On Fri, 14 Apr 2006 16:50:40 GMT, raden wrote:

In message , Christopher Tidy
writes
Hi all,

I'm thinking of building an electronic clock control circuit which uses
the 50 Hz mains frequency for time keeping. The reason for this is that
the clock dial is rather large, so probably wouldn't run for long on
battery power, and I don't fancy spending £40 buying a programmable
quartz oscillator chip.


From my point of view I'd regard an acceptable error as 5 minutes every
6 months. Does anyone know the typical time error seen on the UK grid,
or where I might find this information? Any suggestions would be much
appreciated.

There won't be any cumulative errors.


It has to be significantly more accurate than that

Power stations have to be in sync with one another - which requires good
accuracy and stability

True they have to be phased up to the grid exactly before they connect
to it, or *BANG* turbine blades through the turbine hall roof. I've
been to a power station where it had happened. If they connect
successfully then they'll stay in sync.

The exact frequency is not overly critical but is kept as accurate as
possible for the benefit of users who depend on the frequency being
accurate, steelmills rolling steel for instance.

FWIR the control console at "Grid Control Centres" used to have a
standard synchronous electric clock showing grid time, and a clock
showing exact GMT (How ??, unless exact 50Hz was distributed about the
country) . It was normal for "grid time" to lose a bit during the day,
depending on load, and then make up for it overnight.

Quite a manual process in 1969. ;-)

It must be better now !

DG