Cascading-failure-resilient interconnection for interdependent power grid - Optical network

The interdependence between communication networks, e.g., an optical backbone network, and power grids is a critical issue to take into account when designing and operating both systems. In fact, failures in one network may cause further failures in the other network and vice versa. This is because nodes in power grids (i.e., power generators, loads or interchange nodes) are controlled and managed by telecommunication equipment, which, in turn, rely on the electricity grid for their power supply. Therefore, failures occurring on a limited portion of one network can cascade multiple times between these two networks, and a robust “interdependency network” (i.e., consisting of the interconnections between nodes in the two networks) is needed. This paper investigates the problem of designing a resilient interconnection against interdependent cascading-failures in interdependent power grid - optical networks. We formalize, using an Integer Linear Program, the new problem of Power Grid - Optical Network Interconnection (PGON-I), which consists in designing an interconnection between the power grid and the optical network that is resilient to cascading failures, i.e., avoids/reduces cascade. For this problem, we derive analytically upper and lower bounds on the number of interconnection links which ensure resilience against cascading failures initiated from a single node-failure. Starting from the analytical model, we develop a heuristic algorithm to solve large instances of the problem. Our results show that the higher the difference between the number of nodes in the two networks, the more interconnection links are needed to ensure resilience against failures cascade.