Travelling wave fault location principle for hybrid multi-terminal LCC-MMC-HVDC transmission lines based on C-EVT

This paper considers the fault location problem of hybrid multi-terminal high-voltage direct-current (HVDC) transmission systems based on the line-commutated converter (LCC) and modular multi-level converter (MMC). Two issues are addressed in this study: (i) the travelling wave (TW)-based fault location principle and (ii) the method of capturing the high-frequency TW signals. Therefore, a novel TW fault location principle for the hybrid multi-terminal LCC-MMC-HVDC transmission lines is proposed based on the capacitance-divided electronic voltage transformer (C-EVT). Firstly, the TW transfer characteristic of the C-EVT is analyzed. Secondly, a novel TW fault location principle based on the secondary differential voltage TW (D-VTW) is proposed. Finally, a typical ± 400 kV hybrid three-terminal LCC-MMC-HVDC system is used for the case study to verify the high accuracy of the proposed method. Furthermore, its robustness against different fault locations, fault resistances and fault types is also investigated.