Protection of microgrid through coordinated directional over-current relays

Microgrids integrate distributed energy resources to provide reliable, environment friendly and economic power to small/medium sized urban communities or to large rural areas. Due to the existence of generators at all levels of the distribution system and two distinct operating modes, i.e. grid connected and islanded modes, the fault currents in a system vary substantially. With appropriate relay coordination they gain the ability to island generators and loads together. This has a potential to provide a higher local reliability than that provided by the power system as a whole. The protection scheme implemented addresses the existing protection challenges encountered due to the presence of both distributed generators and inverter interfaced distributed generators in the same system. The proposed protection scheme equipped with directional overcurrent relays is tested using ETAP on a microgrid that consists of distributed energy resources like photovoltaic arrays, wind, diesel generator and micro hydro turbine for various fault locations.