高压输电导线局部破损-断裂机理及风险评估

Mechanism and risk assessment of conductors' localized breakage-fracture in high-voltage transmission lines

为了实现高压输电自由导线基于风险指引的检修,根据机械结构可靠性理论,建立了铝股局部破损-导线断裂的风险评估模型;基于该模型,定量评估了破损程度、导线张力、电流负荷、环境温度、散热系数和时间等因素对断线风险概率的影响;并由风险概率分级区间反演计算出了各因素的分级预警区间.研究结果表明:各因素条件下的断线风险概率均与时间成半抛物线形关系,风险概率骤增所对应的阈值分别为导线破损达13.23%以上、张力大于30%极限拉断力、电流负荷大于500 A、环境温度大于35℃以及散热系数小于20 W/(m2·K).各风险因素的重要度排序为破损程度、导线张力、电流负荷、环境温度、散热系数.破损程度、导线张力存在Ⅰ,Ⅱ,Ⅲ,Ⅳ级预警区间,电流负荷存在Ⅰ,Ⅱ级预警区间,而常规条件的环境温度和散热系数一般只存在Ⅰ级预警区间.所建立的定量风险评估模型及分级方法可为输电导线运行安全管理提供参考.

The risk-based maintenance of high-voltage conductors was implemented by establishing the risk assessment model from aluminum strands＇ localized breakage to conductors＇ fracture according to the mechanical structure reliability theory.Quantitative relationships between fracture risk probabilities and breakage degree,tensile force,current,ambient temperature,heat transfer coefficient and duration time were assessed respectively based on this model.And the graded warning intervals of these risk factors were calculated according to the risk probability ranking intervals.The results show that the conductors＇ fracture risk probabilities increase with time in a half parabolic manner.And the threshold values corresponding to the risk probabilities are over 1 3 .23% for breakage degree,30% ultimate tensile strength for tensile force,500 A for current,35 ℃for ambient temperature,and below 20 W/（m^2·K）for heat transfer coefficient.The importance ranking of these risk factors is as followbreakage degree,tensile force,current,ambient temperature,and heat transfer coefficient.There are level Ⅰ,Ⅱ,Ⅲ,Ⅳ warning interval in both breakage degree and tensile force,and level Ⅰ,Ⅱ warning interval in current.While in conventional environment,there are only level Ⅰ warning intervals in ambient temperature and heat transfer coefficient.The established quantitative risk assessment model and ranking method can provide reference for the operation safety management of transmission line conductors.