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1
Content available Measurements of physicochemical and electrical properties of insulating liquids
Zdanowski Maciej
Poznan University of Technology Academic Journals. Electrical Engineering
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2019
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No. 98
181--193
EN
This paper provides a comparative analysis of key physicochemical and electrostatic parameters of Trafo En oil and Midel 7131® synthetic ester, changing in temperature and accelerated thermal ageing. The parameters tested included the density, kinematic viscosity, conductivity and relative electric permittivity. In addition to that, Electrostatic Charging Tendency (ECT) tests of those fluids were performed in a flow system using cellulose and aramid paper pipes. The effect of liquid flow velocity combined with temperature variations and accelerated ageing time on the streaming electrification current generated was determined. The relationship between the fluid electrification degree and measuring pipe material was also investigated.
2
Content available Streaming electrification of insulating liquid mixtures
Zdanowski Maciej, Maleska Marcin
Archives of Electrical Engineering
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2019
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Vol. 68, nr 2
387--397
EN
Extensive efforts have been made for many years by the power generating industry to replace conventional solid and liquid insulation with synthetic materials. Those measures are aimed at increasing the load capacity, improved fire safety and extending transformer life during exploitation. Modern insulating materials include aramid fibre-based paper and insulating fluids made of synthetic and natural esters. The paper presents research results of the electrostatic charging tendency (ECT) of mixtures of fresh and aged mineral oil Trafo En with synthetic ester Midel 7131 and natural ester Midel 1204. The measurements were taken in a flow-through system using the pipes made of metal, cellulose and aramid paper. The influence of the liquid flow velocity, the type of material of the measuring pipe and the mixture content on the level of the streaming electrification current generation was determined.
3
Content available Condition assessment of transformer insulation using dielectric frequency response analysis by artificial bee colony algorithm
Bigdeli M., Aghajanloo J.
Archives of Electrical Engineering
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2016
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Vol. 65, nr 1
45--57
EN
Transformers are one of the most important components of the power system. It is important to maintain and assess the condition. Transformer lifetime depends on the life of its insulation and insulation life is also strongly influenced by moisture in the insulation. Due to importance of this issue, in this paper a new method is introduced for determining the moisture content of the transformer insulation system using dielectric response analysis in the frequency domain based on artificial bee colony algorithm. First, the master curve of dielectric response is modeled. Then, using proposed method the master curve and the measured dielectric response curves are compared. By analyzing the results of the comparison, the moisture content of paper insulation, electrical conductivity of the insulating oil and dielectric model dimensions are determined. Finally, the proposed method is applied to several practical samples to demonstrate its capabilities compared with the well-known conventional method.
4
Content available remote Identification of operating conditions of transformer working in power electronics circuit
Glinka T., Olech W., Kulesz B., Sikora A.
Przegląd Elektrotechniczny
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2014
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R. 90, nr 1
190--192
PL
Transformatory z izolacją suchą są stosowane od ponad 30 lat w energoelektronicznych układach napędowych i pracują poprawnie. Transformatory olejowe z izolacją papierową są stosowane także w układach energoelektronicznych: w małej energetyce, a także w elektrotermii do zasilania pieców indukcyjnych. Izolacja papierowa w tych transformatorach ulega szybkiej degradacji. Powodem jest komutacja zaworów energoelektronicznych. Impulsy prądów komutacyjnych generują napięcia, między uzwojeniem i kadzią transformatora, o pochodnej ponad 100V/μs.
EN
Dry-type transformers have been successfully used for more than 30 years in power electronics ac and dc drives and they operate correctly. Oil-filled transformers with paper insulation are also used in power electronics circuits, for instance in small power plants, in electric heating (for furnace supply). The paper insulation in these transformers degrades quickly. This is due to commutation of power electronics elements, which is accompanied by overvoltages between transformer winding and tank, with voltage change rate greater than 100V/μs.
5
Wpływ impregnacji olejem wstępnie wysuszonej izolacji transformatora na czas i skuteczność suszenia końcowego
Krause C., Wick K., Nachtigall U., Marciniak W. R., Malewski R.
Wiadomości Elektrotechniczne
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2013
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R. 81, nr 3
15-20
PL
Przedstawiono wyniki badań doświadczalnych na dyfuzję wilgoci w suchej i zaimpregnowanej olejem celulozie.
EN
The paper presents results of experimental research regarding diffusion of humidity in cellulose, dry and impregnated with oil.
6
Content available Przyczyny oraz najważniejsze skutki zawilgocenia izolacji transformatorów
Graczkowski A., Gielniak J., Walczak K., Bródka B.
