The problem is than the substations can be a lot more frequent than every 5 miles
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Cost of electrification OHLE vs 3rd rail
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Jozhua
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The MTA run Long Island Rail Road has a 50.3 mile strech of 3rd rail until Ronkonkoma station on the main line.
As does the MetroNorth with it's line to Brewster. But those are both suburban commuter lines, I've travelled the MN line to White Plains and apart from the trains having a greater loading gauge, they are lumbering units on poor track even at about 80mph. It is nothing like even the Portsmouth Direct. Most of the lines out of NYC change to OLE or diesel after about 15-20 miles.
delticdave
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Erm.... MN extended the 3rd rail to the new Southeast P+R station some years ago, with a diesel push-pull shuttle to the new end of the line at Wassaic. There are through rush-hour trains to Grand Central, powered by GE P32 electro- diesel locos, but they only use the 3rd rail south of 125 Street through the tunnel into G.C. As for changing from DC 3rd rail to 12.5 kV AC, that only occurs on the 12.5 kV AC New Haven line, it used to be just after Woodlawn Junction but the 3rd rail was extended to just west of Pelham Station during the N.H. line OHLE upgrading project.
As "lumbering units", I've ridden on 3rd rail MN & Long Island trains, the MN / Connecticut dual voltage units, NJT & SEPTA's silver-liner emu's, & they were all quite nippy, except the SEPTA examples.
Ever since Chris Green devised Network South East
Jozhua
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I found the M8's quite comfortable and fast...certainly a lot better seat-wise than anything the UK has seen!
But NYC is a good example of where 3rd rail can still come in handy. Trying to upgrade the tunnels around Grand Central to OLE would be impossible, however there is a need to keep emissions down in them for safety reasons. The diesels have noticeably less power when they run on 3rd rail into the station, but for the slow section of line into Midtown, probably doesn't matter too much anyway.
Bottom pickup definitely seems like a good option if there were any new installations in 2019 away from the existing network.
I definitely think OLE is the best solution for electrification, however the benefits vs the cost that seems to be involved seems a tad out of whack. Bi-mode diesels reduce pollution, but also negate a lot of the positives of electrification which is lighter and easier to maintain trains.
Dunfanaghy Rd
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I have to say that I have a good laugh to myself every time I read guff from the 3rd rail fan club. I'm fairly confident that none of them can have worked with it.
I have.
It was the best option available when Herbert Jones planned the first electrification from Waterloo for the L&SWR. That was a long time ago, and times (and H&S attitudes) have changed. In the 45 years I spent on the railway the Southern Region had to have modified tampers, we had to have juice protection for basic jobs like Kangoing, &c., &c. It was fortunate that the voltage was low as it was easy to get a belt - I still have some scars from 1975.
Also given the calls on electric supply from the grid, I would of thought that the 20% saving would get a positive response.
Pat
I have.
It was the best option available when Herbert Jones planned the first electrification from Waterloo for the L&SWR. That was a long time ago, and times (and H&S attitudes) have changed. In the 45 years I spent on the railway the Southern Region had to have modified tampers, we had to have juice protection for basic jobs like Kangoing, &c., &c. It was fortunate that the voltage was low as it was easy to get a belt - I still have some scars from 1975.
Also given the calls on electric supply from the grid, I would of thought that the 20% saving would get a positive response.
Pat
swt_passenger
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An RSSB report quoted in one of the many previous discussions on using bottom contact reckoned the max speed was about 60 mph, so it was ruled out for general use. Fine for the DLR type of operation, but not for normal mainline stuff:
HSTEd
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The traction demand in any reasonable scenario is so small that it is not going to make any difference at all on a national scale.
Electricity demand in a post carbon future will be several times what it is today.
And that is before we consider the nice problems that get dumped on the Grid people by the single phase loads from the AC system. Unless you have massive power converters that will introduce losses that start to reduce AC's efficiency advantage.
EDIT:
If you really want new build systems and we don't have to have backwards compatibility, the obvious answer is a four-rail isolated 1500V system.
