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Given some of the discussions here about using power-line frequency for a time signal, I though this might interest some folks.

AP EXCLUSIVE: Power grid change may disrupt clocks

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.

"A lot of people are going to have things break and they're not going to know why," said Demetrios Matsakis, head of the time service department at the U.S. Naval Observatory, one of two official timekeeping agencies in the federal government.

I haven't any idea whether the alarm clock in the bedroom uses line frequency. Not sure there's any way to find out either. Not sure whether this is a nudge to get me to play with building an Arduino alarm clock. It'd be fun though.

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I watched the mains frequency here outside of Boston for a while, varied from 59.95 up to 60.02 Hz.

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 "East Coast clocks may run as much as 20 minutes fast over a year, but West Coast clocks are only likely to be off by 8 minutes. In Texas, it's only an expected speedup of 2 minutes."

So that's about 1/3 second a day.  Two point three seconds per week.  Just under 10 seconds a month.

I don't think it's time to panic yet.

[Reply #3 on:]

Of course YOU live in Colorado where you probably have a nice strong ground-wave time/frequency reference from WWV et.al.  :-)

I've been tempted to drop in at NIST and ask them what time it is. Well, they do offer tours, so I suppose that wouldn't be all that novel. I don't know how immediately beneficial proximity to NIST is for me, directly. If I wanted to build something using the WWV signal, then yeah. What little I've read about using that makes me think that I have other things to spend my time on. (Though there is complete code available.)

Customers of Xcel here have the option of paying more (I think it's %10) to buy power from the wind farm, which is one of the things cited as a reason for allowing some frequency drift.

[Reply #4 on:]

I don't think it's time to panic yet.

Easy for you to say. You probably have a towel.

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I haven't any idea whether the alarm clock in the bedroom uses line frequency. Not sure there's any way to find out either. Not sure whether this is a nudge to get me to play with building an Arduino alarm clock. It'd be fun though.

If it has an internal battery and when when losing power comes back with correct time it's using an internal crystal timebase. If it comes back flashing 12s then it's using line clock reference.

Lefty

[Reply #6 on:]

I've been tempted to drop in at NIST and ask them what time it is.

I call on NIST.  The first time I met with a particular engineer he joked with me, "Don't be late.  I'll know."

[Reply #7 on:]

If it has an internal battery and when when losing power comes back with correct time it's using an internal crystal timebase. If it comes back flashing 12s then it's using line clock reference.

I'll have to put a battery in it and find out.

Thanks, Lefty.

[Reply #8 on:]

It isn't clear (at least they didn't go into any detail) WHY maintaining the mains frequency is more costly than letting it drift. When you are feeding power into the grid you have no choice but to do it synchronously or else blow yourself up.

The frequency of the grid is a product of the rotation of the generators feeding it. While, yes, if one generator tries to drift it will be 'forced' to stay in sync with the grid or bad things happen. But the overall frequency can drift faster or slower then a perfect 60Hz

In order to correct the whole grid, a power station has to force it's generators to run (slightly) slower or faster then the grid. This creates a power flow between the correcting station and all the other stations as the correcting station station is 'pushing' on the other station's generators to go a little faster or slower.

This requires a impressive amount of power to do that is wasted on just slightly changing grid frequency. If they could do this left often == savings.

[Reply #9 on:]

This requires a impressive amount of power to do that is wasted on just slightly changing grid frequency. If they could do this left often == savings.

This is pretty much "it" - but we all know what this means if the go-ahead for wide-scale deployment is approved...

We'll (or our parents, for the younger set out there) all get notices in the mail that will have some platitudes about "a new fee to ensure more accurate time keeping" or some such bull...

So - they'll get to save a few bucks (which will benefit their profit margins) and they'll charge us for it as well (which will also benefit their profit margins). It's a win-win, where we citizens are left holding the (nearly empty) bag.