with long lead times against the opportunities to reconsider circumstances in the future. The ISO used power flow modeling to develop its scenarios to forecast LCR needs. SCE agrees with this approach because it takes into consideration transmission constraints and limitations in specific local areas. DRA proposes using a load and resources table. While DRA’s approach has its benefits, there is general agreement that the ISO’s modeling is more sophisticated and precise. We find the use of the ISO’s power flow modeling to be reasonable for these purposes. Sparks agreed that the precision of the ISO’s power flow simulation is “completely dependent” upon the accuracy of the input assumptions, and that if the input assumptions vary, then the results would vary. Therefore, it is important to consider whether any major assumptions used by the ISO should be revisited. One-in-Ten Year Load, with Two Major Contingencies The first question is whether the ISO’s general methodology is reasonable. In our RA proceedings, we use ISO forecasts with a one-in-10-year load forecast, with two major contingency outages, to assess LCR needs one year in advance. In this proceeding, the ISO for the first time extended this methodology out to 10 years in advance. A number of parties question whether the ISO’s approach is appropriate. CEERT and others raise the issue of whether we should authorize procurement of up to several thousand MW of capacity based on a rare set of circumstances – essentially (as CEJA puts it) a “scenario that two import pathways to SCE’s territory are unavailable on the hottest day in 10 years.” ISO
with long lead times against the opportunities to reconsider circumstances in the future. The ISO used power flow modeling to develop its scenarios to forecast LCR needs. SCE agrees with this approach because it takes into consideration transmission constraints and limitations in specific local areas. DRA proposes using a load and resources table. While DRA’s approach has its benefits, there is general agreement that the ISO’s modeling is more sophisticated and precise. We find the use of the ISO’s power flow modeling to be reasonable for these purposes. Sparks agreed that the precision of the ISO’s power flow simulation is “completely dependent” upon the accuracy of the input assumptions, and that if the input assumptions vary, then the results would vary. Therefore, it is important to consider whether any major assumptions used by the ISO should be revisited. One-in-Ten Year Load, with Two Major Contingencies The first question is whether the ISO’s general methodology is reasonable. In our RA proceedings, we use ISO forecasts with a one-in-10-year load forecast, with two major contingency outages, to assess LCR needs one year in advance. In this proceeding, the ISO for the first time extended this methodology out to 10 years in advance. A number of parties question whether the ISO’s approach is appropriate. CEERT and others raise the issue of whether we should authorize procurement of up to several thousand MW of capacity based on a rare set of circumstances – essentially (as CEJA puts it) a “scenario that two import pathways to SCE’s territory are unavailable on the hottest day in 10 years.” ISO
50374520.docx