Adaptive Voltage Restrained Overcurrent Relaying for Protection of Distribution System with PV Plant

With the integration of inverter based solar photovoltaic (PV) plant in the distribution system, the fault current behaviour changes significantly which limits the application of overcurrent relay (OCR) for line protection. As a solution, voltage restrained overcurrent relay (VR-OCR) can be used for line protection. The loading condition of distribution system further limits the application of VR-OCR. This work highlights the issue with existing VR-OCR scheme and proposes a protection scheme that changes the pickup settings of VR-OCR adaptively to suit the prevailing power system conditions. At a sampling rate of 1200 samples/sec for 60 Hz system, the method updates its setting at each cycle and uses it for protection decisions. Using MATLAB/Simulink, the performance of the proposed scheme is tested for various loading conditions and fault resistances in a PV connected distribution system. Hardware-in-loop testing using real-time simulator OPAL-RT and IEC 61850 communication protocol validates the proposed method in real-time application.