* 11 September 2009 by Paul Marks
* Magazine issue 2725. Subscribe and get 4 free issues.
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PREDICTING how rumours and epidemics percolate through populations, or how traffic jams spread through city streets, are network analyst Jian-Wei Wang’s bread and butter. But his latest findings are likely to spark worries in the US: he’s worked out how attackers could cause a cascade of network failures in the US’s west-coast electricity grid – cutting power to economic powerhouses Silicon Valley and Hollywood.

Wang and colleagues at Dalian University of Technology in the Chinese province of Liaoning modelled the US’s west-coast grid using publicly available data on how it, and its subnetworks, are connected (Safety Science, DOI: 10.1016/j.ssci.2009.02.002).

Their aim was to examine the potential for cascade failures, where a major power outage in a subnetwork results in power being dumped into an adjacent subnetwork, causing a chain reaction of failures. Where, they wondered, were the weak spots? Common sense suggests they should be the most highly loaded networks, since pulling them offline would dump more energy into smaller networks.

To find out if this is indeed the case, the team analysed both the power loading and the number of connections of each grid subnetwork to establish the order in which they would trip out in the event of a major failure. To their surprise, under particular loading conditions, taking out a lightly loaded subnetwork first caused more of the grid to trip out than starting with a highly loaded one.

“An attack on the nodes with the lowest loads can be a more effective way to destroy the electrical power grid of the western US due to cascading failures,” Wang says. To minimise the risk, he says, the grid’s operators should defend the west coast sections by adjusting their power capacity to ensure these specific conditions do not arise.

The US Department of Homeland Security is reviewing the research, says John Verrico, the department’s technology spokesman, who adds that countermeasures are already in the works. “Our engineers are working on a self-limiting, high-temperature superconductor technology which would stop and prevent power surges generated anywhere in the system from spreading to other substations. Pilot tests in New York City may be ready as soon as 2010.”

These precautions are well and good, but there are easier ways to bring a grid down, says Ian Fells, an expert in energy conversion at Newcastle University, UK. “A determined attacker would not fool around with the electricity inputs or whatever – they need only a bunch of guys with some Semtex to blow up the grid lines near a power station.”