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SOCNET  November 2003

SOCNET November 2003

Subject:

Network analyses of power blackouts, and robots making network maps of their world

From:

Rick Davies <[log in to unmask]>

Reply-To:

Rick Davies <[log in to unmask]>

Date:

Thu, 6 Nov 2003 18:36:51 +0100

Content-Type:

text/plain

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*****  To join INSNA, visit http://www.sfu.ca/~insna/  *****

Hi

Have list members read the recent Sci American article on power blackouts in
the USA? It makes a number of interesting observations about the downsides
of excess connectivity in power webs, and how the solution (i.e how to avoid
blackouts) may be via reducing the amount of connectivity, and the creation
of islands of connectedness. The latter part of the the argument reminded me
of the later sections of Stuart Kauffman's book (At home in the universe(?,
1994), where he talks about the usefullness of "patches".

For those who are interested, I have copied the article below (and hoping I
wont be sued), I have also included a link to the online issue it can be
found in.

In the same issue there is an article about how a team / crowd of small
robots can navigate a complex space by creating a map which consists
essentially of a network diagram showing how they all link up to each other
in distance terms (calculated as the difference between sound and radio
feedback from each other)

regards from Rick Davies, www.mande.co.uk
===============
http://www.sciam.com/article.cfm?chanID=sa006&colID=5&articleID=000784B6-E5F
B-1F86-9B8C83414B7FFE87

Healing the Grid
Several near-term solutions can keep the juice flowing
By JR Minkel

If the electric power grid is the nation’s circulatory system, then it
suffered a massive heart attack on the afternoon of August 14 when lights
winked out from Ohio and Ontario to New York. Although no one knows
precisely why a seemingly mundane local system failure cascaded so far,
researchers have long seen tension in the grid and are pondering ways to
minimize the chance of big blackouts.

The grid represents a delicate balancing act: the amount of electricity
sucked from the lines (the load) at every moment has to match the
electricity being generated. If generation slows too much, system
controllers have to shed load, causing a blackout. Further complicating
matters, electricity flows through the grid primarily as alternating
current. So AC frequencies at each station must match but be offset in a
precise manner to keep power flowing in the right direction.
Partial deregulation during the early 1990s allowed some states to separate
their generation and transmission industries. Generation systems boomed, but
transmission lagged behind because of the patchwork of interstate
regulations and jurisdictions. Many policy and grid experts say that in the
short term, the Federal Energy Regulatory Commission should enact nationwide
policies covering transmission system operation, capacity and investment.
The commission could force transmission owners to join Regional Transmission
Organizations that would implement the policies.

Once the government decides how the grid should operate, "we have the
technology to implement it almost on the shelf or coming down the pipe,"
says Paul Grant, science fellow at the Electric Power Research Institute
(EPRI), an industry consortium in Palo Alto, Calif. Currently protective
relays shut down power lines if high currents threaten to make them overheat
and sag, but those lines could be kept functioning with more heat-resistant
lines, which are already available. Generators, which are basically giant
flywheels, switch off if the AC frequency or phase changes rapidly (because
the generators can damage themselves trying to respond); so-called breaking
resistors, which exchange electricity for heat, could help generators make
smoother transitions.

Better communication among power stations would also aid in stabilizing the
grid. Protective relays rely on local information and can be fooled into
disconnecting a line unnecessarily. Dedicated fiber optics would permit fast
comparisons of conditions at adjacent stations, forestalling needless
shutdowns. The Global Positioning System (GPS) could put a time stamp on
each station reading, allowing operators to make better decisions by looking
at successive snapshots of grid conditions. The Bonneville Power
Administration, based in Portland, Ore., and Ameren Corporation, a St.
Louis–based utility, use GPS time stamping.

Once operators get a picture of grid conditions, they could disseminate the
information to faster, smarter switches. Flexible AC transmission system
devices can tune power flow up or down, and superconducting valves called
fault current limiters could enable circuit breakers to disconnect lines in
a safer way. Installing more AC lines or more powerful superconducting lines
alone would increase transmission capacity but could lead to bigger ripples
in the grid if something went wrong. "You’ve got to be able to contain a
major disturbance, and the most common way to do that" is to disconnect
lines, explains electrical engineer Peter Sauer of the University of
Illinois.

Ideally, Grant states, a master computer with a bird’s-eye view would serve
as air traffic control for the grid. Postmortem studies by the industry
suggest that such a global view would have prevented about 95 percent of
customers from losing power during the 1996 blackouts in the western U.S.,
he says. Although experts differ on the feasibility of constructing an
über-computer, most agree that a slightly less ambitious scheme might work.

One such scheme involves an improved control method designed to
automatically quarantine trouble spots and gerrymander the remaining grid
into islands of balanced load and generation. EPRI commissioned
computer-modeling studies of the technique, called adaptive islanding, which
concluded that it could preserve more load than conventional responses.
Massoud Amin, an electrical engineer at the University of Minnesota who
headed the EPRI program that co-funded the research, says adaptive islanding
could be implemented within five years.

Nobody familiar with the power grid expects blackouts to disappear entirely.
If chaos or network theories are right, a chance of large cascading failures
is inherent to stressed or highly interconnected systems. And with every
incremental increase in grid reliability, the cost of the next increment
goes up. So keeping a stash of fresh batteries will make sense for a long
time.

===============

regards from Rick Davies

_____________________________________________________________________
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