Increase In Dissipation Factor Research Articles

Fuzzy Based Condition Monitoring Tool for Real-Time Analysis of Synthetic Ester Fluid as Transformer Insulant

The main aim of the present study is to explore the use of synthetic ester fluid as a transformer insulant. For this, the performance of thermally aged synthetic ester is investigated using corona inception voltage (CIV) measurement, fluorescent analysis, and dielectric spectroscopic studies. Then a fuzzy model is introduced to correlate the outcome of these studies to predict the key performance index and lifetime estimation of insulation structures. CIV tests for the thermally aged ester fluid, under AC voltage show 53.2% and 34% reduction in inception values due to ageing time and ageing temperature respectively. Furthermore, the effect of magnetic field on the performance of thermally aged ester is also studied and a drastic reduction of 54.3% and 39.4% respectively in CIV is observed. Statistical studies also indicate accelerated degradation of the insulation performance under the influence of the magnetic field, showing high scatter in CIV data indicated by decreasing beta values. Other studies such as fluorescent spectroscopy depict progressive shifts in fluorescence maxima and a decrease in emission intensity with ageing. Dielectric spectroscopy results show a manifold increase in dissipation factor due to thermal ageing. A fuzzy monitoring tool uses spectral data as input and at the output indicates the level of deterioration. The Rule-base of the model is framed using dielectric study.

Effects of Filler Configuration and Moisture on Dissipation Factor and Critical Electric Field of Epoxy Composites for HV-ICs Encapsulation

Molding compounds (MCs) are widely used as an encapsulation material for integrated circuits; however, traditional MCs are susceptible to moisture and charge spreading over time. The increase in dissipation factor due to the increase of parasitic electrical conductivity ( $\sigma$ ) and the decrease in dielectric strength $(E_{\mathrm {MC}}^{\mathrm {Crit}})$ restrict their applications. Thus, a fundamental understanding of moisture transport as a function of MC parameters is essential to suppress moisture diffusion and broaden their applications. In this article, we: 1) propose a generalized effective medium and solubility (GEMS) Langmuir model by identifying a set of parameters that control water uptake as a function of filler configuration and relative humidity; 2) investigate the dominant impact of reacted-water on $\sigma $ through numerical simulations, mass-uptake, and dc conductivity measurements; 3) investigate electric field distribution to explain how moisture ingress reduces $E_{\mathrm {MC}}^{\mathrm {Crit}}$ ; and finally 4) optimize the filler configuration to lower the dissipation factor, and enhance $E_{\mathrm {MC}}^{\mathrm {Crit}}$ . The GEMS-Langmuir model can be used for any application (e.g., photovoltaics, biosensors) where moisture ingress leads to reliability challenges.

Conduction Mechanism and Charge Transporting Property of Te90-xSe10Cdx Chalcogenides by AC Conductivity and Dielectric Analysis

The effects of Cd incorporation on the dielectric properties of chalcogenide alloy Te90-xSe10Cdx (x = 0, 10, 15, 20 at. wt.%) have been studied. These are synthesised by melt quenching technique. Frequency dependence of the AC conductivity, dielectric constants (ε′), dielectric losses (ε′′) and dissipation factor in the frequency range 50Hz -5 MHz at room temperature have been reported. Temperature dependent studies in 298 – 473 K at a fixed audio frequency of 10 kHz have also been measured. It is found that AC conductivity, dielectric loss and dissipation factor increase as frequency and temperature increase. Dielectric constant decreases as frequency increases whereas it increases with increasing temperature. Dielectric constant increases while dielectric loss decreases with increasing Cd content in Te-Se matrix. Possible explanations of metal (Cd) induced effects on the conduction mechanism of the Te90Se10 alloy are discussed.

