  We present a threshold-based cardinality minimization formulation to model
the security-constrained economic dispatch problem. The model aims to minimize
the operating cost of the system while simultaneously reducing the number of
lines operating in emergency operating zones during contingency events. The
model allows the system operator to monitor the duration for which lines
operate in emergency zones and ensure that they are within the acceptable
reliability standards determined by the system operators. We develop a
continuous difference-of-convex approximation of the cardinality minimization
problem and a solution method to solve the problem. Our numerical experiments
demonstrate that the cardinality minimization approach reduces the overall
system operating cost as well as avoids prolonged periods of high electricity
prices during contingency events.
