[time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sat Dec 31 11:01:02 EST 2016

On 31 December 2016 at 13:03, EB4APL <eb4apl at gmail.com> wrote:

> Hi,
> I'm not totally sure about the limits, but I have read several times that
> in the UK the nominal supply voltage is 230 V +10%/−6% to accommodate the
> fact that most supplies are in fact still 240 V. The context was that a lot
> of test equipment failed when operated at around 250 V and many input
> capacitors (particularly the ones inside a know brand IEC socket - filter)
> caught fire.
> Wikipedia says that several areas in UK still have 250 V because this
> value is withing the current limits.
> I think that the governing document is British Standard BS 7697: Nominal
> voltages for low voltage public electricity supply systems —
> (Implementation of HD 472 S1).
> Regards,
> Ignacio, EB4APL

I have just been on to the phone of a friend of mine who spent much of his
like working in the electricity generating industry. Working at both
Darlington (coal) and Bradwell (nuclear) power stations in the UK. Among
many other things he said

* He did not know the current specifications limits for certain, but he
said easy to check. (What you say - 230 -6%/+10% does seem to be quoted in
many places, but I guess I should check it out.)
* Supply voltage is likely to be highest about at 2-3 am in Summer
* Supply voltage is likely to be lowest on a cold Winter's afternoon.
* Voltages in use around the county include at the least 11, 22, 33, 66,
132, 275 and 400 kV.
* There's not much standardization of generator voltage - Bradwell nuclear
power station was 11.1 kV.
* There are taps on the 275 kV transformers to keep the 132 kV close to 132
* There are 6 taps on the 11 kV transformers feeding my house to adjust the
voltage. Those can only be adjusted with the 11 kV off - they can't be done
with it online. Essentially this means to change the taps, an area would
need to be powered off.
* If voltage is out of spec, it should be possible to get something done
about it.
* The electricity board can install monitor equipment.
* Since I am right by the 11 kV transformer, and other places further away,
dropping the voltage at my place might put other places too low.

I think short-term I will put the auto transformer in line. I will monitor
the mains, and report it in the summer, when I'm told it is likely to go

It hit 250.04 V in the last hour or so, but I have not seen the magic
figure of 253 V.

I'll get my 3457A calibrated by Keysight, then look to measure this and if
appropriate make a formal request to have the voltage checked, and
hopefully the problems would occur during the time it was monitored.


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