California regulators recommend approving changes to technical details of Tehachapi project

An administrative law judge (ALJ) is recommending that California regulators approve a request to amend their July 11 decision ordering that a portion of the Tehachapi Renewable Transmission Project (TRTP) be placed underground (Docket No. A07-06-031).

In its decision, the California Public Utilities Commission (CPUC) approved undergrounding a 3.5-mile stretch of the project that passes through the city of Chino Hills, Calif., but denied a request by developer Southern California Edison (SCE) that it be allowed to include voltage control equipment on the 500-kV line and instead directed the utility to study the possibility of changing the basic insulation level (BIL) rating for the line.

On Sept. 9, SCE filed a petition for modification, stating that the provisions of the order would be problematic, as the highest rated cross-linked polyethylene (XLPE) cable available that can be used in the 500-kV application is rated at 550-kV, allowing only a 10% deviation from the intended operating voltage.

SCE further noted that undergrounding the transmission line will cause an increase in the transmission line charging current that could, in some cases, cause the voltage on the system to exceed its 550-kV rating. Therefore, the company said, voltage control is necessary to control voltage and prevent damage.

In addition, the utility stated that studying the possibility of changing the basic insulation level (BIL) rating for the line, as directed by the CPUC in its July order, would significantly delay the in-service date of the TRTP, perhaps to as late as 2019.

In the proposed decision approving SCE’s petition for modification issued Dec. 12 by ALJ Jean Vieth, the CPUC approves SCE’s request to remove the basic insulation level study requirement and authorizes the utility to include voltage control equipment for reactive compensation as part of the construction of Segment 8A.

The proposed decision also increases the reasonable maximum cost for Segments 4 through 11 of the project by $23m, which a previous decision identified as the approximate cost based on SCE’s preliminary engineering. However, SCE noted that the estimates that underlie the reasonable maximum cost “have increased significantly.” In response, the proposed order states that the commission will ask for briefs on the issue from SCE, providing additional detail.

The proposed decision is subject to a 30-day public comment period before it can be placed on the agenda for a voting meeting, a CPUC spokesperson told TransmissionHub Dec. 19. The next such meeting will be Jan. 16, 2014.

When completed, the project will be able to deliver up to 4,500 MW of largely renewable energy to Southern California, enough electricity to power three million homes, the utility said.

SCE has called the project “a critically important, high-voltage transmission line, the timely completion of which is essential for California’s progress toward its aggressive renewable energy goals.”

California’s renewable portfolio standard calls for 33% renewable energy by 2020.

SCE is a subsidiary of Edison International (NYSE:EIX).