Abstract
In order to study the wet snow flashover characteristics of 500-kV AC insulator strings under different arrangements, wet snow flashover tests were carried out in the large climate chamber of China Electric Power Research Institute (CEPRI). The wet snow flashover voltages were obtained by the even-rising method and the flashovers were filmed by a camera. The test results showed that the installation of an anti-icing shed of large diameter could increase the wet snow flashover voltage. The distance between the two insulators was a key parameter that influenced the discharge process and the flashover voltage. Under Λ-string arrangement, for common insulators, the flashover performance of iced insulators increased with the connection angle; for anti-icing insulators, the flashover performance increased at first and then decreased with the connection angle. In wet snow conditions, when the connection angle was at the commonly adopted angle of 60°, the flashover performance of the common insulators under the V-string and Λ-string arrangements was almost the same. For anti-icing insulators, however, the V-string arrangement was recommended according to the tests. The results obtained in this study can provide a reference for external insulation design in wet snow conditions.
Highlights
In Winter 2015, the city of Tianjin, in northeast China, was struck by a heavy snowstorm which seriously affected the safe operation of its grid
The flashover performance of the insulator is closely related to the soluble pollution component and its electrical conductivity is normally expressed as equivalent salt deposit density (ESDD)
Increasing the connection angle can reduce the severity of snow bridging, and increase the flashover performance of insulators with common sheds as the connection angle is increased
Summary
In Winter 2015, the city of Tianjin, in northeast China, was struck by a heavy snowstorm which seriously affected the safe operation of its grid. The temperature fluctuated around the freezing point so that the snow melting and freezing processes developed alternately. The wind direction and velocity, as well as other atmospheric parameters were all favorable to the formation of wet snow according to the meteorological data. The snow filled the gaps between the sheds of composite insulators and icicles formed on the edge of the sheds, thereby degrading the insulation strength. It led to multiple flashovers on the 500-kV transmission lines and caused significant economic losses. It is of great significance to study wet snow flashover characteristics of insulators and propose solutions to minimize the flashover incidents
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