A shortage of reactive power was a key cause of the Aug. 14 blackout in the Northeast U.S. and Canada, says a report by the Electric Power Research Institute, Palo Alto, Calif., commissioned by FirstEnergy Corp., Akron, Ohio, and released Sept. 23. Many of the blackout’s earliest incidents occurred in FirstEnergy’s service area. Reactive power is one of several "ancillary services" required for stable operation of electric transmission systems. Powerplant generators produce reactive power, but it doesn’t earn revenue. Some have worried that the growth of the merchant power market would lead to production of less reactive power, resulting in instability in the power system. "This [report] is intended to support the Dept. of Energy’s task force doing a comprehensive assessment on the system," says Richard Lordan, EPRI’s director of transmission and distribution product lines, one of the study’s authors.