Protection of star connected multi-terminal HVDC systems with offshore wind farms

In this paper, a high speed protection technique is proposed for protection of star connected Multi-Terminal HVDC (MTHVDC) systems with offshore wind farms. The fault is detected using high frequency transients created in the current signals due to fault occurrence. In fault cases, the energy of the transients superimposed on current signals is high. Moreover, the faulty line incorporates more high frequency transients than the healthy lines. Therefore, faulted line can be identified by comparing Euclidean norms of the high frequency transients superimposed on line currents. The proposed technique is able to detect fault and identify faulted line in MTHVDC systems including overhead lines and underground cables. Moreover, the identification of faulted line is done in less than 0.1 ms, which means complete safety of converter semiconductor devices during fault. Simulation and relay design are done in MATLAB. Simulation results showed the robustness and reliability of the proposed algorithm.