State-of-the-Art Microgrid Power Protective Relaying and Coordination Techniques

In recent years, a trend shifting from traditional power grids to modern smart grids has emerged formation of microgrids, connecting low voltage distributed generation (DG) units, loads and local storage apparatus to medium voltage distribution system. This revolution in power distribution systems has pledged ample advantages for customers including reliability, quality and efficiency of generated power, as well as eliminating the necessity to construct long transmission lines and excluding subsequent imposed power losses. In contrary to the benefits provided by microgrids, protection of these entities is an enormously perplexing procedure predominantly due to dynamic behavior of microgrids, bidirectional power flow, and high penetration of inverter-interfaced DG sources that has disrupted the conventional operation and coordination of protection relays. This paper presents an analytical appraisal on state-of-the-art protection techniques to address problems associated with microgrid protection. Advantages and disadvantages of each protection technique, as well as proper selection of protective relays suitable for each protection zone have been discussed. Recommendations on protection procedures and effective techniques be employed to resolve the microgrid protection issues have also been presented.