Abstract
Transient current distributions within the grounding systems of a wind-turbine-generator (WTG) tower struck by lightning and its neighboring WTG tower, and transient electric field inside these towers have been calculated using the finite-difference time-domain (FDTD) method. The grounding terminal for the generator inside the lightning-struck WTG tower is connected to that inside the neighboring WTG tower through a long insulated wire. About 40% of the lightning current flows in the grounding grid of the neighboring tower at 30μ s. Inside the towers, the radial component of electric field is most significant. Its peak value is about 1kV/m near the base of each tower when a lightning current having a magnitude of 30kA and a 10-to-90% risetime of 2.5μ s is injected. The electric field decreases with increasing the height of the observation point in the towers. When the grounding terminals are buried below the substructure (the grounding grids are connected via an underground insulated wire), the electric field inside the tower is significantly reduced.
