4
Microgrid Protection
4.1 Introduction
One of the major technical challenges associated with a wide deployment of microgrids is the design of its protection system. Protection must respond both to the utility grid system and to microgrid faults. If the fault is on the utility grid, the desired response is to isolate the microgrid from the main utility as rapidly as necessary to protect the microgrid loads. The speed of isolation is dependent on the specific customer's loads on the microgrid, but it probably requires the development and installation of suitable electronic static switches. Electrically operated circuit breakers in combination with directional over-current protection is another possible option. If the fault is within the microgrid, the protection system isolates the smallest possible section of the distribution feeder to eliminate the fault [1]. A further segmentation of the microgrid during the isolated operation, that is, a creation of multiple islands or sub-microgrids, must be supported by microsource and load controllers.
Most conventional distribution protection is based on short-circuit current sensing. The presence of DERs might change the magnitude and direction of fault currents, and might lead to protection failures. Directly coupled rotating-machine-based microsources will increase short-circuit currents, while power electronic interfaced microsources can not normally provide ...
