The paper presents the results of the conductivity testing of Weidmann electrotechnical pressboard, with a moisture content of 5% by weight impregnated with MIDEL 7131 synthetic ester. Frequency and temperature dependencies of AC conductivity were determined on the basis of experimental results. The approximations of the frequency dependencies of conductivity were made with a step of 100 points per decade. The frequency dependencies of approximated conductivity waveforms at all measuring temperatures were shifted by means of the energy of activating the conductivity to a temperature of 293 K (reference temperature in electrical engineering). Arrhenius graphs were also drawn up, from which the energy activation of relaxation time and the value of the R2 determination coefficient for the selected conductivities were determined. Approximations of Arrhenius's graphs indicate high accuracy, as evidenced by the values of the coefficient of determination close to one. It has been found that the value of the activation energy of relaxation time varies within a very narrow range, which indicates that in the entire frequency range conduction is carried out according to the same mechanism - hopping conductivity.
In the paper presents compares the DC conductivity of the synthetic ester MIDEL 7131 and electrical pressboard Weidman companies impregnated with the same synthetic ester with a different moisture contents. Thee study of thee conductivity for both materials were made for the measuring temperature in the range of 20°C to 80°C and measuring voltages 10 V. In the Arrhenius plots for both materials were been performed linear approximations off experimental results. On the basis of Arrhenius plots for the ester and the sample for the pressboard, the value of the activation energy of the DC conductivity and the determination coefficient R2 was determined. The value of the determination coefficient close to one indicates the high accuracy of conductivity measurements. Comparing the activation energy value of the DC conductivity for synthetic ester and pressboard impregnated with the same ester, it can be concluded that the conduction in pressboard is not caused by the presence of ester in the pressboard.
This paper presents the results of the AC conductivity of electrical pressboard production company Weidman with a water content from 0,6% to 7% by weight, impregnated with MIDEL 7131 synthetic ester. Frequency and temperature dependencies of the AC conductivity were determined. The Arrhenius plots were developed for the whole range of measurement frequencies, from which the activation energies of the AC conductivity were determined. It was found that changes in AC conductivity can be described by means of two activation energies. Each of these activation energies decreases with the increase of the measurement frequency. This may mean, in our view, that these differences are due to changes the environment occurring water nanoparticles. Some of the nanoparticles be are located in the environment cellulose material, while the other part - in the environment the MIDEL 7131 ester.
In the paper presents the influence of electric field intensity on the activation energy of the DC conductivity the electrical pressboard impregnated with synthetic ester in the measuring temperature range of from 20°C to 80°C and the electric field intensity range from 10 kV/m to 1000 kV/m. With Arrhenius plots for pressboard sample about the moisture content 6% wt. and for all of the electric field intensity was determined coefficients of determination R2, which are very close to one. This proves the high accuracy of approximation linear experimental results on the Arrhenius plots and highly accurate measurements of conductivity. It was found that for pressboard sample about the moisture content of 6% wt. impregnated with synthetic ester and the electric field intensity does not affect (in the margin of error) on the activation energy value of the DC conductivity, which is (0.59075±0.01202) eV.
The paper presents investigated the dependencies of DC conductivity electrical pressboard impregnated insolating oil of moisture content and electric field strength. The studies were conducted for measuring temperature in the range of 20 °C to 80 °C and the electric field intensity in the range of 10 kV/m to 1000 kV/m. With approximate waveforms in double logarithmic coordinates conductivity depending on the intensity of the electric field exponential function determined coefficients of determination R2. The value of this ratio is close to unity, which provides high accuracy measurements of conductivity and the exact stability and temperature measurements. It was found that changes in the electric field intensity will decrease the activation energy of conductivity of about 0.01 eV, thus increasing the DC conductivity of about 1.5 times.
In the paper presents the influence of moisture content and electric field intensity on the activation energy of the conductivity DC electrical pressboard impregnated with insulating oil in the measuring temperature range of from 20 °C to 80 °C and the electric field intensity range from 10 kV/m to 1000 kV/m. With Arrhenius plots for each of the moisture content and for all seven of the electric field intensity was determined coefficients of determination R2, which are very close to one. This proves the high accuracy of approximation linear experimental results on the Arrhenius plots and highly accurate measurements of conductivity, accurate stabilization and measurements temperature. It was found that the moisture content of range from 1.15% to 6.5% wt. and the electric field intensity does not affect (in the margin of error) on the activation energy value of the DC conductivity, which is (1.0338 ± 0.02000) eV.
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