Great Western Main Line electrification - ongoing discussion

[whole diary]

[Thatcham Crossing]

It's curious that an aircraft shuts it's engines down when stationery but an HST^▸ (High Speed Train) (and sometimes 165/6) keep theirs running.

If you fly with Flybe on their Q400's (as I have done 6 times in the last year or so), you will notice that they taxy on 1 engine (plenty of pure jets do too, but harder to spot without that big stationary prop).

Jet engines (pure jets and turboprops) really have to be shut down (eg, during turnaround), as they represent a significant H&S^▸ (Health and Safety) hazard if nothing else, aside from burning a lot of fuel and making quite a lot of noise.

In a former life, when I was involved in "weight and balance" on some types of wide-bodied jets, we would allow up to 2 tonnes (for planning) of fuel burn for the aircraft to get from the parking stand to the end of the runway!

One suspects that a stationary HST burns quite a bit. I often notice when they arrive at PAD^» (Paddington (London) - next trains) that the engines are cut within seconds of coming to a halt (on arrival) but seem to be running a good while before departure.

[chrisr_75]

One suspects that a stationary HST^▸ (High Speed Train) burns quite a bit. I often notice when they arrive at PAD^» (Paddington (London) - next trains) that the engines are cut within seconds of coming to a halt (on arrival) but seem to be running a good while before departure.

It's just the inner power car that is shut down at the terminus, primarly I think for air quality reasons - not sure if you remember but Paddington used to be a complete fug of diesel fumes in the 80's when everything was left running - HST's on Valenta engines and Class 47/50's used to leave a lovely aroma  . The 'modernisation' generation of diesel engines (mostly marine derived) were mostly designed to be left running 24/7 and can be very problematic to cold start, especially English Electric types.

Currently HST's are fired up about 10 mins prior to departure when the driver arrives and is presumably doing the brake tests etc

[paul7575]

So that is nearly an inch in diameter.  How thick is the insulation wrapped around that for a 25kV service?

Me thinks that this will become a mighty cable - worthy of its own trough!

I think you could reasonably be looking at 3 inch overall diameter, once the various layers of insulation and armour are added. 

Paul

[TonyK]

It's curious that an aircraft shuts it's engines down when stationery but an HST^▸ (High Speed Train) (and sometimes 165/6) keep theirs running.

If you fly with Flybe on their Q400's (as I have done 6 times in the last year or so), you will notice that they taxy on 1 engine (plenty of pure jets do too, but harder to spot without that big stationary prop).

Jet engines (pure jets and turboprops) really have to be shut down (eg, during turnaround), as they represent a significant H&S^▸ (Health and Safety) hazard if nothing else, aside from burning a lot of fuel and making quite a lot of noise.

Most jet aircraft, both turbofan and turboprop, taxy on one engine these days, purely as an economy measure. Apart from saving fuel, and jet engines are hugely ineffecient at sea level, it reduces the engine running time, and this can be significant at busy airports. The start-up procedure is simple, and most of the systems that take power from the engine will have been started up on the other one. The "angry dog" noise you hear in Airbus aircraft is an indication that only one engine is running - it is the hydraulic power transfer unit pressurising the hydraulic circuit normally powered by the other engine. Indeed, a certain bearded airline owner suggested that aircraft should be towed by tugs to the end of the taxyway with motors off. They don't take long to warm up, unlike the big diesels in the HSTs, I'll bet - there's a lot of oil to warm and circulate there.

Which does rather advance the case for electrification, where no fuel other than enough to keep the lights and aircon running, is consumed by the train whilst standing at the platform.

[patch38]

Angry dog! I always amuse myself imagining there is somone in the hold hacksawing a length of scaffolding pole.

[Electric train]

The cable used for ground level is 400mm² has to be placed in [t]roughing...

So that is nearly an inch in diameter.  How thick is the insulation wrapped around that for a 25kV service?

Me thinks that this will become a mighty cable - worthy of its own trough!

The overall diameter is 63mm

The cable will be the only thing in the trough, the exceptions are earthing conductors, pilot cables used in protection / SCADA^▸ (System Control And Data Acquisition,) although general telecom fibre optic cables can be placed in HV routes it does mean the telecoms teams need an HV switchout should they need to get to the cable.

Oh and there is only 1 HV circuit per trough

[Electric train]

So that is nearly an inch in diameter.  How thick is the insulation wrapped around that for a 25kV service?

Me thinks that this will become a mighty cable - worthy of its own trough!

I think you could reasonably be looking at 3 inch overall diameter, once the various layers of insulation and armour are added. 

Paul

No armour on 25kV cables just a screen, which does not offer mechanical protection, hence the cable being in a trough and not buried direct

[chrisr_75]

They don't take long to warm up, unlike the big diesels in the HSTs^▸ (High Speed Train), I'll bet - there's a lot of oil to warm and circulate there.

Which does rather advance the case for electrification, where no fuel other than enough to keep the lights and aircon running, is consumed by the train whilst standing at the platform.

