  In the past, we have observed several large blackouts, i.e. loss of power to
large areas. It has been noted by several researchers that these large
blackouts are a result of a cascade of failures of various components. As a
power grid is made up of several thousands or even millions of components
(relays, breakers, transformers, etc.), it is quite plausible that a few of
these components do not perform their function as desired. Their
failure/misbehavior puts additional burden on the working components causing
them to misbehave, and thus leading to a cascade of failures.
  The complexity of the entire power grid makes it difficult to model each and
every individual component and study the stability of the entire system. For
this reason, it is often the case that abstract models of the working of the
power grid are constructed and then analyzed. These models need to be
computationally tractable while serving as a reasonable model for the entire
system. In this work, we construct one such model for the power grid, and
analyze it.