Influence of Copper Particles on Breakdown Voltage and Frequency-Dependent Dielectric Property of Vegetable Insulating Oil

The insulating performance of oil is vulnerable to particles especially the conductive particles. This paper investigated the influence of copper particles of micrometer size on the breakdown strength and frequency-dependent properties of vegetable oil. The AC breakdown voltage of contaminated vegetable oil with copper particles of different numbers (ranging from 103 to 106) was measured. The frequency-dependent dielectric properties including volume resistivity, relative permittivity and dissipation factor of the contaminated vegetable oil with copper particles of various volumetric concentrations (0.011%, 0.056% and 0.112%) were measured. Identical experiments were conducted with mineral oil for comparison. Results show that the AC breakdown voltage of vegetable oil decreases with the increase of copper particle concentration. The mineral oil exhibits a similar trend, but the influence of copper particles on the AC breakdown voltage of vegetable oil is less significant than that on mineral oil because of its greater viscosity. The relative permittivity and dissipation factor increase with increasing copper volumetric concentration while the volume resistivity decreases. The influence of copper particles on them is significant at low frequencies and this influence becomes inconspicuous as the frequency increases. Similar results were observed for mineral oil.

Effect of Crystallization Temperature on Electrical Properties of Er3+/Yb3+–SrO.TiO2 Borosilicate Glass

Er3+–Yb3+ doped 22[3SrO.2TiO2].30[2SiO2.B2O3] glass and glass–ceramics are developed and investigated for their electrical properties. The degree of crystallization is varied by means of crystallization temperature ranging from 600 to 1000°C. In glass–ceramic samples, two major crystalline phases, Sr3Ti2O7 and TiO2, are confirmed by diffraction analysis. The best crystallized glass–ceramic (crystallization temperature 950°C) sample shows 100–1 50 times lower impedance in temperature range, 200–300°C, than the uncrystallized glass. Electrical relaxation corresponding to the crystalline phase can be isolated in frequency domain. The glass–ceramic shows a 10–100 times higher dielectric constant than the glass in lower frequency range. This dielectric constant and dissipation factor increase with increasing temperature beyond a threshold value. Curie temperature was not visible in the measured temperature range.

Electrical and mechanical ageing behaviors of used heat-shrinkable insulation tubes

Ageing is strongly related to the external factors acting upon the polymer and to the manufacturing process. It mainly depends on the anti-ageing performance whether heat-shrinkable tubes for switchgear busbar can maintain excellent electrical and mechanical properties during the long term operation. In this paper, the collected samples were applied to the switchgear busbar of 10 and 35 kV in substations of Tianjin Power System. The 10 kV tubes have operated for one, two and nine years and 35 kV tubes for four and six years respectively. Besides, two more kinds of unused samples were chosen to compare with the aged ones. Dielectric permittivity, dissipation factor and AC impedance were tested to assess the extent of ageing. The breakdown characteristics under AC voltage and the trap distribution calculated by measuring the dynamic behavior of surface potential under DC voltage were obtained at room temperature. Moreover, the tests of tensile strength, including breaking strength and elongation at break, were performed to analyze the mechanical properties. Results show that dielectric permittivity and dissipation factor increase with the operating time while the tensile strength decreases. The decline of breakdown strength and AC impedance indicates that insulation capability is reduced by long time natural ageing. The results obtained from the investigation also show the correlation between the trap distribution and the dielectric strength with the operating time.

Effects of accelerated repetitive impulse voltage aging on performance of model stator insulation of wind turbine generator

A high reliability is essential for the insulation system of wind turbine generator because of its high repairing cost. In this paper, three experimental methods based on accelerated aging under repetitive impulse voltage and multi-environmental factors are established to (i) investigate the failure or degradation mechanism during the aging, and (ii) make recommendations on how to assess the functional life and reliability of insulation systems for wind turbine generator. Repetitive impulse voltage stress combined with thermal stress, change of temperature, steady damp heat and salt mist was, in turn, applied to model specimens with different length and section sizes. Some of non-destructive characteristic parameters such as dissipation factor, insulation resistance, and partial discharge inception voltage were measured periodically during the aging. In addition to the residual breakdown voltage, the appearance features and infrared spectrum analysis of specimens were carried out after aging. It has been found that the surface partial discharge generated under repetitive impulse voltage resulted in the degradation of surface insulating material near the slot end. The change of temperature also caused the delaminating of stator insulation from the core slot especially when massimpregnated insulation used in long slot of practical stator. The increase of dissipation factor of insulation system was largely contributed by salt mist and moisture factors especially when the surface or interface of insulation material was damaged. The electrically accelerated aging under about triple maximum repetitive impulse voltage for 1000 h was an effective and feasible method to assess the insulation system of wind turbine generator.

