架空输电线路初伸长计算方法探讨

Discussion on the Calculation Method of the Permanent Elongation of Overhead Transmission Lines

总结并分析了国内外初伸长的预测方法及处理措施,得出了各种计算结果不同的原因。国际大电网预测公式考虑了应力和永久伸长之间的互相循环影响,预测结果和蠕变试验结果接近,可满足工程设计要求。由于规范考虑初伸长求架线应力时,应变值剔除了架线过程中已拉出的塑性伸长,因此规程规范对初伸长的规定均较小。架线时间4~48 h内,架线过程释放的伸长量在14%~24%之间,为提高初伸长预估值的准确性,需根据架线时间调整初伸长或安装降温值。

This paper summarizes and analyzes the prediction methods and treatment measures of permanent elongation of transmission line at home and abroad,and drew the reasons for the different calculation results. The CIGRE prediction formula takes into account the mutual cyclic effects between stress and permanent elongation. The prediction results and the creep test results are close,which can meet the engineering design requirements. When the code takes into account the initial elongation to determine the stress of the wire,the strain value excludes the plastic elongation that has been pulled out during the process of line stringing,therefore the initial elongation specified by the specifications is smaller.Within 4 to 48 hours of stringing,the amount of elongation released during the stringing process accounts for about 14% to24%. To improve the accuracy of the permanent elongation estimate,the initial elongation or installation cooling needs to be adjusted according to the stringing time.