Positive Sequence Impedance Angle-based Islanding Detection Technique in the Presence of Active Distribution System

Integrating Distributed Generation (DG) units powered by renewable energy sources into the power grid has significantly enhanced energy sustainability. However, this has also introduced new challenges, notably the issue of unintentional islanding, which occurs when a DG continues to supply power to a local load while disconnected from the main utility grid. Islanding presents serious risks to personnel safety, equipment, and power quality and complicates grid protection systems. Although various islanding detection methods have been proposed, existing solutions often struggle with false detections, slow response times, or limited applicability to multiple DG configurations. This article presents a novel scheme for detecting islanding events based on the rate of change of the superimposed positive sequence impedance angle (ROCOSPSIA). To test the performance of the proposed method under various islanding conditions (active and reactive power mismatch) and non-islanding events, such as load switching (ON/OFF), energization/de-energization of medium transmission lines, a short circuit on a nearby feeder, and a capacitor bank on the IEEE 13 bus system. The distribution test system has been simulated in the MATLAB/Simulink environment. The simulation results show that the proposed scheme distinguishes islanding events from non-islanding events within a half-cycle.