Effects of conductivity and permittivity of nanoparticle on transformer oil insulation performance: experiment and theory

Sima, Wenxia; Shi, Jing; Yang, Qing; Huang, Sisi; Cao, Xuefei

doi:10.1109/tdei.2014.004277

Cited by 176 publications

(156 citation statements)

References 20 publications

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“…For instance, the discovered role of nanoparticles when being dispersed into base oil is to energise the potential well. Therefore, it will trap the passing electrons and consequently lead to an enhancement of dielectric strength [11]. In spite of this, it has been reported that the addition of conductive nanoparticles in a certain amount reduces the dielectric strength of base oil [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

et al. 2018

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Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe 2 O 3 ) and titanium dioxide (TiO 2 ) as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS) method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS), current-voltage (I-V), and dielectric breakdown (BD) strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric fields.

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Section: Introductionmentioning

confidence: 99%

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

et al. 2018

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“…9 Moreover, positive switching impulse withstand voltage of transformer oil was increased by modification of Fe 3 O 4 nanoparticles. 10 An electron-scavenging model is proposed and generally used to explain these phenomena based on modeling the electrodynamic process in Fe 3 nanofluids. 8,9,11 Some researchers think the potential well generated by induced or polarized charges on the surface of nanoparticles can capture the passing electrons and enhance the breakdown performance of transformer oil.…”

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confidence: 99%

“…8,9,11 Some researchers think the potential well generated by induced or polarized charges on the surface of nanoparticles can capture the passing electrons and enhance the breakdown performance of transformer oil. 10,12 In comparison with the dielectric breakdown strength of nanofluid, its prebreakdown streamer propagation behavior is more important to understand the fundamental modification effect of nanoparticle, which can give valuable insight into the events leading to breakdown. Up to now, there is still dearth of knowledge about streamer propagation behavior in the transformer oil-based nanofluids and its relationship with nanoparticle modification.…”

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confidence: 99%

Effect of Fe3O4 nanoparticles on positive streamer propagation in transformer oil

Wang

Zhou

et al. 2016

AIP Advances

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Fe3O4 nanoparticles with an average diameter of 10 nm were prepared and used to modify streamer characteristic of transformer oil. It was found that positive streamer propagation velocity in transformer oil-based Fe3O4 nanofluid is greatly reduced by 51% in comparison with that in pure oil. The evolution of streamer shape is also dramatically affected by the presence of nanoparticles, changing from a tree-like shape with sharp branches in pure oil to a bush-like structure with thicker and denser branches in nanofluid. The TSC results reveal that the modification of Fe3O4 nanoparticle can greatly increase the density of shallow trap and change space charge distribution in nanofluid by converting fast electrons into slow electrons via trapping and de-trapping process in shallow traps. These negative space charges induced by nanoparticles greatly alleviate the electric field distortion in front of the positive streamer tip and significantly hinder the propagation of positive streamer.

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“…The mechanism of trapping electrons has also been proposed by some researchers [26,38,39] to explain the higher breakdown strength of conducting nanofluids compared to base oils. The conductive nanoparticles capture very rapidly fast moving electrons and convert into slow negatively charged nanoparticles, resulting in the slowing of the streamer propagation (i.e., reduction of streamer velocity) and therefore increasing the breakdown voltage.…”

Section: Discussionmentioning

confidence: 93%

“…As indicated above, such an interpretation through the slowing propagation of streamers remains a subject of discussion; the electronic scavenger additives accelerate the propagation of streamers [29][30][31][32]. Another possibility, which would explain the improvement of the breakdown voltage, is the result of electron trapping by nanoparticles: Conductive nanoparticles trap electrons by charge induction, such is the case of Fe 3 O 4 , while nonconductive nanoparticles, which are Al 2 O 3 , trap electrons due to polarization [39].…”

Section: Discussionmentioning

confidence: 99%

AC Dielectric Strength of Mineral Oil-Based Fe3O4 and Al2O3 Nanofluids

Khaled

Béroual

2018

Energies

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This paper deals with an experimental study of the influence of conductive (Fe 3 O 4 ) and insulating (Al 2 O 3 ) nanoparticles at various concentrations on the dielectric strength of transformer mineral oil. The method of preparation and characterization of these nanofluids (NFs) through the measurements of zeta potential, the real and imaginary parts of dielectric permittivity as well as the concentration and size of nanoparticles using scanning electron microscope images of nanoparticles powders and energy dispersive x-ray spectroscopy analysis are presented. Experimental findings reveal that these two types of nanoparticles materials significantly improve AC breakdown voltage and the magnitude of this enhancement depends on the nanoparticle concentration, and the size and nature (material) of nanoparticles. For a given type of nanoparticle, the effect is more marked with the smallest nanoparticles. The conductive nanoparticles offer higher enhancement of dielectric strength compared with insulating nanoparticle based nanofluids. With Fe 3 O 4 , the breakdown voltage (BDV) can exceed twice that of mineral oil and it increases by more than 76% with Al 2 O 3 . The physicochemical mechanisms implicated in this improvement are discussed. Energies 2018, 11, 3505 2 of 13This cooling property (heat transfer) was at the origin of NFs' development. Nowadays, NFs are used in several fields, like electronics (chips, electronic circuitry components); transportation (the cooling systems of heavy power machines and heat generation parts of vehicles); heating buildings and reducing pollution; nuclear cooling systems; space and defense (space stations and aircrafts); and solar absorption for heat-transfer performance. Indeed, they have preferable better thermal characteristics (thermal diffusivity, thermal conductivity, convective coefficient of heat transfer) than the base fluids. These strongly depend on properties and the volume fraction of the added nanomaterial [7,8]. Furthermore, for a given particles volume, the contact area of the solid-liquid surface between nano-size particles and the suspension fluid is greater than that for micro-size particles. Therefore, the shape and size of particles has a clear impact on heat transfer and thermal conductivity characteristics [9][10][11].The volume fraction of particles (concentration), their shape and size, and the surface contact area between particles and liquid are major parameters that influence not only the thermal properties as indicated above, but also have a very great influence on the dielectric properties of composite materials.

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Effects of conductivity and permittivity of nanoparticle on transformer oil insulation performance: experiment and theory

Cited by 176 publications

References 20 publications

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

Effect of Fe3O4 nanoparticles on positive streamer propagation in transformer oil

AC Dielectric Strength of Mineral Oil-Based Fe3O4 and Al2O3 Nanofluids

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