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

Lin Yang,Fuzeng Zhang,Licheng Li,Yanpeng Hao,Yijie Sun,Zhiqiang Kuang,Yifan Liao

doi:10.1109/access.2020.3012978

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 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 L arc (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 E h (the rain flashover voltage gradient along the insulation height), X and L arc were investigated, respectively. Furtherly, the relationships were studied among Eh, X and L arc . Results indicate that E h has a sharp rise as the number of BS (NBS) is from one to two, however the rise of E h gradually decreases when NBS exceeds two. X decreases while L arc increases with the rise of NBS, however both the change ranges of them continually fall. Furthermore, L arc presents remarkable negative correlation to X because of the effect of the electric field. E h 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.

Highlights

The rain flashovers of insulators often occurred in the power system, which threatened power system security severely [1]–[3]
R2 in Fig. 18 called correlation coefficient greater than 0.96 means there is an approximate negative correlation between the length of water column and the length of local arc at the local position of the sample, which is attributed to the effect of the electric field
The following conclusions can be drawn: 1) The rain flashover voltages of the sample equipped with 1-4 booster sheds (BS) are 39%, 150%, 176%, and 194% higher than that without BS, respectively, which indicates that BS can effectively improve the flashover performance of the sample under heavy rainfall

Summary

Introduction

The rain flashovers of insulators often occurred in the power system, which threatened power system security severely [1]–[3]. According to the statistics of flashover accidents in the Nelson River converter station from 1975 to 2013, the rain flashovers accounted for about half of the total and the most of them happened on the bushings [4]. As for the external insulation flashovers in ± 500 kV DC converter stations in China, the rain flashovers accounted for about 60% [5]. The rain flashovers have been reported in the external insulation flashover accidents. There were a host of experimental researches on the prevention approaches for the rain flashovers on the external insulation of power equipment. Orsino et al found that the flashover voltage of 800 kV post insulator with 3-6 BS (spacing distance of 700 mm) was 18%-24% higher than that without BS under rain of 5 mm/min [6].

Results

Discussion

Conclusion