On Thu, 28 Mar 2013 22:27:49 +0000, The Natural Philosopher wrote:

If 10% dropped off without warning I suspect we'd be into black start
mode. Wind, though variable, doesn't go from 5 GW to 0 GW instantly.

No we wouldn't. Dinorwig can push 2GW into the grid for long enough to
get CCGT up and running,

10% of demand is about double that... Dinorwic couldn't hold the
frequency up on it's own and the automatic frequency trips would activate
knocking even more capacity off the grid and you end up in a cascade to
black, or isolated islands, *very* rapidly.

Remember this is losing 10% without warning, the first thing you'd know
would be alarm(s) that station(s) X, (Y, Z) have dropped off line,
followed very rapidly by low frequency trips as the automatics try to
protect the grid.

Dinorwic can come online flat out in 11 seconds or so, if it's spinning
and synchonised. If it's not it's over a minute that's far to long once
the grid frequency starts to drop.

It was the low frequency trips that gave the blackouts when Longannet and
Sizewell B decided they didn't want to play anymore.

and that's not all there is, hydro wise - there's at least 600MW of
diesel out there somewhere buried under hospitals, telephone exchanges
and data centers, and there is at least another 500MW that you can tell
certain customers to 'shut down' . low voltage can shed a few more
hundred MW as well.

Yes, there is plenty of capacity buried away but not much that is
*instantly* available. It's the first few seconds that are critical, once
the automatics have stopped tripping you can then look at the mess you
have left. What is still connected to what, which stations are still
online, which can be bought back quickly, which will need a day or to to
"reset" having had to emergency vent their boilers and dump the fires.

I'd say that losing 5GW off the grid suddenly is just about capable of
being absorbed at a pinch., 3GW certainly.

1.5 GW gave it quite a head ache for quite a while.

The arguments is not - despite your attempts to make it so - about
ability to cope with occasional transients. Its about the cost of
dealing with constant massive transients day in and day out -
especially with solar. Its not that it cant be done, its the horrendous
COST in doing it.

I agree that the costs of have dual capacity for wind/solar is stupid
what I'm picking up on is the last part of: "Any other event that takes
out more than one power station unexpectdely is likely to be massive
enough so that the loss of 10% of our supply will be the least of our
worries."

The only worry when two power stations went unexpectdely, with the loss
of much less than 10%, was "will the grid stay up".

--
Cheers
Dave.

On 29/03/13 11:33, Huge wrote:
On 2013-03-28, Dave Liquorice wrote:

Dinorwic can come online flat out in 11 seconds or so, if it's spinning
and synchonised.

They keep one (of 4, IIRC) turbine spinning and synchronised all the time.

(Brilliant tour on a wet day in Wales, BTW.)

+1

--
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