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Recent advancements in 3D printing technology have enabled the rapid production of complex structures, yet the dielectric performance of 3D printing materials and their potential for manufacturing electrical components remain insufficiently studied. In this study, a capacitor rated at 10 kV with a capacitance of 1 nF was designed and developed for high-voltage applications. During the production of the capacitor, the insulating and conductive parts were fabricated using a 3D printer. While PLA, ABS, ASA, and PETG were employed as insulating materials, aluminum was chosen as the conductive part. Theoretical calculations and the finite element method were used to validate the measured capacitance of the equipment. The performance of the prototype capacitor was analyzed through partial discharge inception voltages (PDIV), dissipation factor (tanδ), and breakdown voltage measurements. Dissipation factor measurements were performed at 2 and 4 kV voltages in the 50–400 Hz frequency range. The performance of employed materials was comparatively analyzed through experimental and simulation results. Finally, the impact of different insulating materials on the dielectric performance of the prototype capacitors was evaluated. [ABSTRACT FROM AUTHOR]

This study explores the impact of adding conventional mineral oil (10%, 30%, and 50%) to new natural esters (Jatropha-based methyl ester and refined coconut oil). Examining dielectric, fire properties, and gassing tendencies, samples undergo accelerated aging at 130 °C with metallic substances. Results reveal that up to 30% mineral oil enhances or maintains the electrical and physical properties of natural esters, with dissipation factor reduction and viscosity improvement (by a factor of 2 at 50% mineral oil). Overall, mineral oil positively influences the insulating properties of natural esters under the described test conditions, suggesting potential applications in electrical systems. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive methodology for the precise calibration of high-voltage capacitance and dissipation factor (DF) bridges. The technique involves meticulous adjustments using a digital high-precision phase and ratio-measuring system to determine correction factors for DF and capacitance measurements. Unlike other methods that are limited to a narrow range, this approach allows calibration across the entire operational working spectrum of any bridge. While the method has been developed up to 1 kHz, its adaptability for future requirements is facilitated by the developed software. This method has been carried out by calibrating a highly accurate bridge for a capacitor ratio of up to 100, with DFs ranging from −0.01 to 0.01 and currents ranging from 0.1 mA to 1 A. Linear correction factors are established, with their accuracies being rigorously quantified. This methodology achieves expanded uncertainties as low as 3.5 µF/F (3.5 ppm) for capacitance and 2.2 × 10−⁶ for DFs, significantly enhancing measurement reliability across diverse high-voltage capacitor applications. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive methodology for the precise calibration of high-voltage capacitance and dissipation factor (DF) bridges. The technique involves meticulous adjustments using a digital high-precision phase and ratio-measuring system to determine correction factors for DF and capacitance measurements. Unlike other methods that are limited to a narrow range, this approach allows calibration across the entire operational working spectrum of any bridge. While the method has been developed up to 1 kHz, its adaptability for future requirements is facilitated by the developed software. This method has been carried out by calibrating a highly accurate bridge for a capacitor ratio of up to 100, with DFs ranging from −0.01 to 0.01 and currents ranging from 0.1 mA to 1 A. Linear correction factors are established, with their accuracies being rigorously quantified. This methodology achieves expanded uncertainties as low as 3.5 µF/F (3.5 ppm) for capacitance and 2.2 × 10−⁶ for DFs, significantly enhancing measurement reliability across diverse high-voltage capacitor applications.

In most industrialized countries, power transformers built several decades ago are approaching the end of their operational lifespan. The ongoing energy transition, focused on developing 100% renewable energy sources and accelerating global transportation electrification, further exacerbates these assets. Combined with rising electricity demand, there is an increasing risk of critical transformers' degradation acceleration. In this context, understanding the aging mechanisms of the insulation system inside these essential assets, which form the core of every energy network, becomes paramount for today's managers and engineers responsible for their operations. The acids generated through oil oxidation can be classified into two categories: low molecular weight acids (LMAs), which are inherently more hydrophilic and consequently have a greater impact on the degradation rate of solid insulation through hydrolysis, and high molecular weight acids (HMAs), which do not significantly contribute to the degradation of paper insulation. This study specifically addresses the impact of acids generated through oil oxidation—focusing on LMAs. New oil samples were infused with different ratios of LMAs before impregnation. The impregnated paper samples underwent thermal aging at 115 °C. Different physicochemical and dielectric properties were investigated. The investigations revealed that oils blended with formic acid exhibited more adverse effects on the insulation system compared to other LMAs. This information is essential for industry professionals seeking to mitigate the risks associated with transformer degradation and extend the lifespan of these critical assets during the energy transition. [ABSTRACT FROM AUTHOR]

