极性反转时典型油纸复合绝缘的电场特性

极性反转是换流变压器一种特殊的工作状态，因极性反转时空间电荷的作用，绝缘油中会出现极高的危险场强。文中采用ANSYS10.0有限元仿真软件计算了极性反转时板-板、同轴、棒-板及换流变压器阀侧绕组端部局部模型等几种典型油纸复合绝缘电场的场强，绘制了绝缘油及绝缘纸板中最大场强与绝缘纸板厚度、油纸电导比、极性反转时间等参数的关系曲线。在板-板油纸复合绝缘中，增加绝缘纸板的厚度可以降低极性反转时油中及纸中场强。但在同轴油纸复合绝缘中，当绝缘厚度超过一定值后，纸中极性反转场强反而增加。在棒-板油纸复合绝缘中，极性反转场强与绝缘纸板的尺寸及位置关系具有较大的不确定性。延长极性反转时间可降低极性反转时的场强。极性反转场强随油纸电导比增加而增加，且存在饱和现象。

Electric Field Characteristic Calculation on Typical Oil-paper Combination Insulation Under Polarity Reversal

Polarity reversal (PR) is a special working condition occurring during the operation of a converter transformer. Due to the action of spatial charge under polarity reversal an extremely high dangerous electric filed will appear in the insulation oil. By use of ANSYS10.0 finite element method (FEM), the electric field strengths of several typical oil-paper combination insulations, such as plate-plate oil-paper insulation, coaxial oil-paper insulation, rod-plate oil-paper insulation and local model of converter transformer's winding end at valve side, are calculated while polarity reversal occurs, and the relation curves of the maximum filed strength in insulation oil vs. the parameters such as the thickness of insulation pressboard, conductivity ratio of oil to pressboard, the time of polarity reversal and so on, are plotted. In plate-plate oil-paper combination insulation, increasing the thickness of insulation pressboard can reduce the field strength in oil and pressboard. However, in coaxial oil-paper combination insulation when the thickness of insulation exceeds a certain value the field strength within the pressboard under polarity reversal will increase instead. In rod-plate oil-paper combination insulation, more indeterminacy exists in the relation among the field strength under polarity reversal, the size and position of pressboard. Elongating the time of polarity reversal can reduce the field strength under polarity reversal. Field strength under polarity reversal increases with the increasing of the conductivity ratio of oil to pressboard and the field strength in oil and pressboard under polarity reversal will be saturated finally.