Contact with a traction rail will not give you a shock, and the units can have two lighter-weight traction buses instead of a single heavier one.
And as it is isolated then it still counts as a low-voltage system legally.
That seems somewhat wierd given that Metro-North has a five mile stretch between Mount Kisco and Chappaqua that takes only five minutes in the timetable.
Implying the speed is almost certainly above 60mph at peak.....
I'm not sure why bottom contact would be inherently slower than top contact, assuming the same angles on the rail ramps were selected.....
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Jozhua
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A four-rail system does seem like a good idea if it is able to deliver power safely and more efficiently. Could it potentially run AC to eliminate the need for rectifiers or am I being completely bonkers?
Metro-North definitely runs at 80mph on bottom contact 3rd rail.
To clear things up, there's nothing about 750v DC 3rd rail that particularly excites me over normal 25kv AC OHLE, but I really want to see electrification on much more of the network and I really do wonder if the ban on new 3rd rail means we are leaving what, in some cases, could be potentially useful tools on the table. On the Bolton line, even the 319's are an improvement over the 150's and provide a considerably quieter and somewhat faster ride. I definitely think the safety case for not using 3rd rail is strong though and losses are definitely a difficulty faced with this technology.
I'm wondering though, say through a particularly tight tunnel, whether OHLE voltage could be lowered in order for clearances to be reduced? If so, this could save a lot of money on re-building these things.
delticdave
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'Tis shades of the past remerging!.....
I used to live in East London during the DC-AC change on the Gt. Eastern lines & the new 6.25 kV / 25 kV AC electrification on the N.East London lines. Back then, 6.25 kV was chosen to enable the DC / AC conversions (from 1.5 kV) & the new AC network without having to raise any bridges, etc. in the suburbs. 25 kV was used in the outer areas, & the trains were all equipped with dual-voltage transformers.
There were problems with the trains, (& also in Glasgow) so the both areas were converted to 25 kV, after relaxing the clearance requirements.
Modifying the current fleet to operate on 25% of the normal voltage would be expensive, but most electric railways can operate at lower voltages, albeit with lower performance.
I don't know the voltage specifications for new 25 kV traction, back in the day ISTR that 22.5 kV - 27.5 kV was the BR norm.
That was a feature of early BR AC electrification, 6.26kV electrification. I think the train could detect the voltage and adjusted the transformer tappings to suit. But of course, resistance losses are higher due to higher current.
sorry, we must have posted at the same time.
contrex
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There seems to have been a bit of a "whoosh!" I was sarcastically suggesting a "new" method of DC electrification that has, in fact been in use in that form, more or less, by the District and later railways since about 1903.
Completely bonkers!
You lose 36% because of the sine wave vs continuous issue.
Secondly you need to google "skin effect".
AC preferentially (and increasingly so with increasing frequency) conducts nearer to the surface, hence large cross section/ diameter conductors are very inefficient which is why most large AC cables are stranded to reduces losses.
You then end up rectifying the AC on board to produce a DC supply needed to feed the variable frequency 3 phase drives that feed the motors.
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Although the East London Line has been mentioned, Reading Station had a complete re-jig of the third rail platforms in the 2010's and a second electrified (3rd rail) track added over the widened road bridge.
That isn't a new length of 3rd rail 'railway'. The envelope of the 3rd rail safety hazard hasn't effectively been enlarged and there is no connection between the track on platform 6 with the existing down fast platform 7 so the safety case would have been easy to prove. The bridge is right under the station, not a level crossing next to a housing estate.
swt_passenger
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I think most obvious modifications can be “ruled in”, surely even ORR can’t object to things such as extended four tracking proposed between Micheldever and Wallers Ash loops? I remember a few years ago someone (on a platform end) trying to convince me that the mile or so of new up slow line near Eastleigh would have to get OHLE fitted because third rail was now ‘banned’...
I've had a look through 1301/2014 and found the definition of 'renewal' but can't find any appendix that that relates specifically to 3rd rail 'renewals' and 'minor infill works'. I'm assuming that you agree that the changes at Reading are well within the current rules for the use of unprotected third rail projects.
