Inoperability Assessment of Interdependent Critical Infrastructures by Minimal Inoperability Sets Analysis

We consider the inoperability assessment of two Critical Infrastructures (CIs), one dependent on the other. Typically, such inoperability assessment is conducted by generating failures in the 'source' CI and modeling the disruption cascade into the dependent CI. In realistically large CIs, this results in the need of exploring a combinatorial number of accidental scenarios, which becomes infeasible due to the computational burden. In this paper, a novel approach is presented to address the computational issue, which allows identifying the Minimal Inoperability Sets (MISs), i.e., the minimal combinations of failures leading the dependent CI into a partial or fully inoperability state to exhaustively explore the accidental scenarios. A case study of a power CI feeding a water CI is considered.