SCE Calif. Big Creek hydro unit curtailed again

NEW YORK, Dec 1 (Reuters) - Southern California Edison increased and then decreased the output at the 1,000-megawatt Big Creek hydro project in California by Sunday afternoon, the California Independent System Operator said in a report.

On Nov. 26, before the Thanksgiving Day holiday, the plant was curtailed by 630 MW. It was curtailed by just 170 MW on Nov. 28, the Friday after Thanksgiving.

On Sunday, it was curtailed by 775 MW again.

The Big Creek project is located near Big Creek in Fresno and Madera Counties about 225 miles west-southwest of San Francisco.

There are several units in the project, including the 207 MW JS Eastwood pumped storage unit (which entered service in 1987), 19 hydro units ranging in size from 16 MW to 50 MW at Big Creek (1913-1980), the 11 MW Portal hydro unit (1956) and two 94 MW Mammoth Pool hydro units (1960).

Pumped storage plants store and produce electricity to supply peak power demands by moving water between reservoirs at different elevations.

At times of low demand and low power cost, the plant uses electricity from the grid to pump water into the higher reservoir. When demand and prices are higher, the station releases the water back into the lower reservoir through a turbine, generating energy.

One MW powers about 700 homes in California.

So Cal Ed is a regulated subsidiary of Edison International (EIX.N).

Edison International, of Rosemead, California, owns and operates about 14,000 MW of generating capacity, markets energy commodities in North America, and transmits and distributes electricity to about 4.8 million customers in central and Southern California. (Reporting by Scott DiSavino; editing by Jim Marshall)