稍不均匀直流电场下静止与流动变压器油中金属微粒聚集特性

Accumulation Characteristics of Metal Particles in Static and Flowing Transformer Oil Under Slightly Nonuniform DC Field

换流变压器阀侧电压中直流分量的存在会加剧杂质颗粒的聚集,而变压器油流会对其聚集特性产生影响。利用所搭建的变压器油循环流动装置,分别开展了静止和流动变压器油中自由金属微粒在不同电压、微粒粒子数密度及油流速度下的直流聚集试验,采用高速相机拍摄了电极间隙内金属微粒的聚集图像,并记录了微粒聚集过程中泄漏电流的变化。试验结果表明:金属微粒在静止与流动油中均会在间隙中心区域聚集,且聚集的金属微粒不断在电极间往复运动;聚集的金属微粒数及间隙泄漏电流均随电压大小和微粒粒子数密度的升高而增加,随流速的升高呈先增后减的分段式变化规律,低速油流(≤0.02 m/s)促进微粒聚集,而高速油流(>0.02 m/s)抑制微粒聚集。结合油中金属微粒的受力及运动特征,对静止变压器油中金属微粒的运动轨迹进行了分类,阐明了静止油中金属微粒在间隙中心区域聚集的机理,并分析了变压器油流对金属微粒聚集的影响。

The existence of DC component in the voltage on the side of converter valve will aggravate the accumulation of impurity particles,and the transformer oil flow will affect the accumulation characteristics.Therefore,using the built transformer oil circulating device,we carried out the accumulation experiments of free metal particles in static and flowing transformer oil at different voltages,particle concentrations and flow rates under DC field.The accumulation images of metal particles in the electrode gap was taken by a high-speed camera,and the change of leakage current during the accumulation process was recorded.The results show that the metal particles will accumulate in the center area of the gap in the both static and flowing oil flows,and the accumulated particles will constantly move back and forth between the electrodes.The number of metal particles accumulated in the center area of the gap and the value of leakage current through the gap both increase with the increase of voltage and particle concentration,but increase first and then decrease with the increase of flow velocity.Meanwhile,the low-speed oil flow(less than or equal to 0.02 m/s)will promote the accumulation of particles,while high-speed oil flow(higher than 0.02 m/s)will inhibit the accumulation.Combined with the force and motion characteristics of the metal particles in the oil,the trajectories of metal particles in static transformer oil were classified,the mechanism of the metal particles in the static oil to accumulate in the center area of the gap was clarified,and the influences of transformer oil flow on the accumulation characteristics of metal particles were analyzed.