A Graphical Method to Assess the Technical Feasibility of Intentional Islanding of Distributed Synchronous Generators

This article proposes a graphical method to evaluate the feasibility of intentional islanding of distributed synchronous generators. The approach is based on the combination of the performance and restriction curves. These curves are based on the islanding detection capability of the frequency-based protection at the point of common coupling and on the generator protection at its terminals. When relating the islanding detection time, the restriction time and the active power imbalance, the intersection of such curves defines two operating zones: i) the favorable island formation zone, in which the operation of the energized island is stable, and ii) the non-favorable island formation zone, in which the islanding is infeasible. The results showed that the proposed method is a useful tool to adjust and assess frequency-based protection so that an unscheduled islanding event can result in a stable island. In addition, the validation of the results confirmed the coherency of the graphical method.