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NERC Submits Informational Filing related to Order No. 733-A and the August 2003 Blackout Report

      On July 21, 2011, in Docket No. RM08-13, NERC submitted an informational filing in response to Order 733-A on rehearing, clarification, and request for an extension of time.  NERC's filing is intended to “introduce and clarify for informational purposes only” certain aspects of the April 2004 U.S.-Canada Power System Outage Task Force, Final Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations, (the “Blackout Report”).”  Order 733-A discusses tripping of fourteen transmission lines to support the directive pertaining to conditions in which relays misoperate due to stable power swings that were identified as propagating the cascade during the August 2003 blackout.  NERC’s filing clarifies that these fourteen lines did not trip due to stable power swings; ten of these lines tripped in response to the steady-state loadability issue addressed by reliability standard PRC-023, while the last four lines tripped in response to dynamic instability of the power system.  The discussion also identifies two transmission lines that did trip in response to stable power swings related to the reliability objective of the standard directed in Order 733-A. To view NERC’s filing, click here.