Finally got my acquired (from office closure) UPS working under Linux, and it's showing :
UPS Model:Not supported Status: ONLINE UPS temp:25.0 °C Battery:13.50 V Input: 245.0 V
49.9 Hz Output: 244.5 V
with a loading of 13% (one PC, 3 USB drives)
is it me or is 245 quite high for a UK reading, I thought we had reduced to 220 ?
From my vague recollection of a visit to CEGBs London operations, the closer the frequency is to 50Hz, the better the grid is coping with demand. But I can't remember how much they let it drift ....
No, we haven't lowered the voltage in the UK (although that may have happened in places), we've just renamed it! Europe's voltage is "standardised" on 230V. Other countries will have stayed on 220V, etc. The idea is simply that equipment should be suitable for 230V + or - a percentage and that will be okay at the low end of 220V supplies and the high end of 240V supplies - simply so that different equipment isn't required in different countries throughout Europe.
Remember - "they" did not reduce the voltage, "they" declared our nominal voltage to be lower whilst upping the tolerances.
Because manufacturers work to the nominal but allow for the tolerances it mostly works well enough, except for things like filament lamps that tend to blow faster than they used to when they were designed for our *actual* nominal voltage.
"UK nominal supply voltage to 230V with a permitted voltage tolerance of
+10% -6%. In practice it's still 240V, but is allowed to vary by a greater percentage."
and
"National Grid has a licence obligation to control frequency within the limits specified in the 'Electricity Supply Regulations', i.e. ±1% of nominal system frequency (50.00Hz) save in abnormal or exceptional circumstances."
I have a vague memory of them asking permission to make a time adjustment after the Sizewell B/Longannet incident, though with most of the generation still running I can't see the real need, prehaps they didn't in the end.
We didn't do anything. We always provided 240V in the UK
Parts of Europe always provided 220V or 230V.
We have standardised on 230V +10% -6%
Nothing actually changed, it just means that anything from 216.2V to 253V is within tolerance. We carry on supplying 240V and other countries carry on supplying 220V/230V. I have seen up to 252V on my supply (as reported by a UPS) before.
I live in at the end of a cul-de-sac in a small country village.
Until a year or two ago, whenever I had occasion to measure my mains voltage, it was obviously meant to be a nominal 240V. In fact, I recall that 242V was pretty typical reading, with somewhat over 250V being reached on various occasions.
However, a year ago, an old works colleague died, and I acquired some of his electronic bits and pieces - one of which was a home-made purpose-built meter for measuring the mains voltage (the display being a large 1mA meter in a box - ie simple, but effective). I checked the calibration against a couple of 'professional' digital multimeters, and made sure that the reading was 'spot-on' at around 230V.
Since then, I have had it connected most of the time, and it seems obvious that the nominal voltage is now 230V. During last winter's cold spell, it did drop to 214V, but it is rarely below 225V - and I can recall seeing it above 231-ishV. All I can think is that the sub-station transformer has various output taps, and at some time, it has been changed from 240V to 230V.
Is this likely to be an unusual situation, or will it be normal practice to drop the voltage when an opportunity arises (say, during maintenance visits etc)?
IIRC, most, if not all, substations have either remote controlled or automatic tap changing, so if the voltage gets near the end of the acceptable range at the substation, it can be adjusted. If you're close to the substation, you should get pretty good stability, but if you're at the wrong end of a longish line, then your voltage will vary according to what you and the neighboours have got turned on at the time.
It has also been known for the voltage to be reduced under conditions of heavy demand to help reduce the load.
Of course, the "can" in "I can recall seeing it above 231-ishV" should have been "can't".
But if the domestic voltage can be easily change to 230V (which mine now seems to be), is this likely to be a general policy (even if it's on a 'when we get around to it' basis)? Mine has certainly changed, and I'm pretty sure that it's not because of additional local loading. The actual voltage is actually pretty stable - rarely falling below 225V, and I've never seen it above 231V - which I don't think would be the case if unexpected heavy loading was happening.
It is. They constantly have a display of real time derived from the NPL transmitter at Anthorn in Cumbria and system time driven by the mains, and a display of the difference (in minutes and seconds)
You're using "nominal" wrong. Nominal is what it is named/declared to be, not what it actually is. The nominal voltage is 230v-6%+10%. What you have been measuring is the measured voltage.
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