scholarly journals Research on Creeping Flashover Characteristics of Nanofluid-Impregnated Pressboard Modified Based on Fe3O4 Nanoparticles under Lightning Impulse Voltages

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 524 ◽  
Author(s):  
Bingliang Shan ◽  
Meng Huang ◽  
Yupeng Ying ◽  
Mingkang Niu ◽  
Qian Sun ◽  
...  
Keyword(s):  
Electric Field ◽  
Fe3o4 Nanoparticles ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Uniform Electric Field ◽  
Surface Charges ◽  
Depolarization Current ◽  
Before And After ◽  
Lightning Impulse ◽  
Thermally Stimulated Depolarization

Creeping flashover of mineral-oil-impregnated pressboard under impulse stress is a common insulating failure in oil-immersed transformers, arousing increasing attention. Recent studies have shown that the breakdown strength of transformer oil under positive lightning impulse voltage can be significantly improved through nanoparticles-based modification, and Fe3O4 has shown the best improvement in breakdown strength compared to other nanoparticles that have been used. This paper presents the creeping flashover characteristics of pure oil-impregnated pressboard (OIP) and nanofluid-impregnated pressboard (NIP) based on Fe3O4 nanoparticles under positive and negative lightning impulse voltages, respectively. It was found that NIP possessed higher resistance to creeping flashover than OIP. The relative permittivities of oil and oil-impregnated pressboard before and after nanoparticles-based modification were measured, and the results revealed that the addition of nanoparticles led to a better match in relative permittivity between oil and oil-impregnated pressboard, and a more uniform electric field distribution. Furthermore, the shallow trap density in NIP was obviously increased compared to that of OIP through the thermally stimulated depolarization current (TSDC), which promoted the dissipation of surface charges and weakened the distortion of the electric field. Therefore, the creeping flashover characteristics of oil-impregnated pressboard were greatly improved with Fe3O4 nanoparticles.

The Influence of Microstructure on the Surface Charge of Sintered Hydroxyapatite Ceramics

2019 ◽  
Vol 800 ◽  
pp. 25-29
Author(s):  
Darta Ubele ◽  
Liene Pluduma ◽  
Karlis Agris Gross
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Bone Ingrowth ◽  
Surface Charges ◽  
Depolarization Current ◽  
Density Measurements ◽  
Electrical Polarization ◽  
Hydroxyapatite Ceramics ◽  
A Charge ◽  
Thermally Stimulated Depolarization

Hydroxyapatite (HAp) has shown the ability to store a charge induced by electrical polarization a method potential for improved bone ingrowth. In this work electrical polarization was carried out on HAp ceramics with three different microstructures, obtained at three different sintering temperatures. Microstructure of the sintered HAp was evaluated from density measurements and SEM observations. Sintered HAp tablets were electrically polarized in an electric field of 5 kV/cm at 400 °C for 1h. Surface charges investigated by thermally stimulated depolarization current measurements showed 104,8 μC/cm2 for denser tablets, while charge density of 22,8 μC/cm2 was obtained for less dense tablets.

scholarly journals Charge Injection Characteristics of Semi-Conductive Composites with Carbon Black-Polymer for HVDC Cable

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1134 ◽  
Author(s):  
Yanhui Wei ◽  
Mingyue Liu ◽  
Wang Han ◽  
Guochang Li ◽  
Chuncheng Hao ◽  
...  
Keyword(s):  
Carbon Black ◽  
Electric Field ◽  
Bottom Electrode ◽  
Charge Injection ◽  
Experimental Results ◽  
Uniform Electric Field ◽  
Insulation Material ◽  
Electrode Structure ◽  
Depolarization Current ◽  
Conductive Composites

