OT-Power grid changes

(AP) WASHINGTON (AP) - 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.
So will shop motors run slower or faster ?
Best Regards Tom.
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On 6/25/2011 3:09 AM, azotic wrote:

http://www.cbsnews.com/stories/2011/06/24/ap/national/main20074275.shtml#ixzz1QGjmtbRD
We MUST stop using electricity all together, it causes Global Climate Change!
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Lets just convert all the lights to solar power. Then they'll work whenever the Sun's out. Karl
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On 6/25/2011 03:09, azotic wrote:

http://www.cbsnews.com/stories/2011/06/24/ap/national/main20074275.shtml#ixzz1QGjmtbRD
Worst case scenario: East coast clocks at 20 minutes/year.
60 Hz *60 sec. *60 min. *24 hr. *365 day = 1892160000 cycles in a year
20 minutes of extra cycles:
60 Hz * 60 sec. * 20 min. = 72000 cycles
72000 divided by 1892160000 = 3.805175038051750380517503805175e-5
or in non exponential terms: .00003805 which is .003805 percent frequency change. I doubt if any machine motors will notice the difference. The same with almost all digital clocks, which use a crystal to set the frequency, not the grid. Maybe your grandfather's Westclox electric alarm, with the motor, but even most of them were/are self correcting, each time you adjust the time, they get a little bit more accurate.
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Steve Walker
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I have a Westclox LED digital alarm clock that runs twice as fast when I'm on the generator. The generator regulates within about 5 Hz so maybe it double-triggers on noise at the zero crossings. It doesn't like inverter AC either.
I depend on 'atomic' battery clocks to set the off-line computer for TV recording. As long as the government doesn't mess with atoms I should be OK.
jsw
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Both.
As I understand it, the grid frequency isn't perfectly constant now and they have to tweak it to make the count of seconds in an hour or day come out right.
I've built and tuned phase-locked-loops that synchronized to the power line for precision measuring instruments. At that location the grid was stable enough that I didn't see momentary frequency variations, just a lot of SCR switching noise around the zero crossings.
A previous job had been out in the country near a ski resort. Their 200 HP snowmaking machine affected the grid enough that we bought a generator to run the product for acceptance testing.
jsw
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wrote:

"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 speed-up of 2 minutes." This proves three things, though everybody already knew them as facts:
1)There -is- such a thing as a New York Second
2) They're slow down in Texas. and 3) The West Coast is Weird.
<g>

A tad faster, if anything. You'll be more efficient in the shop, Tom.
-- You can't wait for inspiration. You have to go after it with a club. --Jack London
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azotic wrote:

All the traffic light controllers I've seen are microprocessor controlled, and use a crystal for their reference. Does "Cars won't start and elevators won't work. All power plants will shut down at midnight because of Y2K" ring any bells?
--
It's easy to think outside the box, when you have a cutting torch.

