Effects of Cyber Coupling on Cascading Failures in Power Systems

In this paper, we propose a model to investigate the cascading failures in the coupled system (smart grid) that comprises a power grid and a coupling cyber network. In this model, we take into consideration the effects of power overloading, contagion, and interdependence between power grids and cyber networks on failure propagations in the coupled system, and then use a stochastic method to generate the time intervals between failures, thus producing the dynamic profile of the cascading failures caused by the attack of cyber malwares. We study several coupled systems generated by coupling the UIUC 150 Bus System with cyber networks of different structures and coupling patterns. Simulation results show that the dynamic profile of the cascading failures in a coupled system displays a 'staircaselike' pattern which can be interpreted as a combined feature of the typical step propagation profile triggered repeatedly by cyber attacks due to network coupling. Results also show that cyber coupling can intensify both the extent and rapidity of power blackouts. Moreover, the cyber network structure and the coupling patterns affect the propagation of the cascading failures in smart grids. Scale-free cyber networks promote failure spreading, and the higher average cyber node degree also intensifies the spreading. Coupling power nodes with high-degree cyber nodes accelerates the failure propagation compared with random or low-degree couplings.