Research Article

Small vulnerable sets determine large network cascades in power grids

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Science  17 Nov 2017:
Vol. 358, Issue 6365, eaan3184
DOI: 10.1126/science.aan3184

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  • Failure-based resource allocation is insufficient to prevent future catastrophic blackouts
    • Heiko Hoffmann, Computer Scientist, HRL Laboratories, LLC
    • Other Contributors:
      • David W. Payton, Computer Scientist, HRL Laboratories, LLC

    Yang et al. (Reports, 17 November 2017, p. 886) simulated the US power grid and created a systemwide vulnerability map, revealing that only a small percentage of lines (<1%) were vulnerable to overload failure. The conclusion and suggestion in the paper to allocate resources based on failure, however, is ill-founded. In our work (1), we found that such a strategy will still fail in the long run. Focusing resources on the failure-prone parts will result in other parts becoming vulnerable to failure. Specifically, our work showed that a strategy of upgrading failing lines after each cascading failure results in the entire grid becoming self-organized critical. In a self-organized critical system, cascading failures follow a power law, which matches observations of the US power grid (2); so, large failures can occur with non-vanishing probability. Fixing only vulnerable lines leads to the buildup of “stress” in large clusters of lines, which can fail catastrophically, a possibility acknowledged by Yang et al. in the conclusions of the online full-text version. In a self-organized critical system, the statistics of large failures cannot be easily altered in a straight forward way. However, we found a means to influence these statistics; namely, by upgrading lines at random that were not involved in a blackout, which is almost the opposite of a purely failure-based allocation strategy. Simulation results show that our strategy has the potential to reduce the probability of...

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    Competing Interests: None declared.

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