DOE simulations study what triggers a blackout

When an electrical power grid is operating close to capacity, small fluctuations in demand can easily trigger a blackout.

Benjamin Carreras, a physicist at the Energy Department's Oak Ridge National Laboratory in Tennessee, said he has been working for years on computer simulations of the behavior of the power grid as a whole.

His studies, however, are not specific to last month's blackout that hit large parts of the northeastern United States and southern Canada. Carreras and his collaborators at the universities of Wisconsin and Alaska have examined 15 years' worth of data on blackouts of sections of the U.S. power grid.

Edge of chaos

The grid infrastructure has remained more or less the same over the last 20 years, Carreras said, while power demand has been rising. That growing imbalance forces the grid to operate close to so-called critical points that trigger a cascading power outage.

'We live at the edge of the chaos, and it's very easy to go over,' he said.

His model resembles a sand pile in which sand is being added to the top, grain by grain. But the particles do not roll off one by one. Instead they slide off in small or large avalanches. On a graph, the distribution of sizes of these avalanche events resembles the distribution of blackouts, Carreras said.

The research could improve understanding of the general conditions that start the cascades and keep future blackouts from spreading.

The Oak Ridge physicist and his collaborators wrote their simulations in C++ and are running them on single-processor workstations for budget reasons.

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