中文摘要：

为给高海拔地区特高压直流输电线路绝缘子的选择及外绝缘的设计提供参考,在实际高海拔条件下采用恒压升降法详细研究了瓷、玻璃和复合绝缘子的直流污闪特性,其内容主要包括：不同悬挂方式和污秽分布情况对瓷绝缘子污闪特性的影响;2种大吨位玻璃绝缘子直流污闪特性的对比及550 kN玻璃绝缘子V串与I串污闪电压的比较;比较3类绝缘子直流污闪特性。试验结果表明：悬挂方式及污秽分布情况对瓷和玻璃绝缘子有较大影响;复合绝缘子的直流污闪特性明显优于瓷和玻璃绝缘子;爬电距离不是决定复合绝缘子直流污闪电压的唯一因素,合理优化复合绝缘子的伞裙结构可有效提高其单位绝缘高度的直流污闪电压。

英文摘要：

External insulation is one of the key technologies in the construction of ultra high voltage DC （UHVDC） transmission projects in China, to ensure the safety operation of those projects, it is necessary to carry out compre- hensive pre-researches on external insulation. In order to provide a scientific reference for the constructions of UHVDC transmission lines, the flashover characteristics of three kinds of insulators （porcelain, glass and composite insulator） are investigated systematically in natural high altitude area （ 1970 m）. Accordingly, the effects of suspension patterns （I, V and Y-strings） and non-uniform contamination on flashover characteristics of porcelain insulator are analyzed. Flashover performances of two types glass insulators （300 kN and 550 kN） with different leakage distances and unit spacing are studied with I- and V-strings, too. And flashover performances among the three kinds of insulators are compared in the same experimental conditions. Flashover performances of composite insulator are bet- ter than those of porcelain and glass insulator. Therefore, composite insulator is one of the best choices for UHVDC transmission lines. The effects of shed design for composite insulator on the flashover characteristics were investigated in detail. Experimental results indicate that flashover voltage of composite insulator is not determined by leakage distance only. Optimization of the shed design for composite insulator could increase the flashover voltage effectively.