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Frequency Deviations In Continental Europe Are Causing Electric Clocks To Run Behind By 5 Minutes (entsoe.eu)
elgatozorbas shares a short note from the European Network of Transmission System Operators for Electricity (ENTSO-E): Apparently the Continental European Power System has been off since mid-January, causing some clocks to run behind by 5 minutes. How common are these mains-frequency synchronized clocks anyway, and why are they built that way? "The power deviations have led to a slight drop in the electric frequency," reports ENTSO-E. "This in turn has also affected those electric clocks that are steered by the frequency of the power system and not by a quartz crystal... All actions are taken by the transmission system operators (TSOs) of Continental Europe and by ENTSO-E to resolve the situation."
Many phono turntable motors also sync with the mains frequency. I think all the good turntables allow you some speed adjustment but this would still be troublesome.
It was also extremely accurate, when the electric company bothers to compensate for drift. In my experience all these quartz china clocks run fast, some a few seconds and others gain a whole minute a week. It's like having a different time zone in every room (:
Also they have been around since well before crystal oscillator based clocks were economically viable for consumer use. Power companies would tune the frequency to keep them within several seconds. This is going back 50, maybe 60 or more, years. They had an advantage over crystal based clocks in that long term drift was eliminated by the tuning.
Potentially more people than have a 20-year-old clock, the way things are built now.
I actually have a beautiful clock more than 50 years old - it amazed me as a kid: a motor turned a glass plate and the hands, suspended in the middle, had a counterweight that made them appear to keep time while floating.
Mains frequency is normally very stable long term.
Have a look here http://jorisvr.nl/article/grid...
I would say, because of all the new renewable energy providers, it has been a much more difficult job to synchronize every body.
Imagine you have a 10 ton flywheel in front of you and it is rotating at 49.9 times per second but you want it to be 50, and there are 300 little motors all driving the flywheel. Your job is to now coordinate everybody to match 50Hz, but where the load on the flywheel varies minute to minute. In the old days, big old power stations could slowly influence this average frequency, but now there are hundreds of windmills and solar inverters and gas turbines and nuclear and coal, all with their unique issues.
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I had a digital alarm clock given to me when I was 5 years old (1978). I had it until I was ~24. It kept absolutely perfect time from 1978 until 1992, when I went off to college. Iowa State University has its own power grid and power plant. The two years I lived in the dorms on-campus, my alarm clock gained 5 minutes PER WEEK. (Yes, PER WEEK.) I got in the habit of setting it back five minutes every Sunday. I wore out the minute-advance button in those two years, fixed it a couple of times with a soldering iron. 1994 I moved off-campus and got an apartment, and boom, clock worked perfectly again, only set it twice a year for daylight savings. I asked around the engineering department and several people said, yea, ISU's power plant doesn't sync to the city's grid. I've taken apart a lot of things in my life. I've seen tons and tons of clocks' innards. Many of the mechanical ones have synchronous motors, and gearing ratios that completely and totally depend on the power grid being exactly 60Hz. It's been like that for much of the 20th century (one of the clocks I took apart was from the 1950's).
"And the funny thing is, the old technology does it better because the frequency was controlled by a large physical inertia."
It wasn't really just inertia. The generators also act as synchronous motors. Each ends up loaded more by the grid more when they're getting a bit ahead of the "consensus" frequency and less when they get behind. So once they get synchronized they stay that way. (Barring the occasional screw-up - which usually leads to a regional blackout.)
But if they're heavily loaded they slow down, and if lightly loaded they speed up. They have no inherent absolute speed referenc. So the power companies have to keep them "on time" by comparing them to a good time reference and giving a little extra push (with more steam or whatever) when they're getting behind, less when they're getting ahead - or by lowering the voltage (a brownout) or cutting off parts of the grid (rotating blackouts) when the load is getting too big for them to keep up to speed. If they don't, the generators get slowed down a tad and the clocks slow down. (That's what happened in Europe.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
In order to have an electric grid, to have many power stations interconnected, they all need to switch from positive to negative at exactly the same time. The easiest way to have them all running in sync is to agree they'll all run at exactly 50 Hz. That establishes the frequency of the grid as a whole. Then if one generator is slightly ahead of or behind the grid it can sense the difference and speed up or slow down as needed.
You speak as if this is something that is controlled directly and continuously on each generator. In fact, it's not.
Generators, once initially synchronized and connected, also act like synchronous motors. When one gets a tad ahead the load on it goes up, and when it gets a tad behind the load goes down (all the way to negative load - the grid can even give it a push). So they stay in sync (barring catastrophic screwups that usually result in a blackout).
But when the load gets heavy they slow down. So the drill is:
- Use a speed control to give them a bigger push when they're getting behind, smaller when they're getting ahead. This keeps them about on target and adjusts the energy fed to the generators to match the energy pulled from the grid (plus the grid's losses).
- Watch the overall accumulation of cycle-count error. (Easy way: Use a synchronous-motor clock hung on the mains.) Tweak the speed control to push a little harder if the grid is behind, ease off if it's ahead. (Your operation gets paid for what it feeds, so it's no skin off your bottom line to push harder than your share if the others are having trouble keeping up.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
It has nothing to do with the accuracy. Actually the grid will vary about +-0.05Hz.
Actually, I'm pretty sure the grid frequency is allowed to vary by up to one percent, which in Europe would mean +-0.50 Hz, or an order of magnitude worse than what you stated.
I don't know if it's still true, but back when I was a kid here in Canada and the overwhelming majority of electric clocks used the mains frequency to keep accurate time, the grid was required to ensure that the average frequency in any given 24 hour period was spot on 60Hz. So on the whole, mains-powered clocks were as accurate as the people who set them. So much so that the early clock radios and electronic digital alarm clocks didn't have crystals; they simply connected the power transformer secondary to the clock input of a counter via a few passive components and a Schmitt trigger. I still have one of those Radio Shack alarm clocks - dead accurate and stable unless there's a power failure, at which time the backup battery powers up a crappy RC oscillator that drifts like hell.
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Thanks. Interesting post.
Forgive me, but I suppose you spent only a short time in Canada as a kid? Canadians usually say "hydro" rather than "mains" (as Brits do?) because so much of the electricity in Canada is generated hydroelectrically.
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Forgive me, but I suppose you spent only a short time in Canada as a kid? Canadians usually say "hydro" rather than "mains" (as Brits do?) because so much of the electricity in Canada is generated hydroelectrically.
Actually, I've lived in Ontario all my life, and was raised in Niagara Falls. I grew up calling it 'Hydro', (as in "the Hydro's off"), and I still call it that in casual conversation. But when I'm talking more specifically about power in electronic terms I tend not to use the word Hydro. Around here that term also, (and perhaps more often), also refers to any or all of the companies / government entities responsible for generating / delivering / charging for electricity. I'm not sure how I ended favouring 'mains' over 'line voltage', which is what I used to call it and which is probably more common among North American techies. It may have been because I'm also into audio, and in that context the word 'line' can be ambiguous. And / or it may be that one term is shorter than the other and rolls off the tongue more easily. Just a personal quirk of mine I guess...
'The Economy' is a giant Ponzi scheme whose most pitiable suckers are the youngest among us and the yet-unborn.