Neutral earthing in off-shore wind farm grids

The maintenance of offshore wind farms is more complicated than those onshore. The effort associated with cable repairs in terms of time and cost is much larger compared to I similar tasks in conventional distribution grids. Current and voltage stress of the grid following the most common single phase to ground fault primarily affected by the type of transformer connection and the method of neutral earthing. Low impedance earthing leads to high fault currents but the voltage stress is limited. The high fault current, on the other hand, enables easy detection and quick clearance of the fault. Using simulation results, the authors show that for the medium voltage wind farm grid as well as for the 150-kV transmission link to the grid onshore, fault currents stay within acceptable limits in spite of solid earthing. As a result, grounding the neutral solidly offers itself as the most suitable neutral treatment method for offshore wind farms.