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Report on 8/25/05 PDCI Loss & Load Shedding Event

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Summary:

CALIFORNIA ISO CORPORATION, Report on 8/25/2005 Pacific DC Intertie Loss with Subsequent Load Shedding Event

Extract:

EXECUTIVE SUMMARY At 1547 PDT, on Thursday, August 25, 2005, one pole of the Pacific DC Intertie (PDCI) blocked, and within seven minutes the PDCI was taken out of service. As a result, 2,249 MW of generation tripping occurred automatically by a Remedial Action Scheme (RAS) in the Pacific Northwest. In addition, weather/load forecast errors in South of Path 26 (SP26) resulted in under forecasting of load by as much as 2,937 MW. As a result of both the forecast error and the PDCI going out of service, both interruptible and manual firm load shedding totaling approximately 1,750 MW was utilized in the CAISO Control Area to maintain reliability of the interconnected grid. Of the total load interrupted, firm load comprised about 950 MW and was restored after 40 minutes while the remaining 806 MW comprised of interruptible load and was restored after 77 minutes. Path 66 (COI), Path 26, and Path 15 experienced path overloads following the loss of the PDCI, but path violations exceeding time requirements were not incurred.

Document Locations:

• Operational Reports and Audits