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Author Topic: Great Western Main Line electrification - ongoing discussion  (Read 92385 times)
Adrian
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« Reply #840 on: August 12, 2019, 08:29:46 pm »

There is also the question of why a whole class of emus seemed to have a problem re-starting after the power came back on again.  Fitting trains with a backup battery or diesel engine might not help if they shut down and need a technician to come a couple of hours later to persuade them to work again.  I think there was a suggestion that it was the drop in AC frequency that tripped the trains' systems out?

National Grid were saying that they need to consider carefully about what to disconnect to minimise disruption - but when a main railway line presents such a variable and asymmetric load on the grid, is it not one of the first they would choose to shed when trying to stabilise the supply?
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broadgage
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« Reply #841 on: August 12, 2019, 09:07:31 pm »

AFAIK it was the new Thameslink EMUs that could not be re-started after the failure without an engineer.
Some reports suggest that these units trip out on low line frequency so as to prevent the potential generation of harmonics that might interfere with the signalling.
The traction package was probably only tested over a narrow range of line frequency, and then someone decided that "you cant have too much safety" and that everything should stop if the line frequency was outside of the limit.

Although other electric trains work without this feature, it might be a struggle to convince the health and safety industry that this "safety feature" can be removed.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
TonyK
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« Reply #842 on: August 12, 2019, 09:31:20 pm »

They were also a great aid to visual navigation when I used to fly in the local area. Could be seen from 30-40 miles away in all directions when visibility was good.

For me as well. It was particularly useful because of everything around it that needed special treatment by the private pilot, such as RAF Lyneham and Benson, Harwell nuclear research facility, now no longer prohibited airspace, and the run into the airspace minefield that is London. Some landmarks don't look so big from the air - flying to Dunkeswell for the first time, my instructor told me to turn south over the Wellington monument, and I was 7 or 8 minutes away, but I never saw the monument, relying on the turning triangle for the WSR to check position. As TC says, though, the Didcot towers were a very easy spot on a clear day, certainly from 2500 feet, east of Bath.

Decontamination will be a big job. The small purifier house at the old Canons marsh gas works in Bristol took ages - but that was Bristol. Even given the closer proximity to London, it won't be a quick job to start building on a former power station AND ordnance factory.
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ellendune
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« Reply #843 on: August 12, 2019, 09:40:58 pm »

Decontamination will be a big job. The small purifier house at the old Canons marsh gas works in Bristol took ages - but that was Bristol. Even given the closer proximity to London, it won't be a quick job to start building on a former power station AND ordnance factory.

I am not sure, gas works sites are renowned for being some of the most contaminated around.  When it was used for car storage you may have noticed that not many weeds grew on the old Acton Gas Works site!
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TonyK
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« Reply #844 on: August 12, 2019, 09:50:18 pm »

Decontamination will be a big job. The small purifier house at the old Canons marsh gas works in Bristol took ages - but that was Bristol. Even given the closer proximity to London, it won't be a quick job to start building on a former power station AND ordnance factory.

I am not sure, gas works sites are renowned for being some of the most contaminated around.  When it was used for car storage you may have noticed that not many weeds grew on the old Acton Gas Works site!

Reading up, I see your point now. The towers themselves were used only for cooling excess hot water, so shouldn't be so bad. I should think remediation, to use the posh term, is still likely to be a big job, though, given our modern standards.
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didcotdean
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« Reply #845 on: August 12, 2019, 10:02:45 pm »

It was an ordnance depot rather than a factory, although I speculated earlier that you can never be sure what is on a brown field site. Having used the overlay facility of old and modern maps at the National Library of Scotland shows that actually quite a bit of the power station site earlier was not built on but was a recreation ground. There were several ranks of buildings on the southern edge each flanked by railway sidings on both sides, ultimately connected to the West Curve.
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Thatcham Crossing
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« Reply #846 on: August 13, 2019, 08:14:16 am »

Quote
It was an ordnance depot rather than a factory

....as was the depot in Thatcham (just west of the Station) that is now a housing estate.
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Electric train
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« Reply #847 on: August 13, 2019, 05:14:53 pm »

Decontamination will be a big job. The small purifier house at the old Canons marsh gas works in Bristol took ages - but that was Bristol. Even given the closer proximity to London, it won't be a quick job to start building on a former power station AND ordnance factory.

I am not sure, gas works sites are renowned for being some of the most contaminated around.  When it was used for car storage you may have noticed that not many weeds grew on the old Acton Gas Works site!

Reading up, I see your point now. The towers themselves were used only for cooling excess hot water, so shouldn't be so bad. I should think remediation, to use the posh term, is still likely to be a big job, though, given our modern standards.

Don't forget there was a vast quantity of coal used and stored on the site, plus all the ash all of which needs decontamination.

The towers would become a liability, I doubt future owners of the site, local authorities, English Heritage would want take them on and the current own has no business case to continue with the lability
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