Revealing Vulnerability of N-1 Secure Power Systems to Coordinated Cyber-Physical Attacks

Coordinated cyber-physical (CCP) attacks have attracted wide attention in power systems because of their potential to cause severe disturbance including cascading failures. However, as realistic power systems operate within the N-1 security criterion, existing CCP attacks may be in part mitigated. As such, this paper analyzes impacts of CCP attacks on the vulnerability of the power systems that employ the N-1 security constrained optimal power flow (SCOPF). Specifically, a tri-level model is proposed to analyze the CCP attack impacts, whereby the adversary coordinates a physical attack with cyber attacks to initiate and propagate post-contingency overload based on N-1 SCOPF. A methodology utilizing semidefinite programming (SDP) relaxation and primal-dual formulation is proposed to transform the tri-level model into a conic optimization, such that the model can be easily solved by SDP solvers. Case studies on the IEEE 14, 57, and 118 bus test systems demonstrate that the CCP attacks in power systems with N-1 security criterion are able to cause N-1-1 contingency and even trigger cascading failures.