Topic
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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TL;DR: In this article, experimentally obtained moisture equilibrium charts for paper and pressboard insulations in mineral and natural ester transformer oils were presented. But they were only applied to paper insulations.
Abstract: This article presents experimentally obtained moisture equilibrium charts for paper and pressboard insulations in mineral and natural ester transformer oils.
21 citations
01 Nov 2006
TL;DR: In this article, the authors introduced the time-frequency representation in analyzing the acoustic emission signals emitted by partial discharge sources and used seven descriptors to extract the features from each of the spectrogram.
Abstract: The subject matter of this paper is to introduce the time-frequency representation in analyzing the acoustic emission signals emitted by partial discharge sources. Three different types of partial discharge sources used to generate the acoustic emission signals during the partial discharge (PD) occurrences are created in an experimental tank filled with transformer oil. These partial discharge sources are the plain pressboard, the floating metal in the pressboard and the bubble in the pressboard. The acoustic emission (AE) signals are detected and stored as time-frequency representation, in the form of spectrogram, by utilizing the short-time Fourier transform (STFT). Finally, seven descriptors are introduced in order to extract the features from each of the spectrogram. The obtained results also confirmed the ability of the proposed technique to discriminate between different types of PD sources.
21 citations
TL;DR: In this paper, the effect of surface roughness of the duct on streaming electrification is investigated by preparing spiral protuberances with different heights on the inner surface of each pipe.
21 citations
TL;DR: In this paper, a thermally accelerated aging experiment with flowing dry air is performed to investigate the thermal aging characteristics of oil-paper insulation in open-type transformers, and the results demonstrate that exposure to air leads to serious oxidation of oil and rapid increase of acid and dissipation factor.
Abstract: In order to investigate the thermal aging characteristics of oil-paper insulation in open-type transformers, a thermally accelerated aging experiment with flowing dry air is performed. The vegetable oil, NOMEX paper, pressboard, copper and silicon steel are sealed into the aging vessels and further aged, for 216 hours, by supply of flowing dry air at 170 °C. Several important parameters associated with the aging are observed and evaluated during the aging process. It is shown that the degree of polymerization (DP) of pressboard gradually decreases and fits well into the second-order kinematic model. Little deterioration of the NOMEX paper under 170 ° is confirmed by the tensile strength which stabilizes at a certain level after aging. In addition, the logarithm of the furfural concentration in oil is found to have a good linear relationship with DP of pressboard. Interestingly, when the aging time is about 150 hours and DP is 329, the aging process reaches an inflection point at which the DP approaches the leveling off degree of polymerization (LODP) value, the moisture content and the furfural content of oil begin to fall down while the acid number and the dissipation factor of oil increase with a faster rate. However, the viscosity of the fluid, one of the important parameters of transformer operation, does not change significantly. The obtained results demonstrate that exposure to air leads to serious oxidation of oil and rapid increase of acid and dissipation factor, and this way oxygen should be avoided for the open-type transformer filled with vegetable oil.
21 citations
TL;DR: The analysis based on the energy band theory on trap parameters of the constructed multi-core model concludes that the nanoparticle components added in pressboard altered both the depth and density of traps.
Abstract: In order to study the influence of trap parameters on dielectric characteristics of nano-modified pressboards, pressboards were made using the nano doping method with different nanoparticle components. The dielectric characteristics of the modified pressboards were measured, and the trap parameters were investigated using the thermally stimulated current (TSC) method. The test results indicated that the conductivity initially declined and then rose with the increase of nano-Al₂O₃ content, whereas it solely rose with the increase of nano-SiC content. Moreover, the conductivity exhibited nonlinear characteristics with the enhancement of electric field stress at high nanoparticle content. The relative permittivity of modified pressboard declines initially and then rises with the increase of nanoparticle content. In addition, the breakdown strength of modified pressboards exhibited a pattern of incline followed by decline with the increase of nano-Al₂O₃ content, while it always declined with the increase of nano-SiC content. The analysis based on the energy band theory on trap parameters of the constructed multi-core model concludes that the nanoparticle components added in pressboard altered both the depth and density of traps. It is therefore concluded that trap parameters have significant influence on the dielectric characteristics of nano-modified insulation pressboard.
21 citations