Dielectric and Conductivity Studies of Sr[(Mg<sub>0.32</sub>Co<sub>0.02</sub>) Nb<sub>0.66</sub>]O<sub>3</sub> Thin Film

Study of Sr[(Mg0.32Co0.02) Nb0.66]O3 [SMCN] thin films prepared by Pulsed Laser Deposition Technique (PLD) were carried out in the temperature range of 150 to 450K and frequency range of 100KHz to 1.1MHz. X-ray diffraction of the thin film shows single phase formation with monoclinic symmetry. The dielectric properties show enhanced ε' values compared to bulk suggesting promising applications in alternative technologies. Due to simultaneous increase in dissipation factor with temperature the net ac conductivity is found to be decreasing. Technologically important two step activation energy is observed in the film. This property can be used in switching devices. In low temperature region the activation energy corresponds to shallow traps while the migration of oxygen vacancies contributes in high temperature region.

Effect of cation addition on dielectric properties of TbMnO 3

Low-frequency (10 2–10 5 Hz) dielectric properties of TbMnO 3 (TMO) composites adding different cations were investigated from 360 to 77 K. Compared to the parent TMO, it was found that cation addition could reduce dissipation factor, while very high dielectric constant almost remained. Especially addition of Ti ion reduced dissipation factor remarkably. And the additions of Sr ion and Ti ion at the same time resulted in the increase of dissipation factor. It is interesting that dissipation factor decreased again when Sr ion was partly substituted by Ba ion.

Structural and electrical characteristics of R.F. magnetron sputtered ZnO films

We investigated the effects of both bottom electrodes and processing parameters on the physical and electrical properties of ZnO films deposited by R.F. magnetron sputtering. We found that the preferential c-axis growth of deposited ZnO films depends on the type of bottom electrode: Both Al and Au bottom electrodes enhance the growth of c-axis orientation in ZnO films, while no clear evidence for any preferential growth was observed in case of Cu and Si. The resistivity of ZnO films deposited on Au and Al bottom electrodes was greater than 106 Ω cm. The ranges of dielectric constant of Al/ZnO and Au/ZnO samples were 8–14 and 13–16, respectively. Dissipation factors change from 0.02 to 0.05. In general, as c-axis orientation enhances, dielectric constant and dissipation factor increase and decrease, respectively.

Dielectric properties of srtio3 thin films with ca and zr partial substitutions for active microwave applications

The structure and dielectric properties of SrTiO3 thin films with either 5% Ca or Zr substitutions have been investigated. Thin films of these materials were deposited onto (100) LaAlO3 substrates by pulsed laser deposition (PLD) at temperatures of 750°C in 350 m Torr of oxygen. As-deposited films, characterized by x-ray diffraction, were single phase and well oriented with ω - scan widths of < 0.2° for the (002) reflection. The capacitance and dissipation factor were measured at 1 MHz to 1 GHz for the deposited films as a function of temperature and electric field (80 kV/cm) using Ag interdigital capacitors deposited on top of the SrTiO3 films. For unsubstituted SrTiO3, a peak in the capacitance vs. temperature curve was observed at ∼60K. The temperature dependence of the dissipation factor was similar and also exhibited a maximum at 60K with a value of 0.025. A 50% change in the capacitance can be achieved for the SrTiO3 film at ∼80 kV/cm. Substitution of 5% Ca on the Sr site does not change the temperature dependence of the capacitance but leads to an increase in dissipation factor at 60 K to ∼0.05. In addition, the capacitance decreases more rapidly with lower electric fields for partial Ca substitution compared to pure SrTiO3. Substitution of 5% Zr for Ti leads to a dramatic reduction in the capacitance and correspondingly, the field dependence of the capacitance. However, the Zr substituted films have extremely low losses, ∼0.004. The ability to control both the magnitude of the dielectric constant and the losses will make these materials useful for frequency-tunable active microwave applications.

