The effect of acid accumulation in power-transformer oil on the aging rate of paper insulation

Lelekakis, N.; Wijaya, J.; Martín, D.; Susa, D.

doi:10.1109/mei.2014.6804738

Cited by 86 publications

(50 citation statements)

References 14 publications

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“…At disturbance environment of strong vibration, intense electromagnetic field, and so on, whether the system is suitable for in situ analysis of oil-dissolved acids in an operating transformer or not is unclear. (3) In international electrotechnical commission (IEC) standard, the concentration of low-molecular-weight acids is not currently used to diagnose aging state of paper insulation, because the correlation between acids concentration and aging rate has not been fully determined [14]. These unsolved questions or problems above should and will be focused on in our further work.…”

Section: Discussionmentioning

confidence: 99%

“…High-molecular-weight acids (more than 5 carbon atoms), typically stearic and naphtenic acid, have a lower affinity for cellulose due to the hydrophobic nature of the alkyl group C n H 2n+1 [10,11], while, low-molecular-weight acids, typically formic, levulinic, and acetic acid, are more hydrophilic and 90% of which will be absorbed by the oil-immersed paper [12]. The low-molecular-weight acids have a greater influence on the degradation rate of paper by reacting chemically with cellulose (paper) and water through donating a proton (H + ) [13,14]. Cellulose degradation will form more low-molecular-weight acids, which will remain absorbed in paper and accelerate the degradation of cellulose in turn [15].…”

Section: Introductionmentioning

confidence: 99%

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A Novel Method to Directly Analyze Dissolved Acetic Acid in Transformer Oil without Extraction Using Raman Spectroscopy

Wan

Chen

et al. 2017

Energies

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Analyzing the concentration of low molecular acids dissolved in oil is vital in the oil-paper insulation aging diagnostic procedure of power transformers. The existing methods cannot distinguish between different acid types and their strengths. In this study, an improved solution Raman detection platform is fabricated. The direct measurement of dissolved acetic acid, a kind of low molecular acids, is observed in transformer oil without extraction. The Raman shift line of oil-dissolved acetic acid at 891 cm −1 corresponding to H-C-H symmetrical swing and O-H swing modes is taken as its characteristic value. Taking Raman shift line of pure oil at 932 cm −1 as an internal standard, a linear regression curve for quantitative analysis is obtained with a slope of 0.19. The best platform parameter of accumulation number is 300, which is determined by Allan deviation analysis. The current concentration detection limit and accuracy for oil-dissolved acetic acid are obtained at about 0.68 mg/mL and 91.66%, separately. The results show that Raman spectroscopy could be a useful alternative method for evaluation insulation aging state of an operating power transformer in the future.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Novel Method to Directly Analyze Dissolved Acetic Acid in Transformer Oil without Extraction Using Raman Spectroscopy

Wan

Chen

et al. 2017

Energies

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“…This will, in turn, cause and accelerate the deterioration of the insulation, posing a potential threat to the equipment safety. Aging is a phenomenon resulting in slow and irreversible changes in material properties [3][4][5][6]. The process implies the decomposition of vulnerable hydrocarbons resulting in a modification of the macromolecular structure of the liquid and solid materials.…”

Section: Introductionmentioning

confidence: 99%

“…The process implies the decomposition of vulnerable hydrocarbons resulting in a modification of the macromolecular structure of the liquid and solid materials. In general, transformer oil loses its stability gradually and becomes decomposed and oxidized [3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Electrical stress together with heat and moisture, in the presence of oxygen, oxidises the oil producing free radicals, acids, and sludge that are deleterious to the transformer [6,10,11]. Free radicals may be generated by thermal decomposition, electrical discharge, electrolysis at an electrode, mechanical damage, chemical reactions, and high energy radiation and are thus implicated in the ageing process [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Measurement of the Relative Free Radical Content of Insulating Oils of Petroleum Origin

Fofana

Sabau²,

Bétié

2015

Energies

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Oil/paper insulation degradation in transformers involves chemical and physical changes in the materials. Some of the chemical reactions involve very reactive intermediates called free radicals. Free radicals play a major role in a wide variety of ageing processes. The detection of these reactive species in oil may, in principle, provide useful information for monitoring oil degradation. This manuscript details a laboratory technique, which determines the relative content of free radicals in insulating oils of petroleum origin by a spectrophotometric method. Free radicals may be formed in oils under operating or test conditions. The procedure enables the determination of the relative concentration of free radicals, which can act as the precursors of decay products such as charge carriers, oxidized molecules, as well as polymerization products. The technique involves using a reactive free radical reagent, 2,2-diphenyl-1-picrylhydrazyl (DPPH), added to oil to assess free radical concentration. This method is applicable to new, reclaimed, or used oils as well as naturally or artificially oxidized oil (the cause of aging can be chemical, physical, or electrical). In this contribution, free radicals were assessed following electrical discharge application in oil.

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Closer Approach towards the Preparation of Cellulose and Microcrystalline Cellulose from Corn Husks

Anh,

Tai

2024

Chem Eng & Technol

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In this work, cellulose was effectively produced from corn husks by a simple and eco‐friendly method. Major influencing variables for cellulose extraction were examined, and the highest yield of lignin and hemicellulose cleavage was achieved after corn husks were treated in 12.5 wt % NaOH solution at solid/liquid ratio (S/L) of 1:10 g mL−1, 70 °C for 90 min. Subsequent bleaching conducted in 10 wt % H2O2 solution at 80 °C for 90 min produced cellulose with a lightness value (L*) of ∼87, chromaticity indexes a* = −1.85, b* = 2.94 with high purity, 90.86 %, and crystallinity, 64.94 %. Fourier transform infrared, scanning electron microscopy, and x‐ray diffraction analysis showed a clear transition in morphology, structure modification, and crystallinity consistent with the alteration of the chemical composition from raw material to delignified residue and the bleached one. To synthesize microcrystalline cellulose (MCC), the hydrolysis was investigated in H2SO4 solutions of different concentrations and durations via monitoring particle size distribution by laser diffraction spectroscopy. At the most efficient conditions (30 wt % H2SO4, 18 h, 45 °C, 1:10 S/L ratio), the obtained MCC reached an average particle size of 42.68 µm, crystallinity degree of 61.6 %, and cellulose purity of 92.5 %. Meanwhile, similar parameters with 4 N HCl solution produced MCC with the same purity but higher crystallinity (65.6 %), higher mean size, 67.62 µm, and higher aspect ratio. SEM images showed that 4 N HCl caused less detrimental and erosive action, and less fragmentation on cellulose microfibrils compared to 30 wt % H2SO4. The study's outcome supports the feasibility of corn husks to produce cellulose and MCC for further applications.

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The effect of acid accumulation in power-transformer oil on the aging rate of paper insulation

Cited by 86 publications

References 14 publications

A Novel Method to Directly Analyze Dissolved Acetic Acid in Transformer Oil without Extraction Using Raman Spectroscopy

A Novel Method to Directly Analyze Dissolved Acetic Acid in Transformer Oil without Extraction Using Raman Spectroscopy

Measurement of the Relative Free Radical Content of Insulating Oils of Petroleum Origin

Closer Approach towards the Preparation of Cellulose and Microcrystalline Cellulose from Corn Husks

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