A Simplified Model of Wind Turbine for Lightning Transient Analysis as Influenced by Structure of Grounding System

In this paper, the transient behaviour of a WT during lightning stroke is determined considering the high frequency nature of the lightning impulse current through its flow from WT blades to the grounding system. Following the IEC Standard, type-B arrangement is the recommended one for WT grounding which is composed of a horizontal ring supported with horizontal electrodes and vertical rods. The ring is divided into series of linear horizontal conductors. Each horizontal conductor, horizontal electrode and vertical rod is modelled by its π -equivalent RLC circuit. Furthermore, the WT blade is modelled by π -equivalent RLC network. The tower model is simplified by splitting it into vertical cylinders; each cylinder is represented by π -equivalent RLC circuit. The nodal equations of the grounding system and the WT are written at each discrete time instant. MATLAB software package is used to solve the nodal equations and determine the transient response of WT. The results are compared with the case of turbine grounding through a pure resistance as adopted in the literature. The simulation results are then validated by using PSCAD/EMTDC software package.