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Power Grid Change May Disrupt Clocks
hawguy writes with an AP story about upcoming tests of greater allowed variation in the frequency of the current carried on the U.S. electric grid: "A yearlong experiment with the nation's electric grid could mess up traffic lights, security systems and some computers — and make plug-in clocks and appliances like programmable coffeemakers run up to 20 minutes fast."
20 minutes fast over the course of a year.
Most clocks are not electric .Most Run on DC provided by a Crystal oscillator, the line frequency provided by the AC line to run them is irrelevant. only electromechanical electric clocks might be in error
If your laptop power supply is anything like all the ones I've owned, it won't care. According to the label (and testing done while I travel), mine works just fine on nominally 50-60Hz mains power. I imagine it wouldn't really care if you went from 45-65Hz, though I suspect it might get a bit annoyed if you were to go to 400Hz or something extreme.
Any clock with the word "quartz" associated with it is using a crystal timebase to determine how long a second, minute, hour, day, etc. are.
http://en.wikipedia.org/wiki/Quartz_clock#Accuracy
Half a second per day, even if the power goes out and you're running off a battery, no matter if the mains frequency wobbles (which it's designed to do anyway).
http://en.wikipedia.org/wiki/Utility_frequency#Stability
The real question is why do devices add the additional circuitry to count pulses off the mains grid rather than add additional circuitry to actually keep time?
A highly accurate crystal costs in the order for $1 for single quantities. A RTC $1-10 depending on feature set. If you already have a microcontroller you don't need the RTC either. Why are clocks etc reliant on an external signal to keep time? How do they keep time when they run on the battery which is a common backup for every $5 alarm you get?
As for streetlights ... Really? How is this not a system which gets timing from some other central authority. I don't know much about street lights, but is this something that will only affect old small town streetlights, or do the shiny new modern LED powered ones in the city act independently enough that they aren't capable of contacting an NTP server?
Clearly, whomever thought this was a Pretty Neat Idea hasn't read this:
http://yarchive.net/car/rv/generator_synchronization.html
and doesn't understand what happens when you're even a bunch of *degrees* out of sync, much less a few decihertz. We don't have *near* enough HVDC intertie to make this not matter, and I can't imaging how they think this is gonna work -- nothing at all on NERC's website to say what's *really* gonna happen, either.
Love all the warning, too.
I think the organization that's responsible for the reliability of the entire USA power grid has some idea of the need for frequency stabilization when connecting new power sources to the grid. Not that it's relevant for what they are proposing - power plants already know how to sync up their generators to the grid and they don't care if it's 60.001 Hz or 60.002 Hz, they'll take that into account.
The magnitude of this frequency deviation is tiny, 20 minutes/year is about .003% - the power grid can fluctuate much more than than on a daily basis, but until now, it's always been corrected to keep the overall frequency at 60 Hz.
Believe it or not, the engineers that operate the network actually know what they are doing.
The flow of power between tied AC networks is determined by phase, not voltage. To adjust the phase between your generator and that of a neighbor to whom you wish to send power you must run faster than he for long enough to accumulate the desired phase difference. Such adjustments are going on constantly throughout the network and conflict with the requirement to keep the average frequency at exactly 60Hz. Relaxing the latter requirement will make network operations easier and more reliable.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
The word you're looking for is "nitpick".
"Those who consume the bulk of goods are those who make them. We must never forget this secret of our prosperity."
So untrue. Maybe it was done that way in 1930. But not anymore.
You're wrong.
Line powered clocks with crystal oscillators generally use the line for the reference and the crystal for a backup during power failures.
The line has been far more accurate than a cheap crystal - at least until these goons implement their harebrained scheme.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
The US operates three separate power grids: the east interconnect, the west interconnect and ERCOT. They're only connected by DC links and are not phase locked.
You're telling me that an Internet denizen who's only been exposed to this idea for 5 minutes doesn't know more than the engineers who have been running the system for decades?
That goes against everything /. stands for!
Load on the grid shows up as mechanical resistance to the big spinning generators that control the frequency. If there is more load than generated supply, the generators slow and the frequency drops; more supply than load and the turbines spin the generators faster. Maintaining a balance of power is done by keeping the frequency at 60Hz.
