Great Western Main Line electrification - ongoing discussion

[whole diary]

[Thatcham Crossing]

Wires going up between Midgham and Aldermaston observed whilst passing by road earlier this evening.

Railcam's Newbury camera showing infrastructure going up in the area between Newbury and the Racecourse earlier also.

[Bmblbzzz]

Wires all up round Fosse Bridge near Malmesbury. (This might have been noted before, in which case, sorry!)

[martyjon]

Wires all up round Fosse Bridge near Malmesbury. (This might have been noted before, in which case, sorry!)

Some overhead knitting also up between Chipping Sodbury and Westerleigh Junction. looks like the tensioning wire which is fixed at one end and onto a load of weights at tother what I could see as it was wrapped round pulley wheels.

[ellendune]

I saw a lot of knitting in Swindon Station last week though by no means complete.

I also notices some additional switchgear going in at the Dicot feeder is this for the swindon section?

[Adelante_CCT]

I saw a lot of knitting in Swindon Station last week though by no means complete.

[GBM]

I saw a lot of knitting in Swindon Station last week though by no means complete.

Yarnbombing now?

[Thatcham Crossing]

On the B&H^▸ (Berks and Hants - railway line from Reading to Taunton via Westbury), following April's blockade, wires now appear to be up from just east of Newbury Racecourse all the way to just west of Theale. Towney Loop has also been wired.

A lot of infrastructure also went up through Newbury Racecourse (uprights, crossbeams and SPS^▸ (Small Part Steel) but no wires yet), and between there and Newbury itself (some uprights and crossbeams, but still some gaps and no SPS or wires yet).
The Station area itself still has some uprights and crossbeams missing. The new footbridge is now open (without lifts as yet) and I understand the old footbridge will come down during the next blockade (14th - 18th May).

West of Newbury, uprights only so far are in place and extend for at least a few hundred metres west of the Station (beyond Rockingham Road Bridge). This is presumably to allow for electric-only trains to reverse and swop from down to up lines and vice-versa.

[grahame]

On the B&H^▸ (Berks and Hants - railway line from Reading to Taunton via Westbury), following April's blockade, wires now appear to be up from just east of Newbury Racecourse all the way to just west of Theale. Towney Loop has also been wired.

So why ON EARTH do they need all the other stoppages May, June, July, August, October and November?

[Thatcham Crossing]

From my understanding there's quite a lot to do around Reading West still, and between there and Southcote Jct. I'd say most of the metalwork is now up between there and Theale. From what I have witnessed a few days ago there is still quite a bit to do around the Newbury Station area itself. Lots of pics up on railforums.co.uk (Great Western Electrification Progress thread) to back this up.

Local chatter (unofficial) suggests there is a plan to turn the power on to Newbury in September, so it may be that some of those later blocks aren't needed?

[stuving]

I saw a lot of knitting in Swindon Station last week though by no means complete.

I also notices some additional switchgear going in at the Dicot feeder is this for the swindon section?

I'm puzzled by that. The ATFS enclosure at Foxhall Junction looked to be fully populated when first built, so where would they put any new bits?

[ellendune]

I saw a lot of knitting in Swindon Station last week though by no means complete.

I also notices some additional switchgear going in at the Dicot feeder is this for the swindon section?

I'm puzzled by that. The ATFS enclosure at Foxhall Junction looked to be fully populated when first built, so where would they put any new bits?

It seems to be a separate enclosure a few metres to the West

[Adelante_CCT]

From my understanding there's quite a lot to do around Reading West still, and between there and Southcote Jct. I'd say most of the metalwork is now up between there and Theale.

I expect Reading West to Southcote (and onto Theale) would be done over night or weekends to minimise impact on services to/through Basingstoke and freight services accessing Theale. As above I expect the last blockade or two are 'just in case' ones

[Jason]

Still only foundation posts behind the platform at Reading West at the moment.

[stuving]

I saw a lot of knitting in Swindon Station last week though by no means complete.

I also notices some additional switchgear going in at the Dicot feeder is this for the swindon section?

I'm puzzled by that. The ATFS enclosure at Foxhall Junction looked to be fully populated when first built, so where would they put any new bits?

It seems to be a separate enclosure a few metres to the West

I had an opportunity to go and look at this today, and I reckon it's a bunch of isolators or track switches. So that is switchgear in a sense, but not the usual one of protection (circuit breakers). They are usually found on top of Over-Head Line Equipment (OHLE) structures, next to points, allowing each running track to be isolated in case of a failure while keeping the rest in use. That means they are Over-Head Line Equipment (OHLE) components, not part of the ATFS.

As a switch connecting across an insulated gap in the conductor/catenary pair, a position close to the gap is preferred as it keeps the 25 kV wires short. The operating rods can run from the side of the track, where operation is either manual or motorised. However, in this case a small copse of stanchions has been built instead of using the Over-Head Line Equipment (OHLE) supports. That does seem rather odd.

Presumably they will provide isolation of the Over-Head Line Equipment (OHLE) at the four crossovers west of Foxhall junction itself, and perhaps some more as well (there a ten stanchions with I think one switch each). But how will the 25kV connections get to various places above the track? Such leads from the ATFS call for overheight stanchions both side of the line, and ther's no sign of them yet.

Anyway, here's a picture of the forest...

Edit: VickiS - Clarifying Acronym

[stuving]

Incidentally, in that picture the Foxhall Junction ATFS is over on the right, and close to it there is a kind of compost bin halfway up a pole. That is a braking resistor.

These are needed in case there are no trains drawing power when one (or more) are regenerating, so trying to put power back into the supply. However, I don't think this one is sized to do that for very long. IETs^▸ (Intercity Express Train) are required to provide regenerative braking, but to turn this off if the OLE^▸ (Overhead Line Equipment, more often "OHLE") voltage rises above 29 kV. They are allowed 100 ms to do this, so the energy to be dumped is not very large - but the resistor is still needed.

With no resistor the line voltage could rise too fast, so the voltage could still reach a damaging level before the IET reacts. I suspect it is also there to cope if a train "forgets" to turn off its regeneration.