Polarization and Trap Characteristics Modification of Oil-Impregnated Paper Insulation by TiO₂ Nanoparticles.

Meng Huang,Chengrong Li,Bingliang Shan,Yuzhen Lv,Yupeng Ying

doi:10.3390/nano9020174

Abstract

Polarization and traps determine the electrical property of oil-paper insulation, but most attention has been paid to the modification of insulating oil with nanoparticles, so there are is little research about oil-impregnated paper, and the origin for performance variation is not understood yet. In this paper, spherical nanoscale titanium dioxide was prepared by the hydrolysis method and nanofluid-impregnated paper (NP) was fabricated through oil-impregnation. The frequency domain spectrum was measured for polarization analysis, and both thermally stimulated depolarization current (TSDC) and isothermal surface potential decay (ISPD) methods were used to reveal trap parameters. Results show that NP’s low frequency permittivity is much larger, and another peak appears in the spectrum even though the content of nanoparticles is very low. With the addition of TiO2 nanoparticles, TSDC’s amplitude and peak temperature increase, and the trap energy becomes shallower. TiO2 nanoparticles’ strong polarization and high activation energy contribute to NP’s larger interface polarization intensity and activation energy. Furthermore, because of oxygen vacancies, TiO2 nanoparticles offer a transfer site for holes and electrons to escape from deep traps; thus, the trap energy is greatly reduced.

Highlights

Owing to its excellent electrical performance, oil-paper insulation has been widely used as the main insulating material in large quantities of equipment, such as transformers and cables
10 nm TiO2 nanoparticles—the transmission electron microscopy (TEM) image of which is shown in Figure 1—were fabricated, and they were dispersed into the strictly filtered mineral transformer oil (Karamay 25#) which fulfilled the quota by CIGRE working group 12.17.10 through the ultrasonic method [3]
Because of the stable chemical property of cellulose, it is difficult to fabricate fiber with nanoparticles surrounded by cellulose like other solid nano‐dielectrics, such as LDPE/MgO nanocomposites [23]

Summary

Introduction

Owing to its excellent electrical performance, oil-paper insulation has been widely used as the main insulating material in large quantities of equipment, such as transformers and cables. The electrical properties of nanofluids such as breakdown strength and streamer propagation have been markedly improved, and it has been commonly accepted that this is attributed to the variation of dielectric relaxation and trap energy caused by nanoparticles [8,9]. With the modification of nanoparticles, the partial discharge, surface discharge, and breakdown performance of OP can be perfected to some degree [10,11,12] These changes are believed to be strongly linked to dielectric polarization and space charge suppression [11,12]. Anatase-TiO2 nanoparticles were used for modification through the oil-impregnation method, and their effect on polarization and trap distribution was analyzed to reveal the behind mechanism. The oxygen vacancies from TiO2 nanoparticles help the trapped charge to dissipate and will weaken the electric field distribution

Materials and Methods

Frequency Domain Spectrum

Discussion