As an important topic of power system protection, protection algorithm for transmission lines connecting MMC-based converter stations has attracted extensive attention. This article proposes a new time-domain pilot protection based on two-dimensional space projection of dual differential currents for lines connecting converter stations. The dual differential currents, i.e., original and virtual differential currents, are projected into two-dimensional space. Subsequently, the dynamic trajectories of dual differential currents under various circumstances are elaborated. On this basis, the non-operating zone and internal fault index are defined, whereby the criterion of pilot protection is developed. Afterwards, the operating characteristic of the proposed pilot protection is analyzed under various circumstances. The performance of proposed pilot protection is widely assessed using PSCAD and RTDS. The contribution of this article lies in a new time-domain pilot protection based current trajectory of dual differential currents, which exhibits exceptional performance in operating speed, sensitivity, complexity, tolerance to fault resistance, CT saturation and abnormal data, adaptability to operation mode of MMC.