Great Western Main Line electrification - ongoing discussion

[whole diary]

[IndustryInsider]

Don't get too excited now....... Looks like its only the Earth wire. Easier than putting up the actual knitting    But, hey ho, at least some positive (well in this case, earthing) progress at last

Catenary wire, droppers, and contact wire have now been strung for about half a mile on the relief lines in the same location.  Starting to look like a proper electrified railway now. 

[patch38]

The fact it all stayed up in yesterday's conditions is a good start too!

[paul7575]

Catenary wire, droppers, and contact wire have now been strung for about half a mile on the relief lines in the same location.  Starting to look like a proper electrified railway now. 

Is half a mile a typical length of wiring run between tensioners?

Paul

[Electric train]

Don't get too excited now....... Looks like its only the Earth wire. Easier than putting up the actual knitting    But, hey ho, at least some positive (well in this case, earthing) progress at last

Catenary wire, droppers, and contact wire have now been strung for about half a mile on the relief lines in the same location.  Starting to look like a proper electrified railway now. 

As the GWML^▸ (Great Western Main Line) is not going to be the "classic" single S&T^▸ (Signalling and Telegraph) rail and single traction return rail but will be using dual rail return with impedance bonds it is not possible to connect the OLE^▸ (Overhead Line Equipment, more often "OHLE") structures to the running rails and bond the OLE to the structures so the earth wire is being run to tie everything down to a reference.  Even though the OLE has yet to be charged from a source it will pick up an induced voltage whilst not particularly powerful it is never the less could be dangerous enough.

Catenary wire, droppers, and contact wire have now been strung for about half a mile on the relief lines in the same location.  Starting to look like a proper electrified railway now. 

Is half a mile a typical length of wiring run between tensioners?

Paul

The wire runs are a max of 1970 meters, wire runs can be shorter to suit sub sectioning near junctions etc

[IndustryInsider]

I'll try and get a more accurate measurement tomorrow.

[stuving]

As the GWML^▸ (Great Western Main Line) is not going to be the "classic" single S&T^▸ (Signalling and Telegraph) rail and single traction return rail but will be using dual rail return with impedance bonds it is not possible to connect the OLE^▸ (Overhead Line Equipment, more often "OHLE") structures to the running rails and bond the OLE to the structures so the earth wire is being run to tie everything down to a reference.  Even though the OLE has yet to be charged from a source it will pick up an induced voltage whilst not particularly powerful it is never the less could be dangerous enough.

Ah, that explains why there was an earth wire being installed. I did wonder, since in previous AT installations (WCML^▸ (West Coast Main Line)) doing away with the return conductor was given as an advantage. But won't the steel piles, and the structures on them, be earthing the earth wire, in a kind of PME?

[patch38]

I have to ask: 1,970m? Where did that figure come from? It's not a mile and it's not 5% wastage from a 2 km drum. I'm sure there's good explanation but I'm dashed if I can think what it might be.

[stuving]

I have to ask: 1,970m? Where did that figure come from? It's not a mile and it's not 5% wastage from a 2 km drum. I'm sure there's good explanation but I'm dashed if I can think what it might be.

Why would it be a round number? It has to meet number of design requirements, it's not just a free choice. For a kick-off, the temperature range times expansion coefficient of the conductor times the length has to be less than the range of the tensioner minus certain setting tolerances. But in practice something else may set a lower limit.

[Electric train]

As the GWML^▸ (Great Western Main Line) is not going to be the "classic" single S&T^▸ (Signalling and Telegraph) rail and single traction return rail but will be using dual rail return with impedance bonds it is not possible to connect the OLE^▸ (Overhead Line Equipment, more often "OHLE") structures to the running rails and bond the OLE to the structures so the earth wire is being run to tie everything down to a reference.  Even though the OLE has yet to be charged from a source it will pick up an induced voltage whilst not particularly powerful it is never the less could be dangerous enough.

Ah, that explains why there was an earth wire being installed. I did wonder, since in previous AT installations (WCML^▸ (West Coast Main Line)) doing away with the return conductor was given as an advantage. But won't the steel piles, and the structures on them, be earthing the earth wire, in a kind of PME?

