Grid Experiences Heat Stress Test

By Published On: August 10, 2012

With the 2,200 MW San Onofre Nuclear Generating Station down, a statewide heat wave this week tested the grid triggering the first Flex-Alert since the 2011 blackout in San Diego. Utilities appealed for conservation and resorted to demand-response programs to trim load. The California Independent System Operator declared a Flex-Alert the morning of Aug. 9, after forecasting a peak demand of 47,125 MW in its control area for the day, a forecast that ended up on the high side. “We look at the weather and forecasted demand and we make a judgment,” said Kristina Osborne, grid operator spokesperson, following the Flex-Alert, a call for voluntary conservation. The last time demand hit Thursday’s forecasted level was on Aug. 25, 2010, when peak load reached 47,350 MW. The grid stress test came as National Weather Service forecasters predicted the peak temperature would hit 109 degrees in inland valleys around Los Angeles on Aug. 9. In this week’s heat wave, peak load marched upward each day hitting 43,414 MW on Aug. 7, 44,721 MW Aug. 8, and 45,324 MW Aug. 9. The all-time peak CAISO load was 50,279 MW during the heat storm of 2006, when temperatures soared to 116 degrees in Los Angeles area suburbs. The Flex-Alert covers Aug. 10 through Aug. 12, with peak CAISO area demand forecast at 46,800 MW Aug. 10, 43,000 MW Aug. 11, and 43,000 MW on Aug. 12. LADWP saw total demand reach 5,663 MW Aug. 8 and expected it to approach a record high level of 6,000 MW Aug. 9. The muni’s all-time energy demand record was 6,177 MW on Sept. 29, 2010. “We have enough resources to cover it,” said Aram Benyamin, Los Angeles Department of Water & Power senior assistant general manager. He noted that the muni not only called for voluntary conservation, but implemented its demand-response program, plus suspended scheduled maintenance on all its generating units so that all of them are available to meet demand.

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