自然环境下输电导线同时带电压和电流覆冰试验研究

Experimental Study on Icing Accretion of Transmission Conductor with Simultaneous Voltage and Current Under Natural Environment

现有输电导线覆冰试验在非线路运行工况下进行,不能模拟输电线路的真实覆冰特性,为此对高电压和大电流发生器进行隔离和绝缘改造,研制了可同时输出最高电压400 kV和最大电流1 500 A的覆冰试验装置。在自然环境下对LGJ–460/60和LGJ–630/55导线开展了同时带电压和电流覆冰增长试验,得到了覆冰厚度和密度随电压、电流变化的曲线,提出了导线带电覆冰增长模型。试验结果表明:运行电流产生的焦耳热可以通过降低水滴冻结速度抑制覆冰增长;当导线表面电场较小时,电压升高使覆冰水滴极化带电和运动速度加快,从而加速覆冰增长;当电场较大时,导线周围出现电晕和离子束,电晕电流加热及离子与水分子碰撞使覆冰增长随电压升高而减慢;且电场会使冰层表面出现毛刺状的冰树枝,覆冰密度随电压的增加逐渐减小。试验结果能够为重冰区运行输电线路抗冰设计及改造提供指导。

Existing icing experiments of transmission conductor are not carried out under operational condition, so the results can not simulate the real icing characteristics of transmission lines. Consequently, by isolation and insulation improvements of high-voltage and large-current generators, developed the experimental equipment for icing accretion which can output the highest voltage of 400 kV and the maximum current of 1 500 A simultaneously. Icing accretion experiments for transmission conductor with the type of LGJ-460/60 and LGJ-630/55 were carried out with simultaneous voltage and current under natural environment. Icing thickness and density variation curves with operating voltage and current were obtained. Based on the above works, a novel energized icing accretion model of conductor was proposed.Experimental results show that the increase of icing thickness can be restrained through decreasing freezing speed of water droplets on conductor by Joule heat arising from running current. When the electric field around the test conductor is low, the water droplets move faster after being polarized and energized, then icing thickness grows gradually with the increase of operating voltage. When the electric field is increased to the appearance of corona and ion beam around the test samples, the growth of icing thickness can be slowed by Joule heat arising from corona current and collision between ions and water molecules. And burr-like ice treeing will appear on the ice surface because of influences of electric field, also,the density of ice layer decreases with the increase of conductor voltage. Results of this research are available for guidance to the anti-icing design and transformation of operating transmission lines in heavy icing areas.