ASHINGTON, May 5 - As the electric grid
approaches its season of peak strain, engineers say they still
cannot answer the central question of how a power failure in Ohio on
Aug. 14, 2003, became the biggest blackout in North American
history.
Investigators, including officials from the United States and
Canada, say that the eastern power grid - the vast complex of
generators, substations and transmission lines through which the
power failure spread last August - has become so large, complicated
and heavily loaded in the last two decades that it is difficult to
determine how a single problem can expand into an immense
failure.
A report issued by the Energy Department on April 5 put forward
extensive recommendations for reducing the likelihood of isolated
problems, like the failure of transmission lines in Ohio last
August. But the report stopped short of speculating how a local
problem cascaded into a catastrophe that spread from northeastern
Ohio through Michigan, Ontario and New York and into parts of
Connecticut and New Jersey.
Investigators did identify how local failures could become larger
difficulties in a way that had not been previously known: protective
devices called relays could be tricked into shutting down power
lines if they sensed short-circuits that did not actually exist. But
the report only hinted at solutions.
The report has drawn mixed reactions from electricity experts.
While some said it was thorough and balanced, others said that it
reflected a bias by its overseer, the Federal Energy Regulatory
Commission, to de-emphasize ways that deregulation of the electric
market might have affected the system's reliability and
vulnerability.
Robert Blohm, an electricity consultant who first questioned some
of the report's calculations, said in an e-mail message: "We've
charged ahead with long distance markets in electricity without
realizing/understanding the reliability effects which this blackout
brought home."
People involved in preparing the report acknowledged that it
focused on the origins of the blackout and did not fully explain how
it spread. One specialist, Gerry Cauley, the director of standards
at the North American Electric Reliability Council, an industry
group founded after a widespread blackout in the Northeast in 1965,
said it made sense to promptly address the events that started the
blackout because they were easily preventable. The events in Ohio
were "so egregious that they just should have never happened," he
said.
Alison Silverstein, senior energy policy adviser to the
regulatory commission, who drafted much of the report, said in an
interview: "Reliability is about taking care of the basics every
single day. That's what all of those prior blackouts told us. That's
what this blackout told us."
Investigators concluded that power lines initially failed in the
blackout because they came into contact with tree branches. The
inquiry also found that an Ohio utility and a regional power control
agency did not have the computer tools to spot failures as they
occurred and make compensating adjustments.
Focusing on the origins of last year's blackout was easier than
looking in detail at how it spread, experts said. Mr. Cauley said
that lines, substations and generating stations fell in such
profusion that plotting just two or three seconds of events takes
weeks of work. He says he hopes to finish a detailed analysis by the
first anniversary of the blackout.
The report discusses several hypotheses about the spread of the
disturbance, including relays confusing huge power flows with
short-circuits and reacting by shutting down lines. Installation of
relays that can tell the difference is probably years away, experts
said.
A broader question is whether the power failure would have been
less extensive if the system had been set up to tolerate more
disruptions. "Maybe the Midwest would not have gone down," said Jack
Casazza, a transmission expert and consultant. Conversely, he said,
had the relays not tripped, it is also possible that the blackout
might have spread further. "Maybe the whole darn East Coast would
have gone down. I think it's important to know the difference."
The report cautions that "simulation of these events is so
complex that it may be impossible to ever completely prove" theories
about the events. Such a thorough analysis was "not a job we could
do in the time we had available," said David Meyer, senior adviser
to the Office of Electric Transmission and Distribution in the
Department of Energy.
The report notes that some companies on the grid failed to submit
complete data and that some utilities, asked to say when and why
various components of the electric system shut down, did not fully
respond.
The report's focus on initial failures in the blackout contrasts
with similar studies of earlier power failures. In 1978, discussing
blackouts in 1965 and 1977, the regulatory commission said that it
was "not possible to prevent an occasional localized power failure."
The trick, the investigators said then, was to prevent them from
spreading. Ms. Silverstein said that the 1977 blackout was less than
a tenth the size of the 2003 blackout, and easier to diagnose.
