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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... --
Wait... 5 more minutes.
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.
Using the AC mains as a frequency reference works well if the power companies handle things correctly: during the day when demand is high, the mains frequency is not well-controlled and the clocks drift slightly. However, the power company is supposed to keep track of this, using some other precise time reference, and then adjust the mains frequency at night to compensate for whatever got screwed up during the day.
When done right, this results in excellent long-term accuracy for clocks that use this method, because the power companies handle all of the necessary corrections. But without the right corrections, AC mains are a terrible frequency reference.
OP sounds like an idiot. Think for a second, how would you build an accurate motor driven clock? If the mains frequency is accurate then it's pretty easy. Nearly every electric clock built in the last 100 years runs this way. Not until integrated circuits became common did they use crystals. Even then accurate crystals aren't cheap and vary with temperature.
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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.
46137
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).
Apparently, it is much more harder to maintain the correct number of cycles a day with DC sources like some wind and solar.
Only for you as a user of a private DC power system owner/user.
- If you have a DC supply, you have to come up with an accurate time reference built-into, or driving, your clock.
- If you have mains power (and your supplier is on the ball, unlike these European companies), your big power company has access to a good clock (like listening to the United States National Institute of Standards and Technology's (NIST) time reference broadcasts and adjusting the frequency to keep it totalling the right number of cycles per day on the average. (This is easy: Just hang a sync-motor electric clock across the mains and tweak frequency now and then to keep it on time.) Just as expensive, but the power company does it ONCE and keeps ALL THEIR CUSTOMERS' clock on speed.
- If you have a DC system and an inverter, either the inverter is synchronized by something accurate or your synchronous-motor clocks will drift.
I think AC grid power systems have been doing this since Tesla/Westinghouse first started setting them up. It was one of AC's selling points in the Tesla/Edison AC/DC utility wars.
Nowadays, though, WWV transmits an atomic-clock referenced time code signal on a 60 kHz VLF carrier that's detectable anywhere in the US at some time during pretty much every day. Inexpensive clocks are available that use a crystal for the basic timing (achieving accuracies of a fraction of a second per day) and using the radio time signal to resynchronize when available (to avoid accumulating a drift). So a wall clock running on a battery can now do better than a synchronous-motor clock running on the mains.
(Your typical electronic bedside alarm clock, though, doesn't include the WWVB radio. Instead it runs its timer by counting the cycles of mains power, achieving the same long-term accuracy as a sync-motor clock. If it has a battery and crystal oscillator it only uses them to keep (decent) time during power outages.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Why
Because this is an easy way to maintain a very accurate long term time base. Particularly since it was developed back in the 1940's and 1950's. Before we had GPS and automated WWV clock synchronization would have required a large and complex receiver system.
Over a short period of time, the grid frequency might drift a few tenths of a percent up or down. But on a daily basis (usually at night) the system operators will add or remove some generation from the grid, speeding it up or slowing it down. The total number of cycles (at 60 Hz in the USA, 50 Hz in Europe) over a day was corrected to match a precision time base counter.
it fluctuates by up to 5%
That's a bit high for my part of the grid. We had underfrequency load shedding set to begin dropping non critical loads (like rural circuits) at 59 Hz.
Have gnu, will travel.
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
20 years ago the frequency of A.C. in the U.S. was regulated to within about one part in 10^7 according to the IEEE. Not sure what mechanism they used to do that. That's an impressive number.
Circle the wagons and fire inward. Entropy increases without bounds.
The only clock I have the relies on this is the one in the stove. And it's too fast, yes.
All other clocks are either sync'ed by NTP (macOS, iPhone, Linux/BSD) or directly via radio (long wave receiver).
Windows 2000 - from the guys who brought us edlin
A cheap mechancial watch can lose 5 minutes a day and it wasn't the end of the world.
“Common sense is not so common.” — Voltaire