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Old 22nd Nov 2018, 4:46 pm   #201
davidw87
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Default Re: Electric clocks running slow warning

I've analysed historic frequency data on the National Grid website, which gives a frequency reading every second, to work out the deviation in 'grid time' error over the last two years.

I found a blog where some horologists visited the NG Control Room and there's a photo of a screen showing the time error as being -4 seconds at 17:20 on 11/6/16.

Using Excel and the NG frequency data, I've compared how many seconds a clock actually 'counted' since then and the number of seconds it should have counted.

I've checked up to Jan '18 so far and the grid time error was as follows at these points:
mid-Sep '16: -67 seconds
mid-Dec '16: -76s
mid-Mar '17: -133s
mid-Jun '17: -205s
mid-Sep '17: -256s
mid-Dec '17: -224s

I was surprised at how 'out' it was and doubted my calculations, but the average frequency over the entire period is slightly below 50, implying the slowdown shown is correct. I note it starts to correct itself at the end of 2017.

Also, in Jun '17, I tweeted the NG control room and asked what their current grid time error was and they said -7 minutes! They said it was unusually high, but that doesn't tally with my calculations above. I wonder if they gave me the wrong reading.
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Old 24th Nov 2018, 12:28 am   #202
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Default Re: Electric clocks running slow warning

7 minutes does sound like a mistake, misunderstanding, or typo.
There is no generalised shortage of generating capacity in the UK at present.

Any short term problems caused by breakdowns should be easily recoverable by very slightly increasing the frequency afterwards.

Synchronous clocks are less used than in the past, but there still quite a few, and a loss of 7 minutes would be most noticeable.
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Old 26th Nov 2018, 12:12 pm   #203
davidw87
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Default Re: Electric clocks running slow warning

Quote:
Originally Posted by davidw87 View Post
I've checked up to Jan '18 so far and the grid time error was as follows at these points:
mid-Sep '16: -67 seconds
mid-Dec '16: -76s
mid-Mar '17: -133s
mid-Jun '17: -205s
mid-Sep '17: -256s
mid-Dec '17: -224s
I've now completed the checking up to 20 Nov:
mid-Mar '18: -430 seconds
mid-Jun '18: -480s
20 Nov '18: -436s

The substantial slow down between Dec '17 and Mar '18 reflects what posters said here about a slow down in early 2018! It means SEVEN minutes has been lost since 2016 and hasn't been made up.

The table below shows an extract of what I've done. There should be 1,000,000 seconds between each of the dates below. The column on the right shows how many seconds passed based on grid frequency.

This assumes 50.00Hz for 1 second = 1 second, so 49.9Hz for 1 second = 0.998 seconds.

Is my calculating correct?

2018-01-16 07:06:38 +0000 1000012.535
2018-01-27 20:53:18 +0000 999933.8653
2018-02-08 10:39:57 +0000 999952.185
2018-02-20 00:26:37 +0000 999973.1144
2018-03-03 14:13:16 +0000 999983.2907
2018-03-15 03:59:56 +0000 999998.2501
2018-03-26 18:46:36 +0100 999983.658
2018-04-07 08:33:15 +0100 999993.9784
2018-04-18 22:19:55 +0100 999991.3088
2018-04-30 12:06:35 +0100 1000018.474
2018-05-12 01:53:14 +0100 999966.2587
2018-05-23 15:39:54 +0100 1000003.64
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Old 6th Apr 2020, 7:54 pm   #204
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Default Re: Electric clocks running slow warning

My synchronous mains clock suddenly went 2 minutes slow on Sunday morning, no sign of it catching up yet.
Paul's link to http://www.gridwatch.templar.co.uk/ shows the real-time frequency, now up to ~50.1 but about 7pm it was something like 48.9. I thought the demand was at an all-time low during the shut-down of businesses and transport?
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Old 6th Apr 2020, 9:22 pm   #205
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Default Re: Electric clocks running slow warning

As regards frequency I reset both clock-radios when we moved to BST and haven't noticed anomalies yet (although i have only checked mains frequency using a hand-held a couple of times)
I am finding the voltage here to be very stable, and very correct, over the last two weeks.

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Old 6th Apr 2020, 9:28 pm   #206
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Default Re: Electric clocks running slow warning

Over the past couple of months I had been checking my mains electric clock against the pips preceding the 9.00AM news on Radio 4. The clock has varied from about 10 seconds fast to about 40 seconds slow, relative to when I started, but I have no absolute reference to calibrate the mains frequency time against. I haven't checked since adjusting for summertime.

