## 4 Analysis of Ice Shedding Response of Overhead Conductors under Strong Winds
### The Effect of Wind Speed on the Ice Shedding Response of Transmission Lines  
As the source of lift and drag force on the iced conductor, the wind speed will have a great influence on the oscillation process of ice shedding. For the wind speed conditions of 10 m/s and 20 m/s, the bouncing process of ice shedding at a 180\({}^{\circ}\) wind attack angle for different ice shapes is shown in Figure 7. For the circular iced conductor, the longitudinal coordinates of the initial position were basically the same under the action of airflow, and the longitudinal bounce curve was almost the same. Because the airflow resistance under a 20 m/s wind speed was greater, the difference of transverse coordinates of the initial position was 3.21 m, while the difference of transverse bouncing amplitude was less than 1 m. The oscillation curves after ice shedding of elliptical-shaped and crescent-shaped iced conductors were approximate, and the transverse amplitude of the conductor increased significantly with the increasing wind speed, but the difference in longitudinal amplitude  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Wind Attack Angle** & **Ice-Covered Landscape** & **Round-Shaped** & **Crescent-Shaped** & **D-Shaped** \\ \hline \multirow{4}{*}{45\({}^{\circ}\)} & initial coordinate & (1.12 m, \(-\)3.09 m) & (1.27 m, \(-\)3.04 m) & (1.57 m, \(-\)1.6 m) \\  & maximum horizontal coordinate & (1.44 m, 2.86 m) & (1.4 m, 244 m) & (1.57 m, \(-\)1.6 m) \\  & maximum vertical coordinate & (1.35 m, 6.84 m) & (1.27 m, 6.81 m) & (1.13 m, 5.89 m) \\ \hline \multirow{4}{*}{90\({}^{\circ}\)} & initial coordinate & (1.12 m, \(-\)3.09 m) & (1.9 m, \(-\)3.5 m) & (0.52 m, 3.01 m) \\  & maximum horizontal coordinate & (1.44 m, 2.86 m) & (1.9 m, \(-\)3.5 m) & (1.74 m, 3.05 m) \\  & maximum vertical coordinate & (1.35 m, 6.84 m) & (0.93 m, 7.10 m) & (1.74 m, 3.05 m) \\ \hline \multirow{4}{*}{180\({}^{\circ}\)} & initial coordinate & (1.12 m, \(-\)3.09 m) & (0.52 m, \(-\)3.09 m) & (8.82 m, 3.6 m) \\  & maximum horizontal coordinate & (1.44 m, 2.86 m) & (1.68 m, 6.47 m) & (8.82 m, 3.6 m) \\ \cline{1-1}  & maximum vertical coordinate & (1.35 m, 6.84 m) & (1.68 m, 6.84 m) & (8.70 m, 3.59 m) \\ \hline \hline \end{tabular}
\end{table}
Table 1: The coordinates of the span midpoint before ice shedding, and the maximum coordinates during the bouncing process.  
Figure 6: Effect of wind attack angle on the ice shedding bouncing process of transmission lines, and the red and yellow lines represent the projections of curves on different planes, respectively. (**a**) Crescent, 45\({}^{\circ}\); (**b**) crescent, 90\({}^{\circ}\); (**c**) crescent, 180\({}^{\circ}\); (**d**) D-shaped, 45\({}^{\circ}\); (**e**) D-shaped, 90\({}^{\circ}\); (**f**) D-shaped, 180\({}^{\circ}\).  
was not obvious. Therefore, it is important to pay attention to the distance between the ice shedding conductor and the overhead ground wire diagonally above it.  
Compared with the round-shaped, elliptical-shaped, and crescent-shaped conditions, the airflow resistance of fan-shaped and D-shaped conditions increased significantly at a 180\({}^{\circ}\) wind attack angle and 20 m/s wind speed, and the direction of horizontal motion after ice shedding was also opposite to the above three cases. And the jumping amplitude increased significantly, with the horizontal coordinates jumping from the initial 18.36 m and 23.6 m to \(-\)2.48 m and \(-\)4.86 m, respectively. Therefore, it can be observed that the lateral amplitude exceeded 20 m, which represented a high possibility of causing phase-to-phase and phase-to-ground discharge. Under the condition of an airflow velocity of 20 m/s, the longitudinal coordinates of the initial position of the iced conductor were 0.71 m and 4.17 m, respectively. After ice shedding, the fan-shaped iced conductor bounced upwards to 5.75 m, while the D-shaped iced wire bounced downwards to 0.98 m. Compared to the other three shapes of iced conductors, the longitudinal bounce height under strong winds was very small.