Dave Liquorice wrote:
On Mon, 12 Oct 2009 14:47:36 +0100, Dave Osborne wrote:

You will find in practice that most people in the UK get more than 240V.
Here, I am about 80m of cable away from the substation and (at 2.30 p.m.
in the afternoon on a sunny day) have a voltage of 248V (I just measured
it). I expect that later on (about 9.00 p.m.) when it's dark and much
colder, the voltage will drop to 245V or so.

It might but here the volts drop during the working day when the load
is really on the grid. We have our own transformer and about 15m of
240v cable to the meters. From about midnight the volts are up and
pretty steady just under 240, then come 0600 they start to fall
reaching a minimum about 0800 of 230ish. The rest of the day then
generally bounces about with an upward trend back to 240v by
midnight. The weekends have less variation.

http://www.flickr.com/photos/allsorts-60/4004361303/ - Thu 1st Oct
2009
http://www.flickr.com/photos/allsorts-60/4004361301/ - Sun 4th Oct
2009

The stepping is due to the 2v or so resolution(*) of the APC Smart
UPS that is providing the data I'm logging.

(*) WTF it reports to one decimal place when it only ever reports
discreet 2v or so steps is beyond me. This gives a very false
impression of the voltage measurement accuracy.


OK, Thanks for that. Do you measure the voltage at the point of your
supply or somewhere along a final circuit? Does the load on the final
circuit cable have a significant effect on the measured voltage or does
the voltage vary this much at the point of supply?

I work from home and live in a moderate sized commuter town with a small
light-industrial estate. Max demand is winter TV prime-time when the
adverts come on and the kettle gets put on!

Anyway, if you have a shower at work, you would get a better shower if
you get in early...