Abstract
The discharges of water columns and droplets between the sheds make the leakage distance not effectively used, which is one of the main reasons for flashover of composite post insulators under heavy rainfall. To study the influence of shed parameters on surface rainwater characteristics, artificial rain tests were carried out on the large-diameter composite post insulators under the rainfall intensity of 2–15 mm/min. Lwc (the length of water columns at the edge of large sheds), Nwc (the number of water columns at the edge of large sheds), Nwde (the number of water droplets at the edge of large sheds) and Nwds (the number of water droplets in the space between two adjacent large sheds) were proposed as the parameters of surface rainwater characteristics. The influences of large shed spacing, large shed overhang and rod diameter on the parameters of surface rainwater characteristics under different rainfall intensities were analyzed. The experimental results show that, under the same rainfall intensity, with the rise in large shed spacing, large shed overhang or rod diameter, Lwc, Nwc, Nwde and Nwds all increase. Under different rainfall intensities, the trends of the parameters with the change in shed parameters are basically invariant; however, the change ranges of the parameters are different. The increases in the parameters with the rises in shed parameters and rainfall intensity are mainly attributed to the change in the rainfall on the insulator surface. The experimental results can provide references for the quantitative description of surface rainwater characteristics and the design of large-diameter composite post insulators for DC transmission systems.
Highlights
Post insulators are important pieces of equipment for substations and converter stations and play an important role in mechanical support and electrical insulation [1]
Zhang et al carried out rain flashover tests of composite post insulators at high altitudes, and pointed out that the rain conductivity, the rainfall intensity, and the shed parameters had a significant effect on rain flashover voltage
The reason for the sudden increase in Lwc in the process of large shed overhang rising, which is the speed of rainwater flowing to the edge of sheds, which increases as the overhang is from mm to 120 mm, and the water droplets hanging on the shed edge have higher initial velocity, which leads to the significant increase in the length of water columns [28]
Summary
Post insulators are important pieces of equipment for substations and converter stations and play an important role in mechanical support and electrical insulation [1]. Ishiwari et al carried out the artificial rain flashover tests on porcelain and composite insulators, and found that the rainfall intensity, the rain angle, and the shed parameters of insulators influenced the withstand voltage [17]. According to the artificial rain flashover tests under the rainfall intensity of 3 mm/min, Fan et al found that, when the shed spacing was small, the two adjacent sheds were bridged by rainwater, resulting in a reduction in the rain flashover voltage per unit of creepage distance. Zhang et al carried out rain flashover tests of composite post insulators at high altitudes, and pointed out that the rain conductivity, the rainfall intensity, and the shed parameters had a significant effect on rain flashover voltage.
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