Modern lightning protection systems for wind turbine blades with conducting structural elements, e.g., carbon fiber reinforced polymer (CFRP) spar caps, contain equipotential bonding joints to prevent sparking during strikes. Significant current levels are experienced through the joints and the characterization of the electrical contact at the bonding regions is essential for reliable protection. Therefore, this article aims to characterize the contact resistivity of several equipotential bonding joints. The proposed methodology first measures the total resistance of the samples, and then the bulk resistance of the conductive elements is computed using the finite-element method. The latter is required to predict the spreading effects in CFRP components due to the strong anisotropic nature of such materials. After that, the contact resistance is calculated by subtracting the predicted bulk resistances from the measured total resistances. The developed procedure was applied to three typical equipotential bonding materials: expanded copper foil (ECF), biaxial (BIAX) CFRP, and unidirectional (UD) CFRP. Both ECF and BIAX CFRP showed superior contact quality than the UD CFRP, with one to two orders of magnitude smaller contact resistivity.

中文翻译：

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风电叶片防雷等电位连接接头接触电阻的估算

用于具有导电结构元件（例如碳纤维增强聚合物 (CFRP) 翼梁帽）的风力涡轮机叶片的现代防雷系统包含等电位连接接头，以防止在雷击期间产生火花。连接处会承受很大的电流水平，接合区域的电接触特性对于可靠保护至关重要。因此，本文旨在表征几个等电位连接接头的接触电阻率。所提出的方法首先测量样品的总电阻，然后使用有限元方法计算导电元件的体电阻。由于此类材料具有很强的各向异性，因此需要后者来预测 CFRP 组件中的扩散效应。在那之后，通过从测量的总电阻中减去预测的体电阻来计算接触电阻。开发的程序应用于三种典型的等电位连接材料：膨胀铜箔 (ECF)、双轴 (BIAX) CFRP 和单向 (UD) CFRP。ECF 和 BIAX CFRP 都显示出比 UD CFRP 更好的接触质量，接触电阻率小一到两个数量级。