4. Joint Study Methodology

Joint Parties evaluated the need for a Southwest power link for system reliability by utilizing a spreadsheet "matrix" methodology. This approach first calculates the arithmetic difference between projected loads and in-state generation resources (existing and new) to determine whether imports are needed to meet load. Then, it compares the quantity of required imports with available Southwest imports and the existing available transmission import capability to the Southwest. Existing firm exports and imports are also accounted for in the spreadsheet calculations. The spreadsheet then arithmetically determines if there is (1) a shortfall in available imports or (2) a shortfall in available transmission capacity, or both. These determinations were made for each year of the planning period, 2001 through 2011.

The matrix model was benchmarked against a detailed technical study of the Southern California-Southwest transmission system, entitled the "Southern California Long-Term Regional Transmission Study" (Southern CA Study). The study was conducted by the ISO, SDG&E, and SCE in the context of the ISO's annual grid planning process and was completed in February 2001. The study included a detailed power flow analysis that modeled the capability of the transmission system. It examined a single, conservative set of assumptions regarding the development of in-state generation resources. In particular, only one generating station (High Desert at approximately 700 megawatts (MW)) was added to the existing generation to model 2008 system conditions. The technical analysis demonstrated that, given the conservative scenario assessed, major improvements to transmission import capability would be needed to meet reliability requirements in Southern California in the year 2008.

Joint Parties compared the results of the Southern CA Study to the results of the matrix model, using similar assumptions concerning new in-state resources. Joint Parties concluded that the results were consistent, and therefore the matrix methodology was valid.