[time-nuts] Line Voltage - USA

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Wed Jan 4 08:41:43 EST 2017

On 4 January 2017 at 09:34, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

> --------
> >Do you have a reference to this +6%? I've heard from various sources that
> >the UK is 230 -6%/+10%.  If the EU dictates otherwise, then I'm certainly
> >over the 6% limit. I may or may not be over the 10% limit.
> There was a transitional range, but I belive it has expired.
> In 240V countries it was -6%/+10%.
> In 220V countries it was -10%/+6%
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20

I measured my voltage overnight in a peak hold at 255.10 V RMS as close to
the meter as I could. One of the phases goes via a 100 A switch to the
garage. I measured on the input of that switch. At 230+10% the maximum
permissible is 253 V, but mine went to 255.10 V. That was measured on a
Tektronix DMM916 (40,000 counter) meter, which has not been calibrated
since I bought it new about 20 years ago.

I spoke to a friend of mine who worked at the CEGB. He thought I might have
a tough time getting the electricity company to do anything about 2.1 V if
it was expensive for them to do.

I was going to report my findings today at


but having spoken to him, I think I'll monitor for a few more nights and
see if the problem gets worst than 2.1 V outside the specification.

The specification of the meter is +/- 0.7% + 4 counts, so measuring at 253
V (maximum permissible mains voltage), the meter specification is +/- 1.81
V, so there's no doubt that a measurement of 2.10 V above the maximum with
a meter that's not recently been calibrated, is a bit on the dubious side.

Perhaps I need something a bit more convincing before reporting this. I was
thinking of buying a Keysight handheld, but whilst some are cheap, anything
with a reasonable amount of functionality is quite expensive.


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