中文摘要：

换流变压器阀侧绕组与出线装置同时承受交流、直流、交直流叠加电压作用,其内部油纸复合绝缘材料的沿面放电特性与以往交流电力变压器存在较大差别,而相关研究又明显不足。为此使用CIGRE MethodⅡ推荐的典型球-板电极结构,利用脉冲电流法对交直流复合电场下油纸绝缘沿面放电过程中放电信号进行了统计,分析并提取了沿面放电统计特征图谱的多个典型特征参数,对油纸绝缘在交直流复合电场下的沿面放电发展过程特性进行了研究。该研究中首次使用沿面放电发展特征参数的变化规律将交直流复合电场下油纸绝缘沿面放电发展过程划分为4个阶段：爬电起始阶段、爬电发展阶段、爬电加速发展阶段以及临界击穿阶段,并对比分析了纯交流电压和交直流复合电压作用下油纸绝缘沿面放电相同阶段特征参数变化规律的差异性。结果表明：交直流复合电压作用下沿面放电对绝缘纸板的破坏强度要高于纯交流电压下,沿面放电发展速度要快于纯交流电压下,交直流复合电压中的直流电压分量对油纸绝缘沿面放电发展具有加速作用。

英文摘要：

The valve windings and outlet device of convert transformers withstand several types of voltage, including AC, DC, combined AC-DC voltages, etc. The characteristics of surface discharge of oil-paper insulation in converter trans- formers can be quite different from those of AC power transformers. Therefore, we used the typical ball-plate electrodes configuration proposed by the CIGRE Method II to study the discharge signals generated in the surface discharge process of oil-paper insulation under combined AC-DC voltage. The spectrum diagrams of the signals were investigated and some typical feature parameters were extracted for analyzing the surface discharge process. According to the variation patterns of the typical feature parameters, for the first time the surface discharge process of oil-paper insulation under combined AC-DC voltage was divided and characterized into four stages, namely, the initial stage, the developmental stage, the ac- celerating stage, and the critical breakdown stage. We also compared the feature parameters of surface discharge under AC voltage and under combined AC-DC voltage in different stages. It is found that, compared with those under AC vol- tage, surface discharges under combined AC-DC voltage bring more severe damage to insulation paper and they develop faster, which could be explained by the DC voltage component＇s effect of acceleration.