计及细观尺度结构的电力变压器绕组短路电磁力分布规律研究

The failure rate of power transformer due to electromagnetic force caused by external short circuit is high. The structure of the transformer is complex. From macroscopic to mesoscopic, the structural scale spans three orders of magnitude. The winding damage accidents are mostly caused by the microscopic structural deformation. Hence, it is of great theoretical significance and engineering application value to study the short-circuit electromagnetic force distribution characteristics of power transformer winding considering meso-scale structure. In this project, firstly, the multi-scale modeling and calculation method based on information transmission will be proposed. By establishing the refined macro/micro scale calculation model, the calculation method of short-circuit current and magnetic leakage field considering the meso-scale structure characteristics of transformer windings will be obtained. Secondly, the experimental method of magnetic leakage field simulation of transformer windings with meso-scale structure will be studied. Three-dimensional multi-point synchronous measurement of the leakage magnetic field will be used in local mesoscale model to verify the rationality and accuracy of the calculation model. Finally, the influence of transformer winding structure parameters on the distribution characteristics of short-circuit electromagnetic force will be studied. The distributions of short-circuit electromagnetic force of transformers with typical structure and size will be obtained, and the statistical characteristic relationship between winding process differences and electromagnetic force distribution will be established. The project research will reveal the influence mechanism of the meso-structural parameters of the transformer winding on the short-circuit electromagnetic force, and provide support for the short-circuit design and protection of the transformer.

电力变压器因外部短路产生电磁力引起损坏的故障率居高不下。变压器结构复杂，从宏观到细观，结构尺度跨三个数量级，而绕组毁损多由细观结构形变引起。因此，开展计及细观尺度结构的电力变压器绕组短路电磁力分布规律研究，具有重要的理论意义和工程应用价值。项目首先提出信息传递多尺度建模计算方法，通过建立精细化宏/细观尺度计算模型，获得计及变压器绕组细观尺度结构特征的短路电流与漏磁场计算方法；其次，研究变压器绕组细观尺度结构漏磁场模拟实验方法，通过进行绕组缩比模型和局部细观尺度模型的漏磁场三维多点同步测量，验证计算模型的合理性与准确性；最后，研究变压器绕组结构参数对短路电磁力分布特性的影响规律，获得变压器典型结构和尺寸下短路电磁力分布规律，建立绕制工艺差异与电磁力分布的统计特征关系。项目研究将揭示变压器绕组细观结构参数对短路电磁力的影响机制，为变压器抗短路设计和防护提供支撑。

因外部短路引起的绕组形变故障约占变压器故障总数的30%，是电网安全运行迫切需要解决的重要问题，而解决这一问题的关键在于能够准确计算分析短路电磁力。国内外学者围绕变压器短路电磁力计算方法与分布特性开展了大量研究，建立了短路电磁力静态计算方法，获得了短路电流最大峰值下电磁力宏观分布特性，但未考虑多股多根导线并联、导线换位、工艺偏差等绕组细观结构的影响。因此，计及绕组细观结构影响，开展变压器短路电磁力计算方法和分布特性的深化研究，具有重要意义。.项目取得的研究进展如下：.分析了变压器绕组匝导线多股多根并联结构的细观特征，推导了耦合并联导线回路电压平衡约束的绕组匝导线电流分布数值计算矩阵，建立了匝导线短路电流分布稳态计算方法，实现了每根导线电流的准确快速计算。典型变压器绕组计算结果表明，与三维有限元方法相比，电流分布计算偏差小于3%，计算时长缩短了2个数量级以上。研究了换位结构的空间位置参数表征方法和线饼辐向工艺偏差的概率分布，构建了变压器宏观与细观结合的漏磁场计算模型，考虑了换位结构、线饼间距变化、辐向工艺偏差等细观结构和铁心非对称结构的影响。.基于上述短路电流和漏磁场计算模型，研究了短路电磁力静态计算流程，形成了计及绕组细观结构的变压器短路电磁力静态计算方法。典型变压器计算结果表明，与不考虑细观结构影响相比，绕组中部换位结构处轴向短路电磁力线密度由接近零值增大至4.2 kN∙m-1，辐向工艺偏差使辐向短路电磁力最大增加了22.6%，细观结构对电磁力分布的影响不容忽视。.针对形变故障率较高的110 kV变压器典型绕组结构，研究了螺旋式、连续式两种结构形式的短路电磁力静态分布，获得了细观结构影响下的电磁力空间分布特征，匝导线电流分布不均匀会使最大电磁力增加，换位处的轴、辐向电磁力发生大幅突变，工艺偏差使辐向电磁力波动变化。考虑细观结构影响计算分析电磁力对变压器抗短路能力校核与优化设计非常必要。