Speaker
Ingve Simonsen
(NTNU)
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.
