Accuracy of UK power grid time control?

You did not tell us what the drive mechanism is. If it was similar to the Simplex/IBM master clocks of the time it most likely advanced every minute by a pulse to an electromagnet.
Now there are several ways you could generate that. A Small timer motor with a cam like a washing machine timer. Or an Electronic cct synched by the mains.
If it is for your bedroom you may not want it after the first few hours as the electromagnet noise will drive you bonkers.
Reply to
John G
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Depends where you are, I used to have outages a couple times a year, now the house I'm in I've had exactly one outage in almost 2 years and it was a pretty good storm that went through.
Aside from that though in both the US and UK the mains frequency has excellent long term stability. It may gain or lose a few seconds over the course of the day but it will be dead on over weeks/months.
Reply to
James Sweet
Jack Denver schrieb:
Great idea! In order to save the odd $40 for a quartz oscillator (read the OP!), you spend at least $100 on a UPS device. :-)
SCNR and best regards, OP
Reply to
Olaf Peuss
I did but you probably missed it in my second post. It's a stepper motor, as I believe is common on many slave dials made in continental Europe, but relatively uncommon in the UK.
The noise is almost all produced by a ratchet which prevents reverse rotation of the rotor. It isn't quite as disturbing as the "clunk-click" of the Gent mechanisms - it's more of a muffled "kerthunk".
Chris
Reply to
Christopher Tidy
Some future use for the dips in mains frequency use to reduce National Grid load
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starting at heading Dynamic Demand Appliances Bill [HL]
" Dynamic demand appliances contain a low-cost electronic microcontroller. This listens to the mains hum, which runs at a frequency of around 50 hertz. The signal can be detected through every plug socket connected to the national electricity supply. Through this signal, the dynamic demand appliances can sense whether the National Grid is under stress and adjust the time at which they use electricity. The technology is suitable for appliances that already switch on and off during the day on a "duty cycle", such as domestic and industrial fridges, freezers and water heaters.
Millions of such appliances acting together would smooth out demand for electricity. " -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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Reply to
n cook
My cheap and nasty Casio digital watch seems to have lost 2 minutes after I left it first in my old car, and then in my old car in the shed. Neither place was particularly warm...
Reply to
Doki
In message , n cook writes
Have a look here - an on-line frequency monitor.
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The rest of the website covers the topic of dynamic demand control which is quite interesting (well it is if you work, as I do, for the company that owns 70% of Dinorwig).
Andy
Reply to
Andrew Sinclair
You can download more information than you ever wanted to know about the National Grid from here:
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I've pasted two relevant snippets below (NGET stands for National Grid Electricity Transmission plc).
1. From the definitions:
Target Frequency ---------------- That Frequency determined by NGET, in its reasonable opinion, as the desired operating Frequency of the Total System. This will normally be 50.00Hz plus or minus 0.05Hz, except in exceptional circumstances as determined by NGET, in its reasonable opinion when this may be 49.90 or 50.10Hz. An example of exceptional circumstances may be difficulties caused in operating the System during disputes affecting fuel supplies.
2. From document BC3, which deals with the frequency control process:
BC3.4.3 Electric Time --------------------- NGET will endeavour (in so far as it is able) to control electric clock time to within plus or minus 10 seconds by specifying changes to Target Frequency, by accepting bids and offers in the Balancing Mechanism. Errors greater than plus or minus 10 seconds may be temporarily accepted at NGET's reasonable discretion.
All very well, but ISTM that the biggest problem with using the mains alone as a time standard is power cuts, after which you'll always need some absolute standard such as MSF, GTS, NTP, etc. to reset your clock.
Reply to
Andy Wade
microcontroller.
What a swiz, I wanted to see what the real time meter would do at 19.15 tonight
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Dr Who returns
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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Reply to
n cook
The traditional approach assuming the outages were brief, was to use a cheap oscillator (an astable mutivibrator) running from a back up battery when the mains feed was down.
DG
Reply to
Derek ^
In message , n cook writes
Wouldn't see any difference. The TARDIS has an internal power supply and is not reliant on a connection to the National Grid.
Whilst it doesn't cover frequency, this site;
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covers system demand (takes a few seconds usually for the graphs to load) and other commercial parameters, today capped out at just over 38 GW demand.
Cheers,
Andy
Reply to
Andrew Sinclair
Thanks very much for those useful snippets, Andy. When it refers to a 10 second error in electric time, do you know if it refers to a 10 second error from the true time at any instant (assuming that the sychronous clocks were set to the correct time at an instant when the electric time was correct), or a 10 second cumulative error week on week, month on month, etc.? It isn't immediately clear to me. You're also right to point out that you need some kind of absolute time standard if you care about that sort of accuracy. I don't: all I'm interested in is whether the grid is accurate enough to make this rather cool clock keep time for day-to-day purposes, and it seems that the consensus is that it will be fine.
Best wishes,
Chris
Reply to
Christopher Tidy
IIRC it is actually 100% spot on in the long term.
However it tends to go plus minus several seconds during the day as peak loads tend to slow the generators..they then overrun a bit in the off peak hours to catch up.
BUT as a matte of standard and poossibly even law, they always do get it right over the long period.
Reply to
The Natural Philosopher
All wrong.
Clocks essentially filter out all the trash, the long term accuracy is guaranteed by the generating companies, and the one thing that gets you is really power outages only.
But that was teh one thing you don't mention.
Reply to
The Natural Philosopher
On big tower clocks (which often had difficult access for adjustment) one standard solution was to make all power cuts last a multiple of 12 hours exactly, either manually or with a battery-powered crystal oscillator.
Reply to
Tony Williams
Any connection with the tradition/obligation ? that any broken civic clocks should have their hands set to 12.00 ?
Seriously aside, is there any problem for civic clocks in seriously leaning towers? One near me , if picture outside of a file is downloadable here
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my assistant holding a plumbob to show the lean or otherwise part down on
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-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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Reply to
n cook
I assumed it means the former, i.e. ±10 s 'absolute' error, but "electric time" is not defined in the extensive definitions/glossary section, nor do the strings "electric time" or "electric clock" appear anywhere else in the complete Grid Code document (546 page PDF!). For your latter interpretation they'd have to specify the accumulation period, and I can't see any such specification.
Reply to
Andy Wade
Yes, that's why I was careful to say "the biggest problem with using the mains alone ..."
Cheap clock radios are the only things I've seen that have used crude RC oscillators to cover mains outages, and their timekeeping is utter crap - 5 min error in half an hour!
Reply to
Andy Wade

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