The effect of the soft segment of polyurethane on copolymer‐type polyacetal/polyurethane blends

AbstractMechanical blends of copolymer‐type polyacetal (POM) with ester‐based and ether‐based polyurethane (PU) are immiscible over the 0–50% PU compositional range. The PU elastomer was added to the rigid POM matrix to increase its toughness. The mechanical, physical, thermal, dielectric, and dynamic mechanical properties and morphology of POM/PU blends were investigated. The notched Izod‐impact strength of blends reaches a maximum at 10 wt % PU. The tensile strength, Young's modulus, volume resistivity, crystallinity, and density decrease with increasing concentration of PU. The elongation of blends reaches a maximum at 20 wt % PU. The dielectric constant and dissipation factor increase with increasing PU content. From dynamic mechanical measurements, as the elastomer content increases, the height of the damping peak also increases, but there is no transition temperature shift. SEM shows that the blends exhibit a continuous morphology with domain size varying from 1 to 10 μm for PU. However, at a concentration of 50 wt % PU, the dispersed PU particles tend to aggregate. Characterization of morphology by a metallurgical microscope has shown that the crystalline materials in the pure POM and the blends exist in a spherulitic superstructure.

ChemInform Abstract: Dielectric Behavior of Hot‐Pressed AlN Ceramic: Effect of CaO Additive.

AbstractFor all AlN samples studied (0, 0.5, 3.0, and 7.0 mol% CaO), it is found that the dielectric constant and dissipation factor increase appreciably at higher temp. (&gt; 450 K), the increase being more pronounced at lower frequencies.

Dielectric Behavior of Hot‐Pressed AlN Ceramic: Effect of CaO Additive

Temperature and frequency dependence of dielectric constant and dissipation factor has been studied in hot‐pressed samples of , with and without additive of (0.5–7.0 mole percent). It is observed that, in all the samples, the dielectric constant and dissipation factor increase quite appreciably at higher temperatures (>450 K), the increase being more at lower frequencies. At a particular temperature and frequency, dielectric constant and dissipation factors increase after putting 0.5 mole percent in pure . However, at higher concentrations (>3 mole percent), these parameters decrease. The results have been explained in terms of space charge polarization.

Dielectric properties of pyrophyllite as a function of water vapor pressure

The effects of water vapor pressure on the dielectric constant and dissipation factor of pyrophyllite have been measured in the frequency range 0.05–10 kHz. Both the dielectric constant and dissipation factor increase with increasing vapor pressure and decreasing measuring frequencies. This result has application in electrical measurements made in pyrophyllite-media high-pressure devices.

Resins and reinforced plastic laminates for continuous use at 650°f—II

AbstractThis paper is the third in a series describing work done under Air Force sponsorship to develop high temperature polyimide laminates for radomes and other parts for supersonic aircraft.Twelve resin compositions are described and evaluated. Most were prepared from benzophenonetetracarboxylic dianhydride and one or more aromatic diamines. Modifying linkages such as amide, ether, benzimidazole, and oxadiazole were present in some cases.A variety of precure and pressing conditions were studied, best results being obtained with a fully cured prepreg pressed at about 700°F and 200–1000 psi. Most of the laminates were made with E glass cloth, but some work was done also with S glass, Refrasil, and carbon cloth.Initial flexural strengths on E glass of 35–60,000 psi at room temperature, and 20–40,000 psi at 600°F were observed for the better resins. On S glass, slightly higher strengths were observed together with values of about 10,000 psi at 700–1000°F. Aging data on E glass laminates show retention of at least 10,000 psi flexural strength at temperature for about 250 hrs. at 650°F, 1000 hrs. at 600°F, 5000 hrs. at 527°F, and 30,000 hrs. at 482°F.Dielectric constant and dissipation factor at 10 Gc were found to be nearly constant at 3.5–4.4 and 0.005–0.01, respectively, for temperatures up to 662°F and for aging up to 1000 hrs. at 600°F. At frequencies of 60 c and 1 Kc, an increase of dissipation factor with temperature was found and was used as a measure of Tg.

