Insight into microgrid protection

Microgrids consist of a combination of generation resources and load, forming an electrically sustainable entity. Although the feeder configuration, including location of circuit breakers or switches, and selection of protective devices can change from one microgrid to another, some characteristics like size of microgrid and behavior of sources feeding a fault remains similar. Due to the non-uniformity of configuration, no definite choices of protection schemes have emerged. This paper analyzes the performance of three most commonly used principles of protection - overcurrent, distance, and differential - on a microgrid topology based on three actual microgrid designs. Importance and implementation of safe islanding and resynchronization are also discussed. Though this research was done primarily for microgrids at United States military bases, the analysis and conclusions may be applied to microgrids in general.