山区大高差500kV输电线路脱冰跳跃高度的计算方法

Calculation Method of Deicing Jump Height of 500kV Transmission Line with Large Height Difference in Mountainous Area

超特高压输电线路不可避免地经过高海拔和重覆冰的山区,大高差输电线路脱冰造成的不平衡张力和导线跳跃会对其电气及机械性能产生重要的影响。针对爬坡、翻山和跨谷等三种典型的山区500 kV输电线路,建立了5档导线-绝缘子脱冰跳跃模型,通过附加力法得到了高差形式和高差角对导线跳跃高度幅值和不平衡张力的影响规律。结果表明:脱冰档存在高差时高侧绝缘子挂点受到的不平衡张力比低侧大,随着高差角的增大,低侧绝缘子挂点受到的不平衡张力加速减小,在30°时较高侧悬挂点受到的不平衡张力可达较低侧的3.06倍;相较于跨谷型,翻山型脱冰档两侧受到的不平衡张力更大,随着高差角的增大,翻山型与跨谷型的不平衡张力与跳跃高度均呈相反的变化趋势,在30°时翻山型不平衡张力达到最大值为30 454.6N,跳跃高度达到最小值为10.02 m,此时跨谷型不平衡张力达到最小值,跳跃高度达到最大值;通过分析弧垂差、跳跃高度幅值及线路高差角之间的关系,拟合得到大高差输电线路导线脱冰跳跃高度的计算公式,对线路设计和运维具有重要的工程价值。

Ultra-high voltage transmission lines inevitably pass through mountainous areas with high altitude and heavy icing. Unbalanced tension and conductor jump caused by ice-shedding of large elevation transmission lines will have an important impact on their electrical and mechanical properties. A five-span conductor-insulator ice-shedding jump model was established for three typical 500 kV transmission lines in mountainous areas, such as hill climbing, cross-mountain and valley crossing. The influence of elevation difference form on the amplitude of conductor jump height and unbalanced tension was obtained by the additional force method. The results show that the unbalanced tension on the higher side of the insulator is larger than that on the lower side when the height difference exists in the ice-shedding gear. With the increase of the height difference angle, the unbalanced tension on the lower side of the insulator decreases rapidly, and the unbalanced tension on the higher side of the insulator at 30° is 3.06 times that on the lower side. Compared with the valley-crossing model, the unbalanced tension on both sides of the ice-shedding model is larger. With the increase of elevation angle, the unbalanced tension and jump height of the mountain-crossing model and the valley-crossing model show the opposite trend. At 30 °, the unbalanced tension of the mountain-crossing model reaches the maximum value of 30 454.6 N, and the jump height reaches the minimum value of 10.02 m. At this time, the unbalanced tension of the valley-crossing model reaches the minimum value and the jump height reaches the maximum value. By analyzing the relationship among sag difference, jump height amplitude and line height difference angle, the calculation formula of ice-shedding jump height of transmission line conductor with large elevation difference is fitted, which has important engineering value for line design and maintenance.