Railway electrification - ongoing (sometimes very!) technical discussion

[whole diary]

[grahame]

The quickest way to increase electric mileage is to make the Voyagers bi-mode.

Has anyone suggested converting half of the class 43 fleet primary electric power (essentially their diesel engines are used to make electricity anyway, right?) and running trains with one electric and one diesel power car?  There' an awful lot of diesel mileage that doesn't need to be on both east and west coasts, some of it coming up cross country.

[simonw]

Network Rail, and of course DfT^» (Department for Transport - about)/HMG, have to commit to a 25 year programme to fully electrify all rail track throughout Britain and N Ireland.

This is not a simple or cheap option, but a proper long term commitment will allow training and equipment to used efficiently, rather than on very expensive short term projects which do not make full use of these.

[Rhydgaled]

Network Rail, and of course DfT^» (Department for Transport - about)/HMG, have to commit to a 25 year programme to fully electrify all rail track throughout Britain and N Ireland.

This is not a simple or cheap option, but a proper long term commitment will allow training and equipment to used efficiently, rather than on very expensive short term projects which do not make full use of these.

I wouldn't say 'all track' within 25 years, but I would agree that a long term commitment is needed to a fixed budget every year to be spent on electrification.

[Electric train]

The quickest way to increase electric mileage is to make the Voyagers bi-mode.

Has anyone suggested converting half of the class 43 fleet primary electric power (essentially their diesel engines are used to make electricity anyway, right?) and running trains with one electric and one diesel power car?  There' an awful lot of diesel mileage that doesn't need to be on both east and west coasts, some of it coming up cross country.

Yes over 30 years ago!!!!  The ECML^▸ (East Coast Main Line) services to Aberdeen from London KX were planned to be electric loco one end class 43 the other, this is why some of the class 43 had nose surgery to fit buffers and screw couplings.

Class 43 were designed to operate in tandem this was the design choice in the early 1970's to keep the mass of the traction power unit down especially the un-sprung mass of the power bogies, the track engineers concerns of the effects on track geometry at increased speeds (125) where there was a high cant, also the un-sprung mass effects the ballast formation on plain line.

The Bo-Bo choice over Co-Co (class 47 50 55 etc) at the time also limited the power rating of the traction motors, class 43 have dc traction motors the revolution being in class 43 the use of a 3 phase alternator and SCR (silicone controlled rectifier)

[John R]

Yes over 30 years ago!!!!  The ECML^▸ (East Coast Main Line) services to Aberdeen from London KX were planned to be electric loco one end class 43 the other, this is why some of the class 43 had nose surgery to fit buffers and screw couplings.

Not quite. The hybrid sets were put into service to enable full electric running to Leeds early, as the Mk 4 sets were not available.  The original plan was that the Class 43 would run as a DVT^‡(resolve), but engineers quickly found that having the loco idle was far from ideal, so they were soon run under full power, resulting in a rather nippy combination of >6,000 hp.

(Source:  Modern Railways Special on East Coast Electrification by Colin Boocock, 1991)   

[Electric train]

Yes over 30 years ago!!!!  The ECML^▸ (East Coast Main Line) services to Aberdeen from London KX were planned to be electric loco one end class 43 the other, this is why some of the class 43 had nose surgery to fit buffers and screw couplings.

Not quite. The hybrid sets were put into service to enable full electric running to Leeds early, as the Mk 4 sets were not available.  The original plan was that the Class 43 would run as a DVT^‡(resolve), but engineers quickly found that having the loco idle was far from ideal, so they were soon run under full power, resulting in a rather nippy combination of >6,000 hp.

(Source:  Modern Railways Special on East Coast Electrification by Colin Boocock, 1991)   

Agree, memory fade on my part   

I believe the intention was to later deploy them onto the Aberdeen's but that never came about for the reason you gave, so the standard HST^▸ (High Speed Train) combo remains

[Rhydgaled]

[quote author=Electric train link=topic=5066.msg211715#msg211715
Not quite. The hybrid sets were put into service to enable full electric running to Leeds early, as the Mk 4 sets were not available.  The original plan was that the Class 43 would run as a DVT^‡(resolve), but engineers quickly found that having the loco idle was far from ideal, so they were soon run under full power, resulting in a rather nippy combination of >6,000 hp.

I think you mean >8,000hp; according to Wikipedia a class 91 has 6,480 hp by itself without an IC125 power car helping.

