Speaker
Ingve Simonsen
(NTNU, Trondheim)
Description
Our contemporary societies rely more and more on a steady
and reliable power supply for their well-functioning. During
the last few decades a number of large-scale power blackouts
have been witnessed around the world, and this has caused
major concerns among politicians and citizens. In this talk
we will mention a few major power blackouts and discuss the
sequence of events and why they occurred. These empirical
examples show that major power blackouts often are results
of a cascading of failures (a "Domino effect"). We will
introduce a generic (random walk) model for the study of
cascading failures in networks, and investigate the impact
of transient dynamics caused by the redistribution of loads
after an initial network failure (triggering event). It is
found that considering instead the stationary states, as has
been done in the past, may dramatically overestimate (by
80-95%) the robustness of the network. This is due to the
transient oscillations or overshooting in the loads, when
the flow dynamics adjusts to the new (remaining) network
structure. Consequently, additional parts of the network may
be overloaded and therefore fail before the stationary state
is reached. The dynamical effects are strongest on links in
the neighborhood of broken links. This can cause failure
waves in the network along neighboring links, while the
evaluation of the stationary solution predicts a different
order of link failures.
