Power-Grid Experiment
June 26th, 2011Via: AP:
A yearlong experiment with America’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.
Since 1930, electric clocks have kept time based on the rate of the electrical current that powers them. If the current slips off its usual rate, clocks run a little fast or slow. Power companies now take steps to correct it and keep the frequency of the current — and the time — as precise as possible.
The group that oversees the U.S. power grid is proposing an experiment that would allow more frequency variation than it does now without corrections, according to a company presentation obtained by The Associated Press.
Officials say they want to try this to make the power supply more reliable, save money and reduce what may be needless efforts. The test is tentatively set to start in mid-July, but that could change.
I think that as long as it is kept within reason, minor frequency variations will have little effect. It will only affect ‘old fashioned’ clocks that keep time by the rate of a small electric motor running the hands. Digital and battery powered clocks will not be affected.
Aside from clocks, the things to keep in mind would be anything driven by an electric motor where the rate is highly sensitive. An electric drill, no problem. If it goes slightly faster or slower you won’t even notice. Most specialized equipment where the rate is highly sensitive already incorporates electronic speed regulator drives in their design, and these too will likely tolerate minor (+/- 10%) frequency variation. In all probability, I would guess, the actual frequency variations they are proposing to allow will be in the range only 1 or 2% at the most.
Why the man thinks “people are going to have things break”, I have no idea, if all we are talking about is frequency (hertz) variation. But if for some reason there will a significant increase in the number and severity of voltage spikes on the line, then he would be right. Then it would be electronic and digital equipment at much greater risk of failure.
We already have localized frequency instability in most power grids. Our system is old and it suffers instability and inefficieny. Also, power companies have been fiddling around with power line carrier communication systems for some time. This does effect the power factor correction circuits contained in many devices. These circuits are designed to compensate for the capacitive loading effects of power electronic devices and to make them more immune to power fluctuations. If, as Crates said, the frequency shifts are small, no real effect may be noticed. However, large enough shifts in the abscence of amplitude variations will have an impact on many common power electronic devices. I worked with lighting controls. The controls, and ballasted lights don’t like these shifts and can behave badly. The P.F.C. components on the front end of the device could overheat and suffer from reduced life span. Also, it makes fluorescent lights “breathe”, which is irritating. I spent a lot of time at customer sites diagnosing these problems and correcting them. It could be a real pain.