Flashover Performance of Pre-contaminated and Ice-covered Composite Insulators to be Used in 1000 kV UHV AC Transmission Lines

Abstract

A method is introduced for testing insulators under icing conditions. The method is based on and developed from those described in the standard of IEC60-1, IEC 60507 and IEEE Task Force on Insulator Icing Test Methods, which give instructions to test insulators under pollution. Then, the paper explores the effects of various factors, including ice thickness, pollution severity on the surface of insulators before ice accretion, atmospheric pressure, and shed profiles, on the flashover performance of short samples of two different types of silicone rubber (SIR) composite long rod insulators intended for ultra high voltage (UHV) ac transmission lines. The experiments were carried out in the multi-function artificial climate chamber in the High Voltage and Insulation Technological Laboratory of Chongqing University, China. The experimental results reveal the regularity of the effects of ice thickness, pollution severity and atmospheric pressure on the average flashover voltage of two types of composite insulators. Those can provide reference for the outdoor insulation design for UHV ac transmission lines.Index Terms -UHV, Composite insulator, silicone rubber, icing flashover, low air pressure, outdoor insulation.

DC Flashover Performance of Ice-Covered Composite Insulators with Parallel Air Gaps

“…However, when the flashover occurs along the surface of ice-covered insulator, U50% decreases with an increase of SDD. For example, for Sample A with h of 100 mm and d of 10 mm, when SDD was 0.05 mg/cm 2 , the U50% was 71.3 kV; when SDD was increased to 0.08 mg/cm 2 , the U50% was 64.6 kV with an decrease of 9.3%; for Sample B with h of 100 mm and d of 10 mm, when SDD was 0.05 mg/cm 2 , the U50% was 46.9 kV; when SDD was increased to 0.08 mg/cm 2 the U50% was 42.6 kV, with the latter decreasing by 9.2%, so, when the discharge path is along the insulator surface, the influence of SDD on U50% of ice-covered CI/PAGs is consistent with that of ordinary ice-covered composite insulators [18,19].…”

“…The available research results show that the flashover voltages of ordinary insulators decrease with the increase of the ice thickness d and the U50% can be expressed as a power function of d with a negative characteristic exponent [1,13,18,19]. The test results in this study also reveal that with an increased ice thickness d, the U50%s of iced CI/PAGs decreases gradually.…”

“…For ordinary insulators, with the increase of contamination parameter SDD, U50% decreases accordingly in a power function [18,19]. The test results in Tables 3 and 4 present that when air gap breakdown occurs on the ice-covered CI/PAG, there are some deviations as to the U50% under different SDDs, but such differences are small and within the experimental tolerances.…”

“…Based on the above analysis, the ice thickness exhibits more effects on DC negative flashover voltage of Sample B than on that of Sample A. When the parallel air gap distance is relatively large and flashover occurs along the insulator surface, the influence of ice thickness d on U50% of CI/PAG is the same as that of ordinary ice-covered composite insulators [17][18][19][20]. For Sample A with h of 100 mm and SDD of 0.05 mg/cm 2 , when d = 10 mm, the U50% was 71.3 kV; when d = 20 mm, the U50% was 59.2 kV, with the latter dropping by 16.7%.…”

“…There is a nonlinear relationship between the 50% discharge voltage U50% and air pressure P, shown as follows [18][19][20]:…”