Dynamic Deformation of Pendant Drops on the Edge of High-Voltage Bushing Sheds Under Extreme Rainfall

Abstract

Flashover accidents on high-voltage bushings frequently occur under extreme rainfall, which is generally attributed to the bridging of adjacent sheds by pendant drops, a result of the dynamic deformation of pendant drops. We numerically investigate the effects of the parameters of pendant drops and the electric field on the dynamic deformation of pendant drops on a 500 kV transformer bushing under extreme rainfall and verify the simulation results by artificial rain experiment. The dynamic deformation of pendant drops is described by solving the Navier-Stokes equations and using the level set method. The results show that the maximum length of the pendant drop increases with the increase in the initial diameter and the initial mass flow rate, respectively, but decreases under the electric field. The main influencing factor on the maximum length of the pendant drop alters with the variation of the initial diameter and the initial mass flow rate in the absence of the electric field, whereas the initial mass flow rate is the unique main influencing factor in the presence of the electric field. Furthermore, the variations of the maximum length and breakup time of the pendant drop are elucidated by the instability of the pendant drop.

Experimental Investigation on Influence of Shed Parameters on Surface Rainwater Characteristics of Large-Diameter Composite Post Insulators under Rain Conditions

“…Moreover, 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 105 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]. (2) Under different rainfall intensities, the trends of N wc , N wde , N wds and L wc with the change in large shed overhang are identical.…”

“…Moreover, 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 105 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]. Moreover, the reason for the sudden increase in L wc 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 105 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].…”

Discharge Behavior and Morphological Characteristics of Suspended Water-Drop on Shed Edge during Rain Flashover of Polluted Large-Diameter Post Insulator

“…As mentioned above, the existence of these water-droplets is due to the good hydrophobicity of the materials. Previous studies have shown that the maximum electric field strength of the water-droplets on the upper shed appears at the interface between the liquid and the shed surface, where air is ionized [3][4][5][6][7][8][9][10][11][12][13][14]. These corona discharges did not further develop into an arc, because the shape of the water-droplets on the upper shed did not change significantly, resulting in no further distortion of the electric field intensity around the water-droplets.…”

“…In real applications, the whole post insulator is composed of several sections. It has been found that when the insulation height is less than 10m, the pollution flashover voltage of the post insulator increases linearly with the increase of insulation height [5][6][7][8][9][10][11][12][13][14][15]. Therefore, only one section of the entire insulator was used in this test to reduce the test voltage.…”

“…Pollution, fog, icing, and rainfall are the main causes of flashover of outdoor insulation equipment in power grids [1][2][3][4]. According to the traditional cognition, the flashover voltage of polluted insulators in fog is lower than that in rain [5,6]. Consequently, in order to provide the most stringent data for design and application, the pollution flashover performance of insulators needs to be carried out under the most severe conditions.…”