US Power Mains Frequency

[cr0sh]

I think nsaspook's explanation is likely the closest to the "correct" one; I doubt this change has anything to do with making our clocks more accurate, but has more to do with the power grid as a whole. From my understanding, when the total load on the system changes, and they have to bring on more generators to keep up with the demand, they have to sync the output frequency of those generators to the grid as a whole, or issues occur (I'm not sure what - but I would bet there are feedback issues, waveform instabilities, probably some form of losses, maybe other generators being slowed down/out of sync - I obviously don't understand it all, but my limited understanding says it would be a -bad thing-). Keeping these timing/frequency issues as small and accurate as possible probably has more to do with keeping the entire grid operating efficiently and properly (and any extra costs to do so will be passed on to you and me, and any savings that come out of the changes will be added to the bottom line/profits - of course)...

 

[MrAl]

Thank you MrAl for an outstanding post that provides several things to think about. I admit I have no clue how many people are using clocks that rely on mains frequency. We use small battery powered alarm clocks at the bedside here. More interesting and what I can't find, is the numbers. Like what they will consider a "new" allowable deviation. I also like the political perspective which is quite true. I hear my father's words as they echo in my head "Ronald, I give you an inch and you take a mile". While initially I was sort of unsure, maybe this really needs more attention. You really made some good points.

Ron

Well thank you Ron, very nice of you to say.

I too wish we had more numbers in front of us so we can understand the complete ramifications of something this country-wide.

You know what is funny, if they find a cost benefit to lowering the frequency more and more each couple of years, eventually we will be running on DC (ha ha ha, big chuckle). Now wouldnt Mr. Edison be happy to hear about that if he were still around

 

[KeepItSimpleStupid]

One of the reasons cites for the "experiment" is for stability of the grid.

Suppose the utility is buying power from somewhere else ( a regional supplier). The utility has no choice but to sync to the system it has no control over.

If the transmission line is DC of the regional power source, then they could fiddle the resultant frequency.

Renewables such as solar because it's inverter based will do a lot of LOCAL power factor correction. That's one of the beauties of renewables.

One of the problems is that you have to take it when you can get it. If there is wind and sun, you use the wind and the sun. Particularly wind. Wind generators HATE to be operated unloaded.

Now, this is the reason: "To create stability in the power grid"

What will it affect negatively?

The old basic electric wall clock. Synchonous timers. Pool filter backwash timers?.

Analog strip chart recorders attached to AC mains goniometers for x-ray diffraction, but who does that anymore? That would be a real problem.

Clocks like they had at my high school which aparently were pullsed every second by a master clock, so they were all in sync. I have no idea what the master time base is/was.

I gave you one example that used to matter. Anyone have any others?

 

[Pommie]

From my understanding, when the total load on the system changes, and they have to bring on more generators to keep up with the demand, they have to sync the output frequency of those generators to the grid as a whole, or issues occur (I'm not sure what - but I would bet there are feedback issues, waveform instabilities, probably some form of losses, maybe other generators being slowed down/out of sync

I believe the way they sync the generators is to simply power them from the grid as a motor and then just turn on the steam.

I can see the cost savings in not maintaining the average but what would be the disadvantage to me, besides time keeping, if it permanently ran at 59Hz?

Mike.

 

[Pommie]

OK, I'm officially confused,

The North American Electric Reliability Corp. runs the nation's interlocking web of transmission lines and power plants. A June 14 company presentation spelled out the potential effects of the change: 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.

How can a national grid run at different frequencies? Wouldn't you get some very interesting beat frequencies occurring?

Mike.

 

[KeepItSimpleStupid]

Picture trying to run a turbine from hydro, nuclear or fossel fuel at exactly 60 Hz.

Now lets run an inverter at 60 Hz

the error bars are different.

the expected speedup is probably dependent on what the domanent electricity generating technology is.

 

[Reloadron]

OK, I'm officially confused,


How can a national grid run at different frequencies? Wouldn't you get some very interesting beat frequencies occurring?

Mike.

Because the national grid is actually 3 grids broken down geographically that looks a little like this. A Google of "national power grid" will bring up some good maps. And there sits Texas of all places alone unto itself.

Ron

 

[Birdman Adam]

Ron, that website is really cool! I clicked "Power Plants' and was able to view all the current plants, what energy sources they use, output in MW, etc.

From what I have read, all generators within a system must be in sync. If they bring in one even a tiny bit out of phase from the rest, it will be very strongly 'jerked' into phase. Maybe even twisting the shaft, more likely blowing over-current protection, etc, etc.

Of course that is relating more to the sine wave, not as much the frequency. You could have two generators at a perfect 60Hz, but be 180 degrees apart. (Don't parallel them like that!!!)

