While weather events like Hurricane Sandy grab national headlines, they aren’t the only threat to transmission grids. The Northeast Blackout of 2003, one of the largest in U.S. history, is said to have been caused by unpruned foliage and a faulty alarm system that failed to alert control room operators of the need to reroute power. India’s power outage of 2012 was caused by congestion and an inadequate infrastructure. Despite the lessons learned from events like these, stresses on the transmission grid are only going to get worse. Experts cite a number of factors.