The Electrical Degradation of a Low-Loss Capacitor Prepared by Sintering a Glass Powder

The electrical degradation of capacitors prepared by sintering glass powder was investigated in connection with crystallization in the glass and sinterability of the glass powder. Crystallization in glass is responsible for a decrease in volume resistivity and an increase in dissipation factor after a life test under voltage stress at high temperature. These degradations are attributed to an increase in concentration of both mobile alkali ions in the glass matrix and of silver ions from the electrode diffused into the glass matrix, owing to the crystallization. The temperature of life test has more effect on the degradation than the applied voltage stress, and is considered to be a determining factor in the life test of a crystallized glass. While the degradation of a capacitor is also influenced by crystallization, it is more strongly influenced by the sinterability of the glass powder from which it is made. Poor sinterability is responsible for the existence of glass particle boundaries, which results in degradation.

Effects of γ‐irradiation on the loss properties of dielectrics in vacuum

AbstractDielectric constant and dissipation factor of six types of dielectrics were measured during irradiation in a Co60 source. Tests were made at seven frequencies ranging from 100 cycles/sec. to 100 kcycles/sec. by use of the Schering bridge technique. Polystyrene and polyethylene exhibited no change in loss properties when γ‐irradiated to doses as high as 7.7 × 107 and 3.5 × 107 r, respectively. Poly(methyl methacrylate) decreased slightly in dielectric constant and was essentially unchanged in dissipation factor after 5.7 × 107. TFE underwent the most drastic changes. At a very low dose (106 r) the dissipation factor had increased three orders of magnitude (at 100 cycles/sec.) and one order of magnitude (at 100 kcycles/sec.). After peaking, the loss factor decreased slowly. After removal of the source, the loss factor decreased more; then increased rapidly upon admission of air. Both this and the original increase in dissipation factor are indicative of a dipole with a long relaxation time, in which oxygen plays a role. FEP Teflon increased somewhat less than TFE, and the peak was not reached until a dose of 3 × 107 r. Very little effect was produced by the admission of air after irradiation. Dielectric constant decreased with radiation dose. The dissipation factor and dielectric constant of Rayolin N decreased with dose, until a plateau was reached. Very little effect was seen after irradiation, even upon the admission of air. The changes which took place during the radiation period were, as in the case of the other materials, greater at the lower frequencies than they were at the higher frequencies.

Electrical Properties of Evaporated Aluminum Oxide Films

Insulating films of aluminum oxide have been prepared by evaporation of aluminum in a partial pressure of 10−3 mm Hg of oxygen. On exposure to air both dielectric constant and dissipation factor increase to values similar to those observed for anodized films on bulk aluminum. The results can be understood if the initial insulating film is a suboxide similar to the postulated which is normally unstable at room temperature in air or oxygen, decomposing to .

The Relation of Capacitance Increase with High Voltages to Internal Electric Discharges and Discharging Void Volume

A practical means of estimating the fractional volume of gas space in insulation from high-voltage capacitance and dissipation factor measurements has been suggested in this paper. This method has been evaluated by tests on models and various high-voltage insulation specimens. An analysis has been derived relating the observed a-c capacitance and dissipation factor increase with high voltages to the individual electric discharges between the surfaces of gas spaces in insulation.