架空输电线路工程设计低温取值研究

Study on Valuing of Design Low Temperature of Overhead Transmission Line

设计低温的取值直接影响铁塔钢材的选用,现行技术标准缺乏设计低温的明确定义。通过研读相关规程规范,建议架空输电线路设计低温选择“最低日平均气温”作为统计样本,并参照设计风速和设计覆冰重现期赋予设计低温明确的频率涵义,即高压、超高压以及特高压设计低温重现期分别取30年、50年和100年。设计了3组对比试验探讨分析气温随海拔上升的变化规律,结果表明,随着海拔上升,累年极端最低气温、历年最低日平均气温、历年平均气温呈不同程度的下降趋势,其中历年最低日平均气温下降趋势最为明显,直减率0.55~0.72℃/100m,建议架空输电线路设计低温取值时进行海拔修正。

The valuing of design low temperature influences the steel selection of transmission tower directly,while current technical standards lack clear and specific provisions on the design low temperature of overhead transmission line.By analyzing current technical standards,it is suggested that minimum daily average temperature should be taken as the statistical sample of design low temperature of overhead transmission line.Referring to return period of design wind speed and design ice thickness,it is also recommended that the design low temperature return period of HV overhead transmission line should be taken as 30 years and EHV overhead transmission line should be taken as 50 years and the UHV transformation project be taken as 100 years.Three contrast experiments are designed to discuss the changing regulation of temperature with elevation.The main results are shown as follows.With the rising of the elevation,normal extreme minimum temperature and minimum daily average temperature and annual mean temperature presents downward tendency in different degrees.Among them,the decrease of minimum daily average temperature is the most obvious.The lapse rate is between 0.55℃and 0.72℃per 100 meters.So altitude correction is necessary to calculate design low temperature of overhead transmission line.