Lightning protection of wind power generation is becoming an important public issue. Japan in particular suffers from frequent and heavy lightning strikes, such as the notorious “winter lightning” found in coastal areas of the Sea of Japan. Also, it is important to understand the “impedance characteristics” of wind turbine earthing systems from the viewpoint of lightning protection. A report from IEC, TR61400-24, recommends a “ring earth electrode”; however, this concept has not been fully clarified, especially its transient behavior during a lightning strike remains unresolved.
To confirm the effect of a ring earth electrode, this report presents an electromagnetic transient analysis on a foundation and ring earth electrode of a wind power generator using a Finite Difference Time Domain (FDTD) method. The results show that the ring earth electrode provides a low steady resistance with little inductive potential rise. Thus, it is confirmed that the ring earth electrode provides effective lightning protection of wind turbines.
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