Integrated Safety–Security Modelling in Digital Substations

Abstract

The integrated safety–security modelling in digital substations is key in today's smart grid context with the presence of cyber–physical threats. To deal with these problems, this paper adopts a unified framework for co-modelling based on mathematics, which integrates the four aspects of dependency analysis by graph, system methods based on state modelling, attacker-defender optimization and temporal logic verification. A cyber–physical interaction model incorporating the cascading failures and attack propagation is developed for the operational risk dynamics. Bounded disturbance analysis is used to derive stability conditions and the Nash equilibrium and the Hamilton–Jacobi–Isaacs formulations are used to optimize the defensive strategies. Linear Temporal Logic (LTL) and Computation Tree Logic (CTL) are logic formalisms used to provide formal verification to safety and recovery properties. The simulation results indicate that in digital substations a higher accuracy of fault detection (96.8 %), detection rate of cyberattacks (97.5 %), cascading failure containment (94.6 %) and lower response time (109ms) have been achieved.