[swtandgw]

It's been a while since I've posted on the forums (I've been busy with other commitments), but I've noticed something whilst I was taking some spring cleaning down to the new Padworth recycling facilities. Since the bridge by Aldermaston station has been closed off for works, I was wondering if electrification work has already commenced? I've not yet seen OHLE appear on the line, but I think it looks like they're starting off with taking care of bridge clearances first.

[themiller]

Originally Posted by swtandgw

It's been a while since I've posted on the forums (I've been busy with other commitments), but I've noticed something whilst I was taking some spring cleaning down to the new Padworth recycling facilities. Since the bridge by Aldermaston station has been closed off for works, I was wondering if electrification work has already commenced? I've not yet seen OHLE appear on the line, but I think it looks like they're starting off with taking care of bridge clearances first.

This is normal practice so that the teams installing the OHLE have a straight run at it (especially as the plain line work is to be done using the HOOP train. The idea is to complete the civil (concrete and shovel) work before the expensive electrical (masts and wires) part.

[HSTEd]

Once the wiring train goes to work it will be over in a matter of a couple of months, so it will likely be the last thing on the list.

[John55]

Originally Posted by themiller

This is normal practice so that the teams installing the OHLE have a straight run at it (especially as the plain line work is to be done using the HOOP train. The idea is to complete the civil (concrete and shovel) work before the expensive electrical (masts and wires) part.

While it does vary from route to route it is probably wrong to assume the wires and masts are the expensive bit. The UK has very high numbers of over bridges and tunnels along railway lines which can be very expensive to modify or replace and the costs of providing a bulk supply point can be astronomical and then there is the cost of work to the signaling system if that needs replacement or immunisation.

[swtandgw]

Also, wouldn't they have to make preparations on where the transformer stations/feeders/neutral sections are going to go? I probably think that might be the next step before the HOOP train starts the wiring work, although I don't know as I'm not familiar on how previous large-scale electrification projects work.

[L&Y Robert]

Isn't Basingstoke 3rd rail? How does that mesh with high voltage overhead?

[swt_passenger]

Originally Posted by L&Y Robert

Isn't Basingstoke 3rd rail? How does that mesh with high voltage overhead?

You'd just need a suitable changeover section with both supplies overlapping. Standard technology as is seen on Thameslink and at various points on the NLL and WLL.

The only debate is really how complex you make it, which is why it is often suggested that it is better to do the changeover on the branch at a place where all trains stop, rather than in a multiplatformed station like Basingstoke with complex junctions at both ends.

Like in the ongoing discussion about Reading, it might be less complex to changeover in the single track eastern underpass, rather than in X number of platforms.

[jopsuk]

Much of Ashford International is dual voltage too- served by some OHL-only stock these days (Eurostars have all lost their 3rd rail shoes since St Pancras Int opened). Also dual voltage on the high level platforms at Ebbsfleet, and before HS1 was completed, Eurostars were able to change on the move on a long section from just south of Ebbsfleet onto the 3rd rail network. Obviously some dual voltage sections near Dollands Moor for Channel tunnel freight, and there's Drayton Park on the Moorgate line. Dual voltage sections aplenty!

[ole man]

Change of location, Sydney Gardens in Bath has to be the best unspoilt area to watch all kinds of traction.

What will happen when this area gets OLE, will we be subject to the ugly pallaside fencing, and over the top safety measures?

[Kentish Paul]

Yes, platforms 5 and 6 at Ashford International are the changeover points for C395 from OH to 3rd rail. Takes about 30 secs. Faringdon is the Thameslink changeover point.

[relayer]

Three bridges in the Aldermaston area are being raised

[atillathehunn]

I'm sorry this isn't strictly on the topic of the GWML electrification, but this seems to have devolved into a discussion on voltage changes which makes this somewhat relevant.

It is quite straight forward, it seems, to change from 3rd rail DC to overhead AC, but how complicated is it to change voltages within an entirely overhead system? In all the many train journeys I have taken around Europe and the world I'm sure it has happened on a train I have been on, but I clearly wasn't paying attention at that point (can't say the overhead equipment is my primary source of interest on a journey!). Does a diesel shunter come and change you from one platform to another which has the correct voltage overhead, or can you have different systems operating in the same platform and you have a small 'last mile home' diesel engine which allows you to shunt forward into the new section? Probably should put the beer down and pay more attention in the future!

Hope this made sense...

[Nym]

You can just install some clever power electronics on the roof that detect the source and changeover automatically, potentially at speed by use of neutral sections.

[transmanche]

Originally Posted by Nym

You can just install some clever power electronics on the roof that detect the source and changeover automatically, potentially at speed by use of neutral sections.

We used to have changeover between 6.25kV AC and 25kV AC on the fly; on the GEML, LTS and around Glasgow.

[Nym]

Originally Posted by transmanche

We used to have changeover between 6.25kV AC and 25kV AC on the fly; on the GEML, LTS and around Glasgow.

Yup, that's surprisingly simple by using tap changing relays, a baseline rectifier and a solenoid selector.

Use a small transformer to step down to something sensible, pass it through a coil, rectified if you like, and then have a solenoid in this coil that controls your switchover relays on the tap changer for the main transformer.

And if you're running with a tap changer by default, even more simple, jyst integrate it into the Power Controller.