Power Grid Freq Variations To Be Allowed

I smell issues arising with this...
http://www.google.com/hostednews/ap/article/ALeqM5giHrMC9wYlOzOkUg9wNC2jV Kugkw?docId71623ab59694aef9f0a02fe83faca8a
Erik
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I have one issue already. The linked article comes up as unavailable.
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On 6/25/11 7:11 AM, snipped-for-privacy@optonline.net wrote:

A short article here: > http://tinyurl.com/5vk4lc4
Does it really take that much effort to synchronize the grid's frequency?
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Electricity does not just go to homes! There are all sorts of industrial plants / manufacturing plants / chemical plants and so forth which have numerous control gizmos which depend on an accurate power line frequency.
Think of all the things unearthed with the Y2K problem. Same with this. All sorts of stuff out there!
And the 60 Hz power supply has always been a "rock". Something guaranteed to be exact. So electrical engineers have made use of that in many different products which have been manufactured in the past.
Now that "rock" is going to turn to mush?
If they are going to do this, then they should give many years notice prior to doing so. Same as with Y2K. It took a lot of investigation, time, and work to root out all the potential problems...
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So what. Cumulative phase error on rhe grid was allowed to grow pretty large. I think I remember a minute error or more. The total cycle count, however was always corrected, often late at night.
Applications that required accurate frequency provided their own standards. It was a big business for HP and others. Television used a field rate of 60/sex. My entire remembrance of commercial TV has been standards that provided their own synchroinzation that did not require accurate timing from the grid.
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Sam

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Ah, no...
Anyone who has a device with a crystal oscillator timebase knows that the device has to be reset to the correct time occasionally. On the other hand, plug-in devices that use the 60 Hz signal for the timebase have been (up until now) essentially perfect since the signal has been manually twiddled to make it so. (There is actually a 10 second tolerance in the East, less in the West.) And implementation is dirt cheap: you capacitively couple to the power line, use a Schmitt trigger, and some divide-by-60 counters. With better performance at less cost, using the power-line frequency as a reference is the preferred method.
Thing become ambiguous in plug-in devices with "battery backup." These devices do have crystal oscillators to ride out the power outage. When the power is on they can either use the crystal oscillator as reference, or the power line as reference, however the device was designed.
- Jonathan
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In article

I must have lucked out. For about $30 I bought a Pulsar wrist watch at least 15 years ago. I estimate its stability as about one or two parts in 10^7 as long as the temperature does not have extreme deviations. I only reset it when I need to change for daylight savings time or for a new cell. It is about four seconds fast this now. That may be because of the cell having been in the watch for over two years now and it is probably going to fail soon.
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Sam

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On 6/25/2011 22:28 PM, Salmon Egg wrote:

An interesting story, some of the early crystal watches had their accuracy tied to maintaining the crystal temperature. By accounting for the watch being on a human's wrist, the designers were able to design for a specific temperature at the back of the watch.
In some old power plants, we had ovens to maintain the crystal temperature of our frequency base. But curiously, the frequency base was not used for controlling the generator (base-load plant), only the oscillograph for transient plots.
daestrom
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daestrom wrote:
[snip]

Frequency isn't regulated on a per-plant basis. The system operator will monitor the grid frequency and lead or lag from an ideal 60 Hz cycle count. They will schedule generation to be added or subtracted based on these figures. Unless your plant is intended to run islanded on occasion, such frequency regulation is unneeded.
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Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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On 6/26/2011 11:56 AM, daestrom wrote:

A lot of the test equipment from the big old name brand manufacturers had crystal ovens inside for the time base circuitry when I worked a bench tech in a repair depot 30 years ago. Like gold boat anchors and just as expensive. :-)
TDD
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You are the first poster to actually get it correct. Thanks!!!
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wrote:

That hasn't been an accurate statement for quit some time. Whole clocks can be built for the cost of the circuitry involved of syncing the clock to to the power line. Oscillators built into the clock IC are more than accurate enough to maintain accurate clock time over years. Case in point, my trucks clock, 2003 Nissan bought in fall of 2002. Clock has never been set except by the dealer. It is now about 30 seconds off and it has always been about 30 seconds off per my cellphone clock. I never bother correcting it for DST. The Design of clocks Jonathan is talking about used an RC oscillator that was synced to the power line. By design the oscillator was a little slow, this made syncing it to the power line signal easier. Also have a desk clock meant to run on a aaa or aaaa battery but I now have it wired into 4 D cells in parallel. It has maintained accuracy for years also.
Jimmie
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There are, and I have built devices with rudimentary oscillators that sync with the line, but are not so precise, like 555 timers.
Greg
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Seems like the variation allowed, the more variation syncing is problematic. The whole grid is always loosing power to all the stations producing slight variation pulling on each other.
Crystals tend to be stable, but there are times when the crystal makes a steep, then needs to be calibrated. A primary frequency standard uses a quartz oscillator with another correction loop like from cesium standard.
Greg
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"Gz" wrote in message wrote: --------snip-------- Seems like the variation allowed, the more variation syncing is problematic. The whole grid is always loosing power to all the stations producing slight variation pulling on each other. ------- Not really:
a)synchronizing is matching an incoming generator to the grid frequency, voltage and phase. Normal variations in these are not a problem- if they are, then there are more serious problems occuring.
b)There is power transfer between machines- the resultant forces act to pull all machines to the same frequency. You can't run one machine at 60Hz and another at 60.1 Hz. However, the system transmission losses, for short periods of time, may increase or decrease slightly. It averages out.
c) Not correcting time as often will not adversely affect operation of the system - all it means is that there may be (not will be) some more time error before correction. This is really not a big issue.
Don Kelly cross out to reply
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The 60 Hz has never been the "rock" you think it is. While its long term accuracy is pretty good its short term accuracy isnt that great and very rarely exactly 60hz. As a matter of fact my freq counter says it is 60.07xxx Hz, the xxx means that these digits are constantly chnging. Georgia Power used to give a tour of their Plant Hatch facility and one of the topics mentioned was frequency accuracy. I would like a couple of examples of any products that use the power line frequency as a CRITICAL reference as I know of none.
Jimmie
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