500kV交流同塔四回输电线路反击耐雷性能

Back Flashover's Lightning Performances for 500 kV AC Transmission Lines With Quadruple-Circuits on Single Tower

利用EMTP(Electromagnetic Transients Program)电磁暂态计算程序对500 kV交流同塔四回输电线路的反击耐雷性能进行了计算和分析。对杆塔高度、冲击接地电阻及避雷线的设置情况等影响反击耐雷性能因素进行分析,并且利用该程序分析了雷电流作用下,塔身和横担的电位以及导线对其相应的上下横担电位差的分布情况。分析结果表明,在高杆塔情况下,降低冲击接地电阻对耐雷性能的改善效果不大;在中横担外侧加设耦合地线和上横担中部增设避雷线以及适当调整导线与上下横担之间空气间隙的距离可有效的改善输电线路的耐雷性能;在条件允许的情况下,建议降低杆塔高度。

Lightning performance calculation and analysis of back flashover for 500 kV AC transmission lines with quadruple-circuits on single tower was obtained by electromagnetic transients program （EMTP）. Lightning performance influenced by different factors such as grounding resistance, height of tower, and grounding wires was calculated and analyzed in details. Electric potential waveshapes of tower body and crossarms were presented by EMTP, also voltage waveshape between upper or lower crossarms and any given phase conductors. Under the lighting stroke, electric potential of tower body reduces gradually from top to down while that of the top crossarm reduces gradually from one side with lightning stroke to another side without lightning stroke. Voltage everywhere of the middle crossarm is almost same, also of the down one. Voltage between phase conductors and upper crossarm is higher than that between the phase conductors and lower crossarms. As a conclusion, measures to reduce damages brought by back flashover are listed below： reducing height of towers, setting up grounding wires in the center of the top crossarm and both sides of the second crossarm; increasing the air gap distance between phase conductors and their the upper crossarms, etc.