Assessment of N-1 criteria using energy storage

The goal of the Transmission System Operator is to run its power system in a reliable manner, incurring the lowest possible values of SAIDI and SAIFI indices to its consumers. This is achieved by using meshed networks, where after an outage of a line power flows through the remaining lines still satisfy all the technical constraints. However, in some cases it is difficult and costly to ensure parallel lines, which automatically voids the N-1 criterion. This paper examines generalized cases in which an energy storage system is used to increase security of supply. Specifically, energy storage is used to provide N-1 security reserve for a limited amount of time at locations where installation of additional transmission lines is difficult and costly, e.g., remote islands. Besides providing theoretical results, the paper presents a case study based on an Adriatic island within the Croatian power system.