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Old 8th Mar 2018, 4:47 pm   #61
Boom
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Default Re: Electric clocks running slow warning

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God invented time to prevent everything happening at once!
Who was it that said that?
https://en.wikiquote.org/wiki/John_Archibald_Wheeler
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Old 8th Mar 2018, 9:32 pm   #62
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Default Re: Electric clocks running slow warning

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Mains clock 3 minutes slow, I wonder if they will insert cycles to correct it when the load goes down?
Same thing happened last year. My electric clocks 'lost' about 2 minutes, but eventually caught up again. See this thread: https://www.vintage-radio.net/forum/...d.php?p=952189

At that time, there wasn't any severe weather, as far as I can remember. Now my synchronous clocks have gone slow by about 2.5 minutes. I think this started happening just before the big freeze and snowstorms, so perhaps the weather isn't the only contributing factor.

I'm hoping the clocks will be corrected like they were last year. My nixie tube clock lost power altogether last week, so I've had to reset it. It's been fairly stable since then and is now showing the correct time. That means it might end up being too fast, but I'll have to reset it again at the end of March anyway so it doesn't matter much at the moment.
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Old 8th Mar 2018, 11:19 pm   #63
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Default Re: Electric clocks running slow warning

There is a clock specialist in the USA that sells low power mains inverters about 6W capable as I recall, with a crystal as the time base. They are used to power mains synchronous clocks so they are accurate, as the mains frequency, increasingly is not. A small inverter like this not difficult to make, most vintage motor operated synchronous clocks consume 3W or less, sometimes more if they have a dial lamp.
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Old 9th Mar 2018, 9:40 am   #64
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Default Re: Electric clocks running slow warning

Forgive my ignorance, but.. what's the problem? Electric clocks are not meant to be accurate. I've never had an electric clock that didn't need to be adjusted at least once a month.

The only accurate clocks I know are either mechanical clocks or Internet connected ones.
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Old 9th Mar 2018, 9:52 am   #65
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Default Re: Electric clocks running slow warning

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Forgive my ignorance, but.. what's the problem? Electric clocks are not meant to be accurate.
They were (are still?) meant to be accurate over a 24Hr period. Indeed, power station control boards had a special clock comparing a radio-derived time signal with the time determined by the mains frequency.

Any lag during peak loading was meant to be compensated for during light loading. But, as has been pointed out, the generating system is not what it once was with the likes of wind turbine contribution; solar; feed-in, etc... It may be when the latest generation of 'peaker' plants gets going to fill in the shortfall the accuracy will improve.
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Old 9th Mar 2018, 10:31 am   #66
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Default Re: Electric clocks running slow warning

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Originally Posted by ottavio View Post
Forgive my ignorance, but.. what's the problem? Electric clocks are not meant to be accurate. I've never had an electric clock that didn't need to be adjusted at least once a month.

The only accurate clocks I know are either mechanical clocks or Internet connected ones.
Your electric clock that needed monthly adjustment was either not a mains synchronous one or was faulty. Typically, the instantaneous time discrepancy should not be more than 30 seconds. Medium term error over a few days should be zero. The whole electric clock industry from the 30s to the 60s was built around this fact, notably the huge range of Smiths 'Sectric' clocks. ISTR that among the multitude of instruments in a power station control room was always a mains synchronous clock to provide confirmation of long-term grid frequency.

The most accurate readily available clocks nowadays are radio-controlled. I have two sitting in front of me here: one receiving MSF 'Rugby' 60kHz (now at Anthorn) and the other its German equivalent DCF77, 77.5 kHz, near Frankfurt. Unsurprisingly, both read exactly the same time to the second. The Smiths synchronous clock on the wall on the other hand currently lags by approx 1 min 30 seconds, whereas it was pretty well correct in January.

Something has deteriorated in the long-term grid frequency stability system and it would be interesting to get the facts.

Martin
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Old 9th Mar 2018, 10:44 am   #67
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Default Re: Electric clocks running slow warning

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Originally Posted by ottavio View Post
Forgive my ignorance, but.. what's the problem? Electric clocks are not meant to be accurate. I've never had an electric clock that didn't need to be adjusted at least once a month.
Something wrong there, I think. I have a house full of them, all ancient (several from the very early 1930s) but recently serviced. They are (usually) never more than 1/2 minute wrong, and the long-term accuracy has been perfect. They can run for years and years and still be correct to within a few seconds.

I used to rely on mine unquestioningly for all those things that have to be done on-time (catching the bus into town, school pick-up etc.) but now there's an annoying discrepancy between real time and what's displayed.

EDIT: crossed with Martin.
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Old 9th Mar 2018, 11:03 am   #68
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Default Re: Electric clocks running slow warning

“Time is an illusion. Lunchtime doubly so.”

