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

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 article, 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.