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NWPPC Revises Federal Power System Failure Probabilities

by Mike O'Bryant
Columbia Basin Bulletin - January 17, 2003

The Northwest Power and Conservation Council corrected this week a mistake to its December calculations of the Federal Columbia River Power System's loss of load probability (LOLP), saying that there is little to worry about this year and through 2006.

LOLP is a measurement of the likelihood that the regional power system would fail during January through March to meet all power loads and would have to curtail usage.

The new estimate by the Council shows that the LOLP is less than 1 percent in 2003 and only goes up above the industry standard 5 percent during the years 2004 through 2006 under certain dire conditions. In December, Council staff predicted the LOLP in 2003 to be 4 percent and 7 percent in 2004, but that that would rise to 15 percent in 2005 and 2006.

"This is an important revision to what we had before," said Tom Karier, Council member from Washington. "We no longer have concerns several years out. Of course, the caveat is that all power plants in process will be built."

The revision is based on the latest water supply forecast that predicts the January through July water volume in the Columbia River Basin, measured at The Dalles Dam, will be 80,000,000 acre feet of water, which is 75 percent of average runoff. The forecast assumes normal precipitation and snowpack through the remaining winter. Dick Watson, Council staff, said the prediction is early and so there is a great deal of uncertainty in it that ranges from a low 50 maf (47 percent of normal) to 103 maf (103 percent of normal).

Even with the low water supply forecast, Watson said the regional power system would make it through this winter with little threat of curtailments.

John Fazio, Council staff, said the Council's December estimate of LOLP predicted a tolerable level of risk, but that risk rose to intolerable levels in 2005 and 2006. The difference is in the assumptions. he latest data incorporates a more current streamflow forecast (there has been significant precipitation since early December).

"The biggest difference is that before we were dispatching hydro way too aggressively," he said. "That resulted in excessive drafting of reservoirs early in the winter and supply problems later in the winter."

While the 2003 LOLP is likely to remain at less than 1 percent, by 2006 the LOLP could rise under certain conditions. If the load and resource balance estimate is 1,000 megawatts low, for example, the 2006 LOLP would rise to 6 percent. Or, if imports from California are not available during Northwest winter peak loads, the LOLP could rise to 6 percent. Or, if the U.S. Army Corps of Engineers cannot draft storage reservoirs, particularly Grand Coulee Dam, below April 10 rule curves, then the LOLP in 2006 could rise to 10 percent. In the unlikely event that all of these limitations occur, then LOLP would rise to above 50 percent, Fazio said.

During the West Coast energy crisis in 2000 and low water conditions in the Northwest, the Council predicted that the future load and resource balance (2003) would be 2,800 MW short, which would have resulted in an LOLP of 24 percent. Instead, today's load/resource balance is a positive 4,200 MW, nearly a 7,000 MW swing, and LOLP is under 1 percent. About 2,000 MW is due to the shutdown of Northwest aluminum plants and about 3,100 MW is due to new generation that has come on line in the last two years, Fazio said. The Council is estimating there will be about 3,100 MW extra generation in 2006.

Related Sites:
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Mike O'Bryant
NWPPC Revises Federal Power System Failure Probabilities
Columbia Basin Bulletin, January 17, 2003

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