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'[OT]: Power Grid'
2001\02\23@090716 by Mark Peterson

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There is not a single-common power grid in the United States.  At 60 Hz,
the wavelength of the AC cycle is just short of the width of the country,
thus when an east coast utility is generating a crest, a west coast utility
could be synching in on a trough.  Not only can this fact make it difficult
to keep the system synchronous, it can contribute to serious instability.
This is one reason that the country is broken up into several semi-isolated
power pools.  Quite often, the ties between these pools are DC links which
of course are immune to the problems of synchronism.  Much planning and
organizational effort takes place in each of these pools to minimize
cascading effects of system disturbances so as lessen the chances of an
isolated problem bringing down the entire pool area.  The pools themselves
also serve the purpose to "localize" a system collapse to a pool rather
than allowing it to bring the entire country down.

Mark P.

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2001\02\26@110134 by Sergio Picado

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       I've often wondered how the frequency was kept in step throughout the grid.

       I wonder too why most of the rest of the world uses the 50Hz and 220
voltage instead of the 60Hz and 110v.  The line losses might be less at
higher voltages but I would also assume you get "shocked" only once with
220.

       Sergio



{Original Message removed}

2001\02\26@113032 by Bob Blick

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>         I wonder too why most of the rest of the world uses the 50Hz and 220
> voltage instead of the 60Hz and 110v.  The line losses might be less at
> higher voltages but I would also assume you get "shocked" only once with
> 220.

Fluorescent bulbs last longer, other than that I can't think of any
overriding reason for it.

50Hz is really awful with regards to television, the flicker bothers me.
Otherwise PAL format is very nice compared to NTSC. 60Hz PAL would be
great. There's probably some region of the world that does it, television
standards are not standard. There's definitely 50Hz NTSC in some places.

-Bob Blick

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2001\02\26@114655 by Bob Ammerman

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> There is not a single-common power grid in the United States.  At 60 Hz,
> the wavelength of the AC cycle is just short of the width of the country,
> thus when an east coast utility is generating a crest, a west coast
utility
> could be synching in on a trough.  Not only can this fact make it
difficult
> to keep the system synchronous, it can contribute to serious instability.
> This is one reason that the country is broken up into several
semi-isolated
> power pools.  Quite often, the ties between these pools are DC links which
> of course are immune to the problems of synchronism.  Much planning and
> organizational effort takes place in each of these pools to minimize
> cascading effects of system disturbances so as lessen the chances of an
> isolated problem bringing down the entire pool area.  The pools themselves
> also serve the purpose to "localize" a system collapse to a pool rather
> than allowing it to bring the entire country down.

If a failure propogates to an entire 'pool' that is a _very_ bad thing.
Power companies go to great lengths to set up protective relaying, which is
designed to contain an error to a very small area.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\26@162759 by Tony Nixon

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Sergio Picado wrote:
>
>         I've often wondered how the frequency was kept in step throughout the grid.
>
>         I wonder too why most of the rest of the world uses the 50Hz and 220
> voltage instead of the 60Hz and 110v.  The line losses might be less at
> higher voltages but I would also assume you get "shocked" only once with
> 220.

Not so, I've been shocked lots of timess when I was young.

A bit like Bart Simpson..


ZZZt  Ow!   ZZZt  Ow!  etc


Probably what causing the premature greying. It can't be code writing...

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2001\02\26@173306 by David Duffy

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>         I've often wondered how the frequency was kept in step throughout
> the grid.
>
>         I wonder too why most of the rest of the world uses the 50Hz and 220
>voltage instead of the 60Hz and 110v.  The line losses might be less at
>higher voltages but I would also assume you get "shocked" only once with
>220.

Twice the volts - half the current. Over here (240V 50Hz) that means that you
can get 2400 watts easily with smaller (10A) cable. (or 3600W with 15A cable)
I've actually heard 220V/240V is safer than 110V ?  I saw a program a while
back
where Australian medical officers had to be aware of the *increased* dangers of
110V systems. Something to do with the 110V being more likely to stop your
heart whereas the 240V gives you a hell of a belt but can kick it going again !
I know it sounds wrong but hey, that's what "they" said...

