A pilot line protection for MT-HVDC grids using similarity of traveling waveforms

Abstract Protection of dc line faults is a major challenge for the operation of multi-terminal high-voltage dc (MT-HVDC) grids. To avoid blocking converter and system shutdown, ultra-fast protection is required to detect and isolate line fault with the application of hybrid dc circuit breaker. This paper proposes a pilot protection scheme based on improved Hausdorff distance to detect the overhead line fault for MT-HVDC grid. Compared with literature, this protection method owns higher withstanding ability of noise interference, start-up delay and data anomaly. Moreover, the fault segment can be correctly identified as independent of fault location, and protection sensitivity is maintained even under internal ground fault with high impedance of up to 1000 Ω. The issue of dead zone fault recognition is considered and solved in this paper with reasonable sacrifice in the sampling frequency requirement. Based on Zhangbei HVDC grid in China, a four-terminal dc grid model is developed in PSCAD/EMTDC environment for fault simulation, and the data processing is performed in MATLAB platform. The feasibility and effectiveness of this protection scheme are verified by a simulation study that considers different scenarios.