Pruning the power grid
Each summer, power grids are pushed to their limits, as homes and offices crank up the air conditioning in response to rising temperatures. A single failure in the system — such as a downed power line or a tripped relay — can cause power outages throughout a neighborhood or across entire towns. For the most part, though, a failure in one part of the grid won’t bring down the entire network. But in some cases, two or more seemingly small failures that occur simultaneously can ripple through a power system, causing major blackouts over a vast region. Such was the case on Aug. 14, 2003, when 50 million customers lost power in the northeastern United States and Ontario — the largest blackout in North American history. Even more recently, in July 2012, India experienced the largest power outage ever, as 700 million people — nearly 10 percent of the world’s...