That was easy enough when all power came from big generators, with predictable loads. But if you mandate photovoltaics and wind and other forms of power which vary in output, then things are a lot harder. The wind dies and a major wind farm drops a few hundred megawatts? The big generators can't respond quickly enough to keep frequency within its regulated range, so power companies have to install very expensive systems that can react faster.
Utilities are often legally mandated to buy power from renewable sources, but those renewable sources aren't held to any of the grid stability requirements. This ends up shifting an enormous burden of cost onto the utilities, who aren't happy with it. Loosening the grid frequency requirements is a way to make renewable but unreliable power less expensive.
In the 70's I developed a system to control the of the light sensitive coating onto 35mm rolls of film. This ran on a PDP-11 that used the mains cycle to keep time (20ms interupts with the UK's 50Hz supply) and measured the coating by the amount of x-rays reflected by the silver halide in the coating each second.... there were coninual errors in the accuracy of the coating as the time approached midnight.
It turns out that the National Grid was legally required to maintain a 50Hz average from midnight to midnight and would add or subtract cycles in the last minutes of the day in order to meet this requirement.
Five or so years later I was working in the National Grid Control Centre and saw the 2 clocks, one with an independent time source and one running from the mains frequency. The aim of the controllers each night was to adjust the mains frequency to bring the two clocks in sync at midnight.
They understand very well. This isn't about allowing generators to drift out of sync with each other in the short term. It's about not correcting the long-term variations in the grid as a whole.
Household clocks and coffeemakers seem unlikely to be a problem. Most of them nowadays aren't synced to house current, but use quartz oscillators. More likely problems would be old systems which have never been replaced because they've never needed to be; traffic light controllers are a reasonable example.
This is no big deal. What they are talking about here is the additive cycles in a day and not worrying about the compensation process for that.
Some basics:
Anything connected to the 60Hz power is at 60HZ, You can not connect a 61Hz generator to the grid.
In addition, when you connect a generator to the grid, you have to adjust its phase, as you bring it on line.
If the phase angle does not line up you get you get into a "tug of war" between multiple generation sources and that doesn't work.
The sine wave coming out of one generator has to line up with the other sine waves from the other sine waves from the other generators.
60 cycles/sec X 60 sec/min X 60 mins/hour X 24 hours/day = 5.184E6 cycle/day
What the article is talking about is the adjustment of the generating stations on the grid so that at the end of the day you get that exact number of cycles across the grid, not one more not one less. It is "really close" without tweaking but not exact.
It costs money to do those tweaks, to get the numbers on the money. That tweak right now really doesn't serve much purpose anymore.
Noting exciting, or interesting here, this is not Y2K nonsense, move along...
www.effectiveelectrons.com "chips that work" Analog, RF, Mixed Signal
They don't specify how much of a frequency swing they are talking about, but I can think of a few legacy items still in use in the music industry that are affected by line frequency.
1) - The mainstay of every old piano tuner's toolbox is the Conn Strobe Tuner.
2) - There are still thousands of working Hammond B/C series electric organs in use.
3) - Lastly let's not forget the audiophiles and their vinyl record turntables.
In fact anything with a shaded pole induction motor is speed-locked to the line frequency.
Nothing worthwhile ever happens before noon
No. If you take apart a clock radio with 4x7-segment LED display, chances are that it has a 9v battery compartment at the bottom, and an LM8560 inside. It's an IC that's been used for over 30 years and still in production. No matter how cool, modern looking, flashy blue LED display it is, it has the same IC a brown 1980s clock with red LEDs had. It could be a clone or have a different name, but it is that chip.
Guess what: it takes voltage from the transformer, before rectification, into one of the pins. It also has another pin to set 50/60Hz operation. And a SHITTY RC circuit for running off battery (useless, it's off several minutes every hour).
Another thing: most electric things CAN'T be plugged anywhere now. My grey-market XBOX 360 has a 120V power brick (I live in a 220V country). If you live in the USA, take a look at how many electronic stuff at your house doesn't even have a 220/110V switch. The only things you can pretty much plug in anywhere are chargers. Most other stuff either can't, either by design (things with motors or appliances you don't carry around), or by cost (most electronic stuff without a 110/220V switch).
LED alarm clocks still use an LM8560. Go buy one, take it apart, and find the ic with the weird pin spacing (not standard 0.1"). That's the same IC that's been in use for over 30 years. And it still runs on mains frequency (it has a pin to select 50/60hz operation).