Performance evaluation of anti-islanding protection technique for Micro Grids

Micro Grids (MG) have recently gained a lot of momentum in power industry due to market deregulation and environmental concerns. One of the most technical challenges facing MGs is islanding of distributed generators. The current industry practice is to disconnect all distributed generators immediately after the occurrence of islands within 200 to 350 ms after loss of main supply. To achieve such goal, each DG must be equipped with an islanding detection device. Frequency relays are one of the most commonly used loss of mains detection method. However, distribution utilities may be faced with concerns related to false operation of these frequency relays due to improper settings or presence of harmonics generating loads (nonlinear loads). This paper investigates the performance of the frequency relay due to faults at the point of common coupling (PCC) with utility and due to active and reactive power mismatches at the generator bus. Further, the relay operation in the presence of nonlinear loads at the point of common coupling is analyzed. Finally, the relay setting can be accurately determined based on these investigation and analysis.