换流变压器阀侧绕组端部瞬态电场分析

Analysis on Transient Electric Field at Ends of Valve-side Winding in Converter Transformer

为了研究换流变压器阀侧绕组区域的瞬态电场分布规律,即在长时直流电压和极性反转电压作用下的电场分布规律,建立了2个典型的油纸绝缘模型和1个±500kV换流变压器绕组端部简化模型,并利用有限元软件ANSYS对上述模型进行了长时直流电场和极性反转电场分析,主要分析了模型结构、材料属性和试验时间对上述电场分布的影响,得到了直流电场趋于稳态所需时间的影响因素以及极性反转电场的一些特点。最后重点分析了±500kV换流变压器绕组端部的极性反转电场,同时考虑了绝缘纸板的正交各向异性。结果表明,直流电场趋于稳态所需时间的长短与模型结构及绝缘材料的电阻率有关;合理地设置极性反转时间才能保证对变压器油的有效考核。这些结论可为换流变压器绝缘结构的设计及绝缘试验提供参考依据。

In order to draw some conclusion on laws of converter transformer oil-paper insulation of the transient electric field distribution,we established two typical oil-paper insulation models and a±500kV convert transformer winding end simplified model with a complex structure,and adopted a finite element software ANSYS to analyze the long-time DC electric field and polarity reversal electric field.Meanwhile,we analyzed the effect of model structure,material properties and test time on the electric field,and put forward the factors influencing that the long-time DC electric field reached a steady-state and some characteristics of polarity reversal electric field.Moreover,we analyzed ±500kV converter transformer winding and electric field distribution under polarity reverse voltage and the insulation board characteristics when calculating the anisotropy of orthotropic polarity reversal electric field.The results show that the time when long-time DC electric field reaches a steady-state is related to the model structure and the resistivity of insulating materials;reasonably setting the polarity reversal time can ensure the effective assessment of the transformer oil.These conclusions can be used to design converter transformer insulation structure and provide a reference in insulation test.