Eurostars, which are effectively pairs of EMUs that always run coupled together. If your train was only one unit that would be it, but presumably if it had been two or more coupled units then the unaffected unit(s) would have been able to move the other one off the neutral section.
     
  12. DownSouth

    DownSouth Established Member

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    The very slim chance of getting stuck in a neutral section is just one of those risks you take with using electrified railways, but all forms of rail traction have their detriments as well as their benefits. A diesel loco, for example, could run dry and get stranded due to a leaky fuel tank or a forgetful depot worker - but like an electric train getting stuck it doesn't happen too often.

    With the neutral section issue, there are some steps which can be taken to prevent it happening (e.g. don't put neutral sections on the flat, don't put them in places where it's more likely for a train to come to a halt after a signalling-related emergency brake application, etc) by getting the chance low enough to be an acceptable risk.
     
  13. Railsigns

    Railsigns Established Member

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    That's an unusual neutral section, which is there because of a low bridge, not for electrical supply reasons.
     
  14. WatcherZero

    WatcherZero Established Member

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    Easiest way to tell your passing through a neutral section is the air conditioning cutting out for a few seconds.
     
  15. Boodiggy

    Boodiggy Member

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    The train involved wasn't actually stopped in the neutral section. It stopped due to a change of aspect in a signal and stopped close to the neutral section section but not in the 'dead section' and when OHL staff arrived on site and confirmed this the driver reset the VCB and the train moved without assistance.
     
  16. najaB

    najaB Veteran Member

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    Perhaps I'm being dense (okay, almost certainly I'm being dense) but was it not possible for the driver to determine this for him/herself?
     
  17. Peter Mugridge

    Peter Mugridge Established Member

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    I heard a story once where years ago a locomotive got gapped on the WCML and the signalman asked another driver to check what was wrong with the first train as, for some reason, the driver hadn't contacted him.

    So the second train drew up alongside on the adjacent track and the driver asked the first driver what the problem was, to which the second driver replied: "Same as you...!"

    Probably an urban myth, but it makes a good story anyway.
     
  18. Bald Rick

    Bald Rick Established Member

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    You're not being dense. Apparently the driver assumed he was in the neutral, when in fact he wasn't.
    --- old post above --- --- new post below ---
    It's true! I remember it. North Wembley neutral. Red faces all round.
     
  19. A-driver

    A-driver Established Member

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    Like it.

    There was a train wrong routed at Ely north junction a while back-a 317. It took the march road and ran out from under the wires. The assisting 317 went to collect it and found it was slightly too far away so also ended up loosing it's pan. Cue the 3rd rescue train. Could have gone on and on for a while!
     
  20. CyrusWuff

    CyrusWuff Established Member

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    Ditto fairly close to the London end of the platforms at Hackney Downs. Not the clearest of shots I grant you, but this aerial view just about shows up the magnets on the Slow Lines towards the bottom right. Platform ends are just the other side of the bridge over Spurstowe Road.
     
  21. Joseph_Locke

    Joseph_Locke Established Member

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    Perhaps the filament in the Line Light on the driver's desk had blown ...
     
  22. scott118

    scott118 Member

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    The same happened at Coppermill, towards Lea Bridge. 'No wires Wright' still drives (rest days only..) out of NRW, i believe..
     
  23. dk1

    dk1 Established Member

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    This thread threw me when I saw it as Neutral Zone, only ever heard it called a Neutral Section. It has happened a couple of times on the GEML as far as I'm aware with loco-hauled sets. Once at Forest Gate & the other at Manningtree. Both are on the level & where due to driver error.
     
  24. Harlan Cage

    Harlan Cage Member

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    As an aside I note that pantographs so have being removed from many Class 390's with some sets appearing only having only one working pantograph which could potently wcause problems with dead sections. Whilst in the ECML, the other Virgin has inherited Ckass 91's which were upgraded to have 2 pantographs to add resilience in case of failure!

    I appreciate the chance of a train of stopping in a dead section with it's pantograph are low however if there pantograth fails the train is now immobilised!

    HC
     
  25. Boodiggy

    Boodiggy Member

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    The 390s have two pantographs.
     
  26. Elecman

    Elecman Established Member

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    Do you mean the 3rd pan car (U I think) on the 11 coach pendos, they were never fitted with a pan but coach C and H are fitted and remain so.
     
  27. carriageline

    carriageline Established Member

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    All pendos have 2 pantos, only the rear one SHOULD be in use.
     
  28. Zoidberg

    Zoidberg Established Member

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    At the risk of going off-topic, why is that, please?
     
  29. snowball

    snowball Established Member

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    Not an expert, but at a guess

    1) avoid using two pantos because the front one would create waves in the wire that would adversely affect the ability of the rear one to maintain contact

    2) when using only one, make it the back one as it's out of the air turbulence created by the front of the train.
     
  30. The Snap

    The Snap Established Member

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