Abstract:
Microgrids are emerging as an alternative mode of operation for distribution systems integrated with Distributed
Energy Resources (DERs). With appropriate management and control of the DERs, a section of a distribution
system can operate isolated from the main grid thereby enhancing the reliability and security of supply to
consumers. However, the integration of DERs has raised many technical challenges including protection. The
traditional distribution system protection cannot provide reliable protection to the microgrid in the isolated
mode due to the limited short-circuit capacities of the converter-interfaced DERs. This paper proposes the application
of a new voltage-based relay type for the protection of microgrids. The relay algorithm achieves its
protection function through active power differential and sensitivity calculations based on voltage measurements
within a specified protection zone. In the paper, the new relay type is modelled in Digsilent PowerFactory
software and installed at the nodes of a microgrid test system. The performance of the relay type is investigated
under variety of faults. The relay is shown to operate correctly and effectively to detect and identify faults in
both radial and meshed microgrids integrated with inverter-interfaced DER technologies.
