Protecting the grid from the bomb
The US electric grid is designed to keep power flowing to customers by almost any means necessary. But its flexibility may prove to be its downfall.
Because the grid allows power plants to send electricity over multiple routes to any destination within a few hundred miles, it has obvious advantages: if one power line fails, a computer will reroute its load to parallel lines so that the lights stay on. The danger is that if those lines become overburdened, a vicious cycle of “load shifting” and line failures can quickly spiral out of control, causing a widespread blackout.
Daniel Bienstock, a Columbia professor of industrial engineering and operations research, has spent years studying this problem, which is known to power-industry insiders as a cascading failure. By designing computer models that simulate how electricity will flow through the grid in different circumstances, he can identify which sections of the grid are most vulnerable to cascades. Power companies rely on this information to take preventive measures: they may increase the carrying capacity of certain lines or install elaborate monitoring systems in the most vulnerable locations.
This past fall, Bienstock, along with Gil Zussman, a Columbia associate professor of electrical engineering, and MIT’s Eytan Modiano, received a $1 million grant from the Pentagon’s Defense Threat Reduction Agency to study how a cascading failure might be avoided in the worst circumstance imaginable: a nuclear strike intended specifically to start one. The engineers aim to help the government protect the grid against a so-called electromagnetic pulse (EMP) attack, an oft-hypothesized yet never before attempted military maneuver that involves detonating a nuclear warhead in outer space above an enemy country in order to generate a wave of electromagnetic energy that overloads and destroys its grid.
“Our job is to see if you might contain that surge,” says Bienstock, “before it causes the largest cascade we’ve ever seen.”
It starts with a spark
The largest blackout in US history occurred in August 2003, when a power line sagged too close to a tree limb in Walton Hills, Ohio, and shorted out. Workers at the local utility failed to redistribute power appropriately, and within a few hours this minor incident had grown into a massive outage, with fifty million people losing electricity in eight Northeastern states and southern Canada.
“That was a classic cascade,” says Bienstock. “People lost power not because of any shortage of electricity in the system but because the utilities allowed the lines to become overloaded.”
A blackout caused by a nuclear explosion high above the American heartland would likely be worse in every way, he says. For starters, it could affect a much larger area: perhaps one-third of the United States.
“The US grid is actually divided into three sections: the eastern, western, and Texas interconnections,” Bienstock says. “A well-executed EMP attack could easily wipe out one of them.”