Reducing Cascading Failure Risk by Increasing Infrastructure Network Interdependency

Increased coupling between critical infrastructure networks, such as power and com-munications, has important implications for the reliability and security of these net-works. To understand the implications of power-communications coupling, researchers have studied interdependent network models and reported that increased coupling can increase system vulnerability [1, 2]. However, these results come from models that have substantially different mechanisms of cascading, relative to those found in actual power and communications networks. This paper reports on two sets of experiments that compare the network vulnerability implications resulting from simple topological models and models that more accurately capture the dynamics of cascading in power systems. In the first set of experiments, we compare a simple model of intra-network cascading to a power grid model and find that the power grid model reveals that power grids have a higher level of vulnerability, relative to what would be inferred from a topological contagion model. In a second set of experiments, we compare the coupled topological model from [1] to three different physics-based models of power grids cou-pled to communication networks. Again, the results show that more accurate models lead to very different conclusions. In all but the most extreme case, the physics-based power grid models suggest that increased power-communications coupling decreases vulnerability. This is opposite from what one would conclude from the model in [1], in which zero coupling is optimal. Finally, an extreme case, in which communication