Measurement Of Dielectric Loss Factor Research Articles

Discussion on Measurement of Dielectric Loss Factor and Capacitance of Transformer Winding and Bushing

Discussion on Measurement of Dielectric Loss Factor and Capacitance of Transformer Winding and Bushing

Comparing the Performance of γ-Alumina Nanofiller and Titanium Tetraisopropoxide Catalyst in the Rejuvenation of Water Tree Degraded XLPE Cables

This article evaluates the performance of titanium tetraisopropoxide (TTIP) and γ-alumina nanofiller (Al2O3) in rejuvenation and restoration of degraded XLPE underground medium voltage–power distribution cables. These two materials will be injected into aged cables in the form of two rejuvenation composition groups based on silane coupling agents. The injected and aged specimens were then compared in terms of dielectric loss factor (tanδ) measurement, scanning electron microscopy (SEM) analysis, Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray (EDX) analysis. After measurement of dielectric loss factor in 7-day intervals, 1 month after the injection of rejuvenation fluids, it was found that the injected cable specimen dielectric loss tangent in the second group, which contained γ-alumina nanofiller, was lower than the specimens injected with TTIP (first group); even their tanδ was lower than the new unused cables. Microstructures of the rejuvenated and aged specimens were compared by means of SEM analysis and the results indicated that titanium and aluminum nanoparticles filled the water-filled microscopic cavities and modified the polymeric insulation surface. FTIR analysis compared the chemical bonds of the insulation layer in injected and aged cables. EDX analysis also detected the element type and value on the treated insulation specimen surface area. Comparing the four afore-mentioned analysis illustrated that both fluids were efficacious in rejuvenation and rehabilitation of degraded XLPE cable insulations. However, γ-alumina nanofiller performs better than TTIP in rejuvenation of degraded XLPE power cables.

An electromagnetic non-destructive approach to determine dispersion and orientation of fiber reinforced concretes

Including fibers in concretes improves their mechanical properties such as flexural strength, impact load resistance and limited crack propagation. The dispersion, orientation and types of the fibers placed in the concretes affect these mechanical properties. The aim of the study is to propose a standard and a novel prediction method for determining the dispersion and orientation of the concretes in which fibers are reinforced in microwave frequency range. This study demonstrates that determination of both orientation and dispersion of the fibers regardless of the fiber types in concretes is possible by extracting electromagnetic properties of the structures in microwave regime as a nondestructive method. The measurement technique requires sample under test (SUT) and two wideband linearly polarized antennas placed in the front and backside of material under the free space condition. Although there are some studies investigated the fiber content of concrete samples through certain electromagnetic techniques, the proposed novel approach concentrates on the electromagnetic behavior of the fiber reinforced concretes in a very wideband range from 3 GHz to 17 GHz. Unlike the other studies, open space measurement with the help of a vector network analyzer which is capable of measuring up to 43 GHz along with two high gain horn antennas was carried out in the laboratory environment. Time required for exact measurement of dielectric constant and loss factor of the concrete between antennas is less than a minute. A simple and confidential model is carried out to determine both orientation and dispersion of fibers in concrete by observing the changes of dielectric constant and loss factor. The determination of electromagnetic properties of concretes with fibers has potential applications for future nondestructive sensors. In addition, observation of negative dielectric constant and some other electrical properties such as low loss factor and impedance match with free space presented in the study for particular frequency intervals gives a chance for future radome applications in harsh environmental conditions.

Dielectric Loss Factor Measurement in Power Systems Based on Sampling Sequence Reconstruction Approach

Dielectric loss factor (DLF) is an important parameter to reflect the insulation condition of a high voltage capacitive equipment, which is widely installed in power systems. Hence, the accuracy of DLF measurement will directly affect the safety and stability of the power grid. This paper proposed a new algorithm based on sampling sequence reconstruction approach to accurately measure the DLF without being affected by asynchronous sampling and noise. The proposed method first estimates the fundamental frequency of power grid through the operational processing of voltage or current sampling sequence by weighted iteration with the composite trapezoidal rule. And then, the equivalent synchronous sampling sequences of the voltage and current in one cycle are constructed by using the estimated frequency and original sampling sequences through cubic spline interpolation. Finally, the fast Fourier transform results of the equivalent sequences are applied to obtain the value of the DLF. Simulations and experimental results show the effectiveness and practicability of the proposed method.

