Study Of Flashover Performance Of Iced DC Insulator Long Strings

Due to the Western China and the West-to-East Power Transmission, there will be a dramatic increase of EHV DC transmission lines extended through the western high altitude and icing districts. And then, the DC flashover performance and discharge mechanism of iced insulators at high altitude have posed lots of problems and limitation to the design and development of external of EHV DC transmission lines.Based on experiments carried out in an low temperature and low pressure test chamber -with a diameter of 2 meters and a length of 3.8 meters - and in great type and more function artificial climate chamber- with a diameter of 7.6 meters and a height of 11.6 meters, in order to investigate the flashover performance of the iced insulator long strings, this paper analyzes the following:(1) The effects of the contamination simulation method during icing on flashover voltage of iced DC insulators;(2) The flashover performance and process of three types EHV DC XZP-160, LXZP-210, XZWP-160 insulator short strings under high altitude and icing condition;(3) The discharge performance of DC insulator long strings;Based on the test and its effect analyze, this paper obtain main conclusion as following:(1) Both the withstand voltage law and the U-curve law can all obtain the discharge performance of the iced insulators, and the withstand voltage law can not only gain the maximum withstand voltage, also if can obtain minimum flashover voltage;(2) The iced insulator flashover voltage of adopting freezing water conductivity way is higher than the brushing dirtiness way and the former pressure index is higher than the latter;(3) The flashover voltage of three types EHV DC insulators (XZP-160, LXZP-210, XZWP-160) are related power function with the atmospheric pressure and freezing water conductivity. And it obtains the pressure and the dirtiness even index ;(4) That the iced flashover voltage of XZP-160 and LXZP-210 are much higher than that of the XZWP-160; and that due to the fact that the LXZP-210 insulators are much more easily destroyed by local arcs or break by themselves, it is recommended that in high altitude and icing districts the XZP-160 insulator should be employed;(5) The flashover voltage of the long strings iced insulator is power function relation with the air pressure, and it is linear relation with the strings length;(6) During the arc developing along the outer surface of the ice floor, its development need to several phases: electric faint development, arc form, floating arc, arc movement along the ice surface, arc fainting and flashover. The arc development is related pressure and the contamination distribution during icing.