I find it interesting how there are AC-DC-AC interties that allow sections of the grid to power other sections with having to match frequency. How much loss is involved there?

So the reason they use 400Hz in airplanes is to reduce weight of transformers?

 

[Reloadron]

Yeah, the entire grid thing can get real interesting.

So the reason they use 400Hz in airplanes is to reduce weight of transformers?

Pretty much, smaller and lighter which is a big plus when real estate is at a premium and weight is a big factor. The downside is transmission lines can't be of great length due to loss.

Anyway, the power grid is interesting. The bummer is how fragile it really is and in the US pretty antiquated. When a high voltage power line in Ohio can get hot and sag to where it contacts trees and subsequently take out a massive quadrant spanning several states believe me we have problems.

Ron

 

[MrAl]

Hello again Guys,


Now that we are loosing our nice well-kept and free frequency standard maybe it's time to learn how to receive NIST signals for atomic clock synchronization. The frequency is transmitted at 60kHz believe it or not, so it covers a wide area which really includes the whole USA and much more. My clock doesnt want to pick it up for some reason though im not sure why yet.
Anyone else interested in a small project to pick up these signals?

 

[Reloadron]

Hi Ya MrAl

Years ago I used a Spectracom VLF receiver that I aimed for Boulder. I want to think it was like 10 KHz but forget. Today I still use a Spectracom but a GPS version to derive standard frequency and time at work. Anyway, I agree that a good time standard would make for a nice project. One day during my absence the idiots tossed the old (and working) receiver in the dumpster.

Ron

 

[MrAl]

Hi Ron,

I wonder now if anyone makes an IC specifically for detecting the pulse code from NIST for the atomic clock sync.

Also interesting, i was talking with a friend the other day and we starting thinking about the line frequency change coming again. We are now well past the discovery phase where we learned that it was going to happen, and that lead to understanding that some of our clocks and some of our friends clocks were not going to work very well pretty soon, or at least some time in the future anyway. So, with that in mind, we of course next thought about what it would be like to purchase a new clock to replace any that dont work well anymore.

Just what would we look for? The clocks are not going to be marked, "Doesnt work with 60Hz line frequency", and it may be a while where they do get marked, "Works well with the new variable 60Hz line frequency in the USA". In other words, the clocks at the store probably wont be marked "internal frequency generator" or "line frequency required" or something of that nature, so this will mean only one thing at least for now. We'll have to look for "Atomic clock" or something similar to that, that indicates that it syncs to NIST. There wont be any other way to tell for a while until the manufacturers catch up with the swing shift.

Thus it may be a good idea to warn friends and relatives and the nice people on the forum here.

 

[KeepItSimpleStupid]

For your interest. Here is a $10 movement that will pick up NIST stations. **broken link removed**

FWIW. There was a brief article in Circuit Cellar magazine briefly, Sine Wave Synthesizer, July 2011, p26 George Novacek

Ed Niesley had an article of building a WWVB clock in Circuit Cellar issues 235, 237 and 239. George is having trouble receiving WWVB signals because of noise (worse during the day) issues, so his article touches on what
he needs to build a WWVB simulator. He also stated that he purchased a WWVB receiver module from Digikey, a 100 mm long loopstick antenna and a 60 kHz resonator. The antenna came from HKW-Elekronik www.hkw-elektonik.de

There is a standaerds article and a Recommended practices Internet articles referenced as well.
http://tf.nist.gov/stations/wwvtimecode.htm (WWVH Time Code Format)
https://www.electro-tech-online.com/custompdfs/2011/07/2422.pdf (WWVB Recomended Practices for Manufacturers and Consumers

On another forum I have been following, a nylon plant had to install generators to keep the frequency constant because of manufacturing difficulties with their equipment. So, apparently, it can have a high cost for some.

 

[MrAl]

Hi,

Nice links KeepIt, thanks much. I'll have to read some more on this.

One other thing that bothered me a little is that i had to wonder about the reception with other things running near the unit that would have to pick up the signal. I'd have several uC units running nearby and those have been known to interfere with standard AM radio pretty badly.

Also, i havent been able to find out if NIST sends these clock signals out 24 hours a day or just between certain times of the day. I know they do send some signals 24/7 but im not so sure about the atomic clock signals.

 

[KeepItSimpleStupid]

Signals transmit 24 hours per day, but it takes a full minute to synchronize. NIST recommends that a clock synchronize once per day.

One problem is that the "best frequency" to use is dependent on such things as sunrise/sunset.

 

[ben7]

Maybe with the frequency change people will start to go back to the old weight/spring driven clocks

-Ben