中文摘要：

运行中的换流变压器内部绝缘同时承受交、直流电压的作用，其产气特性与交流变压器有一定区别。为此，采用典型柱板电极模型，对交、直流复合电压下，油纸绝缘放电缺陷各发展阶段的油中溶解气体量、产气速率和气体组分进行了试验研究。研究结果表明：交直流复合电压中直流分量比例越高，由开始放电到击穿的时间越长、放电能量、产气量、产气速率越低；可根据产气速率将放电缺陷划分为起始阶段、发展阶段和临近击穿阶段。复合电压中的直流分量越高，放电起始阶段油中分解CH4的体积分数烃类气体与总烃的体积比）越高（〉50％），C2H2的体积分数越低（〈45％），此特性为复合电压下油纸绝缘放电缺陷的早期故障诊断提供了依据。

英文摘要：

The intemal insulation of operating converter transformer is affected by AC-DC composite voltage simulta-neously, thus its gas generating characteristics are different from those of AC transformer. Hence, using the typicalcolumn plate-electrode model, we experimentally investigated the amount of dissolved gas, gas generating rate, and gascomponents in each stage of discharge defect development of the oil-paper insulation under AC-DC composite voltage.The results indicates that higher proportion of DC component in the AC-DC composite voltage will lead to longer timethat takes from discharge inception to breakdown, and will lead to lower discharge energy, smaller amount of generatedgas, and slower gas generating rate. According to the gas generating rate, the discharge defect development can be dividedinto three stages, namely, the initial stage, the developing stage, and the near breakdown stage. Higher portion of DCcomponent of the composite voltage will lead to higher percentage （volume ratio of hydrocarbon gas to total hydrocar-bons） of dissolved CH4 at the beginning stage, over 50 %, and lower percentage of dissolved C2H2, less than 45%. Thisfeature provides a basis for the early diagnosis of oil-paper insulation discharge under composite voltage.