Why is it called a rolling blackout?

It is called a rolling blackout for a reason. The goal is to reduce load by impacting a minimal amount of the system for a designated amount of time and then returning power to the affected area and moving to a different area of the system. The way this will be accomplished on our systems will be by de-energizing the entire substation and not just picking and choosing among individual members. The outage should last no longer than an hour and then the substation will be re-energized and another substation in the system will be turned off.