For the 265-MW Ocotillo Wind project, SDG&E looped the 500-kV transmission line into
the 500-kV switchyard using a ring bus configuration with a fully redundant ac-dc auxiliary
To meet the state-mandated California Renewables Portfolio Standard, San Diego Gas & Electric (SDG&E) constructed, energized and put into service a Sunrise Powerlink project connecting San Diego, California, U.S., to the renewables-rich Imperial County, California. The standard requires investor-owned utilities in California to increase procurement of renewable energy resources (RERs) to 33% by 2020.
The Sunrise Powerlink project includes approximately 117 miles (188 km) of 500-kV and 230-kV overhead and underground transmission lines with several large 230/500-kV substations. SDG&E also is in the process of upgrading its transmission network to accommodate more than 1,000 MW of wind and solar generation.
Location, Location, Location
Most of the RERs are located in isolated desert areas, away from load centers but relatively close to 500-kV and 230-kV transmission line corridors. The remote locations of RERs, extensive time required for permitting and environmental restrictions required SDG&E and RER developers to build high-voltage switching switchyards at remote locations to interconnect the new, clean generation directly into the existing 500-kV and 230-kV transmission line infrastructure.
The switchyards’ bus configuration, equipment specification and method of interception of these switchyards into the transmission grid have been carefully designed and selected to ensure a high level of transmission system reliability and operability while cost-effectively incorporating the large amounts of renewable power generation on the grid.