The Anonymous Widower

Discontinuous Electrification Using IPEMUs

In Basingstoke To Exeter By Electric Train, I started to work through, how short lengths of third-rail electrification could be used to power an electric train with an IPEMU-capability.

Third-Rail Electrification

This picture shows typical third-rail electrification at Kidbrooke station in South East London.

Electrification At Kidbrooke Station


Note the following about the station and the electrification.

  • The two tracks are between two platforms connected by a footbridge, which is a typical layout for hundreds of stations. Some stations might use a subway for connection.
  • The two 750 VDC conductor rails are placed together in the middle of the track, well away from the passengers.
  • There is a gap in the third rail, which I assume is for staff or emergency services personnel to cross the track in an emergency.

It is a simple and very safe layout.

With many years of installing third-rail systems in stations, Network Rail has the expertise to create safe systems in stations with island or just a single platform.

A Typical Electrical Multiple Unit

The Class 377 train is a typical modern electrical multiple unit common on third-rail routes.

  • There are a total of 239 trainsets in service with lengths of three, four and five cars.
  • The trains can work in combinations of two and three trainsets.
  • The trains are a member of Bombardier’s Electrostar family.
  • The slightly older Class 375 trains can be converted into Class 377 trains.
  • The first trains entered service in 2003, so they still have many years of life.
  • Some of the trains are dual-voltage and all could be equipped to use 25 kVAC overhead line equipment.
  • They have a top speed of 90 mph.
  • Bombardier have stated that these trains can be given an IPEMU-capability.

In addition everything said about the Class 377, can also be said about the later Class 379 and Class 387 trains, although these trains are faster.

The traction current supply to the trains has a very comprehensive design, that ensures trains get the electricity they need. Wikipedia says this.

All units can receive power via third-rail pick-up which provides 750 V DC. There are eight pick-up shoes per unit (twice the number of previous generation 4-car Electric multiple units), and this enables them to ride smoothly over most third-rail gaps. The units in the 377/2, 377/5 and 377/7 sub-classes are dual-voltage, and are fitted with a pantograph to pick up 25 kV AC from overhead lines. On these units the shoe mechanism is air-operated so that when powered down, or working on AC overhead lines, they are raised out of the way. 

You don’t hear many reports of trains being gapped these days, when they are unable to pick-up electricity at somewhere like a level crossing.

So there could be a large number of electrical multiple units available with an IPEMU capability, which could be ostensibly 25 kVAC units, but could also pick up electricity from a 750 VDC third-rail.

A Charging Station At Oxted

I feel that Network Rail has the expertise to fit short lengths of third-rail electrification into stations, so that IPEMUs could pick up power, when they are stopped in the station.

These pictures show the recent installation of third-rail in the bay Platform 3 at Oxted station.

Note how the conductor rail is enclosed in a yellow shield.

Could this installation at Oxted, have been done, so that IPEMUs can run a shuttle to Uckfield?

Staff at the station didn’t know, but said the platform is used to terminate or park the occasional train from East Grinstea


IPEMUs To Lowestoft

Imagine such an installation at a station like Lowestoft, which has been suggested as a destination for trains with an IPEMU-capability.

Two Class 156 At Lowestoft

The picture shows two Class 156 trains at Lowestoft station.

Surely, two lengths of 750 VDC third-rail can be fitted between the tracks.

  • The electrified lines would be no closer to passengers, than the third-rail installation at Oxted.
  • The power supply would only be needed to supply electricity to charge the batteries.
  • When no train was in the platform, the electricity supply to that platform would be switched off.
  • The waiting time in the station would need to be sufficient to make sure the battery had enough charge to get to the overhead wires at Ipswich or Norwich.
  • There would be little or no modification to the structure of the station.
  • There would be no electrification needed between Lowestoft and both Ipswich and Norwich.

The biggest problem would be installing the power supply, but it would only be a transformer and rectiofier to provide 750 VDC. It would not have to cope with all the problems of regenerative braking, as the IPEMU capability of the train would take care of that.

It would appear that by using trains with an IPEMU-capability and well-proven simple technology at Lowestoft, the town can be provided with direct electric train services to Ipswich, Norwich and London.

At present the only trains with sufficient speed to not be a restriction on the Great Eastern Main Line, that can be given an IPEMU-capability are Class 379 and Class 387 trains. But Bombardier told Modern Railways, that a 125 mph Aventra is possible.

It would appear that the infrastructure modifications could be very affordable too!

The major cost would be the extra trains, but hopefully an increase in passenger numbers because of the better service would create the cash flow to lease them!

Perhaps the biggest advantage of using IPEMU trains to Lowestoft, is that electrification of the tracks through a beautiful part of East Anglia will not need to be performed.

It should also be said, that what works for Lowestoft, would also work for services to Sheringham and Great Yarmouth.

The technique would also work for branch lines from an electrified main line, where the out and back distance was more than the range of an IPEMU running on batteries. Examples would include.

  • York to Scarborough
  • Doncaster to Hull
  • Edinburgh to Tweedbank
  • Peterborough to Lincoln
  • Manchester to Sheffield

But there are many more lines, where a charging station would bring much-needed electric trains to all over the UK.

Longer Lines

Some longer lines,  where both ends are electrified and the distance is less than sixty miles, like Norwich to Cambridge and Carlisle to Newcastle, could be served by an IPEMU with sufficient range, that was charged at both ends of the line.

