±1100kV输电线路雷电屏蔽特性的模型试验及观测

Model Test Study and Observation on Lightning Shielding Performance of ±1100kV Transmission Lines

雷害是输电线路故障的主要原因之一,而当前±1100 kV特高压直流输电线路雷电屏蔽系统的设计主要借鉴较低电压等级输电线路的运行经验,因此有必要开展模型试验为对±1100 kV直流输电线路的雷电屏蔽性能进行研究。首先针对铁塔表面发生电晕时的电场强度幅值和变化率确定了采用负极性250/2500μs操作冲击电压波,然后开展了以±1100 kV特高压直流输电线路Z38102AL型铁塔为对象的模型比例为1:12.5的平原情况下雷电屏蔽模拟试验,并开展高速摄影观测。进行试验绕击概率统计分析,得到±1100 kV输电线路绕击概率的空间分布近似为抛物线,且正极性工作电压下,线路的屏蔽性能差;杆塔另一侧的负极性导线对靠近高压电极一侧的正极性导线的引雷能力有一定削弱作用,但对避雷线和大地的屏蔽性能影响不大。并将试验结果与交流500 kV线路模型试验进行对比,说明在缩比模型试验中应尽可能采用大的缩比比例,以在负保护角情况下有效避免夸大避雷线的引雷能力,提高模型有效性。根据高速摄影机观测结果分析了绕击输电线路放电过程,并开展电压波形同步分析,说明了导线的负极性电压对迎面流注起始和发展以及下行先导发展的抑制作用。

Lightning damage is one of the main causes of faults in transmission lines.At present,the design of lightning shielding system for ±1100kV UHVDC transmission lines mainly takes reference from the operating experience of lower voltage transmission lines.Therefore,it is necessary to carry out model tests to study the lightning shielding performance of±1100kV UHVDC transmission lines.Negative switching impulse of 250/2500μs was employed according to the amplitude and change rate of electric field intensity at the surface of the tower.Lightning shielding simulation test was carried out in plain environment with model ratio 1:12.5 for Z38102AL type tower of±1100kV UHVDC transmission line,and high-speed photographic observation was carried out at the same time.Test results show that the equiprobability curve of shielding failure spatial region is approximately a parabola,and the lightning shielding failure space of negative conductor is significantly smaller than that of positive conductor.The negative polarity conductor on the other side of the tower has a certain weakening effect on the lightning inducing ability of the positive polarity conductor close to high voltage electrode,but has little effect on the shielding performance of the lightning conductor and ground.By comparing the test results with AC 500kV line model test,it is concluded that the model ratio should be used as large as possible in the test,so as to effectively avoid exaggerating the lightning inducing ability of the lightning conductor under the condition of negative protection angle and improve equivalence of the model.The discharge process was analyzed based on the observations with high-speed cameras,and synchronous analysis of voltage waveforms was carried out.Inhibition of the negative polarity voltage of the conductor on initiation and development of upward streamer and development of downward leader is explained.