The influence of sampling frequency on traveling-wave protection for multi-terminal hybrid HVDC

In a multi-terminal hybrid HVDC system, modular multilevel converter (MMC) has faster control response than line commutation converter (LCC), which makes MMC require shorter action time of the HVDC line protection. For traveling wave protection for HVDC line, the sampling frequency is a factor of protection action time. Based on the PSCAD/EMTDC simulation model of three-terminal hybrid HVDC system, this paper studies the influences of sampling frequency on the performance of travelling wave protection. Firstly, the influence of different sampling frequencies on fault characteristics extraction is analyzed. It shows that the change of sampling frequency mainly affects the criteria based on line mode wave. Secondly, according to the fault characteristics, sensitivity and speed of traveling wave protection at different sampling frequencies are studied. Finally, some suggestions about the selection of sampling frequency are given from the aspects of overall performance of traveling wave protection.