Thermal properties of mixtures of mineral oil and natural ester in terms of their application in the transformer

Nadolny, Zbigniew; Dombek, Grzegorz

doi:10.1051/e3sconf/20171901040

Cited by 22 publications

(15 citation statements)

References 19 publications

(15 reference statements)

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“…The conductivity and viscosity depend to a significant extent on the temperature, and thus they affect other properties of the insulating liquids, which include the carrier mobility, molecular diffusion coefficient, relative dielectric constant, and charge relaxation time. The relative dielectric constant influences the stress distribution in a transformer's insulation system, and thus it determines its electric durability [26][27][28]. When analyzing the data contained in Tables 1 and 2, it can be observed that the ageing processes affect to a different extent the physicochemical and electrical properties of Trafo EN mineral oil.…”

Section: Resultsmentioning

confidence: 99%

“…The authors showed that the content of the mixture significantly determines the change of the tested parameters. Nadolny et al [27,28] presented the research results of thermal properties of Nytro Taurus mineral oil with Envirotemp FR3 natural ester and Midel 7131 synthetic ester mixtures. The authors showed the measurement results of thermal conductivity, viscosity, specific heat, density, and thermal expansion of the created mixtures in a wide temperature range.…”

Section: Research Of Insulating Liquids Mixturesmentioning

confidence: 99%

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Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Zdanowski¹

2020

Energies

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Power transformers are the main element of an electric power system. The service life of these devices depends to a large extent on the technical condition of their insulation system. Replacing mineral oils with natural or synthetic ester (retrofilling process) may increase the efficiency and operational safety of transformers, and also limit their adverse environmental impact. It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues form a mixture with fluid ester, with different physicochemical and electric properties. Streaming electrification is one of the phenomena which, under unfavorable conditions, may damage the insulation system of a forced oil cooled transformer. It is necessary to run prophylactic tests for the ECT (electrostatic charging tendency) of insulating liquid mixtures from the point of view of transformer retrofilling, which is being used more often than before. The article presents the results of studies on selected physicochemical, and electrical properties, and the ECT of mixtures of fresh and aged Trafo EN mineral oil with Nycodiel 1255 synthetic ester. In this regard, the density, the kinematic viscosity, the conductivity, and the relative dielectric constant were measured. The molecular diffusion coefficient was determined using Adamczewski’s empirical dependency. The streaming electrification was tested in a rotating disc system. The impact of the rotation time, the diameter, and the disc’s rotation speed on the amount of the electrification current generated were analyzed. In addition, the co-relation between the electrification current and the composition of the mixture was determined using fresh and aged mineral oil. On the basis of the electrification model, the volume density of the qw charge was calculated, which is a parameter defining the ECT of insulating liquids. Based on the results, it was concluded that the synthetic ester is characterized by a higher susceptibility to electrification than the mineral oil. However, combining synthetic ester with a small amount (up to 20%) of fresh or aged mineral oil significantly reduces its ECT, which is beneficial from the point of view of retrofilling power transformers.

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Section: Resultsmentioning

confidence: 99%

Section: Research Of Insulating Liquids Mixturesmentioning

confidence: 99%

Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Zdanowski¹

2020

Energies

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“…An acoustic pressure source modeled on the geometry of the Sonalleve V R V2 transducer (shown in Figure 3) was used. 4178 [17] 1974 [59] 3421 [17] 2348 [17] 1312 [17] 1004 [17] Sound speed, density and attenuation values for air are explained in the text.…”

Section: Acoustic Simulationmentioning

confidence: 99%

Quantitative prediction of the extent of pelvic tumour ablation by magnetic resonance-guided high intensity focused ultrasound

Lam

Rivens

Giles

et al. 2021

International Journal of Hyperthermia

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Background: Patient suitability for magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) therapy of pelvic tumors is currently assessed by visual estimation of the proportion of tumor that can be reached by the device's focus (coverage). Since it is important to assess whether enough energy reaches the tumor to achieve ablation, a methodology for estimating the proportion of the tumor that can be ablated (treatability) was developed. Predicted treatability was compared against clinically achieved thermal ablation. Methods: MR Dixon sequence images of five patients with recurrent gynecological tumors were acquired during their treatment. Acousto-thermal simulations were performed using k-Wave for three exposure points (the deepest and shallowest reachable focal points within the tumor, identified from tumor coverage analysis, and a point halfway in-between) per patient. Interpolation between the resulting simulated ablated tissue volumes was used to estimate the maximum treatable depth and hence, tumor treatability. Predicted treatability was compared both to predicted tumor coverage and to the clinically treated tumor volume. The intended and simulated volumes and positions of ablated tissues were compared. Results: Predicted treatability was less than coverage by 52% (range: 31-78%) of the tumor volume. Predicted and clinical treatability differed by 9% (range: 1-25%) of tumor volume. Ablated tissue volume and position varied with beam path length through tissue. Conclusion: Tumor coverage overestimated patient suitability for MRgHIFU therapy. Employing patient-specific simulations improved treatability assessment. Patient treatability assessment using simulations is feasible.

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“…The transformer windings are located in a dielectric fluid that provides both insulation and winding cooling. Mineral oil, silicone fluid, synthetic or natural esters can be used as a dielectric fluid (CIGRE, 2010;Nadolny & Dombek, 2017;Njombog Tanteh et al, 2014). Experimental studies indicate that the cooling capacity of the alternative liquid worsens with aging due to the exponential decrease of the viscosity with temperature (Ortiz et al, 2018).…”

Section: Passive Cooling With Liquid Heat Transfer Fluidmentioning

confidence: 99%

Review of cooling solutions for compact electronic devices

Galins¹,

Laizans²,

Galins³

2019

Research for Rural Development

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Nowadays, with the rapid development of robotics and automation, there is a need for more powerful, more compact data processing equipment that also emits more heat. Various electronics cooling solutions are already in use, others are in development. Each cooling solution has its advantages and disadvantages. Active cooling usually dissipates heat more efficiently, but passive cooling is more reliable, especially when the electrical system is exposed to aggressive environmental influences. The possibility of using graphene in the manufacture of electrical equipment components is widely studied. Graphene could significantly improve the efficiency of passive cooling because its thermal conductivity is much better than copper.

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Thermal properties of mixtures of mineral oil and natural ester in terms of their application in the transformer

Cited by 22 publications

References 19 publications

Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Quantitative prediction of the extent of pelvic tumour ablation by magnetic resonance-guided high intensity focused ultrasound

Review of cooling solutions for compact electronic devices

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