The Shed Hole Influence on the Electrical Performance of Composite Insulator

Fanghui Yin,Licheng Li,Masoud Farzaneh,Liming Wang,Hongwei Mei,Pingyuan Liu

doi:10.1109/access.2020.3042245

Abstract

In recent years, shed holes appeared on the surface of in-service composite insulators have been observed in transmission lines in the southern and middle regions of China. Their presence can shorten the insulator creepage distance and therefore may impair the composite insulator’s electrical performance. In this paper, extensive experiments were carried out to study the influence of shed hole (shed hole diameter, shed hole arrangement, shed hole percentage) on the electrical performance including pollution flashover voltage, pollution-rain flashover voltage, dry flashover voltage, wet flashover voltage, and lightning impulse voltage. The experimental results showed that the presence of shed hole had insignificant impact on the dry flashover voltage, wet flashover voltage, and lightning impulse when the shed diameter was 1.0 mm. However, the shed hole influence on the pollution flashover and pollution-rain flashover performance was appreciable. When the shed hole diameter is 1.0 mm, both the pollution flashover voltage and the pollution-rain flashover voltage are higher with alternating arrangement than that with straight-line arrangement. With the same shed hole diameter and pollution degree, the electrical performance of pollution-rain flashover is better than the pollution flashover. It is also found that the diameter of shed hole is increased by 3% to 60% after the pollution flashover test.

Highlights

Since 1980s, silicone rubber composite insulator has been widely used in the high voltage transmission system for its light weight, high mechanical strength, and ease of installation [1,2]
As the presence of shed holes may short out the sheds thereby reducing the creepage distance, the main objective of this study is to investigate the electrical performance of composite insulators with shed holes under various adverse conditions
The pollution flashover voltage generally decreases with the increase of shed hole percentage, shed hole diameter, and equivalent salt deposit density (ESDD)

Summary

Introduction

Since 1980s, silicone rubber composite insulator has been widely used in the high voltage transmission system for its light weight, high mechanical strength, and ease of installation [1,2]. In three ultra-high voltage (UHV) AC transmission lines which were put into service in China in 2016, the proportion of composite insulators consisted of about 60 % of all line insulators. Great progress has been made in the composite insulator technology, there are still many problems need to be resolved Since they are normally operating outdoors, their mechanical and electrical properties could be degraded for being subjected to adverse environmental conditions such as high electric field strength, high temperature, and severe pollution, etc. Temperature rises from 3.3 K up to 11.4 K were observed at the high voltage ends of composite insulators suspended on tower #N242. It was found that about 12 to 22 shed units at the high voltage ends of all composite insulators had shed holes.

Objectives

Methods

Results

Conclusion