A direct current transmission line fault protection method utilizing characteristic current differences

Direct current (DC) transmission systems have longer transmission distances and larger transmission capacities, making them an important transmission method for the future. When a fault occurs in a DC transmission system, the harmonic currents in the line will exhibit significant differences in direction and waveform. Based on the condition of harmonic currents, a fault protection method for DC transmission lines can be designed, which can reliably distinguish between internal and external faults. In light of this, this paper proposes a fault protection method for DC transmission lines utilizing the characteristic current differences. This method defines the current matching error, protection initiation criteria, and criteria for distinguishing between internal and external faults of the DC transmission line. Finally, a model is established in PSCAD software to simulate and analyze the effectiveness of the proposed method. The simulation results show that the proposed method can effectively judge internal and external faults of DC transmission lines, featuring simple principles and ease of implementation, which has certain value for improving the safety and stability of DC transmission system operation.