Due to the weak infeed characteristics of converters and the influence of control strategies

the fault current magnitude and phase of inverter-based resources (IBRs) are highly controllable

leading to poor transition resistance tolerance of conventional distance protection schemes. Under high transition resistance conditions

especially during asymmetric faults

distance protection on the IBR side of the transmission line may fail to operate correctly. This paper proposes a distance protection principle based on adaptive compensation using characteristic harmonics. By employing the high controllability of power electronic converters

the method monitors the variation of the converter’s output equivalent impedance in real time. According to the severity of the fault

the converter injects characteristic harmonic signals adaptively to compensate for the magnitude and phase of the IBR-side fault current. The protection logic is built on the relationship between the measured impedance and a preset impedance at the harmonic frequency. This approach reduces the influence of transition resistance from the protection principle and effectively addresses the malfunction of distance protection under weak infeed conditions. The proposed protection is independent of converter capacity or the installed capacity of the new energy station. It offers strong tolerance to transition resistance and demonstrates strong immunity to noise. Simulation studies based on a modified IEEE 9-bus test system in PSCAD/EMTDC confirm that the proposed scheme is suitable for transmission line protection involving inverter-based renewable energy sources.