Values Of Dielectric Dissipation Factor Research Articles

DIELECTRIC DISSIPATION FACTOR IN THREE-CORE POWER CABLES

This article is devoted to the analysis of components of variance of the results of measurements of dielectric dissipation factor of insulation layers between the conductive elements of the construction of three core power cables with paper impregnated insulation in a common sheath. The analysis of components of variance was carried out by applying presented relations for the direct calculation of the dielectric dissipation factor. The accuracy of presented relations for the calculation of variance components was verified. The results of carried out analysis have shown that the variance of the dielectric dissipation factor measurements is mostly determined by the variances of multiplication of measurements of aggregate values of dielectric dissipation factor and coefficients depending on the partial capacitances of tested three core cable.

Study of the Impact of Initial Moisture Content in Oil Impregnated Insulation Paper on Thermal Aging Rate of Condenser Bushing

This paper studied the impact of moisture on the correlated characteristics of the condenser bushings oil-paper insulation system. The oil-impregnated paper samples underwent accelerated thermal aging at 130 °C after preparation at different initial moisture contents (1%, 3%, 5% and 7%). All the samples were extracted periodically for the measurement of the moisture content, the degree of polymerization (DP) and frequency domain dielectric spectroscopy (FDS). Next, the measurement results of samples were compared to the related research results of transformer oil-paper insulation, offering a theoretical basis of the parameter analysis. The obtained results show that the moisture fluctuation amplitude can reflect the different initial moisture contents of insulating paper and the mass ratio of oil and paper has little impact on the moisture content fluctuation pattern in oil-paper but has a great impact on moisture fluctuation amplitude; reduction of DP presents an accelerating trend with the increase of initial moisture content, and the aging rate of test samples is higher under low moisture content but lower under high moisture content compared to the insulation paper in transformers. Two obvious “deceleration zones” appeared in the dielectric spectrum with the decrease of frequency, and not only does the integral value of dielectric dissipation factor (tan δ) reflect the aging degree, but it reflects the moisture content in solid insulation. These types of research in this paper can be applied to evaluate the condition of humidified insulation and the aging state of solid insulation for condenser bushings.

Application of Low Frequency Dielectric Spectroscopy to Estimate lifetime of Low-Voltage EPR Insulation

This paper deals with the application of integral values of dielectric spectroscopy as the characteristic values from 10Hz to 1Hz for estimating the lifetime of low-voltage ethylene propylene rubber( EPR) insulation cables aging in the lab. The elongation-at-break and the dielectric dissipation factor (tanδ) were measured to study the characteristics of curve and to analyze sensitive measurement range. Based on the failure criterion of elongation-at-break, the correlation between the mechanical and dissipation curve was investigated and the effectiveness among three ways to assume values of dielectric dissipation factor was compared. Meanwhile, a time multiplicative shift factor was found with the same characteristics value at different aging temperatures and a prediction equation after selected reference temperature was obtained. Combined with integral equation of the deterioration tendency under reference temperature, a life model of dielectric dissipation factor integral for insulation material was derived. Results showed that testing parameters on integral value of tanδ had a contrary tendency with elongation-at-break and reflected the degradation trend in sensitive range within 10Hz~1Hz. Compared life model calculation results with measurements of cable in field, the measurement error was 3.33%. It had been found that this method could effectively evaluate the aging lifetime of low-voltage cable EPR insulation materials.

Dielectric and thermoanalytical behavior of poly(p-phenylene sulfide) polymers

Poly(p-phenylene sulfide) polymers, both highly linear and crosslinked, were investigated to determine how their structural differences affect their dielectric and thermoanalytical behavior over a temperature range from room temperature to 300 degrees C. The T/sub g/ of the crosslinked type was 3 degrees C higher than that of the linear type according to the differential scanning calorimetry (DSC) measurement, suggesting a slight lag in micro-Brownian motion in the amorphous phase. Permittivity and dielectric dissipation factors as well as global thermally stimulated current (TSC) spectra were similar below T/sub g/. The linear type showed larger permittivity and dielectric dissipation factor values above T/sub g/, due to interfacial polarization. The linear type showed a strong rho peak at approximately 160 degrees C in the global TSC spectra, suggesting the release of injected space charges trapped at the crystal/amorphous interfaces, while the crosslinked type showed a weak rho peak at approximately 190 degrees C in the spectra, suggesting a decrease of the interface effect due to crosslinking.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Some dielectric properties of electron-beam evaporated yttrium oxide thin films

Thin films of yttrium oxide have been fabricated by the direct electron-beam evaporation, in an oxygen atmosphere, of 99.9% yttrium oxide powder. Such films, ranging in thickness from about 2000 Å to 15,000 Å, have been observed to be quite stable and free of pinholes over areas as large as 0.5 in. × 0.5 in. At 1000 Hz and 25 °C the lowest value of dielectric dissipation factor (tan δ) obtained was 0.00255, decreasing to a value of 0.0024 at 100 kHz. Bridge measurements on such films forming capacitors of the type AlY 2O 3Au further yielded an average dielectric permittivity value ε′ = 13.5 ± 1.5 and a temperature coefficient of capacitance of + 320 p.p.m./°C. Typical breakdown field strengths were in the order of 2.8 × 10 6 volt/cm for such capacitors as large as 0.065 μF, whilst the measured resistivity of the dielectric was estimated to be > 2 × 10 14 Ω cm .