The dry mass for one of the MTU^▸ (Motor Traction Unit) prime movers in the GWR^▸ (Great Western Railway) HST's is around 7930kg, so I suspect they will hold much of their oil temperature for many hours after shutdown! The main issue with cold starting in a large Diesel engine is getting enough heat into the fuel for it to combust, rather than oil temperature. The more modern prime movers (such as those fitted in the reengineered HST's) are designed to be shut down and restarted frequently - locos in the US that are stabled tend to shut down and restart automatically to maintain basic 'life support' and air pressure. As I recall, 60's engines didn't have any sort of pre-heat, so were reliant solely on the compression of the fuel/air mixture in the cylinders to generate heat for combustion.

There's some fairly amusing clips on YouTube of assorted preserved English Electric types cold starting. Worth a search/watch as you can see how the start process progresses as heat is gradually built up in the cylinders and the engine goes from partial combustion at the start (dense white smoke) gradually through to normal running (grey/black smoke) via lots of pops, bangs, smoke rings and firey exhausts!

[chrisr_75]

There was a bi-lingual crew from BBC^» (British Broadcasting Corporation - home page) Wales so I suspect there will be something from them on screen later in the week.

This popped up this morning:

http://www.bbc.co.uk/news/uk-wales-south-east-wales-37553620

There could well be something related on the BBC Wales/S4C news this evening

The anticipated video clip has surfaced on the BBC, not sure if a certain forum member is featured in the background...

http://www.bbc.co.uk/news/uk-wales-37569550

[Steevp]

Angry dog! I always amuse myself imagining there is somone in the hold hacksawing a length of scaffolding pole.

Thank you! I have always wondered what that noise was - hacksawing a scaffold pole made me realise exactly what was being talked about - never thought the answer to the question I'd had for years would have been answered on a railway forum 

[TonyK]

Thank you! I have always wondered what that noise was - hacksawing a scaffold pole made me realise exactly what was being talked about - never thought the answer to the question I'd had for years would have been answered on a railway forum 

That's education! You can now smile smugly next time you're sat next to an anxious passenger, and say "That? Oh, it's just the hydraulic power transport unit. After the other engine is switched on, it does a quick self-test, then goes quiet."

The dry mass for one of the MTU^▸ (Motor Traction Unit) prime movers in the GWR^▸ (Great Western Railway) HST^▸ (High Speed Train)'s is around 7930kg, so I suspect they will hold much of their oil temperature for many hours after shutdown!

And that's education too, possibly more appropriate to here! I've seen some video of those cold starts - it is difficult to tell when the engine actually has kicked in on some of them.

[Western Pathfinder]

Thank you! I have always wondered what that noise was - hacksawing a scaffold pole made me realise exactly what was being talked about - never thought the answer to the question I'd had for years would have been answered on a railway forum 

That's education! You can now smile smugly next time you're sat next to an anxious passenger, and say "That? Oh, it's just the hydraulic power transport unit. After the other engine is switched on, it does a quick self-test, then goes quiet."

The dry mass for one of the MTU^▸ (Motor Traction Unit) prime movers in the GWR^▸ (Great Western Railway) HST^▸ (High Speed Train)'s is around 7930kg, so I suspect they will hold much of their oil temperature for many hours after shutdown!

And that's education too, possibly more appropriate to here! I've seen some video of those cold starts - it is difficult to tell when the engine actually has kicked in on some of them.

In times gone by it was not unknown to place a newspaper soaked with lighter fluid into the air intake of a Mayback engine light it up and then try to start the bugger from cold !.

[TonyK]

The anticipated video clip has surfaced on the BBC^» (British Broadcasting Corporation - home page), not sure if a certain forum member is featured in the background...

http://www.bbc.co.uk/news/uk-wales-37569550

I thought the rail would be more curvy, to avoid wearing the pantographs down.

[Noggin]

The anticipated video clip has surfaced on the BBC^» (British Broadcasting Corporation - home page), not sure if a certain forum member is featured in the background...

http://www.bbc.co.uk/news/uk-wales-37569550

I thought the rail would be more curvy, to avoid wearing the pantographs down.

AFAIK^▸ (as far as I know) it's staggered like regular OLE^▸ (Overhead Line Equipment, more often "OHLE"), you just can't really see it in the clip.

[didcotdean]

Thank you! I have always wondered what that noise was - hacksawing a scaffold pole made me realise exactly what was being talked about - never thought the answer to the question I'd had for years would have been answered on a railway forum 

That's education! You can now smile smugly next time you're sat next to an anxious passenger, and say "That? Oh, it's just the hydraulic power transport unit. After the other engine is switched on, it does a quick self-test, then goes quiet."

And if the self-test fails it tries again and again and gets louder and louder.

Happened to me earlier this year taxiing to the runway on a flight back to the UK^▸ (United Kingdom) from Madrid. Credit to Iberia though in that they rustled up another plane and we were transferred across. Benefit of being at home base I guess.