Improvement of reliability in active networks with intentional islanding

DERs are gaining more and more importance in distribution and they are predicted to drastically change the whole distribution system. Distribution network will be no longer a passive termination of transmission network and the concept of active network has been recently introduced to indicate a new kind of distribution with DERs actively involved in system management and operation. Intentional islanding, i.e. the use of DG to supply portions (cells, microgrids) of distribution network during upstream line faults and scheduled interruptions, can be a valuable option to reduce the number of service interruptions. In the paper, an algorithm for the optimal allocation of automatic sectionalizing switching devices has been improved for the maximum exploitation of intentional islanding. Line faults and overloads have been considered as causes of interruptions. Stochastic models have been adopted to assess the probability of overloads and of properly functioning intentional islands. The application to real world case studies has highlighted the benefits achievable with intentional islanding as well as the inability of common reliability indexes (e.g. SAIFI, SAIDI) to properly perceive advantages that are inherently local.