高海拔地区大吨位绝缘子直流污闪特性研究

为了研究实际高海拔条件下大吨位瓷和玻璃绝缘子染污放电特性,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设计提供参考,在实际海拔1970 m条件下,利用±250 kV直流污秽试验电压,采用恒压升降法,对大吨位瓷和玻璃绝缘子的直流污闪特性进行了详细研究。试验结果表明:大吨位瓷和玻璃绝缘子的直流污闪特性相差不大;盐的种类、灰密大小及污秽分布情况对大吨位瓷绝缘子直流污闪特性影响较大;伞形对绝缘子表面电弧发展特性影响较大,使得不同伞形绝缘子的直流污闪电压差别较大。因此,在高海拔地区特高压线路外绝缘选型和设计中要充分考虑这些因素的影响。

External Insulation Characteristic of Ultra High Voltage Transmission Line in High Altitude Area

It is necessary to carry out comprehensive pre-researches on external insulation uo ensure these projects to be operated safely.In order to provide a scientific reference for the constructions of DC transmission lines in high altitude areas,the flashover characteristics of two kinds of large tonnage insulators(porcelain and glass insulator) were investigated systematically in natural high altitude areas(1970 m).In the experiments,solid layer method was used and 50% flashover voltages(U50%) were determined by the up-and-down method with negative voltage.The arcing behavior on natural polluted insulator surfaces was observed using a PCI-2000S high speed camera.Experimental results indicate that suspension patterns(I,V and Y-strings),different kinds of soluble salt,NSDD(non-soluble deposit density) and un-uniform contamination have a significant effect on the flashover characteristics of porcelain insulator.These factors are important for outdoor insulation design for DC transmission lines,which are neglected in most laboratory experiments.Flashover performances of two types of glass insulators(300 kN and 550 kN) with different leakage distances and unit spacing were studied,too.It is shown that the development path of arcs on insulator surface is greatly influenced by the profiles,resulting in different flashover performances for the two types of glass insulators with different profiles.Meanwhile,comparison of the flashover performances between porcelain and glass insulators was carried out in the same experimental conditions.Experimental results indicate that the flashover characteristics for glass insulators are similar to those for porcelain insulators.