Enhanced islanding detection in smart interface protection systems of distributed generation

The widespread presence of distributed generators (DGs) and storage systems (DSSs) in electricity grids has increased the risk of islanding occurrence. This phenomenon must be suitably managed by Distribution System Operators (DSO), in order to avoid adverse situations, in terms of grid-protection problems, equipment damage, safety hazards, power quality problems and so on. Currently anti-islanding protection functions are handled by interface protection systems (IPSs), which are built in accordance with relevant standards for DGs and DSSs connection to power systems. However, some problems may occur in case of operation within the so-called non detection zone (NDZ). This paper presents an analysis of main standard requirements for IPSs and anti-islanding protection. Starting from this, the possibility is investigated of improving the islanding detection effectiveness, by adopting an hybrid solution, based on both local measurements and communication between DGs/DSSs and DSO. The analysis is supported by some simulation results reproducing a real case study for the distribution network of Ustica Island (Mediterranean Sea).