The Wanderer wrote:
On Tue, 8 Mar 2011 10:27:33 +0000, Ian Jackson wrote:


Before Christmas, the typical 'normal' voltage was 230V, occasionally
going up to 235. However, when the really cold weather started, after
around 5pm, the voltage would start to drop and, on several days,
regularly fell to 215V. The lowest (checked on a couple of digital
meters) was 214.4V.

Routine load shedding, it's been happening for decades. 5% then 10% load
shed, acheived by a voltage reduction, I'll let you work out the percentage
reduction in voltage to get the reduction in load.

After that it's rota disconnection as happened in the 1970s.


Yep. Think of the grid as a huge generators to which lots of little
engines are geared. As demand goes up the voltage and frequency start to
fall..the whole contraption is 'climbing a hill'

Throttles are opened on all the engines online, and new ones are geared
to it to help a bit. Meanwhile the word goes out for anyone who can do
without the grid to get off it, and if anyone has any backup power units
spare, could they please start them..


If the whole shebang cant make it over the top, then passengers are
thrown out till it can.

You will get far more familiar with this as more silly wind power is
added to the grid.