Lightning surge analysis on wind farm with interconnecting grounding wire using circuit model for vertical conductor

Grounding circuits of wind power generators are often interconnected for reducing grounding resistance. Lightning surge on a wind farm is investigated by means of circuit analysis method with a model circuit expressing a vertical conductor in this paper. The interconnected grounding system may spread the lightning surge. All the lightning current is discharged from the bottom of the struck wind turbine tower in the case of the independent grounding. In the case with the interconnected wires, about 10 % of the lightning surge current propagates to the next wind turbine tower through the wire. Although the interconnected grounding system reduces the steady state grounding resistance, the effect of the interconnected grounding system on the transient current and voltage characteristics have to be taking into account for a lighting protection of a wind farm.