Mechanical problems fell California power plants

With 2,200 Mw of electricity out of service due to power plant failures, the California Independent Transmission Operator Tuesday called its 12th Stage 2 emergency so far this summer.

The outage and continuing heat wave in southern California prompted the ISO to request utilities to curtail about 1,200 Mw of interruptible load among customers who volunteer to reduce demand in exchange for lower electricity prices.

That's almost double the 740 Mw in interruptible load the grid operator asked to be implemented Monday.

Southern California Edison Co. said the agency directed SCE to reduce its electrical load by 660Mw.

Earlier in the day, the ISO asked for bids on 2,000 Mw of supplemental power to meet the estimated peak load of 43,218 Mw, topping Monday's adjusted peak demand of 43,087 Mw.

The main transmission artery to the south, Path 26, is being utilized to maximum capacity today to deliver power to the region, the ISO said.

Calling in interruptible load will "help us over the peak," said an ISO spokeswoman. She said the grid operator does not expect to have to call a Stage 3 alert, signaling reserves have fallen below 1�%.

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 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.