This study aimed to determine the infrared (IR) spectra of the main optical properties of poly(methyl methacrylate) (PMMA). This is a simple and original method for obtaining spectra of the main optical properties from the reflection–absorption spectrum. Infrared reflection spectra of the main optical properties of PMMA were obtained from the complex relative permittivity using the Drude–Lorentz model for permittivity. Classical dispersion analysis of the reflection–absorption spectrum of poly(methyl methacrylate) films cast on a metal mirror was performed. The method is based on an iterative least squares fitting process of the experimental reflection–absorption spectrum of the polymer with the corresponding theoretical spectrum obtained from the complex permittivity Drude–Lorentz model. This approach is original for obtaining the relative permittivity and subsequently obtaining the main optical properties of the polymer film: complex electric modulus, energy loss function, optical constants, absorption coefficient, penetration depth, dissipation factor, and complex optical conductivity. In addition to the findings of other articles, some optical properties of PMMA films have been presented, which may be useful for studying PMMA-based composites or copolymers. Please confirm if the author names are presented accurately and in the correct sequence Author 1 Given name: [Maria Laura ] Last name [Strugariu]. Author 2 Given name: Sorina Gabriela Last name [Șerban] Author 3 Given name: [Antonia Maria ]Last name :[Berdie] Also, kindly confirm the details in the metadata are correct.Yes [ABSTRACT FROM AUTHOR]

Polyimides (PIs) are widely used materials due to their high thermal stability and potentially low dielectric constant (Dk) and dissipation factor (Df). However, Dk and Df values tend to increase at higher frequencies. Therefore, there is a significant need to reduce the Dk and Df values of PIs, which is the main purpose of this study. This research considers multiple factors, including the ring structures and conjugations on the conformation of the PI backbone. The effects of five‐membered and six‐membered PIs and the conjugated length of benzene and naphthalene structures in the repeating units on the thermomechanical and dielectric properties are systematically investigated. As a result, the PI with a six‐membered imide contributes to higher thermal stability, with a glass transition temperature higher than 350 °C, a thermal decomposition point of 529 °C, and a lower Dk of 2.7–2.8. Still, it exhibits a lower molecular weight than that of a five‐membered imide. On the other hand, PIs with esterified structures show an extremely low Df value, 0.002–0.005. This situation can be attributed to the vital correlation between the Df and the volumetric dipole moment. This study also presents the different properties arising from ring structures and conjugations. Meanwhile, the relationships between Dk and volumetric polarizability and between Df and volumetric dipole moment are confirmed. This work provides a guideline for the structure−dielectric relationship of PI at a high frequency of 10–40 GHz. [ABSTRACT FROM AUTHOR]

This paper introduces a resonant switched capacitor converter (RSCC) topology that enhances the operational efficiency by utilizing devices with reduced ratings. The RSCC eliminates bulky magnetic elements, yielding increased power density, modular structure, and compact size compared with switched inductor topologies. Significantly, all the switched capacitors in the proposed converter and approximately 50% of the switching power devices are explicitly rated for the input voltage enabling its use for high‐power applications. A compact inductor is utilized for resonant operation, and the switching frequency of the converter is significantly reduced leading to reduced switching losses and improved efficiency. Zero current turn‐ON and turn‐OFF of the switching devices is achieved. Elimination of load‐side bulky capacitor using inherent output voltage ripple reduction is achieved by aligning the switching phases of the converter such that individual capacitor voltage ripple gets cancelled out. The work extensively covers the analysis of the converter in steady‐state and the effect of non‐idealities during the resonant operation. Further, a detailed design of the topology with a discussion on component selection is presented. The operation of the proposed converter is systematically analyzed through a series of simulation results generated, and the converter is further validated by developing an experimental prototype at a power of 200 W with an efficiency of 95.83%. [ABSTRACT FROM AUTHOR]

