Reply #8: The WaPo is having an online chat with the

[Robbien]

Co-director of Carnegie Mellon Electricity Industry Center. I submitted a question about Bush's use of the term rolling blackout and whether it was used appropriately because rolling blackouts usually refer to planned events. This was his answer:

M. Granger Morgan: Power companies do sometimes turn power off power in first one and then another area when they don't have enough power to meet all the demand, and I guess some folks call that a rolling blackout.

What Mr. Bush meant was that the blackout cascaded across the region and first one and then another system had problems and protective devices disconnected things. In that sense it rolled rapidly across the north east.