On 30/04/2013 06:15, harry wrote:
On Apr 29, 11:46 pm, The Other Mike
wrote:

There was someone on another group in the past few months, maybe uk.railway? I
think the poster was possibly German, and they were claiming that on the German
grid, the system frequency during the loss of 1.5 - 2GW of generation (this
was a one trip, one site event) with a system loading of 50GW was about 0.05Hz.

Yes you read that right zero point zero five hertz. So that's a larger loss than
the Sizewell B Longannet incident of 2008 that resulted in a frequency of around
48.8Hz. No, I didn't believe it either!

Not got any measurements in Germany but the frequency moves about in Italy about
the same as the UK.

--

Frequency, load and efficiency are separate issues.


I've never understood why a load on the grid _must_ affect frequency.
(and yet it does...)

A generator is shoving out a certain amount of power into a load. If the
load increases (reduces its resistance) either the power goes up, or the
voltage comes down.

I can see why the easiest way for the voltage to come down is for the
generator to slow down. The coils aren't going through the fields as
fast, so you get less power consumed. In the case of the grid, where all
the generators are synchronously locked, if they all slow down then the
grid frequency drops.

But why can't you just control the current into the field coils to keep
the frequency spot on, and let the volts go up and down?

Andy