Selective Short Circuit Scheme-Based Protection for AC Microgrid

Microgrid is a combination of Distributed Generation (DG), loads & Energy storage systems basically a distribution system to cater to the load of a small community, colony or remote village, which may be operated to run either in grid tied or in an independent mode. There may be an impact on the grid side due to the addition of distributed generation (DG) particularly due to a change in the magnitude and direction of short circuit currents resulting in a major impact on the distribution side, causing false tripping or fail to trip the over-current protection relays in the power system. However, the protection logic designed must be able to meet the three basic protection needs namely selectivity, sensitivity and reliability in both modes of operation. The new protection logic frame must be adaptive and very sensitive in order to detect and isolate the minimum level fault currents very fast, ensuring a minimal interruption to the power system. In this paper, the protection issues are reviewed and an advanced protection scheme for AC Microgrids is developed and proposed. Here, one of the major challenges found while designing an AC microgrid is relay coordination. Simulation tests are conducted by applying three-phase fault in a 9-generator, 2-bus system designed using ETAP software.