Watching Don Coffey’s latest video and the 805 changes over to diesel engines at Crewe station but there looked like a fair distance of OHLE out past the EMU depot towards Holyhead. I’ve noticed similar things with TPE using electrification toward Ulleskelf as well. I’m sure there’s a very simple answer!
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Why do bi-modes not use every last metre of OHLE?
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Similar to the Merseyrail battery units which switch at/just after Fazakerley station on the way to Headbolt Lane, even though the next station (Kirkby) still has third-rail power - it'll likely be a SOP to ensure the switch over isn't forgotten and becomes drilled/second-nature.
a_c_skinner
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Developing this can it not be automated reliably?
Bletchleyite
Veteran Member
It's also so if it goes wrong the unit is less likely to be stranded. Units have used the electrification closer to Kirkby where it has, so its presence is useful. Presumably it's also used deliberately on occasions so it's kept clean?
TransportHub
Member
Also changing power supply in a station means if something goes wrong (the engine has a fault say) it's much easier to deal with a platformed train than one blocking the line
It's one of those things that I really feel should be automated, as then it would allow for discontinuous electrification.
E.g. Trundle out of complex terminus throat on diesel/battery as it was too expensive to wire, then when you're clear, the pantograph automatically goes up to draw power as you accelerate to line speed. Then as you're decelerating it goes down (as the wires haven't gone away), and the diesel/battery kicks on again to help you coast into the station and then continues until the next patch of wiring.
E.g. Trundle out of complex terminus throat on diesel/battery as it was too expensive to wire, then when you're clear, the pantograph automatically goes up to draw power as you accelerate to line speed. Then as you're decelerating it goes down (as the wires haven't gone away), and the diesel/battery kicks on again to help you coast into the station and then continues until the next patch of wiring.
Snow1964
Established Member
Yes, and this has come up in numerous threads, on bimodes, potential BEMUs, and potential electrification add on threads.
Many of the ends of the electrification are historic, just beyond where a fully electric train would reach its shunt limit. This was fine when trains were pure electric only, but ideal wire end locations for multiple mode trains are different and there should be longer run offs (even lengths with unenergised wires etc. for few hundred metres to avoid de-wirements).
Without these extended over runs, an abundance of caution is often used, changing over early. It is the railway using a bodge to get round the problem, rather than fixing the source of the problem.
Whilst there are some bimodes that don't work very well with cold diesel engines, so they get started up early. In most cases it is because the end point of wires (or third rails) have not been extended hundreds of metres to allow seamless transition of power at a location where train is not accelerating.
So in a way a simple answer is the ideal infrastructure modifications were not included when multiple mode trains were ordered, so having to change power modes early to avoid errors and/or problems.
Bletchleyite
Veteran Member
I think in some places it is automated using balises (so it isn't done at the wrong location)? Though I'm not sure where.
DaveyJones
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Because Merrill's Bridge on West Street in Crewe is just after the end of the Electrification...
hexagon789
Veteran Member
Doesn't LNER use "APCO" (Automatic Power Change Over) balises, at least on certain of their routes?
There's definitely some of those changeover points in Scotland - Dunblane for instance.
It's used at Stowmarket to accelerate the bi-mode 755s off the GEML as soon as possible. They depart Stowmarket pan up, engines running (?), and they drop the pan before Haughley Jn where the wires end.
I don't have specific data, but I'm almost certain this is helpful for speeding up the northern part of the GEML. Possibly required for the new timetable with all EMU intercity services calling at Stowmarket as well.
zwk500
Veteran Member
In addition to the other answers, putting the pantograph up at speed needs extra considerations about the additional forces and vibrations placed on the wire. Putting it up in the station minimises the risks of this.
APCO is used on quite a wide range of routes, and changeover points are marked in the Sectional Appendix.
APCO is switchable based on the route set so the pan isn't lowered if the train is continuing on an electrified route.
swt_passenger
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Yes it can be, it’s triggered automatically in various places by lineside equipment. Many of the locations even show in RTT EG as XXX APCO. (Auto power change over.). But it will only be automated if it’s a normal dynamic changeover location in the long term. There’s no real need for auto on a route where every train stops and it’s convenient to change in the platform.
However some TOCs have chosen not to rely on APCO at certain places and change over manually anyway. When a route is being progressively wired like TPE it seems as if they only move the APCO location some time after the boundary point changes.
It’s possibly worth a quick search on APCO - there are discussions going back about 4 or 5 years.
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Chathill south of the border, where the wires continue but there’s not enough power for all trains.
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There's also a long length of OLE on the Shrewsbury line which ends at the Rope Green Bridge on Rope Lane but it probably hasn't been used in decades.
