Power System Vulnerability Analysis: A Centrality Based Approach Utilizing Limited Information
Vulnerability assessments play a key role in determining appropriate mitigation strategies to counter credible cyber threats to a power system. Yet an assessment of the vulnerability of the electric grid to a cyber attack is dependent on the resources and capabilities of an attacker. Through an application of conventional principles of warfare to a potential cyberwar on the power grid, a framework for credible attack scenarios can be conceived. From such a framework, it is proposed that a severe threat of concern would involve a coordinated attack on specific power system cyber assets resulting in the malicious outage of multiple generators or
lines throughout the power grid. It is further concluded that a coordinated attack scenario would likely involve selection of targets from a simplis tic analysis based on limited information.
Since centrality measures only require system topology and branch impedance information to rank contingencies, they present the potential to aid attackers in targeting specific buses and lines that maximize the adverse reliability impact to the power grid. In order to establish the utility of centrality measures, a statistical comparison of contingency ranking schemes based on centrality measures with those of more conventional power flow based methods was performed. Such statistical tests indicate the strongest evidence in support of closeness and edge betweeness centrality as tools for N-1 contingency ranking schemes.However, since a cyber attacker has the capability to cause multiple simultaneous contingencies, a novel approach to utilizing centrality measure for N-X contingency vulnerability assessments is developed and validated against a power flow based performance index. Since centrality based vulnerability assessments can serve as physical attack signatures, power system security may be enhanced through the creation of early detection and mitigation applications capable of thwarting an unfolding coordinated cyber attack.
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