Pressboard

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

Electrical–thermal aging characteristic research of polymer materials by infrared spectroscopy,

Abstract: Traditional insulation paper (pressboard) used in power transformers has weaknesses such as poor thermostability, low breakdown voltage, and high permittivity, which leads to its degradation or even breakdown over time. For this paper, in order to judge if they could be used as new insulation materials for transformers, polycarbonate and polyester films were selected for electrical–thermal aging tests in temperatures of 110°C and 130°C in comparison with the insulation paper. Several infrared spectral tests were carried out on the three materials under a scanning electron microscope to analyze their electrical–thermal aging characteristics, mechanical behaviors, and degrees of polymerization. The functional group whose absorption peak intensity decreased drastically with aging was referred to as the characteristic functional group, and its peak absorption intensity was used to reflect its aging level. This paper found that the polycarbonate had a better aging resistance than both the insulation paper and PET. Copyright © 2014 John Wiley & Sons, Ltd.

Electrostatic Hazard in High-Power Transformers: Results of Ten Years of Experience With ${P}^{\prime}$ Capacitive Sensor

Abstract: In a high-power transformer, oil flowing on pressboard surface is suspected to be responsible of electrostatic hazards and failures. Different methods of risk assessment have been proposed to understand and prevent it: ministatic tester in the Westinghouse protocol, ministatic tester in the spinning disk measurement, monitoring of tangent delta, dissolved gas measurement, etc. At P' Institute of Poitiers, an original sensor was developed and used for quantification of the electric charge generated and of accumulated charge for an oil flow onto the surface of a transformer pressboard insulated from ground. Operational for ten years, this bench has been used to study over a hundred couples of oil/pressboard, pairs of new oil and pressboard, pairs of aged oil and pressboard, pairs of suspicious oil and pressboards, etc. This paper presents a comparative analysis of these ten years of experience. This analysis provides, among other results, a critical electrostatic hazard assessment in transformers and an attempt of discrimination tentative of a suspected transformer.

Enhancing flashover strength along oil/pressboard interface using nanofluids

Abstract: One of the weakest paths for electrical discharge in power transformers is oil/pressboard interface. So, in this study it is aimed to enhance the flashover resistance of such interface through using the concept of nanofluids. Nanofluid impregnated pressboard were prepared using two different types of nanoparticles. These types are Alumina (Al2O3) and Titania (TiO2) which have different values of zeta (ζ) potential that had been experimentally measured. Flashover tests are carried out at pressboard interface with nanofluids and mineral oil. Three conditions of oil flow are considered, static and turbulent dynamic flow with two different circulating velocities. Flashover strength of nanofluid impregnated pressboard was tested for different weight fractions of nanoparticles and was compared to that of the base mineral oil. In each test, the value and polarity of applied AC voltage at the instant of flashover was recorded. Weibull distribution was used for analyzing flashover strength data. The polarity at which flashover occurred was positive in all tests. Physical mechanisms have been discussed considering electron trapping and double layer model of nanoparticles.

Apparatus and method for making pressboard from poly-coated paper using relative movement of facing webs

Abstract: Apparatus and process for fabricating pressboard from shredded paper coated with a thermoplastic material and a pair of facing webs includes placing the shredded poly-coated paper (18) between the two travelling webs (12,14) to form a composite, the composite then being passed in a manner to differentially shift the travelling webs relative to each other for enhanced bonding of the shreds to themselves and to the facing webs, by pressing them through a series of heated rollers (46-52) defining a serpentine path while heating the thermoplastic material above its softening point, and pressing the composite together.

The microscopic morphology of insulation pressboard: an image processing perspective

Abstract: To analyze the changes in microscopic morphology of the pressboard under surface partial discharge conditions, some methods such as enhancement, denoising, segmentation, optimization, edge detection, expansion, and corrosion were used to process scanning electron microscope images of the pressboard, so as to extract the fiber width, hole size, and surface roughness. Experiments show that after different thermal aging times, the trends to change in the microscopic morphology of insulation pressboard under partial discharge are different; the microscopic morphology of the pressboard is changed by the breaking of the chemical bonds in the internal structure of the fiber. At a degree of polymerization of 500, the insulation life is only about half of its original value: at this time, the corresponding fiber width is 91.1% of the unaged pressboard fiber width, and the corresponding roughness is 0.162. At a degree of polymerization of 250, the insulation pressboard is nearing the end of its life: at this time, the corresponding fiber width is 79.2% of that of the unaged pressboard, and the corresponding roughness is 0.225.