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2001\02\27@035426 by Vasile Surducan

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The real reason for some countries have 220v/50Hz ( or between 49 and 50
Hz like sometime frequency is in the East of Europe ) are the equipment
and not concern about neon bulbs, television or our health.
After all huge transformers have been built for 10Kv or 20Kv to 380V
( this men 220V betwen each phase and ground ) it's to difficult to switch
to a better standard.
However 120/60Hz is not one of these...like SECAM is not better than PAL
Vasile


On Mon, 26 Feb 2001, Bob Blick wrote:

{Quote hidden}

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2001\02\27@081613 by uter van ooijen & floortje hanneman

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>         I wonder too why most of the rest of the world uses the 50Hz and
220
> voltage instead of the 60Hz and 110v.  The line losses might be less at
> higher voltages but I would also assume you get "shocked" only once with
> 220.

Nope, 50 times a second. And as often as you touch it, which can be quite a
number of times if, as in my case, your are not a donkey. (Dutch proverb: a
donkey will hurt itself only once on the same stone).
Wouter

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2001\02\27@095049 by Sergio Picado

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       I assume that damage to a human being is related to the amount of current
going through the body and the path.  I'm sure that other variables are
involved.

       Still, I have asked power plant engineers as to the 50 - 60 Hz 110 - 220v
difference between countries and not one has been able to answer with
certainty.

       Sergio





{Original Message removed}

2001\02\27@170325 by Gennette, Bruce

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I don't know if this is true or not - but it sounds like it is -

Edison needed 2 alternators to supply the DC power for his original street
lighting.  The AC from the alternators had to be synchronised (originally
with a solid steel shaft between the alternators).  For further extension of
the system other engineers used the AC in (close to) the form that was
available from the original alternators - 120V 60Hz.

Engineers in other countries either copied this directly, or did their
homework to see that end user wire size could be reduced by a factor of 4 by
doubling the supply voltage and that 220V phase-to-phase was easily handled
by available insulation at the time.  The change from 60 to 50Hz reduced
shaft speed by 17% without creating noticeable flicker in lighting (100
flashed per second is not detectable).

Anyone who actually knows how the diverse systems arose please tell us all
the truth.

Bye.





       {Original Message removed}

2001\02\28@043508 by John Walshe

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I was once told that the US 60Hz system was chosen because at that frequency
the transformers would spend less time(or no time) in saturation and thus
the higher frequency saved energy.
John

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2001\02\28@090109 by Bob Ammerman

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Early AC power systems in the US were 25Hz.

When I was in high school I was on the lighting crew.

Power for the auditorium and stage lights came into the building at, IIRC,
3+ kV and down into a 'relay room' which contained three very large
transformers to bring the voltage down to floating 120V delta (a strange
story in itself).

The nameplates on those old transformers read 25Hz!

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\28@100340 by Alan B. Pearce

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>The nameplates on those old transformers read 25Hz!

Then I guess you had no problems with switching transients getting out and
upsetting other people :)

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2001\02\28@111624 by Bob Ammerman

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> >The nameplates on those old transformers read 25Hz!
>
> Then I guess you had no problems with switching transients getting out and
> upsetting other people :)

Yeah, these things were pretty big iron.

And we didn't have much in the way of transients: dimming was done with huge
rheostats, no 'dimmer hash'!

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\28@115045 by Herbert Graf

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> > >The nameplates on those old transformers read 25Hz!
> >
> > Then I guess you had no problems with switching transients
> getting out and
> > upsetting other people :)
>
> Yeah, these things were pretty big iron.
>
> And we didn't have much in the way of transients: dimming was
> done with huge
> rheostats, no 'dimmer hash'!

       Hehe, I worked at one theatre where they used AMX-192 for everything but
still had those rheostat dimmers. THEY WERE HUGE!! We called them
"Frankenstein Dimmers". The dimmers were about half a meter tall and the
handles you used to dim were above a meter long. Obviously they weren't
hooked up, but the thought of running a show with those things was just
funny to me! I can't imagine how HOT it would have gotten in that small
lighting booth with those dimmers being used. TTYL

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