Semi-conductive composites composed of carbon black-polymer play an important role in uniform electric field in high voltage direct current (HVDC) cable. They also affect space charge behaviors in the insulation material. However, the charge injection characteristics of semi-conductive composites are not detailed. In this work, the electrode structure of ‘Semi-conductive composites- Insulation material- Metal bottom’ (S-I-M) is proposed, and the currents formed by injected charges from semi-conductive composites are characterized by the thermally stimulated depolarization current (TSDC) method. Further, the experimental results based on the structure of S-I-M are compared with the traditional electrode structure of M-I-M (Metal upper electrode- Insulation material- Metal bottom electrode) and the simplified cable electrode structure of MS-I-M (Metal upper electrode-Semi-conductive electrode- Insulation material- Metal bottom electrode), respectively. The experimental results show that the semi-conductive composite plays an important role in the charge injection process and it presents a different tendency under different compound modes of temperature and electric field. For the low electric field (E ≤ 5 kV/mm) and the low temperature (T ≤ 50 °C), the current caused by the accumulated charges follows the rule, IS > IMS > IM. For the low electric field and high temperature (T > 50 °C), the current caused by the injected charges follows the rule, IMS > IM > IS. This phenomenon is closely related to the interface characterization and contact barrier.

Effect of Polarization Treatment Time on Inhibition of Low Temperature Degradation in Y-Doped ZrO2

2012 ◽  
Vol 529-530 ◽  
pp. 601-604
Author(s):  
Yu Tsuchiya ◽  
Naohiro Horiuchi ◽  
Miho Nakamura ◽  
Kosuke Nozaki ◽  
Akiko Nagai ◽  
...  
Keyword(s):  
Low Temperature ◽  
Treatment Time ◽  
Space Charge Polarization ◽  
Surface Charges ◽  
Depolarization Current ◽  
Orientation Polarization ◽  
Polarization Mechanism ◽  
Thermally Stimulated Depolarization ◽  
Effect Of Surface ◽  
Acceleration Test

Effect of surface charges induced by polarization treatment on Low Temperature Degradation (LTD) in 3mol%Y-doped ZrO2 was studied. Samples were polarized by applying voltage (7kV/cm) at 200°C for various time (1~30min). LTD acceleration test was conducted using polarized samples. LTD was inhibited on negatively charged surface in all the polarized samples, which is independent on polarization time. We carried out thermally stimulated depolarization current (TSDC) analysis for investigate polarization mechanism. Two polarization elements were confirmed: orientation polarization and space charge polarization. A comparison of the result of LTD acceleration test and TSDC analysis indicates that orientation polarization is considered superior element in inhibition of LTD.

Characteristics of Mineral Oil-based Nanofluids for Power Transformer Application

2017 ◽  
Vol 7 (3) ◽  
pp. 1530 ◽  
Author(s):  
I. H. Zakaria ◽  
M. H. Ahmad ◽  
Y. Z. Arief ◽  
N. A. Awang ◽  
N .A. Ahmad
Keyword(s):  
Electrical Properties ◽  
Breakdown Strength ◽  
Power Transformer ◽  
Atmospheric Pressure Plasma ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Before And After ◽  
Cold Atmospheric Pressure Plasma ◽  
The Stability ◽  
Physical Changes

Trends in the field of nanomaterial-based transformer oil show most of the conducted works have focused only on the transformer oil-based nanofluids but limited studies on the stability of transformer oil-based nanofluids. Since mineral oil-based nanofluids still can produce the sedimentation, thus the cold-atmospheric pressure plasma method is proposed to functionally modify the Silicon Dioxide (SiO<sub>2</sub>) nanofiller in order to enhance the electrical properties of the mineral oil-based nanofluids. The AC breakdown strength oil samples before and after modification were measured. It was found that the plasma treated nanofluids have higher AC breakdown voltage compared to pure oil and untreated nanofluids. Also, Fourier Transform Infrared (FTIR) Spectroscopy has been used in this study to analyse the physical changes of oil samples. It is envisaged that the added silica nanofiller has significant effect on electrical properties of the transformer oil-based nanofluids which would enable to the development of an improved class of liquid dielectric for the application of power transformer.

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