Modeling lightning current distribution in conductive elements of a wind turbine blade

In this paper we present a numerical analysis of lightning current distribution in the conductive elements of a wind turbine blade. They include lightning down conductor, blades spar caps made of carbon fiber reinforced polymers (CFRP) and protective copper mesh placed on the spar caps. The problem is solved in frequency domain by using the finite element method. Anisotropic electrical conductivity of CFRP laminates was considered in the modeling. We have analyzed two cases when CFRP elements are covered by the copper mesh and without such protection. In the first case due to the skin-effect the most of the current flows through the external highly-conductive surface of the copper mesh. However the thin mesh can be easily damaged by lightning. In the second case an extreme result of such failure is modeled. It was found that even the placement of additional down conductors will not prevent lightning current from flowing through CFRP elements leading to delamination of the laminates.