To address the performance deterioration of conventional longitudinal current differential protection for transmission lines during low-voltage ride-through (LVRT) operation of photovoltaic (PV) plants

where controlled output behavior invalidates power-frequency current amplitude relationships

a novel current differential protection scheme with enhanced tolerance to high transition resistance is proposed. First

considering the dynamic output characteristics of PV plants under LVRT conditions

the phase characteristics of the positive-sequence fault current components at both terminals are analyzed under various fault scenarios

along with the phase-advance phenomenon under high-resistance faults. Then

a protection operating index and an adaptive restraining criterion are constructed by combining magnitude and phase differences of the positive-sequence fault current components at both ends of the faulted line section

thereby significantly enhancing the protection's tolerance to transition resistance. Finally

a representative PV plant transmission line model is built in PSCAD/EMTDC for validation under multiple scenarios. The results demonstrate that the proposed scheme offers high sensitivity

weak dependence on fault type

fault location

and new energy penetration level. It can still operate reliably under high-resistance faults.