I assume for the Crewe route that the electrification is original (or at least pretty old), and just runs to the depot to enable depot moves. The wiring may not be suitable for full line speed, and will not have been designed for regular pan-up/down events, or with automatic beacons. Bi-modes are new on the route and without infrastructure work you can't just assume that they will be fine on a section of wiring like this.
It would be nice to get the acceleration out of Crewe done on the wires, but the Everos are already realising huge benefits between Euston and Crewe, so you definitely don't want to hold anything up waiting for small optimizations like this.
Ulleskelf is a pretty short-term limit of electrification so it's perhaps not worth the same amount of tuning you might do elsewhere. In any case, if the trains are not heavily accelerating or braking then the benefits of being on the wires for a mile or two aren't that great.
It would be nice to get the acceleration out of Crewe done on the wires, but the Everos are already realising huge benefits between Euston and Crewe, so you definitely don't want to hold anything up waiting for small optimizations like this.
Ulleskelf is a pretty short-term limit of electrification so it's perhaps not worth the same amount of tuning you might do elsewhere. In any case, if the trains are not heavily accelerating or braking then the benefits of being on the wires for a mile or two aren't that great.
swt_passenger
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I’m sure one point that came out of the GWML wiring thread was that the changeover areas were wired to the same standards as anywhere else, but by defining a limited area they could target additional inspections. That is, the tension and support in an APCO section doesn’t get enhanced, it just gets more TLC.
Snow1964
Established Member
This actually works both ways, some stations have low speed limits, so the wires are not stressed / tensioned to same level as higher speed sections
Yes can only really install beacons after a diverging junction, because don't want it to affect trains continuing along electrified route. Otherwise would need switchable beacons which only active depending on which route is set with all the complications of linking to signalling (in some ways just more that could go wrong).
Which comes back to comments above, where trains are used that can switch systems on the move, really need to alter the infrastructure (wiring limits) so they can do so, but not at a location when accelerating.
The reverse way to think about it, is what is the point of a bit of electrification to a historic point if it ends where modern multi system trains won't use the last few miles, needs to be extended so it can be used fully to accelerate trains clear of junctions.
hexagon789
Veteran Member
I should remember Chathill, really, given all the discussion of TPE 802s running on diesel under the wires and certain LNER services on Sundays for some years!
GRALISTAIR
Established Member
That was my thought too. Although I am a massive electrification fan and hate diesel running under the wires, operational and other situations have to be considered.
LNW-GW Joint
Veteran Member
The South Wales Metro (CVL) lines north of Cardiff use discontinuous electrification, and rely on automatic power switching using track balises.
The class 756 tri-mode Stadlers use it all the time, with several switch-overs on every run over the non-wired OHLE gaps . The class 398 tram trans shortly to start service will do the same.
The class 756 tri-mode Stadlers use it all the time, with several switch-overs on every run over the non-wired OHLE gaps . The class 398 tram trans shortly to start service will do the same.
D1537
Established Member
On the ECML
Longniddry
Chathill (as mentioned)
Bradbury (between Darlington and Durham)
Pilmoor (between York and Thirsk)
hexagon789
Veteran Member
Thanks, that's useful to know.
it is between Bridge of Allan and Dunblane but closer to Bridge of Allan i assume so they can stop before Dunblane
endofthetunnel
Member
There are automatic balises all over the network and the majority of switching is automated, or would be if a driver forgot.
The balises can be selective so only trains with the right head code are commanded to respond (e.g. all the 1Bxx to Lincoln at Newark are told to switchover) or they can be so called ‘zero balises’ which tell any train to pan down (just before the end of the wires).
Regardless of the automation, it is in most companies interests to do the change over at a station in many cases, just in case of issues with the train, then there’s no stranded passengers or blocked routes.
Some companies do the powering up of engines at stations (eg Hull trains power up at Doncaster but continue to use the wires until Temple Hirst Jn.) so any problems can be found but the OHLE is used as far as possible.
The balises can be selective so only trains with the right head code are commanded to respond (e.g. all the 1Bxx to Lincoln at Newark are told to switchover) or they can be so called ‘zero balises’ which tell any train to pan down (just before the end of the wires).
Regardless of the automation, it is in most companies interests to do the change over at a station in many cases, just in case of issues with the train, then there’s no stranded passengers or blocked routes.
Some companies do the powering up of engines at stations (eg Hull trains power up at Doncaster but continue to use the wires until Temple Hirst Jn.) so any problems can be found but the OHLE is used as far as possible.
halfajob
Member
For example when coming down Dauntsey Bank towards Chippenham where the OLE ends, we tend to drop the pan earlier than the designated area. This is so if there's any issues dropping the pan we catch it early and gives us time to try and figure out what's happened. Whereas if you do it at the sign you've given yourself less time.
matchmaker
Established Member
It's actually around Bridge of Allan - between Cornton No 1 LC and Kippenross Tunnel - although the OLE continues to Dunblane of course.
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