California ISO calls for shedding 1,900 Mw

California's electrical power system continues to teeter on the edge. With peak usage beating earlier forecasts, the California Independent System Operator declared its 13th Stage 2 power emergency Wednesday and called on state utilities to shed all voluntary load available, about 1,900 Mw.


California's electrical power system continues to teeter on the edge. With peak usage beating earlier forecasts, the California Independent System Operator declared its 13th Stage 2 power emergency Wednesday and called on state utilities to shed all voluntary interruptible load available, about 1,900 Mw.

The ISO said demand is trending about 1,000 Mw higher than usage forecasts. Wednesday's peak has been revised to 44,070 Mw, up from earlier estimates of about 43,617 Mw. The agency ordered Pacific Gas & Electric Co., Southern California Edison Co. (SCE), and San Diego Gas & Electric Co. to curtail load among customers who volunteer to reduce demand in exchange for lower electricity prices.

SCE said the grid operator asked it to reduce its electrical load by 664 Mw�enough power to serve about 500,000 homes.

Tuesday the agency asked for a total reduction of 740 Mw in interruptible load.

The ISO also said about 2,122 Mw of electricity remains out of service due to power plant failures from working overtime to meet high electrical demand. Earlier in the day, the ISO asked for bids on 2,000 Mw of supplemental power to meet the estimated peak load.

If reserves fall below 1�%, the grider operator will declare a Stage 3 alert. By some estimates, the ISO is getting very close to that level.

During Stage 3, rolling blackouts are instituted to avoid bringing the system down. Involuntary disruptions were called in the San Francisco area earlier this summer.

Throughout the summer, the ISO has instituted nearly continuous so-called "no touch" maintenance days which keep power plants available, while increasing the likelihood of mechanical failure.

The California ISO is chartered by the state to manage the flow of electricity along the long-distance, high-voltage power lines that make up the bulk of California's transmission system.

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