Increased loadability of transformers using natural ester and cellulosic materials as high temperature insulation systems

Vasconcellos, Vagner; Sbravati, Alan; Zanetta, L.C.; Rapp, Kevin; Lombini, Luca; Nazzari, Stefano; Scatiggio, Fabio; Valant, A.

doi:10.1109/mei.2018.8445430

Cited by 19 publications

(17 citation statements)

References 2 publications

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“…Estudos de envelhecimento mostraram que a composição óleo vegetal isolante mais papel isolante tem sua vida estendida, pois a presença de água no óleo vegetal é consumida no processo de hidrólise do triacilglicerol (molécula do OVI), gerando ácidos graxos de cadeia longa (CARGILL, 2007). O processo de hidrólise favorece o deslocamento de mais moléculas de água do papel isolante para o fluido isolante para que se mantenha o equilíbrio químico, ou seja, indiretamente esse deslocamento promove a secagem do papel isolante, o que resulta na extensão da sua vida útil (CARGILL, 2007;VASCONCELLOS et al, 2018). A Figura 4 ilustra a degradação do papel isolante com a utilização de óleo vegetal isolante versus óleo mineral isolante.…”

Section: Figura 2: Pontos De Fulgor E Combustão Dos Fluídos Dielétricosunclassified

Análise De Desempenho Do Transformador De Potência Isolado a Óleo Vegetal Em Relação Ao Transformador De Potência Isolado a Óleo Mineral

Almeida

Muniz

2020

Ifes Ciência

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A utilização dos transformadores de potência é imprescindível para a continuidade de operação do sistema elétrico. Um dos componentes importantes do transformador é o óleo isolante, responsável por seu isolamento elétrico interno e sua refrigeração. Com a crescente preocupação ambiental, viu-se a necessidade de buscar novas alternativas para o sistema de isolamento dos transformadores, uma vez que o óleo mineral isolante é proveniente do petróleo, considerado tóxico, nocivo ao ambiente e de baixa biodegradabilidade. Pesquisas atuais mostraram que o óleo vegetal isolante é uma alternativa a ser considerada por empresas do setor elétrico, por ser um fluido biodegradável, com ponto de fulgor e combustão elevados, sendo caracterizado como um fluido com maior segurança. Este trabalho analisa as vantagens técnicas e operacionais da utilização do óleo vegetal isolante comparado com o óleo mineral isolante. São verificadas suas características físico-químicas, implicações ambientais em caso de derramamento, bem como implicações de segurança quanto ao ambiente de instalação. Conclui-se que o óleo vegetal apresenta vantagens na maioria dos aspectos operacionais e ambientais e também nos requisitos de instalação para segurança e confiabilidade operacionais.

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Section: Figura 2: Pontos De Fulgor E Combustão Dos Fluídos Dielétricosunclassified

Análise De Desempenho Do Transformador De Potência Isolado a Óleo Vegetal Em Relação Ao Transformador De Potência Isolado a Óleo Mineral

Almeida

Muniz

2020

Ifes Ciência

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“…The free volume of gas molecules in oil is an important factor influencing the diffusion behavior of gas molecules. Based on Fox and Flory's free volume theory [17], the occupied volume (V O ) and the free volume (V F ) constitute the total volume (V T ) of the polymer according to Equation (1). The free volume is scattered in the whole polymer in the form of the void, and it is because of the free volume that the molecules in the polymer are in motion.…”

Section: Free Volumementioning

confidence: 99%

“…However, some disadvantages of mineral oil, such as low flash point, poor biodegradation rate, and non-renewability, would cause a large number of troubles. Therefore, an increasing number of scholars keep their eyes on the insulation properties of natural ester oils and their applications [1,2]. The benefits of natural ester oils contain increased fire safety, higher moisture tolerance, and reduction of cellulose degradation [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Difference Analysis of Gas Molecules Diffusion Behavior in Natural Ester and Mineral Oil Based on Molecular Dynamic Simulation

Hao

Chen³

et al. 2019

Molecules

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Natural ester, as a new environmentally green insulating oil, has been widely used in transformer. In an oil-immersed transformer, the normal aging, thermal failure, and discharge failure could easily lead to the decomposition of the oil-paper insulation system and produce different kinds of gases. Studying gas dissolution in natural ester and mineral oil could provide assistance in applying criteria to make a diagnosis of different kinds of faults in the transformer. In this paper, the molecular dynamics method was used to investigate the diffusion behavior of seven fault characteristic gases (including H2, CO, CH4, C2H2, CO2, C2H4, C2H6) in natural ester and mineral oil. The simulation parameters of free volume, interaction energy, mean square displacement, and diffusion coefficient were compared between the natural ester and mineral oil. Meanwhile, the influence of temperature on the diffusion of gas molecules in two kinds of oils was also analyzed. Results showed that the free volume, the interaction energy, and the relative molecular mass of gas molecules were the factors influenced by the diffusion of gas molecules in natural ester and mineral oil. The order of the diffusion coefficients of gas molecules in natural ester was as follows: H2 > CH4 > CO > C2H2 > C2H4 > CO2 > C2H6 and that in mineral oil was as follows: H2 > CH4 > CO> C2H2 > C2 H4 > C2H6 > CO2. By comparing the diffusion behavior of gas molecules in natural ester and mineral oil, it was found that the smaller free volume and higher interaction energy of gas molecules in natural ester were the major reasons for the gas molecules to be more difficult to diffuse in natural ester. The rising temperature could enhance the free volume and reduce the interaction energy between gas molecules and oil. The diffusion coefficient of gas molecules increased exponentially with the follow of temperature. However, the temperature didn’t affect the ordering of diffusion coefficient, free volume, and interaction energy of gas molecules in natural ester and mineral oil.

