基于导线径向温度和蠕变的导线弧垂计算方法

输电线路弧垂是线路安全运行的重要指标，针对输电导线温度非均匀分布和蠕变带来的弧垂计算偏差，本文开展了径向温度和蠕变对弧垂计算模型影响程度的研究。首先，基于导线的物理构成和结构特征建立了导线的有限元模型，对不同运行状态下的输电导线进行有限元仿真，分析了不同运行状态下的导线径向温度分布规律；其次，建立了考虑径向温差的导线应力、导线径向热膨胀和蠕变的弧垂计算模型，基于力平衡原理研究了考虑径向温差的导线径向热膨胀、导线应力与伸长量的关系，分析了蠕变与伸长量的关系，并通过伸长量与弧垂的关系函数得到导线弧垂；最后，为了验证该弧垂计算模型的准确性和实用性，本文基于陕西某110 kV实际输电线路进行了验证。结果表明：对于本现场实际运行的导线来说，蠕变对弧垂计算的准确性影响最大，其次是导线径向温差，最后是径向热膨胀；在忽略导线径向温差、径向热膨胀和蠕变时，弧垂计算的误差范围为-45.2%~-30%，最大误差高达45.2%，而本文的优化模型计算误差小于1.1%；当忽略导线径向温差和径向热膨胀时，导线弧垂计算存在误差，且随着径向温差的增大，忽略导线径向温差和径向热膨胀带来的弧垂计算误差也逐渐增大。

Calculation Method of Conductor Sag Based on Radial Temperature and Creep

The sag of transmission lines is an important index for the safe operation of transmission lines. However, the deviation of sag calculation was caused by non-uniform distribution of temperature of transmission lines and creep. Based this problem, the research that the influence degree of radial temperature and creep on sag calculation model was studied in this paper. Firstly, the finite element model of conductor was established based on its physical composition and structural characteristics. Considering different operating conditions, the radial temperature was analyzed by finite element simulation. Secondly, considering the radial temperature difference of stress, the radial thermal expansion and creep, the model of sag calculation was built. Based on force balance principle, the relationship between the radial temperature difference of the radial thermal expansion, stress and strain was studied and the relationship between creep and strain was analyzed. Then sag was calculated by function that the relationship between strain and sag. Finally, in order to verify the accuracy and practicability of the sag calculation model, the model was verified by a 110 kV transmission line in Shaanxi Province. The results show that the influence on the accuracy of sag from largest to smallest were creep, radial temperature difference and radial thermal expansion based on the 110 kV transmission line in Shaanxi Province. Without taking into account the radial thermal expansion and creep, the error of sag was in the range from -45.2% to -22%. And the maximum error is 45.2%. The optimization model of sag in this paper is less than 1.1%. According to the above improved sag algorithm, when the span is larger than 100m, the creep influence on sag can not be ignored, and with the increase of the gap, the creep influence on sag is more. When the influence of radial thermal expansion on the sag is ignored, the error of sag is existed. And with the increase of radial temperature difference, the influence of radial thermal expansion on the sag becomes greater.