IEC TR61400-24 [1] suggests interconnection of grounding systems of wind turbines through horizontal electrodes (in the form of insulated or bare conductors) to achieve low steady-state grounding resistance. The effect of interconnection on the lightning surge response of wind turbine grounding depends on the wave propagation characteristics through the interconnected wire. This report presents the fundamental propagation characteristics of current pulse through an interconnection wire of wind turbine groundings using FDTD method.