Abstract
Electric power transmission systems are a key infrastructure,
and blackouts of these systems have major consequences
for the economy and national security. Analyses of blackout data
suggest that blackout size distributions have a power law form over
much of their range. This result is an indication that blackouts
behave as a complex dynamical system. We use a simulation of
an upgrading power transmission system to investigate how these
complex system dynamics impact the assessment and mitigation of
blackout risk. The mitigation of failures in complex systems needs
to be approached with care. The mitigation efforts can move the
system to a new dynamic equilibrium while remaining near criticality
and preserving the power law region. Thus, while the absolute
frequency of blackouts of all sizes may be reduced, the underlying
forces can still cause the relative frequency of large blackouts
to small blackouts to remain the same. Moreover, in some cases,
efforts to mitigate small blackouts can even increase the frequency
of large blackouts. This result occurs because the large and small
blackouts are not mutually independent, but are strongly coupled
by the complex dynamics.