Pressboard

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

Charge behavior in Palm Fatty Acid Ester Oil (PFAE) / Pressboard composite insulation system with charged oil flow

Abstract: Palm Fatty Acid Ester Oil (PFAE) is expected as one of the substitutes for mineral oil of transformers owing to not only the high biodegradation but also the good insulation performance. In this paper, the electric field strength and its time transition in PFAE / Pressboard composite insulation system??under charged oil flow were directly measured by using Kerr electro-optic technique. We found that the electric field was generated by space charges in PFAE and was temporally changed with charge behavior. By comparison with high charging mineral oil, we clarified that the feature of the charge behavior in PFAE was similar to that in the mineral oil, but the behavior of electric field was different due to the variation of electric properties such as permittivity, relaxing time and charge density.

Dielectric properties of oil-soaked pressboard as affected by water

Abstract: The effect of water, in amounts capable of being absorbed from a normal atmosphere, upon the dielectric properties of oil-soaked pressboard has been investigated over the temperature range from 20° to 90° C. Curves relating loss tangent, permittivity and electric breakdown strength of 0.2-in thick material with absorbed moisture and temperature have been plotted, and from these a final relationship between dielectric loss and breakdown strength has been obtained. With the data provided it is possible to make a fair estimate of the one-minute breakdown value of the material for any temperature between 20° and 90° C from a dielectric-loss measurement made at a small fraction of the breakdown voltage. Abnormalities in the loss-tangent/temperature characteristics resulting from the unequal distribution and subsequent migration of the absorbed water?effects likely to be experienced when moisture is absorbed after oil impregnation?are described. Brief reference is made to the implication of these findings in connection with the testing of the applied insulation.

Investigations on the flashover characteristics of ester oil impregnated pressboard under the influence of nanoparticles

Abstract: Surface discharge is the kind of partial discharge that occurs along the surface of the solid insulation in contact with the gas or liquid insulation It degrades the solid insulating materials and reduces the life time of the equipment In order to prevent the surface discharge, the influence of the SiO 2 nanoparticleson the partial discharge characteristics of the oil impregnated pressboard insulation is to be investigated And now a days, the natural esters are preferred as the alternative for the mineral oil To employ natural ester in the transformer, we have to investigate the properties and changes in the characteristics of the solid insulation with the natural esters In this work the flashover characteristics of pressboard samples with pure transformer oil, Rice bran oil (RBO) are also to be analyzed The experiments are carried out on the 1 mm, 3 mm thickness pressboard samples by using sphere to sphere electrode configuration under the AC voltage The result shows that nano ester fluid improves the partial discharge inception voltage (PDIV) and flashover characteristics of oil impregnated pressboards

A contribution to modelling and experimental studies of flow electrification in transformers

Abstract: As part of the research program of Electricite de France on static electrification in power transformers, on one hand an experiment has been carried out at the University of Poitiers to simulate the oil path in a transformer and on the other hand the 3D Computational Fluid Dynamics software ESTET developed at the R&D centre of Electricite de France has been extended to the modelling of the phenomena. The experimental devices has enabled us to study in a pressboard duct the wall current response to a heat transfer step produced from the outer side of the duct and to calibrate the interfacial charge transfer laws used in our simulation. So we can characterise the influence of parameters such as velocity, temperature, moisture, transient and steady states on the phenomena. This paper shows that some parameters sets lead to important dielectric stresses in the pressboard which might be the cause of the hazardous discharges observed in power transformers.

Charge behavior in flowing charged oil/pressboard composite insulation system based on electric field measurement

Abstract: Electrostatic charging may occur in oil immersed power transformers because of a flow electrification phenomenon. In this paper, we directly measured the time variation of electric field strength in the flowing charged oil using an electro-optic Kerr effect to clarify the charge behavior in the flowing oil/pressboard (PB) composite system. We discussed the measurement results from the viewpoint of charge behavior. Finally we found that the charging process is dependent on the three different electric fields, i.e. applied field, space charge field and counter field by accumulated charges, and is finalized by the balance of these fields.