Dielectric Loss Factor Measurement of High Voltage Capacitive Apparatus based on Harmonic Analysis Method

Dielectric Loss Factor Measurement of High Voltage Capacitive Apparatus based on Harmonic Analysis Method

Method of Measurement of Capacitance and Dielectric Loss Factor Using Artificial Neural Networks

Abstract A novel method of dielectric loss factor measuring has been described. It is based on a quasi-balanced method for the capacitance measurement. These AC circuits allow to measure only one component of the impedance. However, after analyzing a quasi-balanced circuit's processing equation, it is possible to derive a novel method of dielectric loss factor measuring. Dielectric loss factor can be calculated after detuning the circuit from its quasi-equilibrium state. There are two possible ways of measuring the dielectric loss factor. In the first, the quasi-balancing of the circuit is necessary. However, it is possible to measure capacitance of an object under test. In the second method, the capacitance cannot be measured. Use of an artificial neural network minimizes errors of the loss factor determining. Simulations showed that the appropriate choice of the range of the detuning can minimize errors as well.

Development of a multi-temperature calibration method for measuring dielectric properties of food

In the most commonly used, open-ended coaxial probe method, dielectric properties of food products are measured after calibrating the instrument at 25 °C using air (open circuit), short (short circuit) and deionized water. Measurement accuracy may be compromised when dielectric properties are measured at temperatures other than 25 °C. The main objective of this study was to systematically perform calibration at multiple temperatures, quantify measurement errors and develop a method for multitemperature calibration to measure dielectric properties of materials over a wide temperature range. The dielectric properties of deionized water were measured from 1 to 90 °C after calibrating the dielectric measurement system using air, short and deionized water at six different temperatures (1, 25, 40, 55, 70, and 85 °C). The temperature-dependent dielectric properties of water calibrated at six temperatures were then compared with the reported values at two typical microwave frequencies of 915 and 2450 MHz. The results showed that the 25 °C calibration is valid for dielectric constant measurement, but not valid for dielectric loss factor measurement at temperatures far from the calibration temperature. Multitemperature calibration is helpful for reducing errors and improving the accuracy of the temperature-dependent dielectric properties measurement, especially for low-loss materials. Calibrations at two temperatures (25 and 85 °C) within the range studied were found to be suitable for the temperature-dependent dielectric properties measurement. The dielectric properties of lasagna components (ricotta cheese, pasta, and meat sauce) were measured using this multitemperature calibration method.

Non‐bridge circuit with double quasi‐balancing for measurement of dielectric loss factor

This study presents the synthesis and implementation of non-bridge quasi-balanced circuit designed to measure the dielectric loss factor. Synthesis is performed on the basis of the well-known bridge circuit. The equations of detected signal have been derived and their processing equations have been developed using a general model of a quasi-balanced circuit. Then, a structural diagram describing the processing of signals in the two states of quasi-equilibrium has been derived. An example of a virtual implementation of the derived circuit has been presented.

A novelty digital algorithm for online measurement of dielectric loss factor of electronic transformers

There are many inherent performance limitations using traditional algorithms for online measurement of dielectric loss factor including synchronous sampling, no interharmonics and power system frequency must be invariable. In a non-stationary signal environment where power frequency fluctuation and interharmonic components exist, there is no guarantee of measurement accuracy by using traditional methods. The paper proposed a high-accuracy digital algorithm for online measurement of dielectric loss factor of electronic transformers. Theoretical basis of the new algorithm is based on a new data processing procedure including data truncation and data addition which compensates phase distortion as a result of the spectrum of addition data contains offsets. The algorithm can accurately extract the fundamental signal and calculate dielectric loss factor. Measured results from simulations and practical engineering projects show that the new algorithm has good application feasibility without being affected by the limitations rendered above.

Predicting interactive behavior of cytokines and their receptors by dielectric thermal analysis and thermogravimetry

Cytokines and soluble cytokine receptors serve as important protein biomarkers for chronic and infectious disease diagnosis. The development of biosensors capable of detecting cytokines or their soluble receptors in patient bodily fluids is a growing area of research. In an ongoing series of studies to understand the thermal analytical behavior of cytokines and their soluble receptors, dielectric thermal analysis (DETA) and thermogravimetry (TG) were used in investigations to determine if differentiations based on dielectric properties (e.g., conductivity) of the proteins could be identified. Permittivity (e′) and dielectric loss factor (e″) measurements were performed over a frequency range of 0.1–300,000 Hz. Up to 20 min, water associated with the samples was conductive, interacting with the proteins and affecting the temperature-dependent relaxation spectra of proteins. A trend analysis revealed differences between surface charge at 0.1 Hz and bulk charge at 300,000 Hz. In addition, the greatest change detected among proteins was due to the conductivity (dielectric loss factor). Beyond a 20 min drying time, the observed conductivity was due to intrinsic properties of the proteins with limited dependence on frequency. A 100% water loss was obtained for samples within 20–30 min by TG. Sample drying by TG could serve as a preparatory step in drying protein samples for further DETA and DSC analysis.

