Impact of Dynamic Voltage Support on Memory Polarized Mho Relay in Presence of Grid Following PV Generators

This paper investigates the influence of dynamic voltage support on Positive Sequence Memory-Polarized (PSMP) mho relays in the presence of Grid Following Photovoltaic (PV) generators. The widespread integration of Inverter-Based Resources (IBRs) has significantly altered power system dynamics. Traditionally, memory polarization in mho elements has ensured reliable operation during close-in faults. A dynamic expansion of mho characteristics results from the use of memory voltage for polarizing the mho elements, enhancing the resistive reach in systems dominated by Synchronous Generators (SGs). However, the fault current characteristics of IBRs differ from SGs, potentially compromising the dynamic mho expansion behavior. This work explores how dynamic voltage support employed by large-scale PV generators affects the expansion of PSMP mho characteristics. The PV generators used in this study have reactive power priority and Low Voltage Ride-Through /High Voltage Ride-Through capabilities and are compliant with the IEEE Standard 2800-2022.