中文摘要：

在交直流复合电场下，换流变压器的油纸界面会积聚电荷，使得油纸界面的电场发生畸变，容易引发沿面放电。为揭示交直流复合电场下油纸界面电荷对其沿面闪络电压的影响，采用针-板沿面放电模型，测量了交直流复合电场下油纸绝缘的沿面闪络特性，通过静电电容探头法测量了直流电压作用下沿面放电模型油纸界面的电荷分布。研究发现，负极性直流叠加交流电压下的油纸沿面闪络电压高于正极性直流叠加交流电压下的情况。原因是油纸界面积聚了与外施直流电压极性相同的界面电荷以及相同条件下油纸界面积聚的负极性电荷密度要大于正极性电荷密度。

英文摘要：

Under the condition of compound AC-DC electric field the space charge that would be cumulated at the oil-pressboard interface of oil-impregnated pressboard insulation for converter transformer makes the electric field around the oil-pressboard interface distorted, and the surface discharge on the barriers is easy to be caused. To reveal the impact of oil-pressboard interface charge on its surface discharge voltage under compound AC-DC electric field, a needle-plate test is adopted to measure the surface flashover characteristics of oil-impregnated pressboard insulation under this condition, and using electrostatic capacitive probe the surface charge distribution at the oil-impregnated pressboard interface of surface discharge model under DC high-voltage is measured. It is discovered in this study that the surface flashover voltage of oil-impregnated pressboard insulation under negative polarity DC voltage superposed with AC voltage is higher than that under positive polarity DC voltage superposed with AC voltage. The reason of such a phenomenon is that the interface charge, which is of the same polarity as the imposed voltage, cumulates on the oil-pressboard interface and the negative polarity charge density is higher than positive polarity charge density under the same condition.