Last edited by emeritus; 6th Apr 2020 at 9:34 pm.
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Old 6th Apr 2020, 9:34 pm   #207
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Default Re: Electric clocks running slow warning

Quote:
Originally Posted by Julesomega View Post
My synchronous mains clock suddenly went 2 minutes slow on Sunday morning, no sign of it catching up yet.
Paul's link to http://www.gridwatch.templar.co.uk/ shows the real-time frequency, now up to ~50.1 but about 7pm it was something like 48.9. I thought the demand was at an all-time low during the shut-down of businesses and transport?
There has been an unusual pattern of both demand and supply over the last couple of weeks, with very large amounts of wind and solar energy being generated. There were even news stories on Sunday of some people on special contracts receiving credits for their electricity use during the day. These are strange times for the Grid as well as the rest of us.
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Old 6th Apr 2020, 10:30 pm   #208
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Default Re: Electric clocks running slow warning

I have several synchronous clocks now, and I leave several of them (the ones in my radio shack) set to GMT, so I didn't pay a lot of attention to what time they were showing when I reset everything else a week ago. However I have now adjusted the two with sweep seconds hands to indicate the exact time, and will keep an eye on them as the days go by.

Sorry, that sounds as if I have nothing better to do than watch time passing, which is far from the truth...!
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Old 7th Apr 2020, 12:22 am   #209
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Default Re: Electric clocks running slow warning

According to this site the average frequency for the past 24 hours was 49.98Hz
http://mainsfrequency.uk/fm-last10m
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Old 7th Apr 2020, 12:59 am   #210
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Default Re: Electric clocks running slow warning

Thanks for posting the link to that frequency monitor I will do a comparison between my own frequency meter and it tomorrow, but the meter's behaviour looks the same as what I've observed before in terms of rate of change etc
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Old 7th Apr 2020, 8:33 am   #211
Phil G4SPZ
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Default Re: Electric clocks running slow warning

Yes, thanks Bill. As well as the real-time and historical displays, there's a lot of very interesting information on that website.
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Old 7th Apr 2020, 12:46 pm   #212
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Default Re: Electric clocks running slow warning

Quote:
Originally Posted by AC/HL View Post
According to this site the average frequency for the past 24 hours was 49.98Hz
http://mainsfrequency.uk/fm-last10m
Which means, over a 24-hour day, there were 4,318,272 cycles.

There should be 4,320,000. So that's 1,628 cycles missing. This would move the seconds hand by 32.56 seconds, so, half a minute slow ties up with the observations.
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Old 7th Apr 2020, 3:57 pm   #213
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Default Re: Electric clocks running slow warning

Guess I should use the time to make the effort to get my inverter telemetry back online since the server packed up ..... I suppose the mains frequency could be of interest to someone!
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Old 7th Apr 2020, 4:24 pm   #214
Phil G4SPZ
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Default Re: Electric clocks running slow warning

Two of my non-self starting synchronous clocks stopped simultaneously at just after 12.30 today, but another kept going, along with the kitchen appliance clocks. Around this time, the frequency had risen quite rapidly, but there's no obvious reason why two synchronous motors would have lost sync and stopped as a result.
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Old 7th Apr 2020, 5:41 pm   #215
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Default Re: Electric clocks running slow warning

We used to rely on the frequency for easy time keeping. Maybe it's time! to reconsider. The short term variability can only get worse as rotating mass is gradually replaced by renewables. Radio-controlled clocks are now commonplace.
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Old 7th Apr 2020, 6:07 pm   #216
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Default Re: Electric clocks running slow warning

My SunDial clock keeps perfect time. Its Solar powered, y'know.
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Old 7th Apr 2020, 8:42 pm   #217
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Default Re: Electric clocks running slow warning

It's pretty impressive, really, that a VCR-sized box can take any random voltage DC and convert it to AC precisely in step with whatever is already there, handling about ten or twenty times as much power through it as it could comfortably dissipate; yet "let go the rope at once if it sees nothing pulling on the other end" for the benefit of anybody working on the mains side.

I suppose it's basically an arbitrary function generator with a thwacking great class D amplifier tacked on the output, with the twist being that it determines what it's supposed to generate by sampling the existing waveform while the PWM output is off .....

I must see how mine handles a loss and reconnection of mains. (It's handled loss of DC every night and re-establishment every morning, so that's less interesting ) There are big, scary isolator switches -- black and white on the DC side, yellow and red on the AC side -- right next to it in the loft, so I could have a look one Lunchtime while it's got plenty of DC available!
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Old 7th Apr 2020, 9:42 pm   #218
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Default Re: Electric clocks running slow warning

Trickie Dickie, I would wager that if you go out and check it in the next couple of hours, it will be reading incorrectly!
I am afraid LUNAR time makes a solar device look silly. You should have a good clear but incorrect time if you check it.
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Old 7th Apr 2020, 10:26 pm   #219
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Default Re: Electric clocks running slow warning

I checked my meter against the one on the site and the two are exactly in sync which is good
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Old 8th Apr 2020, 12:14 am   #220
Phil G4SPZ
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Default Re: Electric clocks running slow warning

Quote:
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Radio-controlled clocks are now commonplace.
Agreed, but I have three of them and only one appears to stay in step with 'true time' all the time. The other two seem to drift randomly and re-synchronise every now and again. It's only a few seconds, granted, but seconds count when we're counting mains cycles.

I downloaded a free app for the smartphone (many are available) which provides a clear analogue display with sweep seconds hand, and that seems accurate.
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