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Streaming electrification of insulating liquid mixtures

100%

Zdanowski M. , Maleska M.

Archives of Electrical Engineering

2019

tom Vol. 68, nr 2

387--397

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.

Applicability of the FRA method for characterization of insulation of power transformers

100%

Serdyuk Y. V. , Podoltsev A. D. , Gubański S. M.

2004

tom Vol. 40, nr 15

82-85

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.

Streaming electrification of insulating liquid mixtures

100%

Zdanowski M. , Maleska M. , Zdanowski M. , Maleska M.

nr 2

Measurements of physicochemical and electrical properties of insulating liquids

100%

Zdanowski M.

tom No. 98

181--193

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.

Condition assessment of transformer insulation using dielectric frequency response analysis by artificial bee colony algorithm

88%

Bigdeli M. , Aghajanloo J.

2016

tom Vol. 65, nr 1

45--57

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.

Wpływ impregnacji olejem wstępnie wysuszonej izolacji transformatora na czas i skuteczność suszenia końcowego

75%

Krause C. , Wick K. , Nachtigall U. , Marciniak W. R. , Malewski R.

tom R. 81, nr 3

15-20

Przedstawiono wyniki badań doświadczalnych na dyfuzję wilgoci w suchej i zaimpregnowanej olejem celulozie.

The paper presents results of experimental research regarding diffusion of humidity in cellulose, dry and impregnated with oil.

Spektrofotometria w bliskiej podczerwieni jako metoda diagnostyczna zawartości wody w izolacji papierowo-olejowej

63%

Bródka B. , Mościcka-Grzesiak H.

Przegląd Elektrotechniczny

2008

tom R. 84, nr 10

136-140

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).

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).