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Pressboard

About: Pressboard is a research topic. Over the lifetime, 1123 publications have been published within this topic receiving 9089 citations.


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Journal ArticleDOI
Jiefeng Liu1, Xianhao Fan1, Yiyi Zhang1, Hanbo Zheng1, Chaohai Zhang1 
TL;DR: In this paper, a fitting fingerprint database (FFD) technique was used for condition prediction of aging and moisture content of cellulose insulation in transformers, which can be used as a powerful tool for predicting the condition of transformers.
Abstract: The results of frequency domain spectroscopy (FDS) will be affected by moisture which often leads to an unreliable condition prediction of oil-immersed cellulose insulation in transformers. In view of this, a solution is proposed in this study by adopting a fitting fingerprint database (FFD) technique, which can be utilized for condition prediction of aging and moisture content. In the current work, the relevant fingerprints that could characterize the insulation aging condition and moisture content are extracted from the FDS curves and the DC conductivity of the transformer oil. The FFD is then constructed by fitting fingerprints. The accuracy of the reported FFD technique is verified from tests on oil-immersed pressboard prepared in the lab and a transformer from the field. In this respect, the present contribution highlights FFD might be used as a powerful tool for condition prediction of oil-immersed cellulose insulation in transformers.

32 citations

Proceedings ArticleDOI
05 Jul 2004
TL;DR: In this paper, the measurement results of polarization and depolarization currents (PDC) on oil-pressboard samples were presented and the measurements were carried out under different condition and the results compared.
Abstract: In this paper the measuring results of polarization and depolarization currents (PDC) on oil-pressboard samples will be presented. The measurements were carried out under different condition and the results compared. For repeatability purpose the samples were provided at specific condition. Moisture of samples was measured by Karl Fischer titration method. To obtain a quantitative parameter from PDC for the evaluation of the moisture content of the solid insulation, the depolarization current curves are decomposed to basic exponential functions. Obtained results show a relation between magnitude of mid decade (100 s - 1000 s) approximate exponential function and moisture content of solid insulation.

32 citations

Journal ArticleDOI
TL;DR: In this paper, a nine-element dynamic stiffness and damping representation for transformer pressboard is described based on these measured results and the physical nature of oil-immersed pressboard.
Abstract: Data on the dynamic stress-strain characteristics of transformer pressboard during transient loading like that occurring in power transformer coils during short circuits are presented for wide ranges of preload stress, peak stress, and temperature. A nine-element dynamic stiffness and damping representation for pressboard is described which is based on these measured results and the physical nature of oil-immersed pressboard. It is shown that the representation accurately duplicates the highly nonlinear dynamic stress-strain characteristics of pressboard over wide ranges of conditions and provides a means for reliably calculating the large transient forces and displacements that can cause failure of transformer coils during short circuits.

31 citations

Proceedings ArticleDOI
08 Jul 2007
TL;DR: In this article, the authors showed that the combination of cellulosic paper and pressboard and mineral oil is still the most efficient and economic way to insulate power transformers.
Abstract: The combination of cellulosic paper and pressboard and mineral oil is still the most efficient and economic way to insulate power transformers. One of the drawbacks of cellulose is its highly hygroscopic nature. The hygroscopicity is caused by the cellulose molecule itself, whereas the rate of water absorption is influenced by many parameters. Thin, low-density papers exposed to a warm and humid climate show a much higher rate of water absorption than thick high-density pressboards exposed to a cold and dry environment. Impregnating cellulosic insulation materials with oil slows down the rate of water absorption, yet the moisture content at equilibrium is the same as for non-oiled materials. Tests for the determination of the sorption isotherms showed that data published in 1960 could be matched very well. But the tests also showed that the raw materials have a significant impact on the sorption curves.

30 citations

Journal ArticleDOI
TL;DR: In this paper, the reliability of oil-pressboard insulation system used in high voltage direct current (HVDC) convertor transformers can be affected by the presence of space charge.
Abstract: The reliability of oil-pressboard insulation system used in high voltage direct current (HVDC) convertor transformers can be affected by the presence of space charge. In this paper, the space charge behaviors in a 0.5 mm thick oil film combined with a 1mm thick impregnated pressboard have been investigated by the pulsed electroacoustic (PEA) technique under 12 kV/mm and 20 kV/mm at room temperature for both short term and long time tests. Two types of oil with different aging status were used for comparison. The results show that a charge peak is quickly formed at the interface between oil and pressboard with the same polarity as the electrode at the oil film side. However, the dynamics of the interfacial charges are very different for fresh oil and aged oil samples. The maximum electric field occurs in the middle of the pressboard, which is significantly enhanced in the aged oil samples. Compared with the Maxwell-Wagner (MW) polarization, more space charges are formed in the insulation system. It needs much longer time to reach steady state, depending on the status of the oil. The interfacial and bulk effects result in a significant electric field enhancement in the middle of pressboard, especially in aged oil samples.

30 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202266
202140
202059
201966
201882