Arizona Nuclear Power Plant Shutdown Wreaks Havoc in Southwest
By John G. Edwards, Las Vegas Review-Journal -- June 16
Nevada Power Co. narrowly avoided an outage following the unexpected shutdown of all three units at an Arizona nuclear power plant, Mark Shanks, director of regional transmission for the Las Vegas-based electric utility, said Tuesday.
Shanks said the electrical frequency at Nevada Power didn't drop below the
trip point but did in Arizona and New Mexico, causing temporary outages.
"It got very close," he said. "From a supply perspective, we
didn't see any impact at all from having these units down," Shanks said.
Nor did he believe the incident cast uncertainty on power reliability for the
summer.
"I think the system held together very well," Shanks said. "It
wasn't a major breakup. It did create some havoc in Arizona and New
Mexico."
The nuclear plant inspectors planned to look at the causes of the shutdown
and the response.
Nuclear regulators were concerned that diesel generators that are supposed to
provide backup power did not do so, said Victor Dricks, a spokesman for the
Nuclear Regulatory Commission.
The units are supposed to each have two diesel generators that will operate
if power is lost. Only one of the generators at Unit 2 worked properly, Dricks
said.
The plant shut down as a fail-safe on Monday morning after a disruption in
the western power grid. The disruption caused roughly 65,000 Arizona customers
to lose power for about an hour. Customers in New Mexico and Northern California
also were affected.
Power was restored using alternative supplies, said Jim McDonald, a spokesman
for Arizona Public Service Co., the utility that operates the plant 50 miles
west of Phoenix.
It was expected to take several more days for Palo Verde to be operational
again, McDonald said.
Monday's shutdown was the first time all three units at the plant, one of the
nation's largest nuclear facilities, automatically shut down because of a
disruption.
By Tuesday, APS officials had concluded that the outage started with the
failure of an insulator on a large transmission line in northwest Phoenix. The
failure should have tripped breakers that are designed to isolate the problem
and protect the rest of the grid. But the breakers also failed, causing Palo
Verde and a nearby gas-fired plant to shut down.
The disruption caused about 30,000 customers in Phoenix and 35,000 customers
in Tucson to briefly lose power. In Albuquerque, N.M., about 16,000 customers
lost power for five to 12 minutes, and in San Jose, Calif., about 5,000 people
lost power, according to the East Valley Tribune.
Palo Verde supplies power to about 4 million customers in Arizona, New
Mexico, Texas and California.
The Associated Press contributed to this report.
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