Performance comparison of voltage and frequency based loss of grid protection schemes for microgrids

Microgrids have recently gained attention in the electric power industry. This can be attributed to the benefits they offer over traditional grids. Such benefits include a more cost effective way of expanding power grids and a dual mode of operation. Microgrids can function while connected to a utility grid or as an island. However, the possibility of undetected/unwanted islanding is a major concern. Sophisticated protection schemes are required to determine whether to island a microgrid or maintain its connection when a fault originates from the utility side of a microgrid. This paper evaluates the performances of an under/over voltage relay and a rate of change of frequency (ROCOF) relay. These protection schemes are compared for different fault types and locations. The test network and protection schemes developed in this paper are modeled using Matlab Simulink. Results show that the ROCOF relay, which was blinded to some grid faults, has a lower performance than an under/over voltage relay.