Pomiary Automatyka Kontrola
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2009
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R. 55, nr 1
41-43
PL
W artykule przedstawiono najważniejsze przyczyny zawilgocenia izolacji. Omówiono rozkład chemiczny celulozy prowadzący do wydzielania wody. Przedstawiono wpływ zawilgocenia izolacji celulozowej na dynamikę starzenia termicznego, którego miarą jest stopień polimeryzacji. Omówiono wpływ zawilgocenia izolacji na zjawiska ważne z punktu widzenia eksploatacji transformatorów.
EN
A problem of power transformer insulation moistening is very important. High level of moisture in paper insulation is responsible for decreasing mechanical and electrical strength, and also it can generate very dangerous phenomena like e.g. bubble effect. The authors collected all important information that allows understanding a mechanism of water generation in paper-oil insulation. The analysis of the processes on the material structure level allows also explaining how the process of cellulose aging results in degradation of power transformer functionality. The first part of the paper presents the process of cellulose chemical decomposition, especially as a result of oxidation. Figure 4 shows various reactions of cellulose oxidation. This process is the main source of water particle creation and leads to decreasing the cellulose chain length (DP - Degree of Polymerization) and, in consequence, the mechanical strength of paper. An important factor which accelerates the decomposition process is temperature. High temperature is also responsible for gas formation in oil-paper insulation. In the second part of the paper the influence of insulation moistening on processes important for transformer operation is described. Among others, there are mentioned the most crucial effects such as: bubble formation, increase in dielectric losses and partial discharges activity, decrease in mechanical properties and deterioration of oil quality. Taking into consideration the all described aspects, the authors conclude that the moistening level of power transformer insulation should be monitored as a very important factor determining its exploitation.
7
Content available remote Spektrofotometria w bliskiej podczerwieni jako metoda diagnostyczna zawartości wody w izolacji papierowo-olejowej
Bródka B., Mościcka-Grzesiak H.
Przegląd Elektrotechniczny
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2008
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R. 84, nr 10
136-140
PL
Spektrofotometria w bliskiej podczerwieni może być wykorzystana do wyznaczania zawilgocenia wyrobów celulozowych impregnowanych olejem. W artykule przedstawiono widma absorbancji wody, oleju, papieru nieimpregnowanego oraz impregnowanego. Wytypowano pasmo diagnostyczne wody (1920 nm).
EN
Near infrared spectroscopy may be used as a tool for estimation of moisture content in oil-impregnated cellulose. This paper presents absorbance spectra of water, oil, unimpregnated and impregnated paper. Special diagnostic area in spectrum for water detection was determined (1920 nm).
8
Content available Zależność między deskryptorem Arms a ładunkiem pozornym dla wybranych form wyładowań niezupełnych
Kucharska B.
Diagnostyka
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2008
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nr 2(46)
125-128
PL
W artykule scharakteryzowano pojęcie deskryptora emisji akustycznej Arms oraz ładunku pozornego wyładowań niezupełnych. Przedstawiono układ do generacji wybranych form wyładowań niezupełnych oraz pomiaru ładunku pozornego i emisji akustycznej. Pokazano przykładowe wyniki pomiarów. Oceniono przydatność mierzonego deskryptora do opisu zjawiska wyładowań niezupełnych.
EN
In the article the acoustic emission descriptor Arms and the apparent charge of partial discharge were characterized. The system generating the chosen forms of partial discharges and measuring apparent charge and acoustic emission was presented. The results of measurement were illustrated. Usefulness of the descriptor for the analysis of partial discharges was evaluated
9
Infrared and near infrared spectroscopy as measurement methods of moisture content in oil-paper insulation.
Bródka B.
Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje
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2007
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Vol. 46, nr 19
104-108
EN
This paper discusses two methods of moisture content estimation jn oil-paper insulation. The advantages and disadvantages are presented, as well as the example research results for each method. The samples of oil-impregnated paper insulation of varied moisture content were the investigated objects. The methods discussed in the paper were verified by means of Karl Fischer Titration method and moisture equilibrium between air and paper curves.
10
Applicability of the FRA method for characterization of insulation of power transformers
Serdyuk Y. V., Podoltsev A. D., Gubański S. M.
Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje
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2004
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Vol. 40, nr 15
82-85
EN
Frequency response analysis (FRA) is usually used for diagnostics of mechanical deformations and displacements of transformer windings caused by electromagnetic forces during short circuits. In general, a high frequency response of a transformer is affected by the properties of all transformer components, and, thus, the FRA carries information about the state of the whole transformer including its main electrical insulation. From this point of view, the FRA might be considered as an alternative to the existing methods for assessment of the insulation. In the present paper, the applicability of the FRA is analysed using a high frequency model of a transformer, which takes into account the complex structure of the oil-paper insulation and frequency dependencies of the dielectric permittivities of the insulation components as well as winding resistances. A sensitivity analysis of the computed frequency responses to the variations in geometrical structure and complex permittivities of the components is presented.
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