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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 Article
TL;DR: In this article, a simulating device of the transformer oil-impregnated pressboard insulations was designed, and the infrared spectrum was used to prove that the oil-paper insulation has been aged.
Abstract: Transformer oil-paper insulation is a typical composite dielectricAnd its dielectric properties will change significantly during aging processTo investigate the characteristic parameters of dielectric response phenomena of transformer oil-paper insulation aging,a simulating device of the transformer oil-impregnated pressboard insulations was designedDepolarization current of the samples during accelerated electrical aging process at the same temperature was measuredAnd the infrared spectrum was used to prove that the oil-paper insulation has been agedBased on Debye model,the resistance and capacitance of the maximum and minimum time constants branch are calculatedThe results reveal that,the transformer condition can be obtained from Debye modelIn Debye model the parameters Rmax and Cmax are related to aging condition of oil,and Rmin and Cmin are related to aging condition of paper

2 citations

Journal ArticleDOI
E. Henry1
TL;DR: In this article, the authors present a series of tests which established the need for special precautions and procedures in the thermal evaluation of sealed insulation systems containing appreciable quantities of cellulose, and a modification of the test procedure is suggested as a practical solution.
Abstract: "The Proposed IEEE Test Procedure for the Evaluation of Insulation Systems for Electronic Power Transformers" is based on the principle of accelerated thermal aging. In order to accelerate the thermal aging sufficiently to accomplish the evaluation in a reasonable time, the test temperature is often higher than the chemical stability temperature of some of the components of the system. This instability may render the system unsuitable for the use of this test procedure unless a way can be found to reduce the effect to a usable level. One of the more commonly used materials of this type is cellulose. With suitable resins and adequate embedment techniques, which in - cludes thorough impregnation, cellulose (papers, pressboard, etc) has been demonstrated to give good service at temperatures well above the previously accepted maximum temperature of 105°C. In this situation, one or more of the test temperatures will be sufficient to cause limited chemical decomposition of the cellulose. This does not necessarily render the material ineffective as a dielectric and incapable of evaluation by comparison, but a by-product of this decomposition is water which is chemically liberated. The water thus produced must be eliminated as it forms, otherwise failures will result which are not truly due to thermal aging as encountered at normal operating temperatures. This paper describes a series of tests which established the need for special precautions and procedures in the thermal evaluation of sealed insulation systems containing appreciable quantities of cellulose. A modification of the test procedure is suggested as a practical solution. This modification is considered to have a minor effect on the test results and permits comparison evaluations which otherwise are not possible.

2 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a parallel electrodes system with a compound structure of pressboard barrier and oil gap to evaluate an appropriate level of ac test voltage for 1000-kV transformers, which is necessary to make an accurate estimation of ac V-t characteristics.
Abstract: To evaluate an appropriate level of ac test voltage for 1000-kV transformers, it is necessary to make an accurate estimation of ac V-t characteristics. For the level of impulse test voltage, V-N characteristics are important to evaluate effects of impulse stress repetition. Since both of the characteristics are dependent on insulation structures and manufacturing processes of transformers, it is important to make accurate simulations on transformer insulation for reliable insulation data. To obtain some of the basic data for 1000-kV transformer test levels, long-time ac V-t tests and impulse V-N tests of up to 1000 times voltage application were carried out on an insulation model simulating fundamental structure of shell-form transformers. The model is composed of a parallel electrodes system with a compound structure of pressboard barrier and oil gap. The tests showed the following characteristics: ac V-t characteristics of up to several ten days could be described by two lines, each representing short-time and long-time characteristics. V-N characteristics of lightning and switching impulse were expressed by relatively flat lines, which showed a decrease in breakdown voltage by less than 10 percent after 1000 times impulse application.

2 citations

Proceedings ArticleDOI
01 Aug 2014
TL;DR: In this article, the authors measured the conductivities of different densities of HVDC pressboard and oil and found that electrical conductivity increases with an increase in the density of the pressboard fibers, and that a larger number of fibers per volume causes a higher conductivity than a smaller number.
Abstract: In HVDC (high voltage direct current) insulation systems, the conductivities of the insulating materials pressboard and oil are the relevant material parameters that determine the field distribution. The pressboard conductivity depends on various parameters, which can be categorized in service-parameters (e. g. time of energization, water content, impregnating fluid) and parameters during pressboard manufacturing (e. g pressboard density). Measurements of pressboard with different densities are performed by using a step response measurement in time domain. At first, the materials are impregnated with gas. It is found that electrical conductivity increases with an increase in pressboard density. The reason is that gas has a much lower conductivity than pressboard and therefore, a larger number of fibers per volume causes a higher conductivity than a smaller fiber number. Afterwards, pressboards with different densities are impregnated under vacuum with two types of mineral oil (a low-conductive oil and a high-conductive oil). For the low-conductive oil, the influence of the pressboard density is little, because conductivities and electric field stresses are similar, both for pressboard fibers and for oil. By impregnation with the high-conductive oil, the pressboard pores have a much higher conductivity than the surrounding pressboard fibers and thus the conductivity of the oil-impregnated pressboard depends on pressboard density again. In this case, a low-density pressboard has therefore a higher conductivity than a high-density pressboard corresponding to the different fiber volume and oil volume. The pressboard density can be modified during manufacturing and the designer can choose which pressboard density and which oil with a certain oil-conductivity should be used in a certain HVDC apparatus leading to desired conductivity values for the oil-pressboard system.

2 citations

Patent
30 Nov 2016
TL;DR: In this article, a high efficiency hot press for connecting calculator winding displacement is disclosed for there is the line in the current hot press of solution and is arranging the problem that welding quality is poor that leads to line row and display screen with the first interconnect of hot pressing.
Abstract: The utility model belongs to the technical field of the calculator is manufactured, a a high efficiency hot press for connecting calculator winding displacement is disclosed for there is the line in the current hot press of solution and is arranging the problem that welding quality is poor that leads to line row and display screen with the first interconnect of hot pressing. The utility model discloses a frame is provided with the moving workpiece platform that is used for placing the work piece in, be provided with telescopic cylinder in the frame, and the telescopic cylinder lower extreme is connected with the mounting panel, and the lower extreme on the mounting panel is connected with the hot pressing head, and the hot pressing head has set the heating rod including hot pressboard, hot pressboard, heating rod and outside power intercommunication, the lower terminal surface of hot pressboard is provided with the annular groove, be provided with the compressed air pipe way in the annular groove, compressed air pipe says and communicates with outside compressed air source, the intercommunication has a plurality of air nozzles on the compressed air pipe way, and what each air nozzle inclined installs in the annular groove, and each air nozzle sets up towards the slope of the center directions of hot pressboard.

2 citations


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