Have a look at 7.4.2.9.1 which, rather confusingly, says that the existing U.K. DC network can be extended. However the DfT, in their implementation plan say “There is no intention to increase the size of the UK’s DC third rail network “.
Wychwood93
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The use of 'intention' in the latter does not mean that it could not happen! #108 mentions 4-tracking from Weston (Wallers Ash loop north) to Micheldever - this was raised in the early days of Railtrack - nothing happened then and the addition of 2 miles of 4-track would need all sorts of additional work and, thus, money - without bringing signalling into the equation! Even if it was to be considered a 3+ mile section of 'dynamic loop' would possibly be too short. You could possibly double or triple stack intermodals and other assorted freight traffic - but would have to unleash them at some point! Part of the newish up slow into Eastleigh from Stoneham should, if it was an issue, have had some sort of 'grandfather' status as there were World War 2 sidings there.
Personally, I think Marshlink makes more sense as AC electrification to Ashford. Given the speed of it, it's effectively two routes feeding in opposite directions from Hastings, so through passengers having to change there between a 3rd rail Southern service and a AC Southeastern one should be fine. If it provides the impetus to redouble the line before wiring it too, then all the better.
Uckfield's a funny one. I think the best thing to do there is wait until the equipment on the East Grinstead branch is up for renewal and to wire up both branches up to either Oxted or South Croydon, then transfer them to Thameslink which has suitable dual-voltage stock.
The North Downs line...can't really see any good options there due to the multiple short shared sections with 3rd rail. Probably best left unelectrified for now so as to not complicate an eventual conversion of the various lines it interacts with, as if you railed it up then converting those lines becomes a much more complicated problem.
Uckfield's a funny one. I think the best thing to do there is wait until the equipment on the East Grinstead branch is up for renewal and to wire up both branches up to either Oxted or South Croydon, then transfer them to Thameslink which has suitable dual-voltage stock.
The North Downs line...can't really see any good options there due to the multiple short shared sections with 3rd rail. Probably best left unelectrified for now so as to not complicate an eventual conversion of the various lines it interacts with, as if you railed it up then converting those lines becomes a much more complicated problem.
swt_passenger
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Wallers Ash to Micheldever 4 tracking still seems to be supported a bit more recently, in the current Wessex route study, the diagram implies the whole length between Popham and Wallers Ash tunnels.
But whatever the practicalities of building it, if it is upgraded I expect it will definitely still be DC.
Wychwood93
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DC - yes! Even Popham south to Wallers Ash tunnel north would, given it wouldn't be exactly that, be a touch under 4 miles. Useful, perhaps, if the platforms at Micheldever could reflect this - the old up main platform would then be on the up slow, the current up main platform would be the up fast, the current down main platform would, logically, be the down fast - which leaves us with where the down platform would be...…….. - you would have to have one to make things easier? A new build - would probably need lifts etc. Just a thought.
Edit: on reflection for a short while this could be better in the speculative and totally bizarre ideas section!
The original question here was cost of electrification, 25Kv vs third rail. And the answer, actually as all engineers know, is there is no comparison. 3rd rail needs little or no civils, the power feeder arrangements are no more costly, the actual 3rd rail installation readily goes in over a weekend (I actually saw this happen, on Stratford to North Woolwich), etc.
Before we start saying about the cost of lineside substations, that North Woolwich line was just installed, switched on, done. Unlike Crossrail also at Stratford, installed in a huge lengthy operation, finally switched on, blew every fuse imaginable, and delayed the whole project by nine months while all the ruined items were reordered …
There are still comments on obscure abstract principles rather than reality. Discussion above about extended loops for freight services between Winchester and Micheldever, whether these should be an isolated little bit of 25Kv on a third rail system. Does nobody notice that all the intermodal and other freights out of Southampton it is to facilitate are handled by diesels? Does it need electrification at all?
