In article ,
"Andrew Mawson" writes:
Chris,

OK it's going back a few years, but when the CEGB had their National
Grid Control Centre at Park ST London SE1 the number of cycles per day
was very accurately ensured to be correct (A pair of Ferranti Argus
500 Process Control computers each had an ultra accurate crystal
clocks in them feeding displays in the control room) and the Control
Enginners could let the frequency drift a tad hour by hour but had to
get it right over 24. They dispersed the control to various regional
centres (Winnersh, St Albans and three others I cannot remember but I
think that the principle remains the same.

I'm out of touch now, but CEGB used to keep UK power grid at
50Hz +- 0.1Hz. No one ever came up with a good reason it had
to be that accurate, but they did it "just because they
could", to quote someone I spoke with at the Winnersh control
room about this some years back.

I wrote a more detailed article about this a few years ago,
which discusses various notable historic events, like how the
power grid had to handle the majority of the UK using the toilet
at the same instant, which resulted in the largest ever surge in
demand on the UK power grid (which with advanced planning, it
handled just fine)...
http://groups.google.com/group/sci.e...1a4f753?hl=en&

--
Andrew Gabriel