500kV同塔4回线路不平衡绝缘的耐雷水平

目前我国500kV同塔4回线路主要采用平衡高绝缘配置,每相导线配置31片155mm绝缘子。针对典型杆塔竖塔,杆塔高度较高,易绕击相与反击闪络相为上层两回线路,提出了不平衡绝缘方案,即上层两回线路采用31片绝缘子,下层两回线路26片绝缘子。在评估采用不平衡绝缘后的防雷水平时,采用改进电气几何模型(EGM)与电磁暂态程序(EMTP)计算杆塔在不同雷电等级、地面倾角以及杆塔接地电阻等情况下耐雷水平的计算结果表明,2种绝缘配置(平衡绝缘与不平衡绝缘)的线路耐雷水平相差很小,若地面倾角<15°,接地电阻<15Ω,则竖塔可以采用不平衡绝缘配置方案。比较耦合地线以及三地线提升线路反击耐雷水平的效果后认为,当杆塔采用平衡高绝缘时,三地线反击耐雷水平优于耦合地线。当杆塔采用不平衡绝缘时,在接地电阻为5～15Ω时,三地线防反击效果优于耦合地线,当接地电阻>20Ω时,耦合地线防反击效果更佳,并对改进竖塔防雷提出了建议。

Lightning Performance of Quadruple Circuit Transmission Line with Voltage 500 kV on the Same Vertical Tower Under Unbalance Insulation

Nowadays,most of the insulation selection for quadruple circuits on one tower is high balance insulation,namely,31 pieces of 155 mm insulators per phase.While,for typical quadruple circuits on one tower or vertical tower,its upper two lines tend to flashover under lightning overvoltage.Consequently,we introduced a new insulation selection for vertical tower,namely,unbalance insulation.For upper two lines,we applied high insulation: 31 pieces of insulators,per phase,however for lower lines,26 pieces of insulators per phase.To evaluate the lightning performance of vertical tower after the unbalance insulation was applied,we calculated the tower’s light performance under different circumstances by EGM and EMTP.The calculation shows that,when ground elevation is under 30° and grounding resistance is under 15 Ω,the lightning performance of the tower after being applied with different insulation configuration shows little difference.The lightning performance of coupling earth wire and triple grounding wires were also analyzed.Applied the high balance insulation,tower with triple grounding wires has better lightning performance.While under the unbalance insulation configuration,triple grounding wires’ lightning performance is better when grounding resistance is between 5~15 Ω,the coupling earth wire has better performance when the resistance is bigger than 20 Ω.Recommendation on improving the tower’s lightning performance has been introduced.