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Author Topic: Power outage strands trains  (Read 3703 times)
broadgage
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« Reply #15 on: August 10, 2019, 12:56:16 pm »

AFAIK there was not any plan to fit IETs with "transit sized" engines to limp home.
What WAS planned was that IETs would have a standard type of engine across the various IET variants. The true bi mode units have multiple engines so as to give a performance under diesel power suitable for daily main line operation.
The nominally electric units have just a single engine of the same type, for limited performance when the electric power is not available.
All the IETs for GWR are of the bi mode type with multiple engines, 3 engines on the 5 car units.

Some of the IETs for use by other TOCs are the nominally electric variant, with but a single engine for emergency use. IIRC they can reach about 30 MPH on this single engine, most useful in case of emergency but obviously far short of the performance needed for regular use.
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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.
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« Reply #16 on: August 10, 2019, 12:58:10 pm »

The term used in India is "load shedding". I understand this has a technical usage but there it's used in a far broader sense to describe the (pretty much daily) interruptions to the electricity supply whatever their reason.
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Bmblbzzz
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« Reply #17 on: August 10, 2019, 01:00:29 pm »

Continuing the international theme, overhead supply was deliberately cut several times in Poland in the early 2000s because PKP were hugely in debt to the electricity generators. Signalling continued to function though.
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grahame
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« Reply #18 on: August 10, 2019, 01:07:53 pm »

AFAIK there was not any plan to fit IETs with "transit sized" engines to limp home.

There was .. top speed specified on the all-electric units (801) under diesel was 30 m.p.h; how that compare to a transit's engine I don't know.

WikiPedia tells us

Quote
According to LNER, the Azuma fleet will not only increase capacity but also improve reliability and resilience, especially at times of disruption, since even the Class 801 EMUs are fitted with a single diesel powerpack
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« Reply #19 on: August 10, 2019, 01:34:23 pm »

More important than keeping moving, arguably, is the hotel power for many hours that a diesel engine will provide, so heating, lighting, air-con and toilets stay operational keeping passengers comfortable.  IETs also have bags of space for emergency water and food supplies.
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SandTEngineer
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« Reply #20 on: August 10, 2019, 01:51:18 pm »

All signalling centres since at least the mid-1960s have had some form of diesel generator backup.  More modern centres also have UPS backup.  However, in lots of cases, but not all, this does not extend to the lineside supplies that are usually area specific, so if one gets a total outage a relatively small area is affected (on average not more than 5-6 miles).  As it happens older mechanical installations can be more resilient that modern systems because everything is obviously mechanically operated, or if electrical, uses primary or secondary cells Grin

Track circuits will naturally 'reset' themselves after power restoration and only show clear if not occupied by any vehicles.  Axle Counters will also reset but the affected section will not show clear again until the first train through the section is correctly counted in and then counted out again.  Some axle counter systems are fitted with UPS to overcome some, but not all of those issues.

Signals will go out but will restore when power returns.  The aspect displayed will depend on what the track circuits/axle counters are telling the signalling system at the time.

AWS will fail to the warning status regardless of signal aspect.  The permanent magnet part of it ensures that.

TPWS will fail until power is restored.

Points sometimes have battery backup systems, but not in all cases.

And just for noting; the diesel generators are always tested on-load every thirteen weeks (well they used to be when I once had maintenance responsibility for them).
« Last Edit: August 10, 2019, 02:16:17 pm by SandTEngineer » Logged

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onthecushions
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« Reply #21 on: August 10, 2019, 08:24:53 pm »


I'm left wondering what should be the driver's response to all the signal lamps going out - is a full brake application to be made with only the train's tail light protecting the rear, is the AWS warning immediate, can it be cancelled if there is no TPWS?

Nervous flyer!

OTC
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SandTEngineer
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« Reply #22 on: August 10, 2019, 08:28:16 pm »


I'm left wondering what should be the driver's response to all the signal lamps going out - is a full brake application to be made with only the train's tail light protecting the rear, is the AWS warning immediate, can it be cancelled if there is no TPWS?

Nervous flyer!

OTC

No need to worry.  No light in a signal when there should be one is classed as a danger (stop) signal.

The AWS warning will sound a Horn in the cab if there is no power to it (its worked by a permanent magnet).  That indicates to the driver to obey the signal and if the driver doesn't acknowledge that the emergency brake is automatically applied.
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« Reply #23 on: August 10, 2019, 09:04:27 pm »

"More power stations needing repairs than usual".........................??  Wink
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Bmblbzzz
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« Reply #24 on: August 10, 2019, 10:19:55 pm »

"More power stations needing repairs than usual".........................??  Wink
...mean more stations without power!
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bignosemac
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« Reply #25 on: August 11, 2019, 01:53:44 am »

The term 'power outage' has been around for well over a century. Yes, it may be from American English originally but I see nothing wrong with that. Language evolves, words and phrases live and die by usage. I used to decry 'train station' but now realise that it's perfectly acceptable. As long as the reader/listener comprehends then that's really all that matters.

Or should we have a prescriptive 'English Academy' (modelled on the Académie francaise) that tries to preserve the language in aspic and rails against words and phrases from other languages, and from international variants of English?

