Non-unit ROCOV scheme for protection of multi-terminal HVDC systems

Nowadays, high voltage direct current transmission systems are being selected over the traditional alternating current transmission for very long transmission distances. However, there are still some unresolved challenges, most of them in terms of protection of the system. If using traditional protection systems used in alternating current grids, the characteristics of a DC fault make it complicated to clear and dangerous to power electronic components. Hence, there is a need of very fast fault detection and clearance. This paper proposes a full-selective protection system based on a rate of change of voltage. The process of selection of the threshold needed to discriminate fault conditions is described. In addition, the performance of the protection algorithm is analysed. The influence of parameters such as the fault location and fault resistance is evaluated. A comparison with similar algorithms found on the literature is presented at the end.