A differential zone protection scheme for microgrids

Microgrids are small networks of loads and sources that can operate either connected to the grid or islanded. In order to operate in islanded mode, the microgrid must have a new protection scheme as classical distribution protection is inadequate. This work develops a differential zone protection scheme that works by comparing current measurements from several devices on the boarders of the zones. This method is as effective at detecting microgrid faults as digital relay differential protection schemes at significantly lower costs. The optimal placement of zones and devices is formulated. A case study shows that the optimal placement solution can reduce costs by more than 50% when compared to having a relay at each line segment.