IV. Possible Configurations of a Tehachapi Transmission Project

SCE, the ISO, and Oak Creek presented several alternative configurations and routings of potential Tehachapi upgrades.

SCE's 2002 conceptual study developed reconnaissance-level plans for transmission upgrades sufficient to transport power from 2,500 MW of new wind generation, which is the capacity of potential projects identified by wind developers in response to SCE's 2001 solicitation. According to the results of this conceptual study, wind generation would be delivered by a 66 kV collector system to four new 230/66 kV substations. Two new 60-mile double circuit 230 kV lines would transmit the power, with one line terminating at the Pardee substation and the other at the Vincent substation. SCE estimated that this project would cost $586 million plus right-of-way costs.

SCE's conceptual study suggested that the Tehachapi transmission upgrades be phased to meet the needs of three levels of new wind generation: (a) less than 1,140 MW (the double circuit 230 kV line to the Pardee substation, with one circuit energized initially), (b) from 1,140 MW to 1,400 MW (adding the first circuit of the double circuit 230 kV line to the Vincent substation), and (c) more than 1,400 MW (adding the second circuit of the line to the Vincent substation).

SCE reports that, in addition to the 2,500 MW of wind generation analyzed in the 2002 conceptual study, it received requests for conceptual studies of transmission needs for an additional 770 MW of wind generation in response to its 2003 solicitation undertaken in response to the January 29, 2003 ALJ ruling. It had not performed those studies at the time of the hearings.

The ISO submits that alternative ways to connect Tehachapi wind generation should be studied before a decision is made regarding which transmission upgrades are preferable. The ISO identified several alternative configurations which it stated may provide regional transmission benefits, in particular, a needed expansion of transmission capacity in the Fresno area, which is served by PG&E. In one alternative, a new substation would be constructed where PG&E's Helms-Greg and SCE's Big Creek-Rector 230 kV lines cross, in order to establish a new phase shifted 230 kV tie between PG&E and SCE. The ISO and SCE report that this could add between 300 and 400 MW of capacity on SCE's Big Creek 230 kV system. Another option would construct a phase-shifted tie-line between SCE's Magunden and PG&E's Bakersfield 230 kV substations, which are five miles apart. This alternative could add a further 300 to 400 MW of capacity. Another alternative would be to add a second circuit to the existing single-circuit Sagebrush 230 kV line, which could add 500 to 1000 MW of capacity.

Oak Creek recommends that certain modifications to the transmission project developed through SCE's 2002 conceptual study be analyzed. One modification would connect the new collector substations in a ring configuration, so that all of the wind generation would have a backup path in case of circuit failure. Other alternatives suggested by Oak Creek would connect the existing Antelope-Bailey 66 kV system to the new 230 kV system, or shift some existing load and wind generation from the existing 66 kV system to the new 230 kV system, as a means of relieving existing reliability problems.

Subsequent to the Tehachapi hearings, the utilities submitted transmission plans in another phase of this proceeding, detailing transmission upgrades that would be needed to accommodate the amounts of renewable generation identified in the CEC's Plausible Resource Scenarios developed pursuant to SB 1038. SCE reported that 500 kV rather than 230 kV transmission system upgrades would be needed to support the 4,060 MW of Tehachapi wind generation identified in the CEC's Plausible Resource Scenarios. SCE estimated that such upgrades could cost $1.9 billion.⁶

The record demonstrates that large-scale transmission upgrades capable of transporting power from multiple wind projects will be needed if Tehachapi wind is to contribute significantly to California's renewable power goals.