One would hope they test with the real (reactive) load rather than BFO resistor... Not to mention the sets (I hope they have more than one) are going to be quite hefty, a megawatt or two thats a FBBFO resistor...
When 9/11 happened, the power went off at the site hosting some kit we had in New York. Gensets kicked in and our kit stayed up, although some circuits went red on my network map because both Deutsche Telecom's fibre rings in NY went through the basement of one of the towers.
A couple of hours later the hosting folks noticed the temps going up in the diesel sets. On investigation they found the air-intake filters were clogged with fine dust from the towers' collapse. So they fixed that. After a couple of days they were low in diesel, and a tanker had to come in under armed guard to refuel them.
The hosting site was at 25 Broadway, right opposite Wall Street. It may still be for all I know - I've not been back since. Last time I was there was end Aug, 2001.
stabilise
Just make the rules state that all generation connected to the grid has to be dispatchable with agreed, notice periods, rate of change, minimum run time etc. How the generator achieves this is up to them, windmill with batteries in the tower, liquid air?
anxiety
battery.
So National Grid said things were back to normal after 20 mins and the loss of 1.5 GW of capacity. Lets say the recovery was linear over the 20 minute period so the total amount of energy required from alternative sources is (1.5 GW * (20/60))/2 = 250 MWHr.
Lets now assume that each car is plugged in via a domestic 7kW "fast" charger that can suck or blow at 7 kW. 20 min at 7 kW is 2.33 kWHr per car. So the number of cars plugged in needs to be 250 MWHr / 2.33 kWHr =
107,296. Then you have to have some form of control system...
Not something suitable for a hospital site, but I was involved in the testing of a couple of 24MW generators - it was indeed a big resistor! It was actually three, being three phase and each consisted of two parallel vats of salty water with an electrode in. Varying the depth the electrodes was used to vary the resistance. The water was continuously pumped into the bottom and overflowed from the top (to keep a constant depth), was pumped through air-blast coolers, into a tank and then back into the bottom of the vats.
The system was capable of sinking 30MW.
SteveW
Not at all.
If the instant power to keep the grid stable had been available, areas of the grid likely wouldn't have tripped out and the sitation would have been much simpler and quicker to get back to normal.
Yes, just has you do with any other supply source to the grid.
SteveW
I was working in an HMP years ago when there was a power cut. The emergency generator started up, ran for ten seconds, then died. Luckily it was during lock-up.
Bill
Apparently, grid-connected domestic solar PV inverters are required to shut down if the frequency drops below a certain value, 48.something.
This would instantly make a bad situation even worse for a while.
My theory is that the frequency dropped because demand exceeded supply then different protection systems had different sensitivities and the ones that were most sensitive tripped out first until the demand fell in line with the supply. Maybe Network Rail have more sensitive protection that some other users?
Just a theory but any comments?
Except on this occasion the 'shortage' occurred during the rush hour.
In article snipped-for-privacy@4ax.com, Scott snipped-for-privacy@gefion.myzen.co.uk> scribeth thus
Notwork fail, well the people who operate the trains have a stinky pile of poorly designed poo called the Class 700 which it now appears needs a fitter to turn up to reset it when the power drops out.
Made by Siemens, you'd think that German engineering could do better?..
Anyone know why this is?
So what? There are millions of vehciles that are not commuting at rush hour. Some work late to avoid the peak, some leave early, some are retirees, housewives, carers, many have picked up the children and are home before rush hour. There are over 30m cars on the road in the UK and around 15m people drive to work.
SteveW
Sorry Steve, but I think there's a little too much belling-the-cat around this suggestion.
My guess is that it could be due to interference monitoring equipment on the trains.
Because it is vital that no electrical interference is created in any signalling systems (of which there are a number of varieties) modern trains have complicated and sensitive monitoring of the current they draw from the supply.
If any frequencies are detected in a number of forbidden bands, then it shuts down. Because of the safety significance, it seems that a quick reset has deliberately been provided.
Whilst I am no longer in the business, whilst I was working on the Class 357, a similar monitor was being developed for the first time. Set up in line with the initial demanded performance, it was in danger of shutting down every time it passed one of the older units in service, as they created such distortion in the supply waveform.
Chris
You mean the train shuts down and stops?
I assume you missed a "not" there, yes? :-)
Thanks for this explanation. While I take the point you are making, I think the travelling public has higher expectations.
Can trains be controlled in any way from the "signal box" (or whatever it is these days). I'm thinking of a reset button on the train, normally not authorised, but which the control room could enable remotely.
Here's more questions: on a long stoppage, the loos become progressively more important compared to heating/lighting, especially if they have powered doors. Do the trains have batteries? How long do they last? Can the train staff power down most of the lights but leave the loo systems functional?
Indeed so. The worst possible consequence would be causing a wrong side signalling fault, such as showing a green light when it should be red. This is obviously taken seriously, so the train is stopped until it has been verified that all is well.
Quite so.
Not as far as I know. There are some isolating switches with security seals that can be operated in particular circumstances. Poor use of one of these recently led to a tube train travelling between stations with some of its doors fully open.
Trains do indeed have batteries. Quite a lot of time is spent attempting to design matters so that their capacity is adequate, and that inessential loads are shed when supply is lost. Getting the relative priorities right is not easy. Sadly, the length of some of the recent delays is far more than can realistically be catered for. With toilets, now that (nearly) all use retention tanks, then their capacity, and adequate water supply will also become an issue.
Chris
What about the worthing chemical cloud ?
It's quite simple really Chris the bloody things are unfit for the job they have to do. The design isn't that good so I read on some railway forums. Its a railway locomotive OK call it an EMU but there are a lot of other EMU sets around that do not fall over if the power fails.
It does seem it was the power failure that did the job, not the frequency variation and if so it should be able to cope with a variation of frequency they as best I work off DC as well. You should not need a tech or a fitter to come out and restart the things they should when the power is re applied start up if they can't do that without a lot of faffing around then, not good enough for the job!
I expect the train operating companies that have them are having interesting discussions with Siemens who make them this week;!..
It was fine on Saturday, except that Worthing councils elf and safety jobsworths had shut the pier, because it was a bit windy !.
There was only a 4.7 metre tide that day, so it would not affect the landing stages and low tide was 13:00 anyway, which meant that the tide was out for most of the afternoon when people were about.
There is always a pong at Worthing at this time of year because all the seaweed that is blown up onto the beach.
Even so it looks like a critcal part of the countries infra-structure (railways) can't handle a public supply outage. Surely the system has UPS's to bridge the gap betwwen loss of public supply and autostart generators kicking in? I don't expect the traction power for the trains to be backed up but the signalling system should not even notice the power loss and know where the (electric) trains have coasted to a halt(*). Having trains that the driver can't "restart" after a power loss strikes me as a bit bloody stupid as well.
AFAICS National Grid performed very well and all supplies where restored in under an hour, we were off for about 30 mins. Our power went off again this this morning due to a local 11 kV fault and it took three hours to restore.
(*) I wonder what it's like to be on board an elecric train doing over 120 mph when it loses the overhead supply?
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