Abstract
In a cascading power transmission outage, component outages propagate
non-locally; after one component outages, the next failure may be very distant,
both topologically and geographically. As a result, simple models of
topological contagion do not accurately represent the propagation of cascades
in power systems. However, cascading power outages do follow patterns, some of
which are useful in understanding and reducing blackout risk. This paper
describes a method by which the data from many cascading failure simulations
can be transformed into a graph-based model of influences that provides
actionable information about the many ways that cascades propagate in a
particular system. The resulting "influence graph" model is Markovian, since
component outage probabilities depend only on the outages that occurred in the
prior generation. To validate the model we compare the distribution of cascade
sizes resulting from n-2 contingencies in a 2896 branch test case to cascade
sizes in the influence graph. The two distributions are remarkably similar. In
addition, we derive an equation with which one can quickly identify
modifications to the proposed system that will substantially reduce cascade
propagation. With this equation one can quickly identify critical components
that can be improved to substantially reduce the risk of large cascading
blackouts.
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