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A Novel Integrated Directional Protection Scheme for Transmission Lines and Busbar of Multi-terminal HVDC System

Multi-terminal HVDC system has a rapid development due to the advantages in flexible operation. However, the traveling wave protection presently in use has exposed the problem of low sensitivity in detecting high impedance grounding fault and the back-up protections have a long time delay. To solve this problem, a novel integrated directional protection scheme for transmission lines and busbar of multi-terminal HVDC system is proposed in this paper. The polarity difference of current fault components between positive direction fault and negative direction fault is employed to identify fault direction. The protection scheme is performed in time domain, and only needs to utilize the single pole current data. Besides, the protection scheme can adapt to multi-terminal HVDC systems of different topologies. Simulation tests show that the proposed protection scheme can correctly identify the fault section and detect the high impedance grounding fault accurately and rapidly.