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Re: East Coast outage?
From: George William Herbert <gherbert () retro com>
Date: Fri, 15 Aug 2003 15:29:23 -0700



Then run parts at 105-110% and it gets really hard.

The power industry designs a grid that runs so close to capacity that if^W 
when something big fails, the whole grid shuts down in a cascade.  They 
know it:

Rubbish again. 

Welcome to the wonderful world of physics. Ask your favourite physics
professor what does

      E1 = E2 

in context of yesterdays events.

That's not really answering the question, and it's also not
entirely right.

For one, even if we naively accept sum(Eproduced) = sum(Econsumed),
that says nothing about the amperage which can safely traverse
parts of the grid intertie wiring, switching facilities, etc.
If *those* are running at or slightly over capacity, and in
particular of all those facilities don't have at least N+1
and preferably N+M redundant actual capacity, then a single
point failure will produce a fatal cascading failure in the
system.  That appears to be what happened.

For two, most of the things that consume power are not in
fact consuming exactly a fixed amount of power.  Light bulbs
go dimmer if you reduce voltage; electrical motors will produce
less power (torque X rpm) if voltage drops, etc.  Minor blips
are happening all the time in major grids, and the voltage is
continuously varying up and down slightly.  If we had to keep
voltage exactly constant, a real AC power system would be
nigh-on impossible to build.

Our concerns with electrical capacity in terms of the interchange
grids having N+1 or N+M capacity, and having systems with enough
robustness and graceful failure modes, and having systems with
enough reserve generation capacity are all legitimate.  A lot of
other people are looking at that now, too.

But you *can't* just simplify this to Ein = Eout.


-george william herbert
gherbert () retro com


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