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“…The DC 50% probability breakdown voltages of contaminated mineral oil with copper particles decreased from 23.8% to 45.0% when the particle concentration increased from 0.1 g/L to 1.5g/L. However, the decline range of the figures for natural ester contaminated by fiber or copper particles showed a smaller drop.Energies 2020, 13, 1818 2 of 16 requirements of green and environmentally friendly insulating oil [1][2][3][4][5]. Since 1990s, researchers have carried out a series researches on the application of natural ester to replace mineral oil.…”

mentioning

confidence: 99%

“…Energies 2020, 13, 1818 2 of 16 requirements of green and environmentally friendly insulating oil [1][2][3][4][5]. Since 1990s, researchers have carried out a series researches on the application of natural ester to replace mineral oil.…”

mentioning

confidence: 99%

Effects of Fiber and Copper Particles on Conductivity and Breakdown Characteristics of Natural Ester and Mineral Oil under DC Voltage

et al. 2020

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The converter transformer is a key equipment in high voltage direct current (HVDC) transmission system. Its oil-paper insulation system in the valve winding and outlet bushing experiences AC, DC, AC/DC, and transient impulse voltages simultaneously. The oil contamination problem is more serious under DC electric field. Therefore, it is significant to investigate the characteristic of particles motion and accumulation under DC electric field. In this paper, first, the movement and accumulation behavior of fiber particles and copper particles in mineral oil and natural ester were recorded and simulated. Then, the influence of fiber and copper particles on the oil conductivity was analyzed. Finally, the DC breakdown strength of mineral oil and natural ester with different particles concentration was compared. Results show that the movement speed of copper particles was larger than that of fiber particles. Fiber impurities were easy to form bridges in mineral oil, while there was no impurity bridge in natural ester. The current density of mineral oil containing particles is larger than that of the natural ester at the same testing time. The DC 50% probability breakdown voltages of oil samples containing fiber and copper particles decreased linearly with the increase of particle concentration, and the decrease rate of DC 50% probability breakdown voltages of oil containing copper particles were faster than that of oil containing fiber particles. Compared to pure mineral oil, the DC breakdown voltages corresponding to 50% probability of contaminated mineral oil showed a decrease from 11.9% to 22.5% when the fiber particle concentration increased from 0.001% to 0.012%. The DC 50% probability breakdown voltages of contaminated mineral oil with copper particles decreased from 23.8% to 45.0% when the particle concentration increased from 0.1 g/L to 1.5g/L. However, the decline range of the figures for natural ester contaminated by fiber or copper particles showed a smaller drop.Energies 2020, 13, 1818 2 of 16 requirements of green and environmentally friendly insulating oil [1][2][3][4][5]. Since 1990s, researchers have carried out a series researches on the application of natural ester to replace mineral oil. There are more than one million natural ester transformers in operation in the world, with voltage levels ranging from 10 kV to 420 k, and their capacities ranging from 6.25 MVA to 300 MVA [6]. Among all the transformers in operation, there are 25,000 large and medium-sized natural ester transformers [6,7].The performance and property of insulating oil have a significant impact on the operation safety of the transformer. Almost one-third of the transformers' damage is caused by insulation problems, among which particles pollution of insulating oil is a significant factor [8]. The existence of impurities in transformer oil is inevitable. The sources of particles mainly include three parts [9-12]: The first part is from impurities left over during the production, assembly, and transportation of transformers, the second...

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Increased loadability of transformers using natural ester and cellulosic materials as high temperature insulation systems

Cited by 19 publications

References 2 publications

Análise De Desempenho Do Transformador De Potência Isolado a Óleo Vegetal Em Relação Ao Transformador De Potência Isolado a Óleo Mineral

Análise De Desempenho Do Transformador De Potência Isolado a Óleo Vegetal Em Relação Ao Transformador De Potência Isolado a Óleo Mineral

Difference Analysis of Gas Molecules Diffusion Behavior in Natural Ester and Mineral Oil Based on Molecular Dynamic Simulation

Effects of Fiber and Copper Particles on Conductivity and Breakdown Characteristics of Natural Ester and Mineral Oil under DC Voltage

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