It should be remembered that the traction return rail(s) are earthy and not earthed this is to ensure the traction return current returns via the return system and not stray via terra ferma this is to reduce interference that stray current would cause.

In PME ie TN-C-S the earth at the user end is derived from the PEN conductor, this is almost the case in the classic 25kV system where the traction rail is connected to the "Neutral" things get a bit more complex when dual traction immune (TI) track circuits are uses with impedance bonds and a whole lot more complex when Auto Transformer system is used to supply traction current. 

Even with axel counters both rails OLE structures will be bonded by an earth wire and not at ever structure, this reduces the number holes drilled in the rail, the track engineer does not seem to like holes drilled in his (her) steel.  However the system designers still have to ensure the RoEP does not exceed the requirements of BS EN 50122

Also an MSC (Mutual Screening Conductor) is placed in the S & T trough routes to improve immunisation these are bonded to the traction return rail(s) every 400 m.

I have to ask: 1,970m? Where did that figure come from? It's not a mile and it's not 5% wastage from a 2 km drum. I'm sure there's good explanation but I'm dashed if I can think what it might be.

Why would it be a round number? It has to meet number of design requirements, it's not just a free choice. For a kick-off, the temperature range times expansion coefficient of the conductor times the length has to be less than the range of the tensioner minus certain setting tolerances. But in practice something else may set a lower limit.

Possibly more to do with either the length of copper BICC could originally draw from a single ingot of copper, or the length of conductor on a cable drum that would fit the railway loading gauge.  Personally I will go with the second one, also due to the weight of 2000m drum of 120mm sq copper.  Joints are not liked in a new wire run as they are a point of failure. 

[ellendune]

I notice that the new A338 bridge at Wantage Road is taking shape.  The position of the abutments is such that the loop on the south (down) side could now be extended through the bridge if required.  Was this a deliberate provision for the future or was it just that it was so close that the additional clearance was required as a safety measure in case of a derailment of a train travelling in the wrong direction in the loop?

Meanwhile in Wiltshire the embankment for the short diversionary road connecting the old Hay Lane alignment to the modern B4005 on the north side of the railway is now up to the full height. This is to allow the old Hay Lane bridge to be demolished at Christmas.   

[grahame]

From Network Rail:

The next Bath Drop-in will be held in the Guildhall on Tuesday 1st December (4.30pm ^ 6.30pm).  Please note the earlier finishing time.
 
Come along and find out more about the work we are doing to modernise the Great Western Railway.
 
Information will be available on the TPOD 2 work planned for next Easter.

I have received an email to recall the email that announced this session.  Will update further as / if I hear more.

[eightf48544]

did a run to London lots of work going on many more O/H mast erected up to Hayes since last t rip at end September..

Work at West Drayton,  Stockley Flyover and Acton underpass also North Pole Depot branded Haitachi for SET^▸ (Super Express Train (now IET)). Is there going to be an entrance at the Padd end of the depot where flyover line branches off?

[IndustryInsider]

I'll try and get a more accurate measurement tomorrow.

Measured today as 0.73 miles by my GPS iPhone app.  That equates to approx 1175 metres.

Is there going to be an entrance at the Padd end of the depot where flyover line branches off?

Two new 50mph entrances/exits have recently been installed, one connects off of the E&C (Engine & Carriage Line - which is the line that leads to the flyover), and the other joins Line 1 a little closer to Paddington on a new formation.

[SandTEngineer]

Work at West Drayton, Stockley Flyover and Acton underpass also North Pole Depot branded Haitachi for SET^▸ (Super Express Train (now IET)). Is there going to be an entrance at the Padd end of the depot where flyover line branches off?

See this post here: http://www.firstgreatwestern.info/coffeeshop/index.php?topic=818.msg172697#msg172697

[Electric train]

North Pole Depot branded Haitachi for SET^▸ (Super Express Train (now IET)). Is there going to be an entrance at the Padd end of the depot where flyover line branches off?

There is still a connection on the West London Line.

If look carefully into the shed an Hitachi unit is often parked inside