  Measures of power grid vulnerability are often assessed by the amount of
damage an adversary can exact on the network. However, the cascading impact of
such attacks is often overlooked, even though cascades are one of the primary
causes of large-scale blackouts. This paper explores modifications of
transmission line protection settings as candidates for adversarial attacks,
which can remain undetectable as long as the network equilibrium state remains
unaltered. This forms the basis of a black-box function in a Bayesian
optimization procedure, where the objective is to find protection settings that
maximize network degradation due to cascading. Notably, our proposed method is
agnostic to the choice of the cascade simulator and its underlying assumptions.
Numerical experiments reveal that, against conventional wisdom, maximally
misconfiguring the protection settings of all network lines does not cause the
most cascading. More surprisingly, even when the degree of misconfiguration is
limited due to resource constraints, it is still possible to find settings that
produce cascades comparable in severity to instances where there are no
resource constraints.
