## 4 Comparison of Wind Loads on Bare and Ice-Covered Overhead Conductors
### Result  
As described above, the major concern in static wind load conditions was the internal force and deformation of the structure. Typical deformation of the long-span CRS with static wind load is shown in Figure 13.  
Tensile force results of suspension cables in different wind speeds were obtained. Based on the structure stability status of self-weight, the increment of tensile force of the suspension cable is shown in Figure 14. The results showed that the tension force of the suspension cable increased with wind speed. While ice thickness increased to 10 mm, the increment was more remarkable than no ice. It is mainly because of a larger windward area of the iced conductor, which leads to a larger wind load. Wind load increased with the span length of the conductor. In order to study the influence of the span length of the conductor on the tensile force of suspension cables, the FE models of long CRS with a different span length of the conductor were analyzed. The results in Figure 15 show that the tensile force of the suspension cable increased with a span length of the conductor, and the increment was marked more while the conductor was iced.  
Figure 14: The influence of wind speed on tensile force of suspension cable.  
Figure 13: Unscaled deformation of long-span cross-rope suspension line by static wind load. (Dotted: undeformed. Solid: Deformed.)The transmission line structure was considered dangerous once the distance between conductors was less than the safety requirement by design. Especially in long-span CRS, the horizontal displacement of the conductor induced by the wind was greater than the traditional transmission line. A diagram of the horizontal displacement of conductors with different wind speeds is shown in Figure 16. According to the obtained results, the horizontal displacement of the conductor was significantly increased with wind speed. When the conductor was iced, the increment was insignificant compared with no ice. In order to figure out the causes of the phenomenon, the FE models of long CRS with different wind speeds and a given ice thickness, 10 mm, were analyzed. As shown in Figure 17, the horizontal displacement of the conductor increased with ice thickness in a small value of ice thickness (0-5 mm) and reduced in a large value of ice thickness (more than 10 mm). The reason for this phenomenon was the joint action of the increase in wind load and tensile force of the conductor induced by ice thickness. On the one hand, wind load increased with ice thickness, which resulted in an increase in horizontal displacement of the conductor. On the other hand, the tensile force also increased with ice thickness, which led the conductor to tighten. According to the obtained results, the horizontal displacement of the conductor did not change linearly with the increase in ice thickness.  
Figure 16: The influence of wind speed on maximum horizontal displacement of conductor.  
Figure 15: The influence of length of spans of conductor on tensile force of suspension cable (wind speed: 10 m/s).  
In order to cross the valleys, the long-span CRS was designed for multi-span, which brings about the increase in flexibility of the structure. The structure was more sensitive to wind load in this condition. Therefore, the wind resistance performance of multi-span CRS was studied to provide the basis for the actual engineering design. The FE model of long-span CRS with a different number of spans was analyzed to compare the influence of the number of spans on the tensile force of the suspension cable and the horizontal displacement of the conductor. The results are shown in Figures 18 and 19. As the results show, the horizontal displacement of the conductor increased with the number of spans but had no effect on the tensile force of the suspension cable.  
Figure 17: The influence of wind speed on maximum horizontal displacement of conductor (fixed ice thickness with 10 mm).  
Figure 18: The influence of number of spans of conductor on tensile force of suspension cable (wind speed: 10 m/s).