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In this paper, the thermal ageing of pressboard impregnated with two kinds of insulation liquids is studied by means of frequency domain spectroscopy which involves the measurement of real and imaginary part of complex permittivity as function of frequency. The magnetic nanofluid was composed by mineral transformer oil as carrier liquid, nanoparticles of magnetite and surfactant. The thermal aging...
The advent of solid-state switches with blocking voltages in excess of 10 kV and new medium-voltage multi-level converter topologies raise issues with respect to the long-term endurance of the high voltage insulation systems exposed to the high-frequency pulse-shaped voltage stresses. In this paper we present a modular dielectric spectrometer specifically designed for aging studies on recessed polymeric...
In order to get more effective and accuracy results of condition evaluation for transformer, a dielectric response function model for frequency-domain dielectric spectroscopy (FDS) is presented in this paper based on dielectric physics in depth study. Firstly, the FDS properties of oil-immersed paper (OIP) are measured in lab. And the effect of the aging states on FDS characteristics of OIP was investigated...
Thanks to its large carrying capacity, excellent insulation property and high mechanical strength, insulated tubular bus has been widely used in power stations. Polytetrafluorethylene (PTFE) film which has been utilized as insulating material for the tubular bus is subjected to a great risk of thermal ageing that may degrade its electrical and mechanical properties. From the viewpoint of safety, it...
To study the feasibility of applying frequency domain dielectric spectroscopy method to the diagnosis of generator insulation aging state. Dielectric spectrum of motor stator bar sample was measured using frequency domain dielectric spectroscopy method under different aging degree and different temperature. Then the relationship of dielectric loss factor and complex dielectric constant with aging...
New aircraft designs increasingly contain more components made from polymer matrix composites, in both primary and secondary roles. This demands new monitoring techniques that emphasize the role played by polymer matrix degradation in the failure of these parts. The polymer matrix does not take significant load in tension but must transfer shear load. The present work investigates changes in surface...
In this paper, the model cables are studied by means of frequency domain spectroscopy (FDS) which involves the measurement of capacitance, the real permittivity and dissipation factor as a function of frequency. Firstly, XLPE cable samples were carried out accelerated thermal ageing at 135 °C. Then, frequency domain spectroscopy was investigated under laboratory condition, including different degree...
The paper deals with the problem of thermal aging of PET and Glass-fibre based composites. These electro-insulating materials are used in high voltage engineering as parts of insulation systems of large rotating machines like turbo or hydro generators. These materials were subjected to accelerated thermal aging to provide more information about the aging effects and allow us to estimate the lifetime...
There is difficult to imagine modern manufacturing of electrical devices without components containing (mainly for technological reasons) organic substances. This fact is mainly concerned to composite materials, in which the bond component is made of organic substance. Most of the electro-insulating materials used in common applications are composite materials. The possibility of the determination...
This paper presents laboratory investigation of treated coconut oil as alternative to liquid insulation of power transformers. Thirteen different virgin and treated coconut oil samples consisting three different brands were used for the investigation. Frequency Dielectric Spectroscopy measurements were conducted on the samples at room temperature and at high temperature of 65°C. The conductivity,...
Kevlar® (poly p-phenylene terephthalamide, PPTA) and PBI (poly benzimidazole) are two high-performance fibers with excellent thermal stability, a feature that makes them suitable for applications in aerospace, automotive and firefighting protective clothing. In a previous study, it was found that the tensile breaking force of yarns pulled from Kevlar/PBI fabric decreased to 50% of its original value...
The dielectric spectroscopy of an impregnated paper and a type of vegetable oil was measured in the frequency domain. In order to investigate the effect of aging on the dielectric response, accelerated thermal aging was conducted on the paper samples and oils samples, respectively. Their dielectric responses were measured at intervals throughout the aging process. Since moisture has a great influence...
“Model” extruded power cables, having a much reduced geometry but using the same extrusion techniques and materials as full-sized cables, have been examined using dielectric spectroscopy techniques to study their thermal ageing effects. Cables insulated with homo-polymer XLPE and co-polymer of XLPE with micron-sized ethylene-butyl-acrylate (EBA) islands were studied by both frequency-domain and time-domain...
In paper the influence of thermal oxidation on nano-modified transformer oil is analyzed. The probes of mineral transformer were doped with different content of C60 fullerenes from 0 mg/l to 512 mg/l. One set of probes were then aged for 64 hours in the temperature of 110°C with the presence of copper inhibitor. Oil parameters such us: resistivity, dielectric loss tangent and permittivity were measured...
In this paper, we present the electrical and physic-chemical behaviours of oil in high voltage transformers, under thermal ageing. Continuous thermal ageing tests were made on transformer oil BORAK22 during 5000 hours at two different temperatures 80degC and 120degC. Here, every 500 hours, the dielectric losses factor, the relative permittivity and the resistivity were measured. Other properties such...
This paper describes the electrical characteristics of insulating oil employed in pole transformers. In the experiment, temperature and frequency were selected as variables, and dielectric characteristic values such as the relative permittivity, the tandelta and the specific resistance of the insulating oil were measured by a WinDETA system. As a result, the dielectric characteristics of the testing...
In the development of metallized film power capacitors, accelerated aging experiments are carried out in order to predict the lifetime of a capacitor under nominal operating conditions. For metallized film capacitors the decrease of capacitance with time is very small even in accelerated aging. Consequently, these experiments require extremely precise measurement methods for the capacitance. We have...
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