The impact of lightning strike to multi-blade on the lightning overvoltage and stresses of arresters in offshore wind farm

This paper establishes a complete lightning overvoltage simulation of an offshore wind farm, considering the electromagnetic effects including the blade, the tower and the power cable based on transmission-line theory. And the influences of grounding schemes of the power cable inside the tower, different WTs struck by lightning, lightning current amplitude and the number of blades struck by lightning on lightning overvoltages of WT are all analysed. The results demonstrate that the grounding of both ends can effectively suppress the lightning overvoltages of WT. Second, the lightning overvoltages of WTs are related to their connection modes in case of lightning strike to different WTs, because of the differences of the equivalent impedance at the outlet of the WTs. Furthermore, the lightning overvoltages of WTs caused by lightning strike to double blades are larger than that caused by lightning strike to a single blade. In the case of the lightning current with an amplitude of 200 kA striking double blades, arresters should adopt multiple parallels connection to ensure the equipment would not be damaged. The distance between the tower and the power cable should be maintained approximately 0.25 m, to prevent the damage to power cable caused by flashover.