InfrastructureStudy: U.S. grid robust, hard to bring down
Reliance on a particular kind of mathematical model — a so-called topological model — for understanding complex systems has led a growing number of researchers to conclude that the U.S. electric grid is exceedingly vulnerable to disruption; two mathematicians now argue that these studies “have ignored the physics of how things actually work — like electricity infrastructure”; an examination of how the grid actually works would show that the U.S. electrical grid is probably more secure that many people realize
Last March, the U.S. Congress heard testimony about a scientific study in the journal Safety Science. A military analyst worried that the paper presented a model of how an attack on a small, unimportant part of the U.S. power grid might, like dominoes, bring the whole grid down.
Members of Congress were concerned. Then, a similar paper came out in the journal Nature the next month that presented a model of how a cascade of failing interconnected networks led to a blackout that covered Italy in 2003.
These two papers are part of a growing reliance on a particular kind of mathematical model — a so-called topological model — for understanding complex systems, including the power grid.
This has University of Vermont power-system expert Paul Hines concerned.
“Some modelers have gotten so fascinated with these abstract networks that they’ve ignored the physics of how things actually work — like electricity infrastructure,” Hines says, “and this can lead you grossly astray.”
For example, the Safety Science paper came to the “highly counter-intuitive conclusion,” Hines says, that the smallest, lowest-flow parts of the electrical system — say a minor substation in a neighborhood — were likely to be the most effective spots for a targeted attack to bring down the U.S. grid.
“That’s a bunch of hooey,” says Seth Blumsack, Hines’s colleague at Penn State.
Hines and Blumsack’s recent study, published in the journal Chaos on 28 September, found just the opposite. Drawing on real-world data from the Eastern U.S. power grid and accounting for the two most important laws of physics governing the flow of electricity, they show that “the most vulnerable locations are the ones that have most flow through them,” Hines says. Think highly connected transformers and major power-generating stations. Score one point for common sense.
“If the government takes these topological models seriously,” Hines says, “and changes their investment strategy to put walls around the substations that have the least amount of flow — it would be a massive waste of resources.”
At the speed of light
Many topological models are, basically, graphs of connected links and nodes that represent the flows and paths within a system. When a node changes or fails, its nearest connected neighbor will often change or fail next. This abstraction has provided profound insights into many complex systems, like river networks, supply chains, and highway traffic. Electricity, however, is strange and the U.S. electric grid even stranger.
In August of 2003 a blackout
