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.

San Diego Gas & Electric Co., substation upgrades

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.

San Diego Gas & Electric Co., substation upgrades