A Directional Protection Scheme for MT-HVDC Grid Based on Traveling Waves

This paper reports a novel directional protection scheme for Multi-Terminal High Voltage DC (MT-HVDC) network system based on traveling waves. Firstly, the conventional directional comparison principle based on traveling waves is presented. The impact of fault current limiting inductor on the traditional direction principle is analyzed in details. Thereafter, a more reliable directional criterion, transient energy of traveling waves, is proposed in order to increase the reliability of applying traveling wave based protection, especially with inductive terminal. The polarities of calculated transient energy at both ends of protected line are reliable criteria to determine internal or external fault. The detailed protection scheme based on the transient energy is presented to reliably determine the fault direction and faulted pole. The effectiveness of the proposed method is verified by a MT-HVDC grid modeled in PSCAD software. The simulation results show the proposed method reliably determine the internal or external faults under different fault conditions including close-in faults and high-resistance faults.