AC microgrid grounding strategies

Grounding strategy of an AC microgrid affects its Line-to-Ground (LG) fault response, personnel/equipment safety, service continuity, insulation requirements, and protection criteria. Therefore, a comprehensive knowledge of the available grounding strategies and their effects is essential for design and operation of the microgrid components and especially its protection. In this paper, characteristics of different AC distribution system grounding devices, i.e., grounding impedance types, are investigated and compared. Subsequently, different AC distribution system grounding configurations including three-wire ungrounded, three-wire uni-grounded, four-wire uni-grounded, and four-wire multi-grounded systems are compared. Finally, AC microgrid grounding requirements are identified based on the unique characteristics and constraints of microgrids.