Thermal performance of transformers filled with environmentally friendly oils under various loading conditions

Salama, M.; Mansour, Diaa‐Eldin A.; Daghrah, Muhammad; Abdelkasoud, Samir Mohamed; Abbas, Ahmed A.

doi:10.1016/j.ijepes.2019.105743

Cited by 68 publications

(24 citation statements)

References 22 publications

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“…Figure 4 depicts the temperature-dependent thermal conductivity performance of Midel 7131 nanofluids with h-BN, MoS 2 , and h-BN/MoS 2 at various filler fractions. The synthetic ester did not show significant temperature dependency (less than 1% at 50 °C): actually, a decrement in thermal conductivity was observed as temperature was increased, similar to other authors’ findings [ 64 , 65 ]. In general, the thermal conductivity of the evaluated nanofluids gradually increased for all the fillers and concentrations studied as temperature was also increased.…”

Section: Resultssupporting

confidence: 90%

Thermal Conductivity Performance of 2D h-BN/MoS2/-Hybrid Nanostructures Used on Natural and Synthetic Esters

et al. 2020

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In this paper, the thermal conductivity behavior of synthetic and natural esters reinforced with 2D nanostructures—single hexagonal boron nitride (h-BN), single molybdenum disulfide (MoS2), and hybrid h-BN/MOS2—were studied and compared to each other. As a basis for the synthesis of nanofluids, three biodegradable insulating lubricants were used: FR3TM and VG-100 were used as natural esters and MIDEL 7131 as a synthetic ester. Two-dimensional nanosheets of h-BN, MoS2, and their hybrid nanofillers (50/50 ratio percent) were incorporated into matrix lubricants without surfactants or additives. Nanofluids were prepared at 0.01, 0.05, 0.10, 0.15, and 0.25 weight percent of filler fraction. The experimental results revealed improvements in thermal conductivity in the range of 20–32% at 323 K with the addition of 2D nanostructures, and a synergistic behavior was observed for the hybrid h-BN/MoS2 nanostructures.

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Section: Resultssupporting

confidence: 90%

Thermal Conductivity Performance of 2D h-BN/MoS2/-Hybrid Nanostructures Used on Natural and Synthetic Esters

et al. 2020

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“…The characteristics of the obtained h-BN nanoparticles are as follows. The size of the h-BN nanoparticles is in the range of 50-70 nm, Young's modulus of 14-60 GPa, and a density of 2.29 g/cm 3 . The h-BN nanofluids were prepared using the below mentioned process with various weight percentages, 0.01, 0.02, 0.05, and 0.1.…”

Section: Materials and Methodologymentioning

confidence: 99%

“…Owing to sustainability, biodegradability and pollutionfree nature of natural ester insulation oils, many researchers and industries investigated such oils for transformer applications [1]- [3]. As a result, several international standards were devoted to these oils such as ASTM D6871, IEC 62770, IEEE C57.155-2014, ASTM D6871, IEEE C57.147-2018, and IEC 63012.…”

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confidence: 99%

Investigation of the Dielectric and Thermal Properties of Non-Edible Cottonseed Oil by Infusing h-BN Nanoparticles

