The Trans Bay Cable (TBC) project in San Francisco, California, U.S., which is owned and operated by SteelRiver Transmission Co. LLC, is now complete.

Transmission experts from Pattern Energy Group developed and managed the construction of the TBC, a 53-mile (85-km) 400-MW high-voltage direct-current (HVDC) submarine transmission line that can transmit up to 40% of the peak power needs for the city of San Francisco.

TBC involves the development of converter stations in both Pittsburg and San Francisco. Power is used by consumers in the alternating-current (AC) form. Because AC power cannot travel efficiently over long distances while buried, it must be converted to the DC form in Pittsburg, and then back to AC once it reaches San Francisco.

In September 2005, the California Independent System Operator chose the TBC project over several other alternatives as the most feasible and fundamentally sound energy transmission project to address the load-capacity issues of San Francisco and northern San Mateo County, while also creating access for these areas to the abundant renewable energy sources of Northern California.

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