The Significance of Mutual Coupling on the Lightning Transient Voltage and Current of Typical Wind Turbine under Different Lightning Strokes

This paper described a computation of lightning electromagnetic transient of the wind turbine lightning protection system using PSCAD/EMTDC software. Blade grounding wire and wind turbine tower were modelled by circuit approach considering their mutual coupling of vertical and horizontal wires using the codes available in PSCAD. The comparison analysis has been performed between models with and without accounting the inductive/capacitive coupling for estimating transient overvoltage at the blade, tower top, and tower base under two distinct lightning current strokes. Also, wind turbine grounding system configuration with an equipotential grounding cable is analyzed to determine discharge current through the low voltage surge arrester under different grounding characteristics. The simulation results show that the mutual coupling significantly affects the tower top/nacelle overvoltage. Moreover, it was found that double peaked lightning current produces strong negative oscillations than standard 2.6/50 $\mu$s lightning. Depending on the uses of the model, the accuracy is enough to compute lightning overvoltage and currents through surge arresters.