Study on Surface Rainwater and Arc Characteristics of High-Voltage Bushing With Booster Sheds Under Heavy Rainfall

Abstract

The flashover performance of insulators can be improved by BS (booster sheds) in the rain, which is mainly attributed to the reasons that BS break up long cascades of water and block connections of arcs. However, surface rainwater characteristics and arc characteristics of bushing have not been quantitatively studied under heavy rainfall. In this paper, the artificial rain tests were conducted on a 500 kV transformer high-voltage bushing equipped with and without BS under the rainfall intensity of 10 mm/min. X (the total length of water column) and Larc (the critical length of arc) on the bushing surface were taken as the feature parameters of surface rainwater characteristics and arc characteristics, respectively. The effects of BS on Eh (the rain flashover voltage gradient along the insulation height), X and Larc were investigated, respectively. Furtherly, the relationships were studied among Eh, X and Larc. Results indicate that Eh has a sharp rise as the number of BS (NBS) is from one to two, however the rise of Eh gradually decreases when NBS exceeds two. X decreases while Larc increases with the rise of NBS, however both the change ranges of them continually fall. Furthermore, Larc presents remarkable negative correlation to X because of the effect of the electric field. Eh rises nonlinearly with the decrease of X, which is due to the change of the wetting uniformity on the bushing surface and the potential redistribution along air gaps in the presence of the local arc.

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.…”

“…However, it is a different story for post insulators used in power stations. Flashover accidents of post insulators in power stations are rare on foggy days, but still occur on rainy days [10][11][12]. Even in a ±800 kV Ultra-High Voltage Direct Current (UHV DC) converter station, there are reports of surface discharge of post insulators on rainy Energies 2021, 14, 1652 2 of 14 days.…”

Effects of dynamic deformation of pendant water drops on the electric field between hollow porcelain insulator sheds under extreme rainfall

“…Therefore, the global maximum electric field between the sheds appears before the secondary water drop reaches the adjacent shed (Figure 9), which possibly induces the discharge in this position. (2) The discharge occurs between the remaining water drop and the secondary water drop that has reached the adjacent shed after the pendant water drop breaks up. The global maximum electric field between the sheds appears after the secondary water drop reaches the adjacent shed (Figure 8), which possibly induces the discharge in this position.…”

“…Insulators in the UHV/EHV substations have been confronted with numerous rain flashover accidents, which seriously threatened power grids [1,2]. Unfortunately, this situation is even worse under frequent extreme rainfall [3].…”