Design of critical infrastructures: application to electrical systems

The recent publication of the 5th revision of TIA 942 standard represents a benchmark framework to design resilient power systems. This standard provides a classification for electric infrastructures in terms of their capacity to tolerate failures and to allow safely maintenance operations. This ranking is not based upon technical specifications, but on system resilience level, that is the capacity to resist to an unexpected destructive event, breakdown or malfunctioning which afflicts the end user. However, this standard is provided only for design purposes. Aim of this paper is to propose an approach by which the current resilience status of a system can be evaluated, in accordance to this standard classification. The proposed technique should allow to easily analyze the gap – in terms of infrastructure topology, components and distribution lines – between an existing system and a generic configuration with a desired resilience level, and thus to suggest the steps to reach the proper availability for the system specific mission. A preliminary version of the technique – which however still leaves some open issues – has been validated with the power system infrastructure that supports one of the largest datacenters in Italy, inside a primary IT Company which has to guarantee a 24/7 continuous operation of its software application, mission critical in the interests of its customers.