Tham khảo tài liệu 'fundamental and advanced topics in wind power part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Verification of Lightning Protection Measures 79 3000m Fig. 11. A typical model of a turbine used in the research. The size of the analysis volume is considerably larger than the turbine in this case 1km x 1km x 3km. fulfilling the inception conditions divided by the height of the analysis volume whereas the term successful upward leader refers to a leader that will propagate upwards self consistently. Having the stabilisation field defined for each point on the structure the second part of the process is to follow the procedure for assigning static leader inception zones finally resulting in individual probabilities as seen above. To understand the basis of the discrete probabilities 3D scatter plots of the successful leader inception points for the orientation 30 to horizontal level are shown in Fig. 12. Here it is clear how the upward leader inceptions occur with a larger distance to the downward leader tip for higher prospective peak currents Left whereas lower prospective peak currents allow the downward leader to approach closer to the turbine before upward leader inception Right . Fig. 12. Scatter plots showing origins of the downward leaders leading to successful upward leader inception. Each colour corresponds to different attachment points. Left 40kA Right 20kA. By evaluating the results presented graphically on Fig. 12 for three different rotor orientations and the four different peak current levels an indication of the attachment point distribution for all possible situations is derived. In practice it is done by counting the number of points with each individual colour and relating them to the total number of points corresponding to the static leader inception zone defined previously . On Fig. 13 examples of the results considering two different rotor orientations and the 18 different points incepting lightning strikes are shown. 80 Fundamental and Advanced Topics in Wind Power Fig. 13. Attachment point distribution along five points for each blade two
