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Blackouts are an emergency measure to prevent a collapse of the power grid.
Rolling blackouts involve switching off entire neighborhoods for about an hour at a time to relieve the strain on the system. A Stage 3 alert means power reserves have fallen below 1.5 percent and rolling blackouts are a possibility. The man who introduced California's power deregulation says it won't die. Last week, a Stage 3 alert was called when the biggest storm to hit the state in three years cut electricity generation at a key nuclear plant. The alert was dropped back to Stage 2 on Friday, when more power became available from other states.