Voltage Function in Directional Over-Current Protection to Enhance the Sensitivity and Coordination Problem in Microgrid with High Penetration of Inverter-Based Resources

Integration of inverter-based resources (IBR) as a distributed generator (DG) in a microgrid has been a trend. Considering that DG integration transforms the short circuit behavior in terms of magnitude and direction in the system, the conventional protection scheme becomes no longer relevant. The major concern of the traditional protection scheme in a microgrid is the relay operating time to clear the fault in a coordinated manner. This paper presents a novel voltage-current model for directional over-current relay (DOCR) that gives the relay capability to reduce the overall relay time operation. The state-of-the-art of the proposed relay architecture relies on the adaptive pickup current threshold, which varies with the voltage magnitude, to anticipate the small fault current caused by the IBR. The improvement of relay sensitivity offers faster tripping time in a coordination scheme. The proposed method is assessed in the IEEE 13 bus distribution system with the integration of DG. The outcome of this study indicates that the total relay time operation using the proposed method is 2.363s. Compared to the conventional method based on the standard equation, the proposed technique significantly reduces the total relay operating time up to 47.67%.