Pressboard

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

Internal temperature pressure measurement device of artificial board and thermal pressure board flan

Abstract: An internal temperature, pressure measuring equipment for man-made hot pressboard, belongs to timber industrial technical field. At present, two kinds of equipment are used to measure the internal temperature, pressure of somewhere in the hot pressboard. The utility model comprises a pressure sensor (6), a temperature sensor (4), a connecting link (3), a pressure-directing capillary (2), a signal-processing and data-collecting box (7), and a microcomputer (8), wherein the back end of the connecting link (3) is connected with the pressure sensor (6) while the front end of the connecting link (3) is connected with the pressure-directing capillary (2), and the pressure sensor (6), the temperature sensor (4) are respectively connected with the signal-processing and data-collecting box (7) which is connected with the microcomputer (8) to collect the temperature, pressure information. The utility model assembles the pressure sensor and the temperature sensor together to realize the accurate simultaneous measurement of the temperature, pressure of somewhere in the board plank, and the utility model is convenient to operate, maintain and repair.

Effects of Dibenzyl Disulfide on Pressboard

Abstract: Pressboard is a hard and rigid board having high with excellent electrical and mechanical properties, is specifically produced for the high voltage and extra high voltage Transformer Industry. Components and insulating sheets of pressboard are used in oil-cooled power transformers and distribution transformers primarily due to their high purity, mechanical strength and optimal oil-impregnability. The components formed of pressboard, such as angle rings, snout segments and end leads, enable an exact adaptation to the electric field conditions prevailing in the transformer. since the 1960's the main insulation of power transformers has been built up as layered oil/board-insulation. The latter represents a hybrid system, consisting of oil filled gaps subdivided by pressboard barriers. Different new mineral oils have differing values of conductivity (about a factor of 10), whereas the conductivity of solid insulation hardly changes. In this paper, observations are made for break down strength of press board insulation of power transformers under different applied voltages.

Partial discharge oscillograms and pulse distribution in transformer oil-pressboard insulation

Abstract: Partial discharges cause degradation of insulation systems and a study of their behaviour can give useful information regarding the state of the insulation system. Partial discharge tests are therefore, carried out as quality checks for the insulation system. A model transformer insulation system consisting of pressboard and transformer oil with uniform field electrode arrangement was tested for its behaviour under partial discharges. The system was allowed to age until failure of the sample occurred in the form of a puncture. Records of partial discharge distributions were acquired along with oscillograms. Oscillograms help in the traceability of the measurement when compared with distributions. A comparative study of the effect of amplifier setting and the pulse repetition rate on the partial discharge distributions and the oscillograms acquired during ageing of the sample has been presented. It is shown that by appropriate threshold on the distribution, distinctive features can be extracted.

Parametric study by electrical analogy : application to flow electrification in power transformer

Abstract: A charge zone named electrical double layer exists at a solid-liquid interface. The liquid flow induces a phenomenon called Flow Electrification: it generates a streaming current (caused by charge convection) and a potential rise in the solid (if this one is insulated from the ground). These potentials may reach values high enough to produce electrical discharges and provoke accidents. Although this phenomenon has been identified a long time ago, its physical description remains unknown (production and displacement of charges, equilibrium, etc.). In this paper we present the results of a parametric study made with an electrical analogy model, which represents the processes taking place when transformer oil flows through a rectangular pressboard duct. The duct's geometry and the materials were selected to compare some of the numerical results to experimental ones. The facility used to obtain these experimental results was developed some years ago as a part of the research program of Electricite de France and the University of Poitiers.

Electrical characteristic comparison of mineral oil and natural ester for transformer applications

Abstract: In this paper, the electrical characteristics of mineral oil compared with natural ester were studies. AC breakdown strength, dielectric dissipation factor, and permittivity of both liquids were investigated. Both new liquids were heated in the oven at 60°C with 200 mbar for 6 hours before starting all investigation, the water contents of mineral oil and natural ester were 18 and 178 ppm respectively. Moreover, the mineral oil and natural ester were used to impregnate the pressboards which were 1.6 mm and 3.2 mm thick respectively. These pressboards were impregnated for 3–12 hours. Then, the AC breakdown voltage of the impregnated pressboards was examined. AC breakdown strength of the liquid insulations was tested according to IEC 60156. The dielectric dissipation factor and permittivity of the liquids with the temperature of from 35°C–100°C were investigated as well. Moreover, the breakdown voltage strength of the impregnated pressboards was examined with the electrodes in accordance with IEC 60243-1. From the test results, mineral oil sample provided lower AC breakdown voltage than natural ester sample. However, mineral oil generated approximately 77 times lower dielectric dissipation factor compared with the natural ester. Besides, natural ester impregnated pressboards had a bit higher breakdown strength than mineral oil impregnated pressboards. Furthermore, breakdown strength of the liquid impregnated pressboard depended clearly the function of time and the pressboard thickness.