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Dive into the analysis of current Weather Sensitivity Code assignments, historical changes, and prospective adjustments based on ERCOT's 2004 review. Explore potential actions to improve methodology and accuracy.
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ERCOT Staff Analysis of Weather Sensitivity Code Changes February 8, 2005
Analysis Background • Analysis based on currently active IDRs • Includes both NOIE and IOU ESIIDs • Includes prospective changes based on ERCOT’s 2004 assignment review • Analysis period is market open to present
Current Weather Sensitivity Code Assignmentsand Change History • About 28% of current ESIIDs classified as weather sensitive, 23% for IOUs and 63% for NOIEs • About 26% of current ESIIDs have had one or more code changes since market open
Weather Sensitivity Code Changes • 80% of IOU, 70% of NOIE ESIIDs with no assignment changes • About 14% of current ESIIDs are changing as a result of 2004 review
Year-by-Year Weather Sensitivity Code Changes • 2002 WS Review was not Performed by ERCOT • 2003 had a significant migration (88% of changes) to WS • 2004 had a significant migration (69% of changes) to NWS • 57% of ESIIDs with 2004 changes were reverting to pre-2003 code
Potential Action Items • Continue using current methodology … current data loading rates lower the impact of applying proxy days • Assign all IDRs to WS … WS proxy day routine okay for most ESIIDs and falls back to NWS proxy day if no suitable days are found • Assign all IDRs to NWS … reduced processing for proxy day routine, may not introduce that much inaccuracy • However … if Initial Settlement is moved from 17 to 10 days, the proxy day routine will be invoked more often … a less accurate routine will increase profiling error • Conduct analysis to improve WS assignment methodology • Look at R-square distributions • Use multiple-year window for the analysis • Incorporate additional variable(s) e.g. summer ratio, kW/kWh minimums • Outlier analysis e.g. some ESIIDs have large year-to-year changes in R-square • Apply dead-bands