Dielectric polarization in Sb2Te3 thin films

Dielectric properties of Sb2Te3 films prepared by thermal evaporation technique onto clean glass substrates using ohmic aluminum electrodes have been investigated in the frequency range of 0.01– 100 kHz and within the temperature range of 293K– 373 K. Both the dielectric constant ε1 and dielectric loss factor were found to depend on frequency and temperature. The activation values were evaluated and good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements were obtained.

Relaxation spectrum of the TlSbSe2 thin films

The dielectric constant and the dielectric loss of TlSbSe2 thin films, obtained via thermal evaporation of TlSbSe2 crystals grown by Stockber-Bridgman technique, have been measured using ohmic Al electrodes in the frequency range 0.2–100 KHz and within the temperature interval 293–353 K. The capacitance are found to decrease with increasing frequency and increase with increasing temperature. The activation energy values were evaluated too. A good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements has been observed.

Digital algorithm based on orthogonal decomposition for measurement of dielectric loss factor

As one of the most important technical indexes for the evaluation of insulation condition, the dielectric loss factor is necessary in preventive experiments and online monitoring of insulation of high-voltage apparatuses in an electric power system. First, the definition of the dielectric loss factor and the impact of the harmonic voltage on that was discussed. Secondly, the voltage and the leakage current were defined as vectors in normed linear space. By using the characteristic of an orthogonal vector in the inner product space, the leakage current signal was decomposed to active and reactive components that were orthogonal. Subsequently, a novel digital algorithm of the dielectric loss factor measurement, which was defined as the ratio of norms of the active current to the reactive current, was proposed. At last, the proposed algorithm was simulated under several conditions such as harmonic voltage and voltage frequency fluctuation. In addition, the proposed algorithm was tested on two electric power capacitors. Both simulation and experiment results were provided and show that the proposed algorithm is simpler and less sensitive to influence factors than the Fourier analysis method.

Dielectric properties of salmon fillets as a function of temperature and composition

Dielectric properties for anterior, middle, tail, and belly portions of Alaska pink salmon ( Oncornynchus gorbuscha) fillets were measured at frequencies between 27 and 1800 MHz from 20 to 120 °C to provide insights for improving the modeling of microwave (MW) and radio frequency (RF) commercial sterilization processes of salmon products. Compositional differences contributed to the observed slight differences in the dielectric properties for different parts of salmon fillet. For all portions of the fillet, similar trends in dielectric constant and loss factor measurements were observed as a function of temperature (20–120 °C). At RF frequencies of 27 and 40 MHz, the dielectric constant decreased with increasing temperature. But at microwave frequencies (e.g., 915, 1800 MHz), an opposite trend was observed. The dielectric loss factor increased with increasing temperature over the tested frequency range. Calculations from electrical conductivity of minced salmon fillets measured at different temperatures suggest that ionic conductivity was the major contributor to temperature dependent behaviors of dielectric properties at RF frequencies.

Dielectric constant/loss measurements in pristine and 75 MeV oxygen-ion irradiated kapton-H polyimide

The dielectric constant (ϵ′) and loss factor (ϵ″) measurements have been made in pristine and 75 MeV oxygen-ion irradiated (fluences: 1.8×1011, 1.8×1012 and 1.8×1013 ions/cm2) kapton-H polyimide in the temperature region 20–240 °C at different frequencies ranging from 1 kHz–4 MHz. There is an overall decrease in ϵ′ in irradiated samples. The decrease in ϵ′ is more in samples irradiated with high fluences. In pristine kapton-H sample, the initial rapid fall in ϵ′ with temperature has been ascribed to the loss in absorbed water (γ-relaxation). The increase in crystallinity, dipolar relaxation (β-relaxation) and space charge relaxation (α-relaxation) governs the high temperature ϵ′. In irradiated samples, the ion irradiation results in an enhancement of γ-relaxation, which significantly affects the low-temperature ϵ′ behaviour. The decrease in ϵ′ with temperature above 40 °C has been associated with the demerization of carbonyl groups due to high-energy ion irradiation. In the high-temperature region (above 140 °C), the radiation induced free radical cross-linking has been held responsible for decreasing ϵ′ with temperature. The loss peaks in ϵ″–T curves appearing around 40–50, 80–120 and 140–180 °C represent the γ, β and α-relaxations, respectively.

