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Offline Chemistry4me

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What are the usual causes of power cuts?
« on: 01/02/2009 01:58:34 »
What are the usual causes of power cuts? ???


 

Offline MonikaS

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What are the usual causes of power cuts?
« Reply #1 on: 01/02/2009 02:24:22 »
Ummm, someone didn't pay the bill? ;D
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #2 on: 01/02/2009 02:24:44 »
Of course not!
 

Offline Don_1

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What are the usual causes of power cuts?
« Reply #3 on: 01/02/2009 12:09:45 »
Some burk did something stupid.
 

Offline graham.d

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What are the usual causes of power cuts?
« Reply #4 on: 01/02/2009 13:30:05 »
I don't know the statistics related to local power cuts, but these are often due to local equipment failure which, in turn, can be related to the weather (lines down for example). Often, cuts due to such effects can be kept to a short period by the nature of the grid system that allows re-supply via a different route.

The bigger problems arise due to the very nature of this grid system. It can happen that local problems can contrive to overload particular power stations. Usually this needs some unfortunate coincidence, but it happens. If a power station gets overloaded (usually the generators cannot maintain the 50Hz, or 60Hz in the USA frequency) they have to be shutdown, Clearly this can, and does, result in a cascade failure over a wide area which can take quite a while to sort out.
 

Offline LeeE

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What are the usual causes of power cuts?
« Reply #5 on: 01/02/2009 14:12:51 »
Locally, probably the biggest cause of power-cuts is road-works and other types of engineering that involve digging up the top few feet of the ground.
 

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What are the usual causes of power cuts?
« Reply #6 on: 01/02/2009 22:30:50 »
I guess the answer to the question will depend upon which part of the World you happen to be in. It could be Israeli shelling, under some circs.
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #7 on: 02/02/2009 00:44:19 »
Quote
It can happen that local problems can contrive to overload particular power stations. Usually this needs some unfortunate coincidence, but it happens. If a power station gets overloaded (usually the generators cannot maintain the 50Hz, or 60Hz in the USA frequency) they have to be shutdown, Clearly this can, and does, result in a cascade failure over a wide area which can take quite a while to sort out.

The only thing is that the power plants are not shut down, but disconnected from the grid. These accidents are avoided by equipment that compares the grid frequency with the power plant frequency, after the frequencies are equal the synchroscope allows the breakers to be close.
 

Offline LeeE

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What are the usual causes of power cuts?
« Reply #8 on: 02/02/2009 04:49:54 »
mmm...  doughnuts synchroscopes

http://en.wikipedia.org/wiki/Synchroscope
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #9 on: 02/02/2009 05:00:27 »
Well, there wasn't a cloud in the sky the other day so I don't think it was caused by the weather.

I don't know the statistics related to local power cuts, but these are often due to local equipment failure which, in turn, can be related to the weather (lines down for example). Often, cuts due to such effects can be kept to a short period by the nature of the grid system that allows re-supply via a different route.
How short is a "short period"?
 

Offline graham.d

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What are the usual causes of power cuts?
« Reply #10 on: 02/02/2009 13:50:01 »
"How short is a "short period"?"

From a fraction of a second (a brownout) to a few minutes.
 

Offline graham.d

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What are the usual causes of power cuts?
« Reply #11 on: 02/02/2009 13:58:11 »
erickejah, it is not an accidental loss of synchronism that is the problem. When a generator is sufficiently overloaded it cannot maintain the rate of rotation and then has to be disconnected from the grid. This removal of supply to the grid then affects other generators trying to take up the load, which then also have to be disconnected potentially resulting in a cascade of failing supply. This can be initiated by a power station fault because a station has to be shut down, though usuually there is sufficient capacity designed in to cope. The problem arises if two power stations simultaneously have a problem.
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #12 on: 03/02/2009 02:12:27 »
 [:I] yes, you are completely right. :D nevertheless, desynchronizing failures still make people think that there is no power, because fluctuations of the frequency that causes equipment to not work at the specified requirements.   
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #13 on: 03/02/2009 03:07:36 »
Another one today, although not at my house. Said on the news that it was caused by a transformer fault, what ever that means...
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #14 on: 03/02/2009 03:17:30 »
Another one today, although not at my house. Said on the news that it was caused by a transformer fault, what ever that means...

it means that the voltage lines feeding that community need maintenance. i think that the transformers that they are saying is of this kind:
« Last Edit: 03/02/2009 03:19:06 by erickejah »
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #15 on: 03/02/2009 03:19:09 »
Thanks dude :)
But that transformer looks really ancient!
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #16 on: 03/02/2009 03:24:34 »
there are also transformers like this:

If they break more people is affected.  :-\
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #17 on: 03/02/2009 03:27:55 »
Well, it has left 74000 people without power!
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #18 on: 03/02/2009 03:56:40 »
Well, it has left 74000 people without power!
i bet it is a 22,000v transformer.
 

Offline Chemistry4me

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What are the usual causes of power cuts?
« Reply #19 on: 03/02/2009 04:34:40 »
How do you know that?
 

Offline LeeE

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What are the usual causes of power cuts?
« Reply #20 on: 03/02/2009 13:42:30 »
In the UK, and to affect 74000 people, it would more likely be a 200-400+ kv transformer.

I just downloaded a nice pdf showing the UK national grid, from the BBC at

http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/14_06_06_powerstations.pdf
 

Offline Vern

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What are the usual causes of power cuts?
« Reply #21 on: 03/02/2009 20:37:39 »
Here in the US from about Oklahoma to the Atlantic coast it is ice storms. Tree branches that overhang power lines get loaded with ice and break off onto the power wires. There is a big push going on right now to keep the tree limbs trimmed.

Trees in home owners yards used to be off limits, but a new ruling allows power companies to trim all they want. I hope it works.
 

Offline ...lets split up...

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What are the usual causes of power cuts?
« Reply #22 on: 03/02/2009 21:00:03 »
We had major power outs in South Africa last year, and it's still not over. The company, Eskom, was informed years before that the more power stations were needed, but the new management ignored it because no one wanted to make a desicion. So now we're in the dark. Often. There's talk of nucleur power which is awesome.

I hate you Eskom.
 

Offline erickejah

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What are the usual causes of power cuts?
« Reply #23 on: 03/02/2009 22:53:17 »
wow! that must be great to avoid power consumption energy loss. What is the frequency in UK? is it 50Hz?

I observed that some coal plants have been close, why is that?
 

Offline LeeE

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What are the usual causes of power cuts?
« Reply #24 on: 04/02/2009 13:26:44 »
Yup, the UK frequency is 50Hz.

Lots of coal plants have been closed, mostly for economical reasons i.e. the price of coal, but it also looks good for environmental reasons too.  The pollutants from coal fueled power-stations could be recovered and prevented from reaching the atmosphere but that then effects the economics, reducing the profits.  We have quite a few mothballed coal mines around the UK and when the technological/economical climate is right I have little doubt that they'll be re-activated.
 

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What are the usual causes of power cuts?
« Reply #24 on: 04/02/2009 13:26:44 »

 

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