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DC Pollution Flashover Performance of Ultra High Voltage Convert Stations Large-Size Composite Post Insulators at High Altitude Areas
Author(s): 
Pages: 93-101
Year: Issue:  10
Journal: Transactions of China Electrotechnical Society

Keyword:  Large-sizecomposite post insulatorDC pollution flashover performancepollution factorspartial dischargearcs on the surfaces;
Abstract: In order to investigate the DC pollution flashover performance of large-size composite post insulator at high altitude, this paper presents two types of large-size composite post insulators. The insulation height of each type is 6.25 m. The artificial pollution tests were carried out at high altitude areas(2 100m) in National Engineering Laboratory for Ultra High Voltage Engineering Technology(Kunming). The pollution flashover voltage U50% was determined by the up-and-down method. The DC pollution flashover performance of large-size composite post insulator with alternating large and two small sheds design is better than that with alternating large and small sheds design. The U50% is related to both non soluble deposit density(ESDD) and equivalent salt deposit density(NSDD) by power function, where ESDD has much more significant effects on U50% than NSDD. Compared with the short-size specimen, ESDD impacts largely on the large-size specimen. The more uneven distribution of pollution, the higher U50% is, but no more than 10%. Within the insulation height range of 6.25 m, the relationship between the length of composite post insulator and the U50% is linear, but the error exists due to the dispersion of test data if U50% of the large-size specimen is directly calculated from the short-size specimen. In this paper, the error was about 15%. The ultraviolet photon number of the large-size specimen is obviously more than that of the short-size specimen. Besides, the distribution of pollution obviously affects the ultraviolet photons number. Since the contaminant on the top side surface of the large-size specimen falls on the middle and lower parts after saturated moisture, the uneven degree of pollution distribute increases, and the ultraviolet photon numbers on the middle and lower parts of the large-size specimen are greater than that on the top part. The partial discharge phenomenon on the middle and lower parts of the large-size specimen are very intense, and the arc propagates widely, even bridges couple of sheds.
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