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Old 11th Nov 2018, 12:42 am   #201
Refugee
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Default Re: Electric clocks running slow warning

It is the answer to a potential question that may well get asked at any time.
Now we can just say go to post #199 for the answer.
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Old 22nd Nov 2018, 4:46 pm   #202
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   #203
broadgage
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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   #204
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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