Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Liao, Ruijin; Lin, Yuandi; Guo, Pei; Liu, Haibin; Xia, Huanhuan

doi:10.1109/tdei.2015.7076783

Cited by 55 publications

(13 citation statements)

References 23 publications

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“…The hygroscopicity of the dried new pressboard and the pressboard coated for PTFE was also compared at here. According to the moisture equilibrium experiment that was done by our team [ 28 ], the dried pressboard samples were placed into a humidity chamber. The temperature of the humidity chamber was set to 60 °C and the relative humidity was set to 60%.…”

Section: Resultsmentioning

confidence: 99%

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

Hao

Liu

et al. 2018

Materials

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Cellulose insulation polymer is an important component of oil-paper insulation, which is widely used in power transformer. The weight of the cellulose insulation polymer materials is as high as tens of tons in the larger converter transformer. Excellent performance of oil-paper insulation is very important for ensuring the safe operation of larger converter transformer. An effective way to improve the insulation and the physicochemical property of the oil impregnated insulation pressboard/paper is currently a popular research topic. In this paper, the polytetrafluoroethylene (PTFE) functional film was coated on the cellulose insulation pressboard by radio frequency (RF) magnetron sputtering to improve its breakdown voltage and the hydrophobicity properties. X-ray photoelectron spectroscopy (XPS) results show that the nano-structure PTFE functional film was successfully fabricated on the cellulose insulation pressboard surface. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) present that the nanoscale size PTFE particles were attached to the pressboard surface and it exists in the amorphous form. Atomic force microscopy (AFM) shows that the sputtered pressboard surface is still rough. The rough PTFE functional film and the reduction of the hydrophilic hydroxyl of the surface due to the shielding effect of PTFE improve the breakdown and the hydrophobicity properties of the cellulose insulation pressboard obviously. This paper provides an innovative way to improve the performance of the cellulose insulation polymer.

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Section: Resultsmentioning

confidence: 99%

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

Hao

Liu

et al. 2018

Materials

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“…They found that the rate of space charge formation can be increased when the moisture content is lower than 7%, but is suppressed when moisture content is higher than 9% [10]. The results of experiments on accelerated thermal ageing have shown that the moisture absorption capacity of insulation paper decreases with deepening ageing degree whereas that of oil increases [11]. The ratio of moisture content in paper to that in oil decreases with decreasing polymerisation according to similar research [12].…”

Section: Introductionmentioning

confidence: 99%

Moisture‐dependent interface and bulk behaviour of space charge in DC‐stressed oil‐impregnated pressboard insulation

Zhou

Che

et al. 2020

IET Generation Trans & Dist

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In this paper, the effect of moisture on the charge behaviour in oil-impregnated pressboard is analysed based on the characteristics of the interface and the bulk. Space charge behaviour and infrared spectra are acquired from a sample with a high moisture content of 1.92% and another with low moisture content of 0.13%. The results show that a greater number of hydrogen bonds form in the high-moisture sample. The threshold fields of charge injection are 1 and 0.6 kV/mm in the low-and high-moisture samples, respectively. The dynamic charge transport in bulk is significantly accelerated by moisture. The drop in the injection barrier at the interface and the accelerated transport of charge in bulk in the high-moisture sample may be associated with the mediating effect of a water layer at the interface and the lower trap energy in bulk caused by the hydrogen bonds, respectively. The combined changes in the interface and the bulk led to the dominant position of negative charges inside the high-moisture sample, regardless of the distribution area or the charge amount.

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“…Recently, it has been realized that thermal aging affects the moisture absorption capacity of insulation paper obviously [22]- [24], i.e., the hydrophilicity of insulation paper is worse with aging. The effects of thermal aging on the moisture diffusion and the equilibrium moisture content of oil-immersed insulation paper have been reported in [5], [14], [23]. However, the characteristics of moisture diffusion in non-oil-immersed insulation paper are different from that of oil-immersed insulation paper [22].…”

Section: Introductionmentioning

confidence: 99%

Modified Expression of Moisture Diffusion Factor for Non-Oil-Immersed Insulation Paper

et al. 2019

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Studying the moisture diffusion in non-oil-immersed insulation paper is helpful to optimize the drying process and improve the drying efficiency of oil-immersed equipment. Moisture diffusion factor (MDF) is the key parameter to describe the moisture diffusion in non-oil-immersed insulation paper. Thermal aging affects the moisture absorption capacity of insulation paper obviously, thus, this paper intends to modify the empirical expression of MDF by considering the effects of thermal aging. The transient moisture contents of non-oil-immersed insulation paper with different thicknesses were measured at 40 • C and 60 • C, respectively. Then, the experimental values of MDF were extracted, and the empirical expression of MDF was modified by considering the effects of thermal aging. Finally, the modified expression of MDF was verified. The following conclusion can be obtained: 1) the equilibrium time constant of non-oilimmersed insulation paper increases with thermal aging; 2) the moisture absorption rate of non-oil-immersed insulation paper decreases with thermal aging, and; 3) the modified expression of MDF is reasonable and effective. INDEX TERMS Non-oil-immersed insulation paper, moisture diffusion factor (MDF), thermal aging, modified expression, equilibrium time constant.

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Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Cited by 55 publications

References 23 publications

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

Preparation Nano-Structure Polytetrafluoroethylene (PTFE) Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

Moisture‐dependent interface and bulk behaviour of space charge in DC‐stressed oil‐impregnated pressboard insulation

Modified Expression of Moisture Diffusion Factor for Non-Oil-Immersed Insulation Paper

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