重覆冰区特高压悬垂型杆塔不平衡张力分析

分别采用有限元分析方法与等线长法计算了典型耐张段的不平衡张力和悬垂串偏移量,这2种方法的计算结果基本一致。通过建立连续7档导线-绝缘子有限元模型,考虑多种线路设计参数的影响,分析了不同工况下重覆冰区特高压悬垂型杆塔的导线张力及不平衡张力。结果表明,覆冰加载模式、覆冰偏心和覆冰风速对不平衡张力影响不大,建议采用换算密度法模拟覆冰荷载并考虑10 m/s覆冰风速。不考虑档距差和高差时,随冰厚、档距和覆冰率的增加,导线不平衡张力百分数逐渐增加,计算得到的不同冰厚下特高压悬垂型杆塔不平衡张力百分数均小于规程规定值。随高差和档距差的增加,有高差和档距差的不平衡张力与无高差、无档距差的不平衡张力比值增大;随冰厚的增加,不平衡张力比值减小。30 mm及以下重覆冰区,不平衡张力百分数按照现行重覆冰区规程规定取值。40、50 mm重覆冰区,应将不平衡张力百分数分别提高至35%和41%。

Unbalanced Tension Analysis of Tangent Towers for UHV Transmission Lines Located at Heavy Icing Area

Both unbalanced tension in typical strain section and end displacement of insulator string due to the unbalanced tension are calculated by finite element analysis(FEA) and equal conductor length method respectively,and calculation results of the two methods are nearly the same.By means of building a finite element model for conductor-insulator in continuous seven spans and considering impacts of various design parameters of transmission line,the tension and unbalanced tension of transmission line erected on UHV tangent towers located at heavy icing area under different operating conditions are analyzed.Analysis results show that there are little influences of ice accretion modes,eccentricity of ice coating and wind speed during icing process on unbalanced tension,thus it is suggested to simulate the load of ice coating by equivalent density method while the wind speed during icing process is taken as 10 m/s.Without regard to span differences and elevations differences,the unbalanced tension percent of conductor is gradually increased with the increasing of ice thickness,span and ice accretion rate,and the calculated unbalanced tension percentages of UHV tangent tower under different ice thicknesses are smaller than those specified in the regulations;when the span differences and elevations differences are increased,the ratio of unbalanced tension of transmission line with span differences and elevations differences to unbalanced tension of transmission line without span differences and elevations differences is gradually enlarged;the unbalanced tension will be decreased with the increasing of ice thickness.For heavy icing areas with ice thickness of 30 mm and lower,the value of unbalanced tension percentages should be taken as that specified in existing regulation for heavy icing area.For heavy icing areas with ice thickness of 40 mm and 50 mm the unbalanced tension percentages should be increased to 35% and 41% respectively.