Power blackouts in the US likely to happen again

Two independent groups of researchers have found evidence of intrinsic weaknesses in the North American power grid. Both analyses conclude that blackouts, like the one that hit New York last summer, are likely to happen again, reports nature.

John Kappenman, a US Government advisor from the Metatech Corporation, told the American Meteorological Society that geomagnetic storms could cause much larger blackouts.

"The threat is greater than anyone had previously thought," said Mr Kappenman.

The sun ejects streams of charged particles that can warp the Earth's magnetic field, producing effects such as the aurora borealis, and capable of inducing a direct current in transformers. This causes huge electrical surges because the grid is only meant to take alternating current.

In 1989, the Quebec power grid was shut down within 90 seconds of one major geomagnetic storm.

The grid becomes far more vulnerable when it grows as it lowers the total electrical resistance of the system, effectively making a bigger antenna for picking up induced current.

In a separate study, Reka Albert and co-workers from Pennsylvania State University constructed a model of the US network, partly to find out why the system failed last year.

They found that the US power grid is an "exponential network" in which most of the network functions without the giant hubs that connect large sections of the network together. However, these hubs are crucial to the power distribution. If the substations that bear the highest loads are the first to break down, failure of just 4% of them leads to a break-up of around 60% of the network, the researchers found.

They conclude that the grid would be more resilient if more small power generating substations were added, or more connections between substations, so that there are more alternative routes when power fails.

However, Kappenman points out this would make the grid's vulnerability to space even worse. To protect it, he suggests fitting resistors at strategic points. These could reduce induced currents by 60 - 70% and cost a few million dollars, he says.



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