May 13, 2008 ARC Event

Tuesday May 13, 2008 from 09:20 EST through 09:40 EST

The Midwest ISO invoked the ARC procedure due to the loss of two generating units for approximately 1,200 MW. The two units tripped within 5 minutes of each other. Up to 46 percent of the operating reserves were utilized during this period to correct the imbalance. There were no ARS events during the procedure