Abstract
Conference Title: 2016 18th Mediterranean Electrotechnical Conference (MELECON) Conference Start Date: 2016, April 18 Conference End Date: 2016, April 20 Conference Location: Lemesos, Cyprus Micro Grids (MGs) are part of the modem trend towards decentralized management of energy production through distributed generation (DG). Further, MG can be interconnected as a controllable element of the power network, or it can be an emergency backup system when a power outage occurs. Moreover, MG can reduce energy losses, operation costs, loading of transmission and distribution thereby deferring planned substation upgrades. However, one of the most technical challenges facing MGs is islanding of distributed generators. Islanding detection methods can be divided into communication-based and local detection-based methods. A large non-detection zone (NDZ) near a power balance situation and unwanted distributed generation tripping due to other network events have also been major drawbacks of traditional passive local islanding detection methods. Rate of change of frequency (ROCOF) relay is one of the proposed passive techniques used to detect loss of mains and has the smallest non-detection zone compared with the other passive methods. However, it has a high possibility of false tripping due to its high sensitivity and can be affected by load power factor, load type, generator inertia constant, feeder length, and presence of multiple generators located at the MG. The current work aims to improve the ROCOF relay performance 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.