Abstract
DC flashover performance of ice-covered composite insulators with a parallel air gap (CI/PAG) is an important technical consideration when such insulators are used to isolate ground wires for the purpose of DC ice-melting. Tests on tension and suspension types of CI/PAG were thus carried out in the artificial climate chamber to investigate their DC icing flashover performance. The influences of parallel air gap, ice thickness, pollution severity and air pressure on DC negative 50% flashover voltage (U50%) of CI/PAG were investigated. Test results show that the parallel air gap affected both the discharge path and U50%. With increasing ice thickness, U50% declined by up to 52%; this effect was more evident when the breakdown occurred in the air gap. The pollution severity affected U50% only when the flashover happened along insulator surface. With a decrease of atmospheric pressure, U50% decreased. U50% and the ratio of air pressure were in a power function relationship with a positive characteristic exponent which was relevant to the discharge path.
Highlights
Icing, an extreme weather condition, is a severe threat to the safe operation of overhead transmission lines around the world
The tested composite insulators with a parallel air gap (CI/PAG) were laid out according to the actual arrangement of transmission lines
This study presented the test results of negative DC flashover performance of ice-covered CI/PAG
Summary
An extreme weather condition, is a severe threat to the safe operation of overhead transmission lines around the world. In China, icing accidents of transmission lines occur frequently due to miscellaneous macroclimatic, microtopographical and micrometeorological weather conditions. Southern China, resulting in the collapse of 8381 transmission line towers (110 kV class and above) and accidents such as blackouts which caused huge economic losses [8]. DC ice-melting for conductors is one of the effective methods to prevent conductor fracture and tower collapse caused by icing on transmission lines [3]. If the icing on ground wires cannot be removed or melted, ground wires are liable to displacement, fracture, or excessive sag which can cause phase-to-ground discharge and outages of the transmission lines
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