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There's still lots of electronics-less units here in Chicago. It's impressive they last years and years just slamming contacts back and forth, all run from a timing motor.
What is the poing of the frequency variation in the first place? it's never explained in the links.
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A control systems group at our university tried to understand the stability of the electrical grid. This was a big, multi-year DOE grant. They wrote a software simulation, with generating plants, loads and transmission lines. As I understand it, they eventually found that the problem is essentially mathematically intractable, but that they were able to establish certain bounds to the solution. What that all means is that the grid is not really very stable at all, somewhat like a whole bunch of masses tied together by a network of springs, and energy being added and subtracted here and there. Resistance of the transmission lines and the huge resistance of resistive loads (incandescent lights and toasters) may be the only thing keeping it from going wildly unstable. They do experience periods of smaller instability now and then, and sometimes have to pull a generating station offline to break the cycle of reactive power bouncing back and forth from one region to another.
So, with that background, **I THINK** what is going on is they think there may be a way to reduce some of these stability problems if they don't try to maintain exact frequency all the time, TOO. Stability is a LOT more important than minor frequency variations.
Jon
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Think about a 60 HZ standing wave.... HOW can that be applied to the grid? It cannot.
Say for example, you had a reference signal leaving Minneapolis, and the peak of that wave will arrive in Chicago some time later. If there is only One single line between these two centers, no problem...
Now add in the grid. The peak of that 60 HZ sine wave arrives at Chicago, and the peak is also traveling from Minneapolis to Denver, then on to Chicago.... The time is not the same for the two possible paths.. There needs to be power moving back and forth...
With the wavelength of signal smaller than the possible distances in the grid, you cannot have it all tied together without recirculating power...
Even if a reference signal was assigned to one point in that example, the reference cannot arrive at various points in the grid intact because being a grid, there are multiple paths for it to follow. Now add in multiple sources driving the grid, and you are left with recirculating power... There is no way to have a "master" reference for the grid...
The ONLY way that I can think of it working would be if all the connecting points were assigned a time stamp reference from a MASTER signal, and you would need tapped Delta transformers at each end of a line. Moving the delta taps could force power to flow in either direction...
A tapped Delta transformer can change the phase angle, without changing the voltage.
Can anyone illuminate this situation? Anytime I have talked to electric power guys, they have never heard of or thought about the fact that the grid cannot be in sync, without having recirculating power..
They always refer to the grid has an infinite source and sink of reactive power... it gobbles up the MVARS, or supplies them to keep the generator perfectly in sync. You can open or close the wicket gates to push more or less power to the grid. The voltage and frequency are locked, but pushing harder against it will push more amps... or pushing softer will push less amps...
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When the grid frequency is constant all the ferroresonance circuits that can blow up due to standing waves do it as they are each energized. If you vary the frequency the ferroresonance parts will suddenly appear at random and the grid would become very unstable. This sound like grid suicide. Many pieces of equipment would not like it.
e.g. High voltage BPD, CVTs or Pot-coupler devices. (Bushing potential devices, Capacitive voltage transformers, potential coupled devices). These high voltage step down transformers rely on capacitive coupler to take a "tickler" current off a high voltage line, typically in transformer bushings as the lead passed through the long insulated tube inside a transformer bushing. The resulting " trickle" current is passed through a series of "tuned" circuits (RLC) to produce a phase and ratio accurate reproduction of the high voltage to be used in protection and/or metering circuits. These take high tech equipment analysis to set them up using the resonant tuned circuits involved. Changing the applies frequency would shift the phase of the protection circuits and the line would get a trip command sent down the communication circuits to open the transmitting ends.
The Eastern Seaboard Grid System has massive groups of Engineers working on these grid synchro problems and the whole self-interest group concepts is a waste of time and mostly nonsense. These circuits already have multiple layers of massive, complex, protection schemes to protect against this kind of thing and history has produced a need for constant improvement of the technology and sophistication of these protection schemes. Contact a Senior P&C Engineer at Hydro One or IESO and you can haggle this out with him until after he retires, and then some, and still not come to a solid conclusion for improvement.
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"Cross-Slide" wrote in message
Think about a 60 HZ standing wave.... HOW can that be applied to the grid? It cannot.
Say for example, you had a reference signal leaving Minneapolis, and the peak of that wave will arrive in Chicago some time later. If there is only One single line between these two centers, no problem...
Now add in the grid. The peak of that 60 HZ sine wave arrives at Chicago, and the peak is also traveling from Minneapolis to Denver, then on to Chicago.... The time is not the same for the two possible paths.. There needs to be power moving back and forth...
With the wavelength of signal smaller than the possible distances in the grid, you cannot have it all tied together without recirculating power...
Even if a reference signal was assigned to one point in that example, the reference cannot arrive at various points in the grid intact because being a grid, there are multiple paths for it to follow. Now add in multiple sources driving the grid, and you are left with recirculating power... There is no way to have a "master" reference for the grid...
The ONLY way that I can think of it working would be if all the connecting points were assigned a time stamp reference from a MASTER signal, and you would need tapped Delta transformers at each end of a line. Moving the delta taps could force power to flow in either direction...
A tapped Delta transformer can change the phase angle, without changing the voltage.
Can anyone illuminate this situation? Anytime I have talked to electric power guys, they have never heard of or thought about the fact that the grid cannot be in sync, without having recirculating power..
They always refer to the grid has an infinite source and sink of reactive power... it gobbles up the MVARS, or supplies them to keep the generator perfectly in sync. You can open or close the wicket gates to push more or less power to the grid. The voltage and frequency are locked, but pushing harder against it will push more amps... or pushing softer will push less amps...
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It is Not really "recirculating", but what IS happening is PHASE shift.

You can have a single frequency (with a "master" reference, and still have as many paths as you want. You WILL have phase shifts between points, but so what?

I am one, perhaps you were not understanding their response.

Not true, they will be in "sync" from a frequency point of view, but not in phase.

Frequency is "locked"ish, but the voltage is not!
You change your local voltage [To a degree] by varying exitation. You also change the level of vars you exchange with the system.
If you are not paralleled with a system, then all you change is the voltage, if you are connected to a very stiff part of a system, all you really cahnge is vars.

Not entirely. YOu puch more power or less power, which means more or less amps, but you can push more amps by vary8ing exitation and hence the vars. So it is POSSIBLE to push more power, and fewer vars and end up at the same amps (Within some farily small limits)
IF you are not connected to a system, opening the gate just increases frequency (=speed ) if your load takes more power at a higher frequency it will also generate more power. If not, then your speed will increase until something destroys itself, or speed related losses reduce the accelerating torque to 0, or an overspeed device kicks in to shut the gate.
jk
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r.

It is some what bogus any way.
The frequency is not stable, ever, it is a CONSTANT dance. Add more load, the whole system slows down (a very little) drop some off, it speeds up. Increase the governor of any power plant, it speeds up too, the reverse if you reduce the governor. The actual frequency meanders quite a bit in the short term, but is constantly being "pushed" towards an intended average.
As far as the coasts being different, it is simple. We are not all one grid, and some parts that are tied together, are tied with DC links.
Not as bad as Saudi Arabia used to be, with one side of the country at 60 Hz and one at 50. But I've heard that they fixed that. jk
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On 06/27/2011 11:40 PM, jk wrote:

The Japanese WISH they had fixed this, but they are still split between 50 and 60 Hz systems.
Jon
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It would make no difference to traffic light timers driven by synchronous motors anyway. They are all tied to the same grid. So if they all ran at 60.1 Hz the traffic lights would be synchronized for 30.05 MPH instead of 30.

I think its got to do with the wind generation lobby. Back in the old days, the grid's total cycle count was brought back to a 'true' 60 Hz count by adding or subtracting generation (usually at night) to accelerate/decelerate the grid as required. But wind sources are notoriously unstable and the requisite trimming efforts would be greater and fall on primarily the thermal plants. The wind people have thrown a few hissy fits on the occasions when grid stability could not be maintained and they were asked to shut down. So this appears to be a compromise to allow wind generation to coexist on the grid without imposing costs on them or thermal plant operators.
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Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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