Islanding detection technique for a distributed generation with perfectly matched load condition

Islanding detection is an important protection issue of distributed generation. Since the overcurrent (OC) protection and OC relay grading is different for island mode and grid connected mode of operation, the conventional protection does not suits to active distribution network. It is essential to know the mode of operation first so that the relay setting may be shifted to island mode as soon as the islanding is detected. The conventional islanding detection methods face problems during the balanced matched load condition of DG as there is no significant change in voltage and frequency. This paper proposes a technique to detect islanding by perturbing the dc link voltage. The detection is done by measuring the harmonics level. The test system is simulated in MA TLAB/Simulink and the total harmonic distortion (THD) analysis is done using Sim power system Block set.