So that leaves longer lines over sixty miles, with no electrification at either end or just one electrified end.

Many, but not all, are through beautiful countryside and would the heritage lobby accept miles of overhead line gantries, marching through the hills and valleys.

I believe that on some longer lines, by using short lengths of third-rail electrification in selected stations, services could be run by electric trains with an IPEMU-capability.

Imagine an electric train an IPEMU-capability, approaching a station on a typical fast line with perhaps a 90 mph speed limit, like say the West of England Main Line, which is not electrified past Basingstoke.

  • As the IPEMU applies its brakes, all of the energy generated by the regenerative braking would be stored in the train’s on-board energy storage, ready to be used to accelerate the train back up to line speed after the station.
  • When the train makes contact with the third rail in the station, if the battery is not full, it can start to charge the battery from the rail.
  • Once the battery is full, the charging would stop.
  • On starting away from the station, the train could use power from the third rail, until it lost contact, after which it would use the energy stored on the train.

I think it should be possible that the train would leave the station with a full battery.

I would suspect that Bombardier and Network Rail are doing all sorts of calculations to find the best strategy, so that IPEMUs can be used to avoid the problems and costs of electrification.

Lines that could be electrified in this way would be ones, where trains stop at several stations along the route. Electricity supply at the stations, is no problem these days, as it could be connected to the mains or to some form of local generation.

It could be a very green concept!

Lines that could be electrified in this way would include.

Selected stations would be fitted with charging and the trains would stop accordingly.

I’ve included the Far North Line because I believe it is possible to electrify the line in this way provided you could get a good enough electricity supply to the required number of stations. Obviously, you may decide not to do it, as you may have enough quality diesel trains.


If you could run electric trains on the Far North Line using charging at stations,  you could run electric trains on any line in the UK.




April 30, 2016 - Posted by | Transport/Travel | , , , , ,


  1. […] Gaps are common on third-rail electric trains as I  wrote about in Discontinuous Electrification Using IPEMUs  […]

    Pingback by Is This The Worst Bottleneck On The UK Rail Network? « The Anonymous Widower | November 20, 2016 | Reply

  2. a while since you wrote this, but … ISTM the longer lines are better suited to hydrogen, which ATM has a much greater range than stand-alone batteries. mentioned tests on Lpool-Chester. This particular stretch is already roughly half electrified (Runcorn-Lpool), so an overhead/battery train would be well suited to this. But the longer-term aim is run trains from Lpool into N Wales, and the further you go from the electrified section, the less well this would work, given the length of time it would take to recharge the battery. Hydrogen could come from Merseyside’s refineries, as mentioned in the article, or produced from a wind turbine somewhere along the N Wales line. This is what the first German line to use the iLint is planning: build a wind turbine at Bremervoerde, which would power electrolysis to feed a hydrogen ‘filling station’ for the trains.

    The same would apply to the north of Scotland, which already has plenty of wind/hydro power which could be used to create ‘free’ hydrogen for trains.

    Of course, in the longer term battery (or indeed supercapacitor) technology can only improve, and may well eventually make hydrogen unnecessary. But for the moment …

    Comment by Peter Robins | August 23, 2018 | Reply

  3. I very much feel that Liverpool North Wales is a possibility for hydrogen, although Transport for Wales have already bought a lot of CAF diesels.

    INEOS at Runcorn have a hydrogen problem. Too much of the stuff. They are actually looking to inject it into the gas network of Liverpool and Manchester for high energy users.

    I also used to work in the plant there in the 1960s, so I knew it well.

    I wouldn’t be surprised to see a mixture of all technologies coming together to create an efficient electric railway.

    Comment by AnonW | August 23, 2018 | Reply

    • yes, another of the iLint lines in Germany, in the Taunus N and W of Frankfurt, is similarly looking to get hydrogen from the large chems industry in Hoechst. As one of the comments in that article points out, such industries might even pay Alstom to take the stuff away!

      Most of the services in Wales outside the proposed metro area look like hydrogen candidates to me. The weakness of current batteries is not only the limited range, but the length of time it takes to recharge. Most scheduled stops at stations are only a minute or two, which I would doubt would make much inroads. Where you could use batteries is in the shorter lines. With Chester-Crewe, there are overhead wires on the Crewe platforms (which extend a couple of km to the depot), and a 3rd-rail on the Chester platforms could recharge at that end (the existing Merseyrail rails are on the other side of the station, so you’d have to cross the tracks to use them). Similarly with Bidston-Wrexham, you have 3rd-rail at B (or alternatively run round the Liverpool loop), and could install one at the Wrexham end too. In these cases, the stop at the stations should be long enough for recharging. Not sure this has much advantage over hydrogen though, which is essentially a drop-in replacement for diesel with the big advantage that it can be generated from renewables. We will see. An advantage of the Vivarail units that will be used on these lines is that the power module is designed to be swappable relatively easily, so they can start off with diesel/battery hybrid and replace with better batteries or other configurations later.

      Comment by Peter Robins | August 24, 2018 | Reply

    • and see

      Trains and buses are much easier for hydrogen than private cars, as they simply need a power supply at the depot, whereas for cars you need a network of filling stations like the current fossil fuel ones.

      Comment by Peter Robins | August 26, 2018 | Reply

      • I also think INEOS will be supportive, as they seem to be developing several plans across the world to use hydrogen profitably!

        Comment by AnonW | August 26, 2018

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: