31st Mar 2018, 9:05 am | #141 |
Hexode
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 471
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Re: Electric clocks running slow warning
Quite right it would seem.
There's me thinking our bedside Pure Tempus-1 is having an 'off-week' since it too, is around 2 minutes behind. How does that work? Surely current technol ... oh wait, yes, of course, DAB I could hook up a DAC90A to a timer I suppose, but we'd be no further forward, it too would end up coming on late ... A lot to be said for our Mantle clock, made Circa 1850-odd, seldom misses a beat (unless its been moved for dusting). I believe my new Fluke DMM can measure frequency, if I get chance, I'll measure the mains over the coming days. Mark |
31st Mar 2018, 9:07 am | #142 | |
Heptode
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Re: Electric clocks running slow warning
Quote:
At least most clocks don't use the mains as a reference any more.
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Stuart The golden age is always yesterday - Asa Briggs |
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31st Mar 2018, 9:25 am | #143 |
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Re: Electric clocks running slow warning
Holding the mains frequency at 50 c/s was more important to the generators when mechanical time clocks were used for setting off peak rates, any constant variation incurred a cost sending a guy eventually to reset the clocks.
Now that the timing is controlled electronically at the meter, it is not important to the retailing companies hence the frequency drift is not deliberately compensated for. The frequency only has to be maintained +/- 0.5 c/s. (going modern Hertz ) We are not tied to the continental supplies, the interconnecting cables are DC. |
31st Mar 2018, 10:37 am | #144 |
Dekatron
Join Date: Apr 2012
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Re: Electric clocks running slow warning
Surely in the case of the old economy7/white-meter thing, a degree of 'scatter' of the clocks would have been a good thing: you wouldn't want them all exact, or the sudden arrival on-load of millions of storage-heaters/immersion-heaters all precisely at the same time when night-rate began would be a significant perturbation to the grid.
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31st Mar 2018, 10:40 am | #145 |
Pentode
Join Date: Jul 2009
Location: Hucknall, Nottinghamshire, UK.
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Re: Electric clocks running slow warning
What an interesting thread, (Well it is to me) and thanks for all the info. Got some timers for lights but they only show approx time so can't tell if they're running slow, and I wouldn't be bothered as long as they were within a few minutes or so of correct time.
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31st Mar 2018, 10:52 am | #146 | |
Pentode
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Re: Electric clocks running slow warning
Quote:
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31st Mar 2018, 11:04 am | #147 | |
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Re: Electric clocks running slow warning
Quote:
The delay in the audible pips is because of delays and buffering in the codec. It's only a rough indicator with compressed digital systems (DAB, Freeview, satellite, internet etc) but shouldn't be more than a few seconds behind. |
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31st Mar 2018, 12:08 pm | #148 | |
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Re: Electric clocks running slow warning
Quote:
But it isn't engineering, it's <sound of thunder in distance> legal! Specific times are promised to users and are advertised. They had better be delivered within specification or the be-wigged hordes will scent money. It could be PPI all over again. The network has to be hardened against abrupt load changes. Kettle usage correlates strongly with football match broadcast half-time and ad breaks in Constipation Street. David
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31st Mar 2018, 12:11 pm | #149 |
Nonode
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Re: Electric clocks running slow warning
My counter says 50.0 Hz at the moment. I calibrated this against an Rb standard a few weeks go so I'm assuming it's right.
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31st Mar 2018, 12:18 pm | #150 |
Hexode
Join Date: Oct 2016
Location: Newport, South Wales, UK.
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Re: Electric clocks running slow warning
Anyone who doesn't have the means to measure the mains frequency can look at http://gridwatch.templar.co.uk . You can also download historical data for analysis if so inclined.
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31st Mar 2018, 12:36 pm | #151 |
Pentode
Join Date: Oct 2012
Location: Dorset, UK.
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Re: Electric clocks running slow warning
I've just come back from my parents' house, they have a 1990's LED alarm clock in the bedroom (definately synchronous), and a less than 1 year old Stoves oven with an LED clock on it. Both of these are 4 minutes slow. The bedroom clock has been changed to BST, though I suspect mother just went round by 1 hour rather than checked the time, the oven clock has not been changed. Although it could be coincidence, it does suggest that the oven clock does take its reference from the mains rather than a crystal, using the mains for timing is not just historical.
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31st Mar 2018, 12:45 pm | #152 | |
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Re: Electric clocks running slow warning
Quote:
I used to work for CEGB, and then PowerGen. |
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31st Mar 2018, 2:02 pm | #153 |
Pentode
Join Date: Oct 2012
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Re: Electric clocks running slow warning
The mains has been used for timekeeping since the inception of the national grid in 1930, and ever since, at least until the coming of the "quartz" clocks in the late 1970's, I would have thought that if the long standing commitment to long term stability had been dropped in favour of an allowable "drift", that a notice to clock and domestic appliance manufacturers would have been issued, perhaps several years in advance, to the effect of "the use of 50Hz mains for timekeeping will no longer be guaranteed after such and such a date", enabling manufaturers to move to a crystal based solution. I can't find anything resembling such a notice on the web, which makes me think that there is a problem rather than a deliberate policy. After all, an uncorrected 0.5% error is equal to 7 min/day, if I bought an appliance with a clock on it that gained or lost even a couple of minutes a day, it would go back as not fit for purpose!
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31st Mar 2018, 3:15 pm | #154 |
Dekatron
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Re: Electric clocks running slow warning
I get the impression that frequency stability used has become poor as the rotating mass of the generating system has been reduced due to wind and solar generation as both of these produce DC that is converted and applied in phase with the grid.
There are less conventional generators with heavy rotors to keep things stable. Gas power stations will have low mass rotors so that they can get from stand still to on line quickly. |
31st Mar 2018, 3:30 pm | #155 |
Hexode
Join Date: Oct 2016
Location: Newport, South Wales, UK.
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Re: Electric clocks running slow warning
I'd agree in the case of short term stability ie reacting to fluctuations in demand, changes in wind speed or the Sun going in and out. What used to happen was that after a day of high demand when the average frequency was below 50Hz they would keep it above 50Hz long enough so that 'cycles per day' was constant. That's what they don't seem to do any more.
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31st Mar 2018, 3:40 pm | #156 |
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Re: Electric clocks running slow warning
It's not so much the rotor mass of gas turbine power stations that makes them fast to get on line so much as it's the thermal mass of the boiler side of conventional coal/steam turbine plant which makes them slow. The moments of inertia of the respective sorts of turbines aren't anything like as different. There's also a difference between the time it takes to bring a plant up from cold and its 'throttle response' once it's running.
David
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31st Mar 2018, 3:42 pm | #157 |
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Re: Electric clocks running slow warning
I suppose we now have to accept that stable mains frequency was a luxury of the past, and maybe it's time now to knock up a few crystal-controlled motor drivers for record turntables.
David
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31st Mar 2018, 4:15 pm | #158 | |
Pentode
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Re: Electric clocks running slow warning
Quote:
You mean in those primitive days when engineering principles like merit order determined power generation? Or when new power stations were planned on a 7 year programme so that we could generate 20pc and more power than peak demand instead of paying industry a premium to switch off because don't have enough generating capacity? Or when I paid one vertically integrated company to generate, transmit and distribute power instead of funding the bureaucracy of more than a score of different transactions to get a kWhr from powerstation to plug? I'll stop for fear of drift. Under BETTA (2004) 'The Market' is the foundation of the electricity industry and the contract is the foundation of the market. Helpfully (?) the contractual conditions under which electricity is supplied are brought together in the national terms of connection: http://www.connectionterms.org.uk Page 434 of sn 2b sets conditions of supply: At all of the above voltages: the supply frequency will be 50 hertz, with a permitted nominal variation of plus or minus 1%. For reasons already discussed, the frequency cannot contractually be set absolutely. The alternative contractual condition to ensure accuracy over - say a year- would be to specify that 1,577,880,000 cycles would be supplied each 365 1/4 days. Adding this additional contractual obligation and accompanying measures for compliance, penalties and compensation might be possible, but not cheap. My choice of language in my previous post was poor. It missed the difference between the possibilities offered by engineering and the dynamics imposed by market economics. What I meant was that a consumer contractual obligation to supply an exact number of cycles per year would be contrary to the efficient, stable supply of power. A couple of open questions. -From the evidence of past practices, is the loss of a dependable average 50Hz another addition to the afore mentioned list of conditions which slowly disappeared with the arrival of BETTA and the market? -Was it ever stated, pre or post grid, (1930s), nationalisation (1940s) or privatisation (2000s) that 50Hz would be a reliable standard for timekeeping: did clock makers base their business on 50Hz +/- 1% or was the standard different? Or have I simply missed something in the grid code? ---------------- BETTA - British electricity trading and transmission arrangements - the regulations which established the current market trading arrangements for power. For those interested, the elexon site provides full historic and real time frequency data at : https://www.bmreports.com/bmrs/?q=de...lingsystemfreq Elexon also provides market reports, including prices, as well as real time and forecast system use by zone across GB, demand, European interconnector flows, solar generation estimates, wind, gas, nuclear supply etc. on a half hourly real time basis. |
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31st Mar 2018, 4:31 pm | #159 |
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Re: Electric clocks running slow warning
My understanding is that the accurate average 50Hz was never a legal requirement, but as back in those "primitive" days the supply system was run for the good of the country these little extras were provided as well as a reliable source of power. NG obviously managed to continue providing this service under the new regime of market forces for nearly 30 years, so it is strange that it has now been quietly dropped. Both the 'dropped' and the 'quietly' are strange, although the latter could be for political reasons.
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31st Mar 2018, 4:33 pm | #160 |
Hexode
Join Date: Oct 2016
Location: Newport, South Wales, UK.
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Re: Electric clocks running slow warning
But as Marteen from the Netherlands says above, the continental grid is currently 'catching up' having fallen several minutes behind. Is there a technical reason why they can do this but we can't or is it just UK policy not to?
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