[time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?
tmiller11147 at verizon.net
Sat Dec 31 14:57:04 EST 2016
----- Original Message -----
From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
<drkirkby at kirkbymicrowave.co.uk>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, December 31, 2016 11:01 AM
Subject: Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob
for the 5370B TI counter?
> On 31 December 2016 at 13:03, EB4APL <eb4apl at gmail.com> wrote:
>> 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
>> of test equipment failed when operated at around 250 V and many input
>> capacitors (particularly the ones inside a know brand IEC socket -
>> 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).
>> 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
> * There are 6 taps on the 11 kV transformers feeding my house to adjust
> voltage. Those can only be adjusted with the 11 kV off - they can't be
> 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
> 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.
There are some devices that benefit from the higher voltage. Motors usually
run cooler and last longer due to the lower I2R losses.
Maybe just use a buck transformer in your lab for the (older) test
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