*4.3. Simulation Setup*

For the lightning attachment point, a part on the conductor at the tip of the blade was defined (point A). In the absence of specifying ground, 0 voltage was applied on the connecting ends of the conductor (points B and C (Figure 1)).

For simulation, electric, transient-thermal, and static structural analysis was chosen using Mechanical APDL solver [32]. As shown in Figure 2, the applied mechanical APDL structure can be seen. By connecting the electric, thermal, and structural sections, it was possible to transfer results from one stage to another, creating a complex simulation environment.

**Figure 2.** Simulation setup for the model.

The first and subsequent return stroke current rise were implemented according to the current standards [12], with an additional 'extreme' level of first and subsequent return stroke and the effects were observed over set amount of time as tabulated in Table 1. The 'extreme' level used referred to the highest recorded lightning peak current [2,5].


**Table 1.** Test parameters for simulations showing the extreme case for LPL [23].

The ambient temperature was set to 20 ◦C, and the blade was set to be fixed at the base. For testing the proposed method, first, the cross-section of the down conductor area was set to the recommended minimum area which was then increased to 100 mm<sup>2</sup> and to 200 mm2. Afterwards, as it has been mentioned in many publications [4,26,33–35] and stated in the standards [7], lightning tends to attach to the tip and to the close approximation of the blades. Therefore, to overcome the destructive heating effect of the lightning, especially at the attachment point on the conductor, a hybrid conductor has been designed. This design consisted of two conductors with different diameters joined together. The larger diameter covered the tip of the blade and ran down at a specific distance from the tip towards the root. The joints of the two conductors could be welded or the whole conductor could be molded to achieve a better transition between the different thicknesses. In total, six case studies were examined with different diameters and a combination of conventional and hybrid methods:

*Appl. Sci.* **2020**, *10*, 2130
