Assessing changes in thermally upgraded papers with different nitrogen contents under accelerated aging

Arroyo-Fernández, Oscar H.; Fofana, I.; Jalbert, Jocelyn; Rodriguez, Esperanza; Rodriguez, Lidia B.

doi:10.1109/tdei.2017.006449

Cited by 28 publications

(14 citation statements)

References 19 publications

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“…Different techniques are used to determine the changes in paper's mechanical performance during ageing, such as tensile strength, flexural strength, folding endurance strength, edge tearing resistance and bursting strength [55][56][57][58][59]. Tensile testing is the technique used in several studies to track the loss of mechanical strength during paper ageing [30,41,45,46,55,57,[59][60][61][62][63][64][65][66][67]. It has been shown that the condition of paper, when chain scission is involved, can be monitored using tensile strength as a reference [41].…”

Section: Frequency Factor (Lnaa)mentioning

confidence: 99%

“…The authors reported that methanol was also stable in Nynas 10XN. During accelerated laboratory ageing, some authors [29,60,62] have observed that the trend toward increasing methanol concentration with ageing duration begins to fluctuate when the paper is near its end of life, with a degree of polymerization~200. These variations are attributed to a modification in the methanol paper/oil partitioning due to a buildup of oil oxidative products in the oil.…”

Section: Methanol Stabilitymentioning

confidence: 99%

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Methanol Marker for the Detection of Insulating Paper Degradation in Transformer Insulating Oil

et al. 2019

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This manuscript presents a comprehensive literature review with the aim to provide readers a reference document with up-to-date information on the field of methanol use as a chemical marker. It has been a little more than a decade since methanol was first introduced as a marker for assessing solid insulation condition in power transformers. It all started when methanol was identified in the laboratory during thermal ageing tests carried out with oil-immersed insulating papers and was subsequently also identified in transformer field samples. The first publication on the subject was released in 2007 by our research group. This review covers the methanol fundamentals such as the analytical methods for its determination in transformer oil, which is generally performed by headspace gas chromatography with mass spectrometry or flame ionization as a detector. Current standardization efforts for its determination include ASTM working group 30948 and IEC TC10. Kinetic studies have confirmed the relationship between methanol generation, the number of broken 1,4-β-glycosidic bonds of cellulose and changes in mechanical properties. Laboratory tests have confirmed its stability at different accelerated ageing temperatures. Several utilities have identified methanol during field measurements, case studies on power and some distribution transformers are presented, as well as transformer postmortem investigations. These field-testing results demonstrate its utility in monitoring cellulosic insulation degradation. Recently, a model of methanol interpretation has become available that allows for evaluation of the average degree of polymerization of core type transformer cellulose winding. Methanol has a role as an indicator of cellulosic solid insulation ageing in transformer mineral oil, and it is expected that in the future it will be in routine use by utilities.

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Section: Frequency Factor (Lnaa)mentioning

confidence: 99%

Section: Methanol Stabilitymentioning

confidence: 99%

Methanol Marker for the Detection of Insulating Paper Degradation in Transformer Insulating Oil

et al. 2019

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“…It also showed that an ethanol indicator could be used to characterize the degradation of insulating paper performance [10]. The research results of Fernandez et al were also consistent with this view [11]. Matharage et al used gas chromatography and ion trap mass spectrometer to detect methanol in aging insulating paper [12].…”

Section: Introductionmentioning

confidence: 66%

A Molecular Dynamics Study of the Generation of Ethanol for Insulating Paper Pyrolysis

Zhang

et al. 2020

Energies

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Cellulosic insulation paper is usually used in oil-immersed transformer insulation systems. In this study, the molecular dynamics method based on reaction force field (ReaxFF) was used to simulate the pyrolysis process of a cellobiose molecular model. Through a series of ReaxFF- Molecular Dynamics (MD) simulations, the generation path of ethanol at the atomic level was studied. Because the molecular system has hydrogen bonding, force-bias Monte Carlo (fbMC) is mixed into ReaxFF to reduce the cost of calculation by reducing the sampled data. In order to ensure the reliability of the simulation, a model composed of 20 cellobioses and a model composed of 40 cellobioses were respectively established for repeated simulation in the range of 500–3000 K. The results show that insulating paper produced ethanol at extreme thermal fault, and the intermediate product of vinyl alcohol is the key to the aging process. It is also basically consistent with others’ previous experiment results. So it can provide an effective reference for the use of ethanol as an indicator to evaluate the aging condition of transformers.

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“…When cellulose ages, its amorphous region is attacked first [14], [31], [32] and this is the form of cellulose which holds moisture most easily [17], [24]. Indeed, several studies have shown that aged paper is capable of holding less moisture than unaged paper [15], [20], [33]- [35].…”

Section: Variation With Insulation Aging a Sorption Isotherm Formulamentioning

confidence: 99%

Improvements to the Construction of Bubble Inception Formulae for Use With Transformer Insulation

et al. 2019

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Moisture in transformer insulation is a topic of major interest to power system equipment operators. Moisture plays a large role in the degradation of insulation within the transformer, impacting on the longevity and the failure rate of this crucial asset. Therefore, understanding of how moisture behaves in the transformer insulation has been the focus of many studies. One particular matter that can occur during high-temperature events is the formation of bubbles of water vapor which are released from the cellulosic paper wrapped on the transformer windings. During such events, the presence of these bubbles could lead to an electrical failure of the transformer, and so it is desirable to be able to set operational criteria which prevent such occurrences. A formula which can predict the temperature at which bubbles will form from the paper insulation can allow operators to restrict transformer operation in order to avoid such situations. However, it has proven difficult to generate a formula with global applicability that is simplistic enough for generic use. This paper assesses the current formula against existing data in literature and compares a suggested alternative, drawing on fundamental science to assist in development of both formulae. The alternative formula is based on a better representation of bubbling activity and requires fewer input variables. Finally, adjustments are suggested to the formulae which allow them to be used more generally throughout the transformer fleet, including on service-aged transformers and with alternative insulation materials.INDEX TERMS Aging, cellulose insulation, degradation, dielectrics and electrical insulation, equipment failure, insulation, temperature, thermal stresses, thermodynamics, transformers. SYMBOLOGYA list of the symbols used in the equations throughout this study, along with their definitions and units (where applicable) is provided in Table 1.

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Assessing changes in thermally upgraded papers with different nitrogen contents under accelerated aging

Cited by 28 publications

References 19 publications

Methanol Marker for the Detection of Insulating Paper Degradation in Transformer Insulating Oil

Methanol Marker for the Detection of Insulating Paper Degradation in Transformer Insulating Oil

A Molecular Dynamics Study of the Generation of Ethanol for Insulating Paper Pyrolysis

Improvements to the Construction of Bubble Inception Formulae for Use With Transformer Insulation

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