Langley Junction

[Aictos]

What's under construction here in the triangle of land here? Foundations have been laid and there's a lot of construction work but what?

 

[Peter Mugridge]

That's where the proposed Heathrow western access will leave the GWML; although that line in itself won't be authorised for construction until 2017, it would make a lot of sense to put provision in for it right now while the route is being rebuilt anyway.


Just had a PM pointing out that Langley Junction is on the ECML, so...ah... err...




Errr... how does one get the "strike" command to work on this forum???

 

[bramling]

What's under construction here in the triangle of land here? Foundations have been laid and there's a lot of construction work but what?

I believe it's part of the conversion of this section of line to auto-transformer OLE. From what I understand the initial section is from Welwyn to Corey's Mill, the other worksites are at Corey's Mill and Welwyn. I am guessing Corey's Mill will be an auto-transformer feeder site (ATFS) and the other two will be sectioning auto transformer sites (SATS), but I could have this wrong.

 

[civ-eng-jim]

Just had a PM pointing out that Langley Junction is on the ECML, so...ah... err...

I was thinking the same! There's certainly some ground investigation work going on around here for the tunnels and dive under box.

Would that proposed junction be named Langley Junction or are all junction names unique so a different name would be required? Heathrow Airport West?

 

[edwin_m]

Junction names aren't unique across the network - for example there is a Norwood Junction in Gateshead as well as one in south London, and Trent Junctions in Gainsborough as well as near East Midlands Parkway.

 

[Aictos]

I believe it's part of the conversion of this section of line to auto-transformer OLE. From what I understand the initial section is from Welwyn to Corey's Mill, the other worksites are at Corey's Mill and Welwyn. I am guessing Corey's Mill will be an auto-transformer feeder site (ATFS) and the other two will be sectioning auto transformer sites (SATS), but I could have this wrong.

What's a Auto-Transformer OLE?

 

[Yew]

That's where the proposed Heathrow western access will leave the GWML; although that line in itself won't be authorised for construction until 2017, it would make a lot of sense to put provision in for it right now while the route is being rebuilt anyway.


Just had a PM pointing out that Langley Junction is on the ECML, so...ah... err...




Errr... how does one get the "strike" command to work on this forum???

its [ s ] and [ /s ](without the spaces) rather than and

 

[snowball]

What's a Auto-Transformer OLE?

OLE means overhead line equipment (sometimes also called OHLE).

The autotransformer system has been discussed a few times in electrification-related threads. It's a system for reducing power losses on electrified lines while allowing more or heavier trains to be run. It has been, or is being, retro-fitted to the southern halves of the WCML and ECML, and used from the start on the GWML and part of the north-west triangle.

Instead of booster transformers at intervals along the line, you have autotransformers (like a transformer but with only one winding). The running rails are connected to a centre tap. The return wire that normally hangs off the electrification masts on small insulators is replaced by an autotransformer wire on big insulators similar to those used for the contact wire and catenary. If the running rails are at 0 volts and the contact wire at +25kV, then the autotransformer wire is at -25kV.

 

[bramling]

What's a Auto-Transformer OLE?

From a Network Rail briefing document:

What is an ATF?
Autotransformer feeders are ‘along track conductors’ energised at 25kV 50HZ. They provide the overhead line system with more power along the route covered, by balancing the load equally across all lines via autotransformers. The system ensures that a healthy voltage is supplied to trains exactly where it is needed. The overhead line equipment is energised at 25kV 50HZ.

What is an AT?
The AT system is therefore a 50kV system fed at 25-0-25kV. Trains are still fed from the contact wire at 25kV, with the supplementary 25kV AT feeder provided. The AT system does not require the booster transformers and return conductors which exist on the WCML. Instead, a return screen conductor is placed close to the S&T route throughout the area covered by the system. This aids interference suppression. Additional cross track bonding is installed to reduce touch potential issues.

Why?
With the continual increase and frequency of trains utilising the WCML and the introduction of faster services between major stations the current OLE system/equipment is quickly approaching its maximum electrical load capacity. As part of Network Rail’s commitment to provide a safe and reliable railway fit for the 21st Century and in order to meet future increases/demand for rail services on the WCML the system needs to be updated, the solution that has been chosen in an Autotransformer (AT) arrangement, this arrangement has been successfully installed and operated in the UK and throughout Europe with great success and will provide a robust electrical supply on the WCML that will meet today’s requirements and accommodate further capacity increases in the future.

The system is currently used on parts of the WCML (progressively expanding), the Midland between Kentish Town and Borehamwood, and also the entire CTRL. The plan is for much of the southern end of the ECML to get the system within the next few years, as will the GWML and Crossrail.

 

[BillMatters]

Is this why there are a load of transformers in Murphy's yard next to Sandy station, as they are being installed on the ECML?