Dielectric properties of sol–gel derived Ta 2O 5 thin films

The dielectric constant and the dielectric loss of tantalum pentoxide (Ta 2O 5) thin films, produced by sol–gel spin-coated process on Corning glass substrates, have been investigated in the frequency range of 20–10 5 Hz and the temperature range of 183–403 K, using ohmic Al electrodes. The frequency and temperature dependence of relaxation time has also been determined. The capacitance and loss factor were found to decrease with increasing frequency and increase with increasing temperature. The activation energy values were evaluated and a good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements were observed.

Effect of Hydrothermic Ageing on Dielectric and Mechanical Properties of Rigid Poly(vinyl chloride)

An accelerated hydrothermic ageing (according to N.F.T. 54043 method) was performed on samples of rigid poly(vinyl chloride). The test consisted of sample immersion in boiling water at 100°C for different exposure periods up to 480 h. The samples were removed from the boiling water every two hours for mechanical and dielectric characterization and color test. The dielectric measurements carried out on aged samples, up to 40 h, showed that the permittivity remained almost constant and its value was found to be 2.3 in the range –100 to +62.8°C. However, as the temperature approaches the glass transition (Tg = 88.3°C), the permittivity was observed to increase rapidly. It was also found that the permittivity of aged samples was lower than that of the non-aged samples. The dielectric loss factor (tan δ) measurements with respect to temperature have confirmed the presence of two relaxations: β at low temperature (around –35°C) and α near the Tg. The combined action of water and temperature reduced the intensity of the corresponding relaxation peaks. The sample color index was evaluated up to 480 h using the SYNMERO scale in order to estimate the degradation extent. Unexpectedly, elongation at break under uniaxial traction remained unaffected by the hydrothermic ageing, meaning that two competing processes were involved simultaneously (sample degradation via chain scission and sample plastification via water absorption).

MEASURING DIELECTRIC PROPERTIES OF HARD REDWINTER WHEAT FROM 1 TO 350 MHZ WITH A FLOW-THROUGH COAXIAL SAMPLE HOLDER

A system for measuring the dielectric properties of cereal grains from 1 to 350 MHz with a coaxial sample holder is presented. Several polar alcohols were used to calibrate and verify permittivity measurements obtained with a signal-flow graph model from the full two-port S-parameter measurements. At the lowest frequencies (1-25 MHz), where the phase measurements are less accurate, a lumped parameter model was used for the dielectric loss factor measurements. The system was calibrated with measurements on air and decanol and verified with measurements on octanol, hexanol, and pentanol. The standard error for the polar alcohols used for verification was 2.3% for the dielectric constant and 7.6% for the dielectric loss factor. Although measurements were taken on static samples, the sample holder is designed to accommodate flowing grain. Dielectric properties measurements at 25°C were taken on four hard red winter wheat cultivars ranging in moisture content from about 9% to 21% with bulk densities varying from 0.66 to 0.83 g/cm3. Most of the data agreed with measurements reported in the literature.

Field dependent temperature shift of dielectric losses peak in TGS

Abstract Dielectric constant and loss factor measurements have been performed in triglycine sulfate single crystals at the vicinity of the Curie temperature (Tc≈48.5°C) as a function of ac driving field (20≤v≤106 Hz) in a wide range of field amplitude (50≥Eo≥0.15V/cm). Well defined shifts of loss factor peak (Dmax), increasing monotonously with the field, not previously reported as far as we know, were observed and analyzed in terms of the energy dissipated within the vanishing hysteresis loops at T≈Tc corresponding to Eo≈Ec(T), coercive field.

Low temperature curing epoxies for elevated temperature composites

A low curing temperature epoxy formulation was characterized as a matrix material for glass-fibre-based composites for elevated temperature use. The formulation comprised a blend of tetra- and trifunctional epoxies and a two-part curing system including a high functionality active amine and an amino-terminated elastomer that, in addition, imparted high toughness to the high aromaticity epoxy matrix. Curing conditions and cross-linking states were studied and optimized using dielectric loss factor (DLF) measurements and differential scanning calorimetry (DSC) analysis in addition to Fourier transform infra-red (FTIR), hardness and molecular weight between cross-links ( M c) calculations. Results indicated that ambient curing conditions resulted in optimal molecular network development. However, curing was incomplete and a curing temperature of 60°C or preferentially 120°C was required to obtain high cross-linking levels. DLF results showed that curing at room temperature proceeds quickly and that the main polymerization peak occurs at 48°C, with an additional peak at 120°C and a glass transition temperature at 160–180°C. Glass fibre-reinforced composites prepared from the preferred epoxy formulation displayed better flexural strength and comparable interlaminar shear strength, compared with a commercial, 120°C curing, prepregged glass composite based on a modified epoxy matrix.