A Non-Pilot Accelerated Distance Protection Scheme Based on RCBO for SLG Faults on IBR-Connected Transmission Lines

High-resistance single-line-to-ground (SLG) faults on inverter-based resource (IBR)-connected transmission lines can cause severe underreach of distance protection because the limited and control-dependent IBR fault current increases the influence of fault resistance on the measured apparent impedance. Consequently, the local Zone-II element may fail to pick up, preventing conventional pickup-dependent acceleration from being initiated. This paper proposes a non-pilot accelerated distance protection scheme for SLG faults that requires neither interstation communication nor local Zone-II pickup. Following remote single-pole opening, the fault-sequence current is reconstructed from the open-pole condition using a segmented nominal-π line model that accounts for line charging. Combining the negative- and zero-sequence boundary equations yields a fault-location residual without an explicit fault-resistance term. The required remote-system source impedance is updated from locally stored prefault phasors, subject to numerical and physical validity checks. Candidate open-pole residuals, a fault-location stability criterion, and a boundary safety margin supervise the acceleration decision. Across 540 PSCAD/EMTDC fault scenarios covering six system configurations, the maximum fault-location error was 1.98%; all 270 tested internal faults within the prescribed acceleration range were successfully accelerated, and all 270 external faults were correctly blocked. The mean post-RCBO trip-decision times ranged from 37 to 45 ms across the six configurations.