et al. 2020

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Vegetable oils have emerged as insulating fluids in transformer applications and as a prominent and effective alternative for traditional dielectric fluids. However, most of vegetable oils are edible causing their application on a large scale to be limited. In the present work, a novel non-edible vegetable oil is developed as an insulating fluid. The developed oil is oxidation-inhibited cottonseed oil (CSO) based nanofluids. Tertiary butylhydroquinone was used as antioxidant. The concept of nanofluids was used to overcome the limited dielectric and thermal properties of cottonseed oil. Hexagonal Boron Nitride (h-BN) nanoparticles at low weight fractions (0.01 -0.1 wt%) were proposed as nanofillers to achieve adequate dielectric strength and improved thermal conductivity. Stability of prepared CSO based nanofluids was analyzed using Ultraviolet-visible (UV-Vis) spectroscopy. Then, the prepared nanofluids were tested for dielectric and thermal properties under a temperature range between 45 • C and 90 • C. The dielectric properties include breakdown strengths under AC and lightning impulse voltages, dielectric constant, dissipation factor, and resistivity, while thermal properties include thermal conductivity and thermogram analysis. The dielectric and thermal properties were significantly improved in CSO based nanofluids. The creation of electric double layer at nanoparticle/oil interface and the lattice vibration of nanoparticles were used to clarify the obtained results. The proposed CSO based h-BN nanofluids open up a great opportunity in both natural ester insulating fluid applications and thermal energy management systems. INDEX TERMSVegetable oils, transformers, nanofluids, dielectric properties, thermal properties. NOMENCLATURE b Absorbance in y intercept BDV Breakdown voltage [kV] c p Specific heat capacity [J/(kg.K)] CSO Cottonseed oil EDL Electric Double Layer Enh. Enhancement h-BN Hexagonal Boron Nitride k B Boltzmann constant [1.3806505e −23 J/K] LI Lightning impulse m Coefficient of molar extinction [M −1 .cm −1 ] NEIO Natural ester insulating oil The associate editor coordinating the review of this manuscript and approving it for publication was Jenny Mahoney.

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“…inadequate legislation (standards-defined operational limits) that make the wider industrial use of natural esters more demanding, along with durability problems in terms of lower lightning impulse (LI) resistance [8], [9], oxidative stability, etc. Esters and natural esters also have many benefits, e.g., a low degree of cellulose polymerization (in the system) compared to mineral fluids [10], a high flash point and fire point [11] and a relatively high ''moisture tolerance'' of its dielectric properties [12], higher permittivity is prone a better electric field distribution in the paper-oil system [42] and esters have better thermal stress performance [43]. However, the moisture effect on the aging of the paper-natural ester oil system has not been deeply studied in terms of its degradation and the specific chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Various Aging Processes in a Paper-Natural Ester Insulation System in the Presence of Copper and Moisture

et al. 2020

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This article adds more information to the problem of natural ester use as an electroinsulating fluid in cellulose paper-oil systems, e.g., for use in power transformers. An accelerated thermal aging (120, 140 and 160 • C) of samples consisting of cellulose paper (transformerboard), a treated natural ester (filtered, basic Al 2 O 3 , 0.53% DBPC), a copper plate and moisture was studied. Research was especially focused on the impact of moisture on the aging of the above system. Samples with three different oil moisture levels (80, 143 and 305 ppm water content) were subjected to thermal aging to display the change in a selection of properties (tanδ, acid number, water content). For a study of the polarization effects, broadband dielectric spectroscopy (BDS) was performed to observe the complex permittivity and conductivity dependencies on the temperature and frequency (±30 • C, 0.01-10 7 Hz). Havriliak-Negami (H-N) diagrams were used to further understand the results. The degradation products during thermal aging were recognized by Fourier transform infrared (FT-IR) spectroscopy. Hydrolysis and hydrogenation occurred in the insulating system with a natural ester aged by elevated temperatures, which is in contrast to CO 2 formation in the case of electric aging. The results showed an increase in the acid number, dissipation factor, and number of hydrolysis and hydrogenation products. Furthermore, changes in polarization were observed as a consequence of the thermal aging of paper-natural ester insulation system with the presence of copper and moisture. INDEX TERMS Aging, dielectrics, hydrogenation, hydrolysis, oil insulation, paper-oil insulating system, natural ester, complex permittivity.

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Thermal performance of transformers filled with environmentally friendly oils under various loading conditions

Cited by 68 publications

References 22 publications

Thermal Conductivity Performance of 2D h-BN/MoS2/-Hybrid Nanostructures Used on Natural and Synthetic Esters

Thermal Conductivity Performance of 2D h-BN/MoS2/-Hybrid Nanostructures Used on Natural and Synthetic Esters

Investigation of the Dielectric and Thermal Properties of Non-Edible Cottonseed Oil by Infusing h-BN Nanoparticles

Various Aging Processes in a Paper-Natural Ester Insulation System in the Presence of Copper and Moisture

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