中文摘要：

高压直流输电系统出现潮流反转或电压陡变情况，换流变压器的油纸绝缘会承受极性反转电压，往往容易造成绝缘失效。为研究此过程中油纸绝缘界面电荷特性，利用静电容探头法测量了极性反转过程和电压陡变条件下油纸沿面绝缘结构界面电荷密度的变化。发现了油纸界面电荷能加强外施电压极性反转时刻的瞬态电场，加强程度与积聚的界面电荷密度成正比；油纸沿面绝缘结构和平行绝缘结构的界面电荷积聚时间差异显著，极性反转过程中会强化电场分布的不均匀程度；建议采用CIGRE推荐电压陡变波形（反转时间〈2ms）作为对换流变压器出厂试验的考核。这些结论对改善换流变压器的绝缘设计和提高其运行维护可靠性有重要意义。

英文摘要：

When the power reversal or voltage-suddenly-change situation appears in the HVDC system, the oil-paper insulation of converter transformer will withstand polarity reversal voltage, which often tends to cause the insulation failure. In order to study the charge characteristics of the oil-paper insulation, the changes of the oil-paper interface electric density in this process were studied based on electrostatic capacitive probe measurement. It is found that the oil-paper interface charge can strengthen the transient electric field at the time of the polarity inversion of the external voltage, and the degree of reinforcement is proportional to the density of the interface charge of the reservoir. The interface charge accumulation time of the surface insulation structure is different from parallel insulation structure remarkably, and the uneven distribution of the electric field is strengthened by the polarity reversal voltage. It is recommended that the voltage abrupt waveform of the CIGRE （reverse time 〈2 ms） can be adopted as the test for the production test of converter transformer. These conclusions are of great significance to improving the insulation design and the reliability of the converter transformer.