Protection Issues in Microgrids with Multiple Distributed Generation Units

The application of local generators in distribution grids has consequences for the protection system. In this paper, protection issues concerning distributed generation are discussed, followed by a discussion of the results of simulations. These simulations concern the effect of local induction generators on protection selectivity in a system with parallel distribution feeders and the effect on fault detection. It is found that local induction generator can pose a selectivity problem in a system with parallel feeders when a line-to-line fault or a double line-to-ground fault occurs. Regarding the fault current detected at the beginning of a feeder, detected current is lowest when a line-to-line fault or a line-to-ground fault occurs. Depending on the relay settings, this can result in a detection problem.