As known, voltage source converter-based high-voltage direct current (VSC-HVDC) transmission system is widely utilised in actual power grid. It is suitable for asynchronous networking, such as the connection of offshore wind farm to main power grid. Generally, as primary protection principle, travelling wave (TW) protection is adopted based on the technologies of ABB and SIEMENS, of which is only transient quantity based protection principle instead of true TW protection principle and has no fault direction discrimination ability. Besides, because of the large capacitances applied on converter station, the voltage TW (VTW) information cannot be detected by the protection units of two terminals. Therefore, this study proposes a novel TW directional pilot protection based on current TW (CTW) and direct current voltage. In the beginning, this study the unusual propagation characteristic of VTW or CTW along with the VSC-HVDC transmission line. Afterwards, this study proposes a novel fault direction discrimination criterion using the integral of instantaneous TW power. Eventually, using PSCAD/EMTDC, a typical VSC-HVDC transmission system simulation model is constructed to verify novel protection's performances.