中文摘要：

换流变压器阀侧绕组同时承受交流、直流电压作用，其内部油纸复合绝缘局部放电性故障与以往交流电力变压器存在较大差别，而相关研究明显不足。为研究油纸绝缘直流局部放电发展过程与绝缘材料理化特性变化规律之间的关系，对典型油纸绝缘缺陷模型在80℃环境中进行了200h直流耐压试验，考察油纸绝缘直流局部放电发展不同阶段统计特征谱图变化规律，并利用高速摄像装置对油纸绝缘针板电极模型的局部放电发生、发展及击穿的动态过程进行观测。同时，为揭示直流局部放电对油纸绝缘的破坏作用，分别通过x射线能量色散谱分析（EDS）、傅里叶变换红外光谱分析（FTIR）研究直流局部放电相应阶段油纸绝缘的理化特征变化规律。试验结果表明：根据油纸绝缘直流局部放电脉冲的统计特征谱图，将其发展过程划分为5个阶段，此过程中伴随着绝缘纸板表面纤维氧元素的增加和羰基含量、油中酸值增加的过程，说明直流电应力对绝缘纸板的破坏作用主要表现在使绝缘纸板表面纤维素分子发生氧化反应，导致绝缘纸板的绝缘性能的逐渐下降，反之，绝缘材料在直流电应力作用下发生损伤，会促进直流局部放电的发生程度加剧。

英文摘要：

The valve-side windings of converter transformers endure combined AC-DC voltage, which is different from traditional AC transformers. Therefore, in order to study the relation between DC partial discharge and the physical and chemical properties of oil-paper insulation, we conducted DC withstanding tests of 200 hours at 80 ℃ on oil-paper insu-lations. Statistical properties were measured in the DC partial discharge process, and the dynamic process of DC partial discharge were observed by using a high speed camera. EDS and FTIR tests were performed as well to reveal the destructive effect from DC partial discharges to insulation paper. The experimental results show that the 200-hours process of DC partial discharge can be divided into five stages due to the phase variations in statistical spectrum; oxygen element and carbonyl group on the surface of insulation paper, as well as the acid value in oil, increase with time. Therefore, it is con eluded that oxidation is an effective factor in the process of DC partial discharge that damages the oil-paper insulation and hence reduces the insulation performance; conversely, the material damage will further enhance DC partial discharges.