Pressboard

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

Flow electrification in power transformers

Abstract: In this paper we examine the flow electrification process appearing in power transformer in which oil is circulating. Our interest is focussed on the physicochemical reaction occurring at the contact between the oil and the pressboard. The study is divided in two sections. In the first one, we present two different models for the process of flow electrification when oil is flowing past the pressboard. The first model assumes that the ions provided by the pressboard are always in sufficient quantity to have a physicochemical reaction in equilibrium on the wall. In the second one we suppose that the wall shearing stress contribute to the production of these ions. In both cases we compute the evolution, in terms of the distance to the entry of the pipe, of the space charge density on the wall, of the total current and of the wall current density. The experimental work is divided into three parts. In the first one, we describe the general device on which we worked and the precautions we took to be sure to measure the flow electrification only. In the second part, we describe the experiments we did on duct 1 in order to get information on themore » migration of the charges from the interface oil-pressboard towards an earthed wall. In the third and last part of that experimental section, on duct 2 we study the phenomenon of charge of the pressboard when it is electrically isolated. Then we conclude with a comparison between the experimental and theoretical results.« less

And space charge in oil-impregnated pressboard under hvdc

Abstract: I Transformer oil a d oil-impregnated pressboard are major insulati g materials in a HVDC (high voltage direct cum nt) converter transformer which provides electrical power transformation between an AC and a DC system. However, the dc component on the alve side of a HVDC converter transformer gives rise to special conditions, regarding space charge for example, for the insulating materialr i .

Static Electrification in Transformer Oil as a Measure of its Aging

Abstract: In this paper the results of aging-oriented examinations of static electrification in transformer oil flowing through pressboard, glass and bras pipes are reported. Samples of transformer oil under examination have various degrees of aging. Changes in static electrification of oil are compared to classical aging indices. As a result, strong relation is found between the electrification of oil and degree of aging.

Experimental Study on Breakdown Characteristics of Transformer Oil Influenced by Bubbles

Abstract: Bubbles will reduce the electric strength of transformer oil, and even result in the breakdown of the insulation. This paper has studied the breakdown voltages of transformer oil and oil-impregnated pressboard under alternating current (AC) and direct current (DC) voltages. In this paper, three types of electrodes were applied: cylinder-plan electrodes, sphere-plan electrodes, and cone-plan electrodes, and the breakdown voltages were measured in both no bubbles and bubbles. The sphere-sphere electrodes were used to study the breakdown voltage of the oil-impregnated pressboard. The results showed that under the influence of bubble, the breakdown voltage of the cylinder-plan electrode dropped the most, and the breakdown voltage of the cone-plan electrode dropped the least. The bubbles motion was the key factor of the breakdown. The discharge types of the oil-impregnated pressboard were different with bubbles, and under DC, the main discharge type was flashover along the oil-impregnated pressboard, while under AC, the main discharge type was breakdown through the oil-impregnated pressboard.