An approach to design interface topologies across interdependent urban infrastructure systems

This paper proposes an approach to design or retrofit interface topologies to minimize cascading failures across urban infrastructure systems. Four types of interface design strategies are formulated based on maximum network component degree, maximum component betweenness, minimum Euclidean distance across components and component reliability rankings. To compute and compare strategy effectiveness under multiple hazard types, this paper introduces a global annual cascading failure effect (GACFE) metric as well as a GACFE-based cost improvement (GACI) metric. The GACI metric quantifies the improvement of the strategy effectiveness per kilometer increment of interdependent link length (ILL) relative to a reference strategy with minimum ILL. Taking as examples the power and gas transmission systems in Harris County, Texas, USA, optimum interface designs under random and hurricane hazards are discussed. Findings include that the strategy based on reliability rankings minimizes the GACFE metric, and decreases the GACI value relative to a reference practical strategy by 10–15% under different power grid safety margins. Such metrics will contribute to coupled utility system design or retrofit given that current guidelines or recommended practices in the utility industry mostly rely on minimum Euclidean distances and are yet to include interdependent effects in their provisions.