# Lightning Protection Methods for Wind Turbine Blades: An Alternative Approach
## 4 ANSYS Workbench Implementation
### 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.  
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].  
The ambient temperature was set to 20 \({}^{\circ}\)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\({}^{2}\) and to 200 mm\({}^{2}\). Afterwards, as it has been mentioned in many publications [4; 26; 33; 34; 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  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Stroke** & **Test Parameter** & **Unit** & \multicolumn{2}{c}{**LPL**} \\ \cline{3-4}  & & & **Extreme (0)** \\ \hline First & \(\Delta\)i & kA & 300 \\  & \(\Delta\)t & \(\mu\)s & 10 \\ \hline Subsequent & \(\Delta\)i & kA & 75 \\  & \(\Delta\)t & \(\mu\)s & 0.25 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Test parameters for simulations showing the extreme case for LPL [23].  
Figure 2: Simulation setup for the model.  
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:  
**Conventional:**  
**A:** Minimal protection level with 50 mm\({}^{2}\) conductor cross-section area;  
**B:** 100 mm\({}^{2}\) conductor cross-section area;  
**C:** 200 mm\({}^{2}\) conductor cross-section area.  
**Hybrid:**  
**D:** Hybrid conductor design for tip;  
**E:** Hybrid conductor design, 2 m on sides;  
**F:** Hybrid conductor design, 5 m on sides.  
The parameters examined from the simulation models were:  
1. Voltage at the attachment point (V);
2. Maximum value of Joule heating in the conductor (MW/m\({}^{3}\));
3. Current density at the attachment point (kA/m\({}^{2}\));
4. Maximum temperature generated by Joule heating in the conductor (\({}^{\circ}\)C);
5. Total deformation caused on the blade due to the heating effect (mm);  
In addition to the existing parameters, another probe was added to hybrid design at the joints of the two conductors to follow the change in the current density:  
6. Current density at joint (kA/m\({}^{2}\)).  
**5. Simulation Results and Discussion**