220kV同塔双回双分裂导线防覆冰舞动的研究与设计

Anti-ice-coating and Anti-swing Study for 220 kV Two-circuit Two-conductor Bundle on Same Tower

笔者从线路设计角度进一步定性分析了单(或双分裂)导线覆冰舞动机理,指出使用现有抑舞装置应注意的问题:单导线(地线)耐张线夹和悬垂线夹的固定导线(地线)结构使固定点附近的单导线(地线)扭转刚度很大,易形成偏心覆冰并诱发舞动,进一步扩散至档内中央;绞制的导线单丝沿线不连续覆冰使单丝应力分布不均,以致导线内部不稳借助风力发生自激震荡。将耐张串高压端直角挂板改为2付内弧U形环,实现环—环连接,使靠近杆塔的单导线能够发生一定角度的轴向扭转;将固定式悬垂线夹和固定式间隔棒夹具分别改为可轴向转动的悬垂线夹和防冰雨型360°回转式线夹,单(或双分裂)导线可绕自身反复发生一定程度的轴向扭转,促使单(或双分裂)导线覆冰均匀,破坏单(或双分裂)导线覆冰舞动的条件。双分裂导线由水平排列改为微斜形排列,改变双分裂导线"索梁"或机翼型水平结构,减少湍流效应,减弱背风侧子导线发生震动、失稳程度,破坏双分裂导线较单导线易舞动的条件;为了满足跳线(串)风偏后对杆塔的安全距离,经放样,线路转角40°以内的外侧跳线均宜加装跳线串支架,其两端设跳线伸缩节。以上"导线松绑"的防舞设计理念已应用于烟台220kV金都输电线路设计中。

The mechanism of ice-coating and swing of single conductor or two-conductor bundle was analyzed for power transmission line design.It was found that in the existing anti-swing devices,the structures on strain clamp and suspension clamp for fixing single conductor（earth line） will lead to a large torsional rigidity in the earth line to form off-centered ice-coating,and further to induce swing which will spread to middle span.Discontinuous ice-coating on individual wire of twisted conductor may causes uneven stress in the wire and instability in the conductor to induce self-excited shake by virtue of the power of wind.If the suspension loop structure of strain clamp is replaced by two negative camber U-shaped loops to realize loop-loop connection,the single conductor and string clamp near tower can make an axial torsion in some angle.If the fixed suspension clamp and conductor spacer clamp are replaced by axially rotational suspension clamp and anti-sleet 360°rotary clamp respectively,the single or two-conductor bundle can repeatedly make axial rotation to some extent to achieve uniform ice-coating and destroy the conditions of ice-coating induced swing.If the two-conductor bundles are arranged micro-obliquely instead of horizontally and the ＇cable-beam＇ or airfoil structure is changed,the turbulence effect will be weakened and the shake and destabilization of sub-conductor at leeward side will be reduced to destroy the swing conditions for two-conductor bundle.In order to keep the safe distance between bridle wire（string） and tower after windage,the outer bridle wire should be equipped with bridle wire string bracket which has expansion bends at both ends if the line＇s turn-angle is within 40 degrees.According to the above analyses,the design concept of free-rotating conductor for preventing swing was proposed and has been applied to Yantai to Jindu 220 kV power transmission lines.