SDG&E seeks to upgrade grid in southern Orange County, Calif.

San Diego Gas & Electric (SDG&E) is seeking a certificate of public convenience and necessity (CPCN) for a project designed to increase reliability in southern Orange County, Calif. The utility filed a CPCN application and environmental assessment with the California Public Utilities Commission (CPUC) May 18 for the south Orange County reliability enhancement project.

The proposed project would provide increased electric network reliability and reduce the risk of a potential system-wide outage affecting all of SDG&E’s customers and substations in the south Orange County area, according to the filing. The California ISO approved the project last year as part of SDG&E’s 2010/2011 Transmission Plan.

“We’ve seen power usage triple in the last 25 or so years,” an SDG&E spokesperson told TransmissionHub on May 21. In addition to commercial and industrial growth, “We’ve also seen the residential side grow, and we’re attributing that to the advances in technology. Your average household is consuming a lot more energy today versus 25 years ago.”

The proposed project includes upgrading transmission lines and substations within the cities of San Juan Capistrano, San Clemente and the unincorporated areas of Orange County, which are in the northern part of SDG&E’s service area.

Under the proposed project, the existing eight-mile, 138-kV transmission lines that connect the utility’s Capistrano substation in San Juan Capistrano and its Talega substation near San Clemente would be replaced with a new 230-kV double-circuit line. Most of the transmission line work will be conducted within SDG&E’s existing right of way.

“The 230-kV line will be able to handle the additional capacity, but we’re really looking at this as a reliability project because this area has grown, and to be only fed by a 138-kV line, we feel that a 230-kV line would be a much more reliable solution for this area,” the spokesperson said.

SDG&E’s proposed project includes rebuilding and upgrading the 1950s-vintage 138-kV/12-kV Capistrano substation. “We need to raze that [substation], and build a new 230-kV/138-kV/12-kV substation, so that’s going to be a substantial part of the project,” the spokesperson said. The Capistrano Substation provides electric service to the majority of customers in San Juan Capistrano.

The project also includes reconfiguring the existing 138-kV transmission lines at the Talega substation, which is located on the Camp Pendleton Marine Corps base on the border of San Diego and Orange Counties.

The southern Orange County portion of SDG&E’s service area has 129,000 customers and represents about 10% of the utility’s total customer load of about 5,000 MW, according to the CPUC filing.

“In the middle of the summer, when everyone is running their air conditioners, the [existing] lines are almost at full capacity,” the spokesperson said. Upgraded lines and substations are going to give SDG&E “more flexibility as well to balance the customer load over more circuits. In the event that we have an outage in that area or we need to do work, to be fed by just that 138-kV line, it gets a little challenging.”

Not only has the south Orange County 138-kV transmission network reached its capacity, its current design is vulnerable to service interruptions due to potential transmission failures. The proposed project will resolve these areas of concern and enhance SDG&E’s delivery of safe, reliable electric power to south Orange County, the utility said in a statement announcing the filing.

The project is estimated to cost between $450m and $500m, with the majority being spent to upgrade the Capistrano substation. If the project is approved by the CPUC, construction could begin as soon as the end of 2013 with completion expected in 2017.

SDG&E is a subsidiary of Sempra Energy (NYSE:SRE)