Re: US Power Outages

[mccoy@communities.com (Jim McCoy)]

Lucky (crypto-leprechaun) wrote:
> At 18:15 8/11/96, Dave Farber wrote:
> >The avalanche behavior of power systems is still not
> >well understood and techniques to prevent such failures are not obvious.
> >Same can be said of telephone and computer networks at different levels.
>
> Does somebody here have a pointer to literature on this topic? A system in
> which small localized disturbances can amplify, propagate through the
> system, leading to catastrophic failure is the worst of all possible
> designs. I fail to understand why a system as important as the power grid
> would display this type of behavior. Why is the grid negatively dampened?

Because the system designed to fail non-destructively rather than risk
a power surge.  Part of the problem is that the power being controlled
moves as fast as any information about the state of the network: all
decisions must be made locally at the switch level.  When a major line
fails the power generation stations can not just "turn off the juice" at
the speed required, the power must either be redistributed or else the
switch overloads and shuts down to prevent a massive power spike.  The
power companies would rather face the ire of consumers without power for
an evening than the outcry that would happen if every toaster, microwave,
and computer on the west coast was fried by the spike caused by 3 gigawatts
being dumped into grids that could not handle the load (not to mention the
long-term blackouts caused by local switching equipment getting fried.)
In this case the system must fail to prevent damage.

The great east coast blackout was caused by a $50 switch which wore out.
The switch happened to control a chunk of load which was re-routed on to
another line, causing a cascade failure as the excess load caused other
switches to fail when it was dumped on to those lines (and the excess
load caused by these other switches tripping accellerated the failure.)
Power distribution is not like telecom, if a phone switch dies the calls
end; the failure does not endanger the upstream switch with overload
from bits not going anywhere.

Imagine that cars on highways had no brakes until they reached an offramp
but the DOT could apply a kill-switch to segments between offramps (tying
this thread into another non-crypto thread on the list :),if a failure in
the roadway caused traffic to stop then all of the upstream traffic would
have to be dumped off the road via offramps that were only one or two lanes.
This would cause further bottlenecks and the kill-switch would need to be
applied to more and more segments upstream to prevent the traffic stopped
or being slowly bled off from causing more problems.  No imagine that
offramp-to-offramp messages were transmitted via messengers travelling
upstream in the carpool lane :)

Even the power company's secret experiments in the cores of nuclear reactors
have not found a way to get around the 186,000 km/s speed limit on everything.

jim