Effects of nanostructure permittivity and dimensions on the increased dielectric strength of nano insulating oils

Katiyar, Ajay; Dhar, Purbarun; Nandi, Tandra; Das, Sarit K.

doi:10.1016/j.colsurfa.2016.09.015

Cited by 43 publications

(33 citation statements)

References 27 publications

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“…Some overall facts have been deduced from these experimental studies. It has been concluded that smaller NPs yields better effects than larger NPs, that there is an optimal concentration of NPs, and that their effect depends on the characteristics of the liquid and the NPs [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids

2018

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Positive and negative streamer inception voltages from ultra-sharp needle tips (with tip radii below 0.5 µm) are measured in TiO 2 , SiO 2 , Al 2 O 3 , ZnO and C 60 nanofluids. The experiments are performed at several concentrations of nanoparticles dispersed in mineral oil. It is found that nanoparticles influence positive and negative streamers in different ways. TiO 2 , SiO 2 and Al 2 O 3 nanoparticles increase the positive streamer inception voltage only, whilst ZnO and C 60 nanoparticles augment the streamer inception voltages in both polarities. Using these results, the main hypotheses explaining the improvement in the dielectric strength of the host oil due to the presence of nanoparticles are analyzed. It is found that the water adsorption hypothesis of nanoparticles is consistent with the increments in the reported positive streamer inception voltages. It is also shown that the hypothesis of nanoparticles reducing the electron velocity by hopping transport mechanisms fails to explain the results obtained for negative streamers. Finally, the hypothesis of nanoparticles attaching electrons according to their charging characteristics is found to be consistent with the results hereby presented on negative streamers.

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Section: Introductionmentioning

confidence: 99%

Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids

2018

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“…Ajay and Purbarun [75] added Al2O3 particles with a size of 25-125 nm to mineral insulating oil. The effects of the concentration, morphology, permittivity, and size of the nanoparticles on the breakdown characteristics of the modified oil were studied.…”

Section: Effect Of Nanoparticles On the Breakdown Voltage Of Mineral mentioning

confidence: 99%

“…Ajay and Purbarun [75] modified mineral insulating oil with nano-Al2O3 with different particle sizes, and then measured the electrical parameters of the samples. The results showed that the dielectric properties increased by 69% when the content of nano-Al2O3 with a particle size of 23 nm was 0.25 wt %.…”

Section: Effect Of Nanoparticles On the Dielectric Properties Of Minementioning

confidence: 99%

Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

et al. 2018

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Abstract:In November 2017, the first ±1100 kV high-voltage direct-current power transformer in the world, which was made by Siemens in Nurnberg, passed its type test. Meanwhile, in early 2017, a ±1000 kV ultra-high voltage (UHV) substation was officially put into operation in Tianjin, China. These examples illustrate that the era of UHV power transmission is coming. With the rapid increase in power transmission voltage, the performance requirements for the insulation of power transformers are getting higher and higher. The traditional mineral oils used inside power transformers as insulating and cooling agents are thus facing a serious challenge to meet these requirements. In this review, the basic properties of traditional mineral insulating oil are first introduced. Then, the variation of electrical properties such as breakdown strength, permittivity, and conductivity during transformer operation and aging is summarized. Next, the modification of mineral insulating oil is investigated with a focus on the influence of nanoparticles on the electrical properties of nano-modified insulating oil. Recent studies on the performance of mineral oil at molecular and atomic levels by molecular dynamics simulations are then described. Finally, future research hotspots and notable research topics are discussed.

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“…This process is called scavenging and consequently the growth of streamers is retarded, resulting in higher BD strength. The size effects of nanoparticles in oils also reveal that smaller size particles have larger surface area to volume ratio and thus have the capability of arresting more number of free electrons per unit volume [29], thereby resulting in decelerated growth of streamers and further enhancing the BD strength. In fact the presence of nanoparticles leading to effective scavenging of free electrons can also be testified via observation the event of corona discharge.…”

Section: Resultsmentioning

confidence: 99%

Streamer evolution arrest governed amplified AC breakdown strength of graphene and CNT colloids

Dhar

Chattopadhyay

Maganti

et al. 2019

Eur. Phys. J. Appl. Phys.

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The present article experimentally explores the concept of large improving the AC dielectric breakdown strength of insulating mineral oils by the addition of trace amounts of graphene or CNTs to form stable dispersions. The nano-oils infused with these nanostructures of high electronic conductance indicate superior AC dielectric behaviour in terms of augmented breakdown (BD) strength compared to the base oils. Experimental observations of two grades of synthesized graphene and CNT nano-oils show that the nanomaterials not only improve the average breakdown voltage but also significantly improve the reliability and survival probabilities of the oils under AC high voltage stressing. Improvement of the tune of ~ 70-80 % in the AC breakdown voltage of the oils has been obtained via the present concept. The present study examines the reliability of such nano-colloids with the help of two parameter Weibull distribution and the oils show greatly augmented electric field bearing capacity at both standard survival probability values of 5 % and 63.3 %. The fundamental mechanism responsible for such observed outcomes is reasoned to be delayed streamer development and reduced streamer growth rates due to effective electron scavenging by the nanostructures from the ionized liquid insulator. A mathematical model based on the principles of electron scavenging is proposed to quantify the amount of electrons scavenged by the nanostructures. The same is then employed to predict the enhanced AC breakdown voltage and the experimental values are found to match well with the model predictions. The present study can have strong implications in efficient, reliable and safer operation of real life AC power systems.

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Effects of nanostructure permittivity and dimensions on the increased dielectric strength of nano insulating oils

Cited by 43 publications

References 27 publications

Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids

Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids

Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

Streamer evolution arrest governed amplified AC breakdown strength of graphene and CNT colloids

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