I don't think I've ever read about sending the 91+IC125 combos to Aberdeen, it was only ever a stop-gap while waiting for the mark 4s as far as I know (although I think some interesting things were done with IC225s and diesel locos on some of the beyond-wires extensions of Leeds services).

[John R]

Yep, thanks for the correction regarding total horsepower.

[onthecushions]

One possible hybrid might be developed through re-use of the ECML^▸ (East Coast Main Line) Mark 4 + class 91 sets with a class 67 (9 of which are stored out of use, it seems) instead of the DVT^‡(resolve).

The 125mph class 67 has a 3200HP engine that delivers 1860kW to rail, about 1.5 HST^▸ (High Speed Train) power cars.

The 91 + HST power car could reach 120mph in 170 seconds! (Semmens).

Paddington - Minehead special anyone?

OTC

[ChrisB]

The 67s were so unreliable @ Chiltern that they got 68s in.

[Rhydgaled]

The 67s were so unreliable @ Chiltern that they got 68s in.

I've read that fuel economy had something to do with that change; whether its true or not I don't know. Either way, it hasn't stopped ATW^▸ (Arriva Trains Wales (former TOC^▸ (Train Operating Company))) using 67s (not yet at any rate), perhaps due to lease costs??

[IndustryInsider]

What sort of service intensity would require switching from the 'classic' mode to that which uses the ATF wire?

[Electric train]

What sort of service intensity would require switching from the 'classic' mode to that which uses the ATF wire?

I believe the original Crossrail plan was to run classic 25kV mode initially with the ATF being commissioned before the full service started, this is quite normal to start in classic and then commission the ATF.

It is difficult to for me to say at what point of service intensity the ATF is an absolute as cannot remember the capacity of OOC^▸ (Old Oak Common (depot)) FS also factors like the OLE^▸ (Overhead Line Equipment, more often "OHLE") wire sizes, characteristics of all of the units in use and the number of trains.  You get to a point where the volt drop effects the performance of the trains and you run the risk of track feeder circuit breakers tripping, although the Route Electrification Engineer should never let Ops get it to that stage

It is possible even when the system is in full operation for it to run in degraded mode (ie classic) that comes with performance risks which the Route should have for the likely scenarios

[onthecushions]

What sort of service intensity would require switching from the 'classic' mode to that which uses the ATF wire?

I think that the physical limitations are the on-load voltage (this must not drop too much on motoring) and the voltage on the return rail. The on-load volts depend on transformer size (modern ones are typically 2x40kVA, rather than formerly 2x10kVA), line impedance (i.e how far from the FS/GSP you are) and motor demand. These are not probably an issue. Track volts is however, as safety touch voltage is assessed as 50V and we don't like to get near that.
A high return current requires the track volts to rise (steel rails aren't dreadfully good conductors) in order to drive the current to earth. This is why the BT (booster transformer) system is used, to suck current from the rails into a return conductor wire, keeping track volts lower. Even better is the AT which both drains current from the rails (lowering volts) and also tops up the overhead line.
These patterns can be modelled by computer using actual timetables so that track volts may be known in advance.
I believe some lightly trafficked lines in the ER (say 2 4-car EMU^▸ (Electric Multiple Unit)'s per hour) work on the classic system permanently. Our 80x's, 387's etc in full cry will certainly need the AT system if our orangemen's hi-vis jackets aren't to sparkle and glow.

As always, I would defer to ET's definitive knowledge in this area.

OTC

[Electric train]

What sort of service intensity would require switching from the 'classic' mode to that which uses the ATF wire?

I think that the physical limitations are the on-load voltage (this must not drop too much on motoring) and the voltage on the return rail. The on-load volts depend on transformer size (modern ones are typically 2x40kVA, rather than formerly 2x10kVA), line impedance (i.e how far from the FS/GSP you are) and motor demand. These are not probably an issue. Track volts is however, as safety touch voltage is assessed as 50V and we don't like to get near that.

OTC

Think you meant 40MVA for modern 400kV derived ATFS, the classic 132kv derived transformers the smallest is 10MVA and the largest is 26MVA, BSEN50122 allows for a max of 60V however as the running rails are bonded to an earthwire every 400 metres and the earthwire is attached to a metal structure banged into the ground every 50 metres the rail to earth voltage is not too much of an issue except under fault conditions when a much higher rail to earth touch potential is allowed