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I am going toput my head on the block and post a note from Tap-L that
seems pertinent here. The author seems knowledgeable and does not
appear to be on this list - if he IS - I apologize. I am cc:ing him
so everybody can bombard him with spam ;-) Hey, maybe he WILL join us.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~ From: James Frysinger <frysingerj@cofc.edu>
To: tap-l@listproc.appstate.edu
Subject: Re: Transmission Lines, or Sammy's Blackout
Date: Sun, 17 Aug 2003 10:50:46 -0400
Reply-To: tap-l@listproc.appstate.edu
Sender: owner-tap-l@listproc.appstate.edu
On Saturday 2003 August 16 16:21, Clarence Bennett wrote:
How many wavelengths around is the Lake Erie Loop?
Less than one. At 60 Hz, with a velocity factor (1/n) of 0.80, the
wavelength would be 4000 km. The velocity factor is actually a bit higher
than this, so the real wavelength would be between 4000 km and 5000 km (the
value in free space).
My father is a retired EE. Before he retired, he was one of the leading
people in the country involved in designing transmission lines (the high
voltage lines that carry power around the grid). His explanation of one
massive blackout in the northeast was what he called "frequency cascading".
Essentially this is a description of what Fourier predicted when one is
presented with a rapidly rising or falling signal. Higher frequencies are
generated around the loop. But in power generation, one learns (as I did on
nuclear powered submarines) that the higher frequency source picks up the
load. So if a transmission line that suddenly goes up in frequency (by
addition of Fourier components), it will suddenly unload power stations
that feed it. For protective reasons, such stations normally shut down.
This is related to the reason that it is hard to cold start a large system
like that. Not only is there one humongous reactive load (mutual cable
inductance, capacitance to ground), but the system is large enough that it
"rings", especially for higher frequency components.
Jim