By the way. I'm just back from a late night walking of the dog around the recreation ground. I had to take a flashlight to see my way along the sidewalks and thru the gates. I was disappointed by all the trash around the soccer fields.
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« Reply #26 on: August 11, 2019, 08:59:39 am »

By the way. I'm just back from a late night walking of the dog around the recreation ground. I had to take a flashlight to see my way along the sidewalks and thru the gates. I was disappointed by all the trash around the soccer fields.

Oh dear. What is a night? Surely you meant to say nite!
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Electric train
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« Reply #27 on: August 11, 2019, 09:27:30 am »

The drop has been reported to be to 48.89Hz.

Another fact that made the response difficult was that there was a high amount of renewables (strong wind) and relatively little thermal plant generating at the time with little inertia in the mix, so the imbalance from the production side needed to come from starting up generation from scratch. Pumped storage was turned on almost immediately followed by the open cycle gas turbines.

This is a known issue with greater reliance on renewables, and there is a contract out at the moment for fast response battery provision.

One of the issues of switching from thermal combustion energy to renewable energy is the national Grid has lost much of its "inertia"  The heavy spinning mass of large steam driven alternators provided a lot of inertia to the Grid meaning voltage and frequency transients caused by faults were more easily absorbed.  Solar, wind nor the dc interconnectors to Europe give much if any inertia to the Grid.

All signalling centres since at least the mid-1960s have had some form of diesel generator backup.  More modern centres also have UPS backup.  However, in lots of cases, but not all, this does not extend to the lineside supplies that are usually area specific, so if one gets a total outage a relatively small area is affected (on average not more than 5-6 miles).  As it happens older mechanical installations can be more resilient that modern systems because everything is obviously mechanically operated, or if electrical, uses primary or secondary cells Grin

Track circuits will naturally 'reset' themselves after power restoration and only show clear if not occupied by any vehicles.  Axle Counters will also reset but the affected section will not show clear again until the first train through the section is correctly counted in and then counted out again.  Some axle counter systems are fitted with UPS to overcome some, but not all of those issues.

Signals will go out but will restore when power returns.  The aspect displayed will depend on what the track circuits/axle counters are telling the signalling system at the time.

AWS will fail to the warning status regardless of signal aspect.  The permanent magnet part of it ensures that.

TPWS will fail until power is restored.

Points sometimes have battery backup systems, but not in all cases.

And just for noting; the diesel generators are always tested on-load every thirteen weeks (well they used to be when I once had maintenance responsibility for them).

The large signalling centres (IECC, ROC & PSB) do have diesel generator backup which typically take 10 to 15 seconds to come on load from a mains power failure, they have UPS systems to cover for this time, in the more modern ROC these have dual supplies either one DNO and one (some even have 2 traction and a DNO) where Traction is not used they will have 2 independent DNO supplies.

The problems arise away from the signalling centres at the remote interlocking / relay rooms etc, these will have 2 supplies either DNO with diesel gen as the second supply, DNO with traction as the second supply, in the case of the Southern they have 2 DNO and lost have a third DNO.

All these power supplies take time to detect the supply failure and operate the change over switchgear, this time can range from 2 to 15 seconds, however the supply may be unstable for a second or so before its detected.

UPS are increasingly used, they are sized however typically for 1 to 2 minuets this is only cover the momentary loss of supply while the mains supply changes over to its back up; the economics of providing a UPS that can cover for an hour becomes unviable (ROC UPS are sized slightly lager than a relay room but will still only typically give 15 to 30 mins)


If it was the Class 700 that caused so many problems then I am sure the TOC, NR, ORR and DfT will be placing pressure on Siemens to solve what the issue was,  at least when the Class 800 come into full service on the ECML they can move independent of the traction power
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Bmblbzzz
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« Reply #28 on: August 11, 2019, 01:55:10 pm »

By the way. I'm just back from a late night walking of the dog around the recreation ground. I had to take a flashlight to see my way along the sidewalks and thru the gates. I was disappointed by all the trash around the soccer fields.
Soccer is a good example of words changing. Its origins are British, as an abbreviation of association to distinguish hooligan's football from the gentleman's union variety (or is it the other way round?).
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stuving
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« Reply #29 on: August 20, 2019, 10:14:42 am »

National Grid's initial report has been published on line by Ofgem. Quaintly, it is marked ESO - HIGHLY CONFIDENTIAL; which maybe it was before it got to Ofgem!

It's not a great surprise - it documents the grid itself doing pretty much what it should, given the loss of nearly 2 GW of generation while meeting 30 GW of demand. A few points I thought worth noting:

1. There was about 1 GW of what they call 'frequency response', meaning extra generation that is provided automatically when the grid frequency drops. That included 472MW of battery storage. I wonder to what extent that will replace spinning reserve ('inertia').

2. The two big generators that disconnected themselves after the lightning strike should not have done so - that is not the expected behaviour.

3. On the other hand, the 500 MW of 'embedded generation' that disconnected due to transients was meant to do that.

4. No supplies for traction power were disconnected, though a few bits of railway (DC, signalling, etc.) disconnected themselves.

5. All those class 700 and 717 trains that turned themselves off and wouldn't turn on without special help did so because of their own transient detection.

6. The frequency never got so low that self-disconnection was expected of grid generators or critical loads - like trains, hospitals etc.  Only some particularly sensitive things, as well as those little 'embedded' generators, are allowed to do that.
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