Analysis and Mitigation of The Lightning Overvoltage in Capacitively Coupling Grid Connected Offshore Wind Turbine

Offshore wind turbines (OWT) are frequently struck by lightning, Because of their high constructions and the harsh marine environment. The high transient voltage from a lightning strike can cause huge damage to the devices of (OWT). In this paper a complete transient circuit model is established for the grid-connected offshore windfarm and an efficient analysis is also presented to evaluate the effect of changing the circuit parameters of blade, tower, grounding resistance, and lightning characteristics. Based on the circuit model, the transient voltage at the most sensitive points of the (OWT) can be determined during direct lightning strikes by ATP-EMTP and MATLAB software. Finally, mitigation techniques are investigated to reduce the overvoltage transients on an offshore wind turbine. This study used the GB50057-94 standard, as it stimulates the worst-case scenario especially in the regions with high lightning-strike probability. The results show that the use of the grounding wire is preferred as an active mitigation technique in offshore wind farms.