Hey Kids, What Time Is It?

Those of you of a certain age (what age is that?) will recall that ancient call. But for the rest of us that may become a reality thanks to a new government program. And what will that program do? It will let the frequency of the grid wander to better accommodate intermittent sources of power like solar and wind. And why is solar intermittent you ask? Clouds. Solar can go from full power to low power and back to full power with the passing of a cloud. And depending on wind speed that can happen rather quickly. With that going on it is tougher to keep the frequency constant. And keeping the frequency within one cycle of the 5,184,000 cycles that are supposed to happen in 24 hours
requires co-ordination.

Regulation of power system frequency for timekeeping accuracy was not commonplace until after 1926 and the invention of the electric clock driven by a synchronous motor. Network operators will regulate the daily average frequency so that clocks stay within a few seconds of correct time. In practice the nominal frequency is raised or lowered by a specific percentage to maintain synchronization. Over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million.

Think of the grid as a huge rotating machine with what amounts to electrical "shafts" between every generator and load. If the speed of the generator and load differ greatly the shaft will break.

The primary reason for accurate frequency control is to allow the flow of alternating current power from multiple generators through the network to be controlled. The trend in system frequency is a measure of mismatch between demand and generation, and so is a necessary parameter for load control in interconnected systems.

Frequency of the system will vary as load and generation change.

So frequency will go up or down depending on supply and demand. A drop in supply (increase in demand) causes the frequency to go down. An increase in supply (decrease in demand) causes the frequency to go up. On an instantaneous basis this is held quite close to keep out of phase current (caused by generators and loads at different frequencies) to a minimum. Phase current requires bigger wires and transformers but delivers no power to the load. Expense without revenue. This is bad for business.

The frequency is generally changed (synchronized) at night when loads are lowest so the amount of phase current is minimized. Obviously it is cheaper and requires less co-ordination to let things drift a little. But when it comes to time a little means a lot. A five minute a month drift will put you off by an hour in a year. (that hour a year is about .01% accuracy). To keep it to 6 minutes a year requires that the grid average frequency be .001% accurate.

What kind of devices will this change affect?

A yearlong experiment with the electric grid may make plug-in clocks and devices like coffeemakers with programmable timers run up to 20 minutes fast.

The group that oversees the U.S. power grid is proposing a change that has the potential to disrupt electric clocks in schools, hospitals and other institutions, according to a company presentation obtained by The Associated Press. It may also mess with the timing of traffic lights, security systems, sprinklers and some personal computer software and hardware.

The biggest disruption will be in traffic flow control. What happens when you end rush hour traffic control twenty minutes early? Well, the electric power guys will be saving money and those stuck in traffic will be losing it.

With everything so interconnected seemingly insignificant changes in one part of the system can have huge effects in other parts of the system. For instance what about getting your alarm clock wake up at the right time to get to work on time? If you use an alarm clock like this one, Sony ICF-C318 Automatic Time Set Clock Radio with Dual Alarm you will be resetting your clock frequently despite the fact that the clock automatically adjusts for daylight savings time. So how do you get the right time? There is your computer or cell phone of course. But if you want something on your wall I like this clock: La Crosse Technology WT-3102B 10-Inch Atomic Analog Clock. It is synchronized to WWVB which is the time standard for North America (good to plus or minus one second or better - depending on some technical details). And what do you know? The frequency it broadcasts at (60,000 Hz) is exactly 1,000 times the desired North American line frequency to within one part in a thousand billion or better. Which is one second in about 30,000 years. Close enough for most work. Our most accurate atomic clocks are about a million times better - currently. And scientists and engineers are working constantly to improve the clocks. In fact of all the fundamental quantities we can measure - length, mass, time - time is the quantity we can measure most accurately although it is the most ephemeral.

Cross Posted at Classical Values

A Clock Setback

In case you haven't heard we are now - for the winter - off daylight saving time. All your manual clocks need to be set back one hour. If that is a hassle - it is - may I suggest this radio controlled clock (sometimes called an atomic clock because it uses the American atomic time standard) from Amazon. The radio signal comes from WWVB near Boulder, Colorado. The frequency is 60 KHz. It updates the time every night so you are always within a second or so and it automatically does Daylight Savings Time. I have one and my first mate loves it. Unlike atomic clocks of the past it is very easy to set up. And this particular version is under $20.

La Crosse Technology WT-3102B 10-Inch Atomic Analog Clock

If you have one of these in your dwelling you will always have at least one clock with the right time. No need to try to figure out if it is fall back or spring forward.

Cross Posted at Classical Values

Atomic Time

I want to tell you about a clock I bought a while back that my mate and I are very happy with. The La Crosse Technology WT-3102B 10-Inch Atomic Analog Clock.

It really isn't an atomic clock. It synchronizes with an atomic clock signal sent out by station WWVB near Boulder, Colorado. If you look at the signal strength maps you can see that the signal is the strongest in the night time hours. Which brings me to how to set up the clock.

At about ten minutes before the hour set the clock to 25 minutes before the hour and insert the battery. Your clock should be reasonably far away from electronic equipment. Especially TVs and Computers. Push the buttons as detailed in the instructions (you get the 4 American continental time zones plus a Daylight Savings on/off option). Then put your clock on an upstairs (no basements) wall that faces to or away from Boulder. When the clock gets the signal it will start spinning. You may have to wait until night to get a strong enough signal. If your building has metal sheathing (siding) the clock may only work in a window facing Boulder.

We put our clock up about 3 ft from a TV set (in a fairly strong signal area - your clock may need to be farther away) on a wall facing Boulder and have never been happier with a clock. We know what time it is to the second. And if the signal is never strong enough? The clock will work as a regular digital clock.

I have had older type atomic clocks that were much harder to set. This one is a piece of cake and I'm super happy to know what time it is. It is especially handy when daylight savings change days come as the clock adjusts automatically. No more clock fiddling to be on time.

Of course you still have to fiddle your alarm unless you have a Sony ICF-C318 Automatic Time Set Clock Radio with Dual Alarm (White). It really isn't an automatic set (WWVB radio) clock. It does adjust for daylight savings and it does have a built in back-up battery so you do not lose the time if the power goes off. The alarm itself is kind of soft, but the radio is loud enough to get you up and it is really obnoxious if you set the radio on top of a running computer. Setting the time and the alarm time are really easy with this radio. However the time does drift some (a few minutes a month). Which is why the atomic wall clock comes in handy.

Update: 31 July 2010 0139z

Commenter rhhardin at Classical Values has some issues with a different model of this clock. They may also apply to the model above. So far I haven't noticed.

Cross Posted at Classical Values