This paper offers a novel passive islanding detection scheme for synchronous distributed generations (SDGs) based on the combination of (dδ/dt) and (dPm/dt). By the occurrence of islanding and grid-connected events, the load angle (δ) and mechanical power (Pm) of SDGs will change. These signals will oscillate during non-islanding events, while they will reach a stable point without any oscillation during islanding events. However, during some grid-connected disturbances such as high impedance faults and small capacitor switching, the oscillations of δ and Pm may not be significant. Therefore, the swing feature cannot be a reliable index and can lead to an inappropriate operation. Hence, to select the best parameters, a combination of four parameters, including dPm/dt, dδ/dt, dPm/dδ, and dδ/dPm is employed. The sensitivity analysis to discriminate islanding from non-islanding events has been reported in the presence of SDGs with various inertia constants, voltage levels, and loads. Based on the results, the combination of dδ/dt and dPm/dt has high accuracy and speed in clustering the occurred events. The efficiency of the proposed approach is tested on the IEEE 33-bus system. It is proved that the proposed approach decreases the non-detection zone to 0.01 MW and 0.01 MVAr of the powers nonconformity.
