  We develop investment approaches to secure electric power systems against
load attacks where a malicious intruder (the attacker) covertly changes
reactive power setpoints of loads to push the grid towards voltage instability
while the system operator (the defender) employs reactive power compensation
(RPC) to prevent instability. Extending our previously reported Stackelberg
game formulation for this problem, we develop a robust-defense sequential
algorithm and a novel genetic algorithm that provides scalability to
large-scale power system models. The proposed methods are validated using IEEE
prototype power system models with time-varying load uncertainties,
demonstrating that reliable and robust defense is feasible unless the
operator's RPC investment resources are severely limited relative to the
attacker's resources.
