Local Measurement-Based Ultra-High-Speed Main Protection for Long Distance VSC-MTDC

To ensure the continuous operation of the voltage source converter based multi-terminal HVDC system (VSC-MTDC), there has been much concern regarding how to isolate the single-pole earth fault by means of protective relaying. However, when the boundary components are not on the dc transmission lines, conventional main protections for the HVDC systems perform less satisfactorily. To solve this problem, a local measurement-based ultra-high-speed main protection is proposed, in this paper. The proposed method is achieved by the cooperation of the single-end directional start-up criterion and the surge arrival time difference between the 0-mode and 1-mode traveling waves. According to the simulation results, the proposed method has satisfactory performance against internal faults and is quite reliable in external fault and operating condition changes. Meanwhile, the reach is also wide enough to cover most of the protected line. Comparison studies are also conducted among the proposed protection and three types of existing protection schemes, highlighting the advantages of the proposed protection in terms of selectivity, operating speed, and resistive tolerance.