Coordination and Selectivity Analysis of Voltage-based Relays for Enhancing Microgrid Protection

This paper presented a detailed protection coordination and selectivity analysis of voltage-based relays used for microgrid protection. This type of protection has been investigated lately as a promising approach to ensure coordination and selectivity in grid-connected and islanded microgrids against short-circuit occurrences. The study considered the voltage-based protection applied in six scenarios of microgrid operation, varying the connection (grid-connected and islanded) and the types of distributed energy resources (synchronous generator, photovoltaic system, and battery energy storage system). The short-circuit analyses considered single-line and three-phase faults applied to the 14 bus CIGRE for different fault resistances. The voltages during the faults were obtained through time-domain simulations by using the PSCAD/EMTDC software. These voltages and the relays' time-voltage curves were used to calculate the relays' operating times. The extensive study presented in this paper revealed that the method was promising for microgrid protection since the voltage-based relay with an adaptive parameter can ensure coordination in grid-connected and islanded scenarios. In addition, the voltage-based relay showed to be sensitive to variations in the fault resistance.