Construction could begin this year on a major addition to California's electric transmission system.

Photo: Greg Aragon Limits on transmission capacity have hamped existing Tehachapi wind farms.

The California Independent System Operator (CAISO) has approved Southern California Edison's $1.8-billion expansion plan for the Tehachapi area of Southern California, where development of the area's abundant wind energy has been hindered by lack of transmission capacity. SCE still must obtain approval by the California Public Utilities Commission, but CPUC last June assured the state's investor-owned utilities that it would allow cost recovery from ratepayers for transmission construction to serve renewable-energy plants.

The proposed Tehachapi Transmission project is a series of new and upgraded transmission lines to deliver up to 4,500 MW of renewable electricity from new wind farms that independent energy companies are proposing to develop in the next several years. SCE initially will fund the project, but recovery will be paid for by all customers in the California ISO coverage area through a transmission-access charge, says Armando Perez, CAISO vice president of planning and infrastructure development.

SCE wants to construct the project in 11 segments, beginning with three segments totaling about 75 miles of 500-kV line. Construction would begin this year, after final project approval from CPUC, says Charles Adamson, SCE project manager. The utility will submit an application with CUPC in April, he says. The rest of the segments are to be completed by 2013.

SCE is performing internal engineering and specifications for the final engineering bid, which will go out for contract in the next two months, Adamson says. He is hoping to get one contractor to build this entire portion. The project will be managed by SCE.

The lines will traverse flatlands, rolling hills, jagged mountains, steep cliffs, canyons and urban areas as they make their way through mostly existing SCE easements, says Adamson. The rest of the needed land will have to purchased from property owners, he says. "But if negotiations aren't successful, we have the right of eminent domain."

Steel lattice towers will be used predominately in the mountains because they are easier to transport in pieces and assemble on site, says Adamson. In the flat country, tubular poles will be used because they have a smaller footprint, he says.

"The biggest problem is the fact that we are going to have a huge amount of wind that has to be controllable in terms of what it does to our load and resources balance on a daily basis," says Perez. "We are studying what additional equipment we are going to have to have in place in order to control the rapid swings in generation that the wind will bring. We'll have all the answers by July."

The California Wind Energy Association praised CAISO's action "because it simultaneously addresses system reliability and improved economics while providing access to renewable resources that our utilities require to meet the states renewable energy goals," said Nancy Rader, executive director, in a statement.