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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."
The reason they did that is because an AC synchronous motor was much cheaper than a quartz oscillator and solenoid like the new ones have.
-- You are in a maze of little, twisty passages, all different... --
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.
A quartz crystal has excellent short-term accuracy, but lousy long-term accuracy.
Diamond engagement rings are like that too.
It must have been something you assimilated. . . .
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).
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
They use a synchroscope to get the generator as close as possible to the grid before switching it in to keep stress low. Once it's switched in, it's effectively locked to the grid frequency and phase.
In "the old days", farmers would use two incandescent bulbs in series connected across the hot lines of 2 generators. They would adjust the speed and phase until the lights went out, then throw a switch to connect them.
In "the old days", farmers would use two incandescent bulbs in series connected across the hot lines of 2 generators. They would adjust the speed and phase until the lights went out, then throw a switch to connect them.
That is fascinating. I had no idea such things were necessary or that 'normal' people had the ingenuity to solve these problems.