The root dielectric response was measured on a minute scale to assess its efficiency for monitoring short-term cadmium (Cd) toxicity non-destructively. Electrical capacitance (CR), dissipation factor (DR) and electrical conductance (GR) were detected during the 24 to 168 h after Cd treatment (0, 20, 50 mg Cd2+ kg–1 substrate) in potted maize, cucumber and pea. Stress was also evaluated by measuring leaf chlorophyll content, Fv/Fm and stomatal conductance (gs) in situ, and shoot and root mass and total root length after harvest. CR showed a clear diurnal pattern, reflecting the water uptake rate, and decreased significantly in response to excessive Cd due to impeded root growth, the reduced tissue permittivity caused by accelerated lignification, and root ageing. Cd exposure markedly increased DR, indicating greater conductive energy loss due to oxidative membrane damage and enhanced electrolyte leakage. GR, which was coupled with root hydraulic conductance and varied diurnally, was increased transiently by Cd toxicity due to enhanced membrane permeability, but declined thereafter owing to stress-induced leaf senescence and transpiration loss. The time series of impedance components indicated the comparatively high Cd tolerance of the applied maize and the sensitivity of pea cultivar, which was confirmed by visible shoot symptoms, repeated physiological investigations and biomass measurements. The results demonstrated the potential of single-frequency dielectric measurements to follow certain aspects of the stress response of different species on a fine timescale without plant injury. The approach can be combined with widely used plant physiological methods and could contribute to breeding crop genotypes with improved stress tolerance. [ABSTRACT FROM AUTHOR]

Recent advancements in 3D printing technology have enabled the rapid production of complex structures, yet the dielectric performance of 3D printing materials and their potential for manufacturing electrical components remain insufficiently studied. In this study, a capacitor rated at 10 kV with a capacitance of 1 nF was designed and developed for high-voltage applications. During the production of the capacitor, the insulating and conductive parts were fabricated using a 3D printer. While PLA, ABS, ASA, and PETG were employed as insulating materials, aluminum was chosen as the conductive part. Theoretical calculations and the finite element method were used to validate the measured capacitance of the equipment. The performance of the prototype capacitor was analyzed through partial discharge inception voltages (PDIV), dissipation factor (tanδ), and breakdown voltage measurements. Dissipation factor measurements were performed at 2 and 4 kV voltages in the 50–400 Hz frequency range. The performance of employed materials was comparatively analyzed through experimental and simulation results. Finally, the impact of different insulating materials on the dielectric performance of the prototype capacitors was evaluated.

Polyvinylidenefluoride (PVDF) is a semi‐crystalline ferroelectric polymer with a wide range of interesting properties and shows potentiality in a variety of technological applications. Flexible thin films of PVDF nanocomposites (NCs) have attracted many researchers due to their tunable electronic properties. This paper reports the synthesis, characterization, and dielectric studies of PVDF‐TiO2 NC thin films. The synthesized films are self‐supporting thin and the average thickness of the thin films is 60 µm measured using a Digital thickness gauge of resolution 0.01 mm. TiO2 nanoparticles are prepared using the combustion method. Commercially available PVDF granules are used to develop PVDF‐TiO2 NC thin films using the film casting technique. The structural study of the prepared thin films is carried out using XRD that confirms the retention of the β‐phase of PVDF. The functional group and bonding nature have been studied using FTIR Spectroscopy. The thermal stability of the NC thin films is studied using TGA. The variation of dielectric constant (DC), dielectric loss (DL), AC conductivity, and dissipation factor of the medium of pristine PVDF and PVDF‐TiO2 NC thin films are studied in the frequency range of 10 Hz to 8 MHz at ambient temperature. The dielectric constant of PVDF‐TiO2 NC thin films increases up to 8 wt% and anomaly for 10 wt% of TiO2 fillers in the PVDF matrix at a lower frequency and found to decrease with increasing frequency. The dielectric loss of NC thin films is high at a lower frequency and decreases with an increase in the frequency that is in good agreement with the Maxwell–Wagner type of interfacial polarization. At lower frequencies, the dielectric constant of PVDF‐TiO2 NC increases with the increase in filler content. AC conductivity shows a sharp increase at higher frequencies whereas the dissipation factor of the polymer NCs remains unaltered with respect to frequency by maintaining the trend. This suggests that PVDF‐TiO2 NC is potential material for energy storage devices. [ABSTRACT FROM AUTHOR]

To decrease the insulation requirements and cost of transformers, the global transformer industry has been relentlessly striving to narrow the gap between net electrical stresses and dielectric withstand capability. One promising solution for high power density equipment is to blend coconut oil (