(Douglas Adams, The Hitch-hiker's Guide to the Galaxy)
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Old 9th Mar 2018, 12:23 pm   #69
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Default Re: Electric clocks running slow warning

I get the impression that solar and wind stations do not help with frequency correction.
They have a 10Khz inverter that may well be able to correct for rectifier loads to some extent but I doubt they will be able to help with frequency as they will just track and synch with what is present at the the point where they are connected to the grid.
Technology is advancing quickly mainly with the power per area of panels.
This can sometimes conflict with the time it takes to get planning permission.
We locally have had an installation go in where the original panels were NLA so they just substituted ones that looked externally the same.
When the sun finally came out the 11KV drop cable blew up leaving a carbon footprint on the pole.
Most solar installations are owned by private companies and there is not yet a standard for frequency correction signals to be sent to them.
If you stand close to a field of solar panels the green boxes sound like giant 405 line TV sets.
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Old 9th Mar 2018, 12:40 pm   #70
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Default Re: Electric clocks running slow warning

Power stations which are able to modulate (and have owners willing to modulate) are sent a frequency setpoint from grid control. They then adjust their output accordingly, using an agreed slope. Everyone else just generates whatever power they want to or have been asked to. All generators generate exactly the same frequency.
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Old 9th Mar 2018, 1:17 pm   #71
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Default Re: Electric clocks running slow warning

An academic paper on 'Impacts of Power Grid Frequency Deviation on Time Error of Synchronous Electric Clock and Worldwide Power System Practices on Time Error Correction' published by

http://www.mdpi.com/1996-1073/10/9/1283/pdf

Based on data from sensors all over the world gathered in 2016, the authors found that Time Error Correction is practised in North America, Western Europe (including the UK), Japan and Australia but not most other countries monitored.

I have found nothing in National Grid documentation available online so perhaps it has been quietly dropped here? I don't know.
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Old 9th Mar 2018, 1:56 pm   #72
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Default Re: Electric clocks running slow warning

Sad if it has, but can anyone think of any modern equipment where lack of long-term mains frequency stability is of any consequence?
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Old 9th Mar 2018, 2:10 pm   #73
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Default Re: Electric clocks running slow warning

This sort of thing regularly happened in the '50's but I seem to remember that they slightly increased the frequency when the load was off in order to maintain the accuracy of synchronous clocks and timers.

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Old 9th Mar 2018, 2:15 pm   #74
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Default Re: Electric clocks running slow warning

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Originally Posted by Nickthedentist View Post
Sad if it has, but can anyone think of any modern equipment where lack of long-term mains frequency stability is of any consequence?
Mains clock radios (and other mains equipment with clocks) traditionally used the mains frequency as a reference. I don't know if this is still the case or if they all use quartz now.

For some reason VCRs and other video recorders have never used synchronous clocks.
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Old 9th Mar 2018, 3:36 pm   #75
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Default Re: Electric clocks running slow warning

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Quote:
Originally Posted by Andrew2 View Post
God invented time to prevent everything happening at once!
Who was it that said that?
https://en.wikiquote.org/wiki/John_Archibald_Wheeler
Ha, thanks. And I believe it was George Bernard Shaw who came up with 'The English are not a spiritual race, so they invented cricket to give them some idea of eternity.'

That's only roughly remembered, I haven't looked it up.
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Old 9th Mar 2018, 3:38 pm   #76
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Default Re: Electric clocks running slow warning

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Originally Posted by paulsherwin View Post
Mains clock radios (and other mains equipment with clocks) traditionally used the mains frequency as a reference. I don't know if this is still the case or if they all use quartz now.

For some reason VCRs and other video recorders have never used synchronous clocks.
Probably because they were expensive enough and enough people wanted to play NTSC tapes in PAL land and vice versa that many were exported and run on transformers to make it worth the couple of bob extra for a quartz clock to avoid the bother of complaints?
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Old 9th Mar 2018, 3:55 pm   #77
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Default Re: Electric clocks running slow warning

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Originally Posted by Nickthedentist View Post
Sad if it has, but can anyone think of any modern equipment where lack of long-term mains frequency stability is of any consequence?
Only time switches which are clocks of a sort. A short term error of a minute or two is of little consequence, but a cumulative error of some minutes a year could be significant.

Far less reliance is placed on mains frequency these days due to the amount of international trade.
A clock radio for example might be sold worldwide, and therefore must work accurately even in countries with poor frequency control. Cheaper to make them all with quartz based timekeeping rather than different versions for different markets.

Until recently, low frequency was a serious matter for large factories and even for the nation as a whole.
Frequency 0.5% low meant that production was slowed by about that amount, but wages, rates, interest on invested capital, insurance and many other costs remained unaltered. This could have a measurable affect on profit.
These days we have less manufacturing, and what we do have tends to use variable speed drives set to the needs of the process, and not locked to line frequency.
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Old 9th Mar 2018, 4:15 pm   #78
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Default Re: Electric clocks running slow warning

My clock radio (Philips, about 12 years old) has battery back-up, but the timekeeping is appalling! Whereas on mains, it's excellent. So I deduce that mains frequency is used normally, and if mains dies a simple RC relaxation oscillator is used as a clock reference.
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Old 9th Mar 2018, 4:46 pm   #79
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Default Re: Electric clocks running slow warning

The only mains-frequency-dependent clock I have here is the central-heating programmer: and as I noted in another thread recently I don't actually use it.

The computers, routers, switches and the CCTV recorder use NTP to sync to a Stratum-1 time server.
20-year-old Sony bedside clock-radio uses RDS-time, as does the Sony radio/CD in the car.
Kitchen clock [old-style one with hands] is quartz-controlled and only needs setting every year when I replace its AA battery.
Shack clock is DCF-locked; my indoor/outdoor weather-station likewise.
My phone either picks up its time from the network or uses GPS-derived time.

Several times a year I have to run the house from a generator. They're not famous for their frequency-accuracy! Not depending on mains frequency makes life so much easier.
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Old 9th Mar 2018, 5:24 pm   #80
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Default Re: Electric clocks running slow warning

It seems from ‘phone calls from some of my customers with Economy 7 heating, that the National Grid has been altering some of the timings controlling the Radio Teleswitches too. I’m guessing this has been done to load shed / shift.

I think it’s all back to normal now.


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