An extensive review on the state-of-art on microgrid protection

Distribution generation (DG) based on renewable energy sources at the distribution voltage level is gaining popularity among utilities and consumers due to numerous technical, economical and environmental benefits. The concept of microgrids (MGs) has been proposed as an attractive alternative to integrate large number of DGs with distribution systems. MGs can operate either in islanded or grid connected mode of operation. The bidirectional power flow and the significant variation in the fault current levels during grid connected and islanded mode of operation imposes significant challenges in designing a proper protection scheme for such system. To solve this problem, recently a number of alternative solutions have been proposed in the technical literature. This paper addresses the protection problems of MGs in detail and critically reviews the existing schemes proposed for MG protection. The most up to date relevant options are described and categorized into specific groups. Finally, a comparative assessment is carried out in which relative advantages and disadvantages of each protection strategy are evaluated.