Fault behaviour of bipolar overhead line based HVDC grids

This paper provides a fault analysis of bipolar overhead line based HVDC grids using HB-MMC converters. The impacts of fault type and fault resistance are shown and the physical behaviour of the transient fault return current is explained. A transformation in modal quantities enables a decoupling of the measured phase currents and voltages. The results are presented in a point-to-point HVDC grid for both phase and modal quantities. It is shown that fault analysis in the modal domain is an auspicious method for fault detection and faulty line discrimination.