中文摘要：

为了研究实际高海拔条件下复合绝缘子自然污秽与人工污秽试验的差异，给高海拔地区直流输电线路的外绝缘设计提供参考，在高海拔条件下，对绝缘高度为1．9m、伞形结构为一大一小的复合绝缘子进行不同附灰密度、不同污秽分布以及盐的不同成分的人工污秽试验，揭示灰密、污秽分布和盐的成分等因素对复合绝缘子直流污闪特性的影响。试验发现，盐密一定、灰密≤1．0mg／cm^2的条件下，灰密修正系数与附灰密度成负幂函数关系；灰密一定的条件下，污闪电压随污秽分布不均匀程度的增加而增加；盐密一定的条件下，盐种类的修正系数与CaSO4贡献率成指数关系。因此，在估算自然污秽条件下复合绝缘子的直流污闪电压及实际工程外绝缘配置时要充分考虑这些因素的影响。

英文摘要：

It is necessary to carry out comprehensive pre-researches on external insulation to ensure these projects to be operated safely. In order to provide a scientific reference for the constructions of DC transmission lines in high al-titudes, the difference of natural contamination and artificial contamination tests of DC composite insulators were carried out at high altitude area （ 1970 m） , Kunming China. In the experiment, the condition studied were ρNSDD ＇distributing of nastiness and components of salt. According to the results of the tests, the influence of the factors （ρNSDD distributing of nastiness, components of salt, etc） on the flashover characteristics of insulators was studied.It was found that ： the relationship between the modified coefficient of ρNSDD and ρNSDD was a negative power function in the condition of ρESDD remained constant and the ρNSDD of insulators was no more than 1.0 mg/cm2 ; the flashover voltage increased with the extent of un-uniform pollution distributing in the condition of PNSDD keeping constant; the relationship between the modified coefficient of the different components and the proportion of CaSO4 was a exponent function in the condition of ρESDD remained constant. These results would be useful in calculating the DC flashovervoltage of composite insulators in the condition of natural contamination, and can also be treated as basis for outdoor insulator selection of transmission lines.