Robustness assessment of the expansion of coupled electric power and natural gas networks under cascading failures

Electricity and natural gas networks are critical infrastructure for society, but the robustness of coupled networks has not been evaluated, even though both systems have strong interactions. This article proposes a novel graph theory-based methodology to assess the structural robustness of the coupled natural gas and electricity transmission networks in Spain while considering their interdependencies. Cascading failures were simulated in 22 case studies with different topologies, and the performance against random failures was evaluated. The results show that the investment programme proposed by both network operators ultimately improves the robustness of the interdependent electricity and natural gas infrastructure in Spain compared to the current system.