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Re: Frequency standard
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But still hasn't told us *why*.
I any case I do hope she has a good plan to properly filter and
average out noise and other fluctuations from her "measurements".

Dave.

Re: Frequency standard

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Yes, but I'm interested in going one better than the website, and actually
calibrating. That was the reason for my original post about dividing down
from crystal oscillators of eg 2 MHz



Re: Frequency standard
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How do you plan on "calibrating" your crystal oscillator?
"Calibration" usually = "traceability".

What is the end purpose of all this measurement anyhow?

Dave.

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What a pompous answer! It is true and is not "dumb" as you assert
Americanly. But I put it to you in good faith as I thought I detected a
smidgeon of real knowledge and was willing to be corrected if you had a
point to make.  More and more you show about 1% of knowledge mixed with 99%
or baseless abuse.

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Have you any credibility with this displayed inability to enter into a
rational discussion. How do you set yourself up as judge of the credibility
of others? I wonder what your qualifications and proven experience are?
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Sound quite plausible to me. Wouldn't bother with a toaster though...

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Back to normal
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I agree with you about that, but no doubt to you (o mighty one) it is
"pointless chat".
What a pity you have no tolerance for mere mortals.
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Suzy



Re: Frequency standard

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But isn't it true, Phil, that more demand than supply will drag down
alternator shaft speed and thus frequency, and vice-versa?


***** Oh dear,haven't you ever heard of a governor and what is designed to
do??
Perhaps your email address says it all!

Brian G.


Re: Frequency standard
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I'm afraid Phil is right. As the load increase beyond what can be
supplied by the machines already online, another unit is brought onto
the grid. Normally some units produce less than their full capacity to
give what is called "spinning reserve". The spinning reserve on the grid
is normally at least equal to the largest unit on the grid so that if a
machine trips off there is enough reserve capacity on the grid to cover
it. When demand exceeds the total capacity of the grid you get "brown
outs". This is done by a system controller switching off an area for a
while to reduce grid load. It's simply a matter of operating a switch
which causes a huge circuit breaker to open and cuts of power to a
suburb or small town. Brown-outs are rotated to different areas so as to
  reduce inconvenience to customers, but power utitiltys usually have
pre-arranged contracts in place to cut off non-essential loads first.
When a unit does trip off accidently, the grid frequency may drop a few
hertz for a few seconds until the spinning reserve picks up the load,
but you wouldn't be able to forecast a problem in advance, you would
only know of the event afterwards when the frequency has dipped.
In general, bigger grids are more stable.

Elmo

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Thanks Elmo. Makes perfect sense, and I was aware of the above. But can we
take this a stage further? Wouldn't monitoring frequency changes give some
idea of when the above routine is failing, and therefore to forecast rolling
blackouts (though not where they are of course)



Re: Frequency standard
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What Elmo is saying is...

There is a very complicated and potentially variable (may involve
human input) transfer function between the load change and the
frequency change.

You want to try to second-guess that, go ahead... you could use that
ability to predict the future to make a killing on the stock market.

Clifford Heath.

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Not really, even with the power station there can be load changes for
operational reasons, for example changing the coal mills from one to
another or starting up a feed-water pump. These operations will cause
small changes in generator output.
Living in a suburb with a hospital will reduce blackouts, living in a
suburb that has high air conditioner usage on hot days is asking for
trouble.

Elmo

Re: Frequency standard

"Clifford Heath"
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** LOL  -   comparison with the often chaotic stock market is very apt here.

Both do go up and down, there seems to be some pattern to it all, but it has
long proved to be beyond rational prediction.

Appears to be characteristic of all complex, interacting, human driven
systems.

Same goes for land values etc.



.......  Phil



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  Not that you have any personal experience in the area eh philthy ?
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  just like your head when felating your speshul friend ?

there seems to be some pattern to it all, but it has
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  rational ?
  well you are excluded then eh philthy ?
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  not your area of expertise either old trout ?
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  Well we can be sure you never having been a land owner operate purely
on "hearsay"
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Re: Frequency standard
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More to the point, it positively responds to any newly-discovered accurate
prediction method by becoming just enough more complex that the method
doesn't work any more, since it's basically a fractal (self-referential)
system. It shares this characteristic with self-awareness. It isn't free
will or anything spiritual that creates intractable complexity, it's just
that self-reference guarantees that the complexity is always *just* out of
reach.

There, from electricity generation to agnosticism in three posts :-). QED.

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Crikey Cliff! You've lost me there...



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    Likewise




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Click! Someone threw a switch. I agree Phil. And have lost a lot of money on
the stockmarket too... until I woke up to the fact that it's pure gambling.



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I quite like the idea of monitoring frequency *and* voltage, the latter
being Phil's contribution when he accidentally made one...



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The voltage at your residence would tell you very little about the grid.
As well as voltage fluctuations caused by nearby loads, there are other
factors caused by reactive power that causes voltages to rise and fall.
Some power lines use capacitor banks to offset the inductance of long
transmission lines. This area is way over my head.

Elmo

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Ah, coming back to me now. Capacitor banks... All a bit over my head too!



Re: Frequency standard
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    Remember the old DATUM microprocessor training board which was in EA
around 1982?
    I wrote some code for mine to watch the mains frequency and it never
deviated from 50Hz by more than a tiny part of 1Hz.
    That was 25 years ago and I don't recall the exact figures but it
was far less than 1.5Hz.


Bob


Re: Frequency standard
No, the electricity supply company couldn't maintain 50 Hz acurately in
the short tern due to load variations and machine response times inter
alia. They supposedly guaranteed the correct number of cycles per day
however. This was in SA and wasn't connected to the national grid which
I imagine would be more stable given the overall "mass" of the system.
We noticed the drift while trying to remove 50 Hz and harmonics from an
audio circuit using DSP. Procedure: Analogue signal - ADC - FFT - set
all non mains related frequency bins to zero - inverse FFT - DAC -
subtract this from original signal.
Worked fine while the mains frequency was constant but as soon as the
frequency drifted, the amount of hum reduction dropped. Eventually had
to phase lock the DSP clock to the mains.
Alan


Phil Allison wrote:
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