Analysis and mechanism of adsorption of naphthenic mineral oil, water, formic acid, carbon dioxide, and methane on meta-aramid insulation paper

Xu, Li Li; Tang, Chao; Wang, Jingna; Tian, Wenxin; Hu, Dong

doi:10.1007/s10853-019-03476-x

Cited by 38 publications

(16 citation statements)

References 27 publications

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“…With the development of quantum mechanics theory system and computer technology, molecular simulation has been widely used in many fields (English et al 2015;Tang et al 2015). In the increasingly complex field of high-voltage insulation, molecular simulation technology has been used to analyze the aging mechanism of insulating materials with remarkable success (Li et al 2019;Du et al 2020). ReaxFF (Adri et al 2001) is a reactive molecular dynamics force field that can describe the formation and breaking of chemical bonds, it is widely used to describe complex chemical reaction processes.…”

Section: Introductionmentioning

confidence: 99%

WITHDRAWN: Microscopic Reaction Mechanism of Formic Acid Generated During Pyrolysis of Cellulosic Insulating Paper

Zheng

Yang

et al. 2021

Preprint

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Cellulosic insulating paper is the component part of the insulation in power transformers. Under thermal stress inside the transformer, cellulosic insulating paper degrades to generate formic acid that will dissolve in insulating oil. In addition, the generation of formic acid further accelerates the aging process of insulating paper. This study took cellulose molecule with DP of 2 that was composed of D-glucose as the research object, the ReaxFF reaction force field was used to simulate the high temperature thermal aging process of cellulose. This study obtained the main reaction pathways of cellulose pyrolysis to generate formic acid. During the pyrolysis process, the number of formic acid molecules presented short-term fluctuations, which was the phenomenon of disappearance and regeneration of formic acid molecules. The combined element tracing method obtained three pathways of cellulose pyrolysis to generate formic acid: 1) The ether group oxygen atom O5(O'5) and C1(C'1) form a carbonyl group to generate formic acid. 2) Dehydrogenation of the primary alcohol hydroxyl group and the attached C atom form a carbonyl group to generate formic acid. 3) Dehydrogenation of the secondary alcohol hydroxyl group and the attached C atom form a carbonyl group to generate formic acid. Statistics found that the generation of formic acid molecules mainly come from the first pathway. The pre-exponential factor and activation energy of the calculated pyrolysis model were consistent with the experimental results. This study designed the accelerated thermal aging experiment of oil-paper insulation. The silanization derivatization method was used to detect the formic acid generated by the aging of insulating paper, which further verified the feasibility of formic acid as an index for evaluating the aging of cellulosic insulating paper.

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Section: Introductionmentioning

confidence: 99%

WITHDRAWN: Microscopic Reaction Mechanism of Formic Acid Generated During Pyrolysis of Cellulosic Insulating Paper

Zheng

Yang

et al. 2021

Preprint

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“…Therefore, it is of great importance to study the glass-transition characteristics of cellulose at high temperature to improve its thermal stability. When studying the glass-transition temperatures of polymers, the most commonly used and reliable method is the specific volume-temperature curve method [23][24][25][26]. The specific volume is the reciprocal of the density, and it is the most commonly used physical quantity in determination of the glass-transition temperature.…”

Section: Glass-transition Temperaturementioning

confidence: 99%

Molecular Simulation of Improved Mechanical Properties and Thermal Stability of Insulation Paper Cellulose by Modification with Silane-Coupling-Agent-Grafted Nano-SiO2

Zhang

Zhou

et al. 2021

Processes

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Cellulose is an important part of transformer insulation paper. Thermal aging of cellulose occurs in long-term operation of transformers, which deteriorates the mechanical properties and thermal stability of cellulose, resulting in a decrease in the transformer life. Therefore, improvement of the mechanical properties and thermal stability of cellulose has become a research hotspot. In this study, the effects of different silane coupling agents on the mechanical properties and thermal stability of modified cellulose were studied. The simulation results showed that the mechanical parameters of cellulose are only slightly improved by KH560 (γ-glycidyl ether oxypropyl trimethoxysilane) and KH570 (γ-methylacrylloxy propyl trimethoxy silane) modified nano-SiO2, while the mechanical parameters of cellulose are greatly improved by KH550 (γ-aminopropyl triethoxy silane) and KH792 (N-(2-aminoethyl)-3-amino propyl trimethoxy silane) modified nano-SiO2. The glass-transition temperature of the composite model is 24 K higher than that of the unmodified model. The mechanism of the change of the glass-transition temperature was analyzed from the point of view of free-volume theory. The main reason for the change of the glass-transition temperature is that the free volume abruptly changes, which increases the space for movement of the cellulose chain and accelerates the whole movement of the molecular chain. Therefore, modifying cellulose with KH792-modified nano-SiO2 can significantly enhance the thermal stability of cellulose.

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“…For many years, insulation of power transformer windings has been made from cellulose (in the form of paper and pressboard) and mineral oil. Currently, synthetic aramid paper [1][2][3][4][5] has been introduced in the production of transformer parts. As a liquid component of the insulation, synthetic and natural esters are used in some transformers [6,7].…”

Section: Introductionmentioning

confidence: 99%

Precise Measurements of the Temperature Influence on the Complex Permittivity of Power Transformers Moistened Paper-Oil Insulation

2021

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The reference characteristics of complex permittivity of the transformers insulation solid component were determined for use in the precise diagnostics of the power transformers insulation state. The solid component is a composite of cellulose, insulating oil and water nanoparticles. Measurements were made in the frequency range from 10−4 Hz to 5000 Hz at temperatures from 293.15 to 333.15 K. Uncertainty of temperature measurements was less than ±0.01 K. Pressboard impregnated with insulating oil with a water content of (5.0 ± 0.2) by weight moistened in a manner maximally similar to the moistening process in power transformers was investigated. It was found that there are two stages of changes in permittivity and imaginary permittivity components, occurring for low and high frequency. As the temperature increases, the frequency dependencies of the permittivity and imaginary permittivity component shifts to the higher frequency region. This phenomenon is related to the change of relaxation time with the increase in temperature. The values of relaxation time activation energies of the permittivity ΔWτε′ ≈ (0.827 ± 0.0094) eV and the imaginary permittivity component ΔWτε″ = 0.883 eV were determined. It was found that Cole-Cole charts for the first stage are asymmetric and similar to those described by the Dawidson–Cole relaxation. For stage two, the charts are arc-shaped, corresponding to the Cole-Cole relaxation. It has been established that in the moistened pressboard impregnated with insulating oil, there is an additional polarization mechanism associated with the occurrence of water in the form of nanodrops and the tunneling of electrons between them.

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Analysis and mechanism of adsorption of naphthenic mineral oil, water, formic acid, carbon dioxide, and methane on meta-aramid insulation paper

Cited by 38 publications

References 27 publications

WITHDRAWN: Microscopic Reaction Mechanism of Formic Acid Generated During Pyrolysis of Cellulosic Insulating Paper

WITHDRAWN: Microscopic Reaction Mechanism of Formic Acid Generated During Pyrolysis of Cellulosic Insulating Paper

Molecular Simulation of Improved Mechanical Properties and Thermal Stability of Insulation Paper Cellulose by Modification with Silane-Coupling-Agent-Grafted Nano-SiO2

Precise Measurements of the Temperature Influence on the Complex Permittivity of Power Transformers Moistened Paper-Oil Insulation

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