Before we start saying about the cost of lineside substations, that North Woolwich line was just installed, switched on, done. Unlike Crossrail also at Stratford, installed in a huge lengthy operation, finally switched on, blew every fuse imaginable, and delayed the whole project by nine months while all the ruined items were reordered …
There are still comments on obscure abstract principles rather than reality. Discussion above about extended loops for freight services between Winchester and Micheldever, whether these should be an isolated little bit of 25Kv on a third rail system. Does nobody notice that all the intermodal and other freights out of Southampton it is to facilitate are handled by diesels? Does it need electrification at all?
It's pointless comparing the electrifying of a run down urban branch line to take maybe 2 or 3, three-car EMUs each maxing out at just over 600kW although their speeds were severely limited on the part single track route, with a new very high capacity commuter route with nine-car EMUs each requiring up to more than 4MW and running on that branch every 5 minutes. The delay caused by the power supply failure at Pudding Mill was not because of difficulties in sourcing replacements, - that took a few weeks. The testing programmes had to be recast at a more cautious pace, the line had enough detractors without suffering the same or similar failure a second time. That feed, because of the large power demand of such a major line comes off the 400kV national grid. So, nothing like the almost light industrial demand of a 6 mile long branch line running no more than 3 slow running three-car EMUs.
There are still comments on obscure abstract principles rather than reality. Discussion above about extended loops for freight services between Winchester and Micheldever, whether these should be an isolated little bit of 25Kv on a third rail system. Does nobody notice that all the intermodal and other freights out of Southampton it is to facilitate are handled by diesels? Does it need electrification at all?[/QUOTE]
The Basingstoke to Winchester section of the SWML is one of the few 3rd rail lines where trains are expected to get anywhere near 100mph. Therefore the power feeds need to be at or near the maximum practicable level for LV DC. Thus the substations are quite near to each other. Nobody would suggest running heavy freight if the main line was to stay DC, as the electric freight locos would need feeds at every signal when they run back onto the mainline. The position with the (currently suspended) electric spine project was that the line would be converted to 25kV OLE from Basingstoke Est Junction where the line joins from Reading, to Millbrook/Redbridge. The view was that much of the infrastructure on that section was life-expired (e.g. the tunnels including parts of the Southampton tunnels), and any structure gauge enhancement required would be achieved during their refurbishment/rebuilding. As far as the yards being run using diesel goes, rail technology has itself moved on and battery capabilites to enable removal of diesel right up to reception roads would be viable. As far as FOCs running diesels where electric power is available is concerned, the gradual tightening of restrictions on polluting traction could be augmented by more competitive track access rates for using the power provided.
I would suggest that your assertion that DC electrification requires little or no Civil Engineering is somewhat flippant. I’m sure there are Engineers here who will tell you otherwise, installing a cable route for the 33kv feeder cable is just one consideration. I’m sure if you talked to the team who “just switched on” the NLL they will tell you there was a modicum of testing before that happened, likewise the Signalling and Telecomms teams.
DC electrifying freight loops ( or passenger ) on an already DC electrified railway would appear to meet the DfT/ORR criteria in that it does not extend the existing DC electrified network.
I know the voltage was double, 1500v DC instead of 750v, but the Woodhead quite straightforwardly had quadruple DC loco coal trains, two at the front and two pushing at the rear, on a 1 in 40 climb from Wath up over the Pennines. And one would follow the other notably closely, as the traditional manual signalboxes were closely spaced. Never seemed to have any issue with 1930s-design power supply. They had regenerative power, but often there would be nothing coming the other way.
Likewise there is 1500v DC operation of freights heavier than anything in Britain in Netherlands (nationwide), much of France, New South Wales in Australia (electric locos now given up for diesel, but were electric in the past), etc.
I have criticised 12-car 25Kv emus in the past for carrying effectively three substations round with them. This was rebutted by saying that technology has moved on, and modern emus need far smaller installations than those of 1960. Fair enough. But why has this advance not equally made the provision of DC lineside substations equally more straightforward and simpler.
I was of course meaning traditional civils - bridge rebuilding, mast installation, etc.
Shame the Crossrail team didn't follow such an approach at first.
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