# Operational Resilience Metrics for Complex Inter-Dependent Electrical Networks
## 6 Discussion  
The Electrical Distribution Network (EDN) is a critical infrastructure that plays a primary role in citizen life. The resilience of an EDN, intended as its service continuity, should be pursued both in business as usual and adverse conditions. These EDN systems should be able to withstand different types of perturbations possibly affecting their functions through a combination of technical solutions and management strategies spanning from intrinsic system technologies to effective operational plans. This work proposed a framework enabling: (1) the estimation of the physical impacts and consequent functional perturbations that might affect EDN, and (2) the testing of the effectiveness of different strategies to achieve operational resilience. Factors that are considered within the framework to set resilient response strategies include: the EDN topology; the technological properties of EDN active elements; the SCADA systems; automation procedures and management efficiency. In particular, the proposed approach is related to a novel integrated metric (similar to the metric proposed in [14]) for operational resilience to be used in systems showing a functional behavior whose management, particularly in crises scenario, might be highly dependent on the functioning of other systems from which it takes operational services. The obtained results show that RecSIM is a valuable tool to assess the resilience of EDN considering either (i) the _normal_ EDN operational procedures and (ii) in case of natural disasters and/or critical contingencies. A primary use of the RecSIM model is in the optimization of the positioning of new automation devices along the network. Automation devices are useful to improve the quality of the EDN response, to improve its capability to isolate the perturbed trunk line. In a limited resource strategy, the positioning along the lines should be attentively considered in order to maximally improve the benefits in terms of controllability and resilience gain. The RecSim model is particularly suited to carry out such an optimization strategy: new device positioning is positioned along the lines and an heuristic strategy can be used to select the possible n-device positioning in a way to provide a sub-optimal improvement to resilience, which will be considered as the objective function for the optimization strategy. This will be the primary application of the RecSim model to the EDN case and will provide new understanding on the use of appropriate optimization strategies to be used in combination with RecSim. A further research direction could consider resilience as a \"systemic\" property. As the rebound from a perturbed to the equilibrium state, in a specific infrastructure (in our case the EDN), is related to the availability of external services (in our case the telecommunication service), which could fail due to the perturbation to the hit infrastructure, the overall efficiency for restoration will thus depend on the properties and the management of both systems. The case could be even more complex when multiple infrastructures are involved: this is the case, for instance, of water distribution networks (WDN) and railway networks [37; 38; 39], where electrical and telecommunication functions are both needed for supporting normal and crisis management. In this respect, the \"Systemic Operational Resilience\" score should be able to gather, in a unique definition, the functionality losses in all the infrastructures that can be hit by a perturbation inserted somewhere in the \"system of systems\", a perturbation that could hit one or the other of the interdependent infrastructure. This will open a \"generalization\" of the two-systems case, which could provide, at the end, the settlement of a unified model for the resilience in the real case of multiple, interconnected infrastructures [15; 40].