response 63 of 99:

Aug 25 23:36 UTC 2003

Monday's (http://ars.userfriendly.org/cartoons/?id=20030825) is also good.
But then, I gather they pretty nearly always are.

response 65 of 99:

Aug 27 03:05 UTC 2003

Speaking of the blackout, I finally got a chance to read Saturday's
NYT article about it.  The details of the timeline are awe-inspiring
in the way massive forces marshalled themselves with such speed, but I
digress....

As it happens the problems began with First Energy in Ohio, but the
vulnerabilities are probably built into the system.  We depend too much
on long-distance transmission of power (which is not terribly efficient
in any case, and should be discouraged by policy) and the communications
system for handling imbalances is people yakking over telephones.  This
is good for problems coming up over the next hour, but totally inadequate
to handle lightning-fast changes over the next ten seconds.  If we are
going to continue as we are, we need to find ways to manage power much
better.  For instance, if First Energy had been able to cut every
air conditioner in Cleveland back to half power in response to the
power lines failing, the problem might never have happened.  If Michigan
had 2 GW of surge power on tap, the local grid would have stayed up
long enough to cut Ohio loose.  Etc, etc.  There are a lot of things
we need to address.

response 67 of 99:

Aug 27 04:50 UTC 2003

Alright, so what moves and what direction does it move?  (Lightning
actually moves from the ground up to the sky, not the opposite which is
what we perceive as we are used to gravity - ie things don't fall into
the sky.)  

Muna is actually what was flowing, electrons are merely like ball
bearings that ease the way and some substances have more electrons
that are greased to ease the passage of muna.  It is entirely possible
that something in Ohio caused muna to rapidly leak out over the ground
and thus the direction of muna flow reversed course.  It is also
possible that somethings in Canada suddenly stopped wanting muna, and
since muna likes to keep moving once it is finally convinced to do so it
headed back home where it came from so the buckeyes may have been the
victims not the cause.  The other problem with muna is that it is hard
to coordinate things.  Some early practioners in the art of muna
movement decided to wiggle the muna to try to coordinate events and that
has worked pretty well so far but the modern problem is that folks are
trying to move muna really long distances and so its sometimes hard to
figure out what has happened after an event as folk don't always know
what time it is as wiggling muna confuses things.

response 69 of 99:

Aug 27 12:59 UTC 2003

Re #66: Then you would have quibbled by saying "it's actually more like
70% the speed of light." ;>

response 71 of 99:

Aug 28 02:47 UTC 2003

What's to stop any given utility from rigging a computerized "fire
curtain" into their central control system, so that (when the larger
grid's getting out of control) they can both cut themselves off from
the larger grid and cut enough of their own load (via blackouts) to
achieve independent, local stability?

response 73 of 99:

Aug 28 06:09 UTC 2003

Do you know why load shedding is disliked (if not anathema)? Load shedding
should go along almost automatically with generation dropouts. 

There is an ultimate technical problem with even using AC, which is phase
matching, which makes grid regulation tricky. Think of having two home AC
generators and trying to put them in parallel (it is even a problem for
load leveling, but phase matching makes it much harder). It would be
easier with DC (also with fewer losses), with the use of modern converters
for voltage shifting.

response 75 of 99:

Aug 28 13:28 UTC 2003

Re #71: That's sometimes done; it's called "islanding".  There are two
problems, though, as I understand it.  One is that the local utility may
simply not have the generating capacity to carry the load once they're
isolated from the grid.  Another is that it becomes difficult to get the
islands back in phase to reconnect them later, without shutting
everything down.

Re #72: Automatic under-frequency load shedding was supposed to have
been implemented after the major blackout in the 70's, but obviously the
systems aren't as effective as people had hoped.  The major blackouts on
the west coast in the 90s (some of which actually did end with the west
coast seperating into three "islands") showed that sequencing automatic
controls so that they trip in a way that limits damage, instead of
causing it to cascade through the system, is difficult.  We don't seem
to be able to model the behavior of these complicated power grid systems
very well.

response 79 of 99:

Aug 28 19:12 UTC 2003

From: <BreakingNews@MAIL.CNN.COM>
Subject:      CNN Breaking News

Major power outage hits south London, cutting subway service 
during evening rush hour.

response 85 of 99:

Aug 29 01:54 UTC 2003

Re: #75
The local utility doesn't need to have enough generating capacity active
"on the island" when they cut it loose from the grid...IF they have the
ability to both measure usage in and blackout a fair number of smaller 
parts of the island.  X times per second, a computer in their central 
switching HQ solves the problem "if we cut to being an island right now,
which pieces of load and/or supply would have to immediately cut to have
our island's grid viably balanced?".  If the larger grid gets too bad to
hand onto, then the computers simultaneously cut off from it and off from
the load and/or supply that the island can't keep up right now. 

Where do the power plants get their 60Hz reference from now?  Or is it
just a brute-force "democratic vote" of the local references on a variety
of pieces of equipment?  Sounds like syncing islands to rejoin is a "we
never bothered to make control systems for that" problem.  

response 87 of 99:

Aug 29 05:32 UTC 2003

I don't know where they get their reference, but I do know that the
frequency wanders during the day, such that clocks that use synchronouos
motors vary daily by several minutes (mostly partly corrected overnight -
see http://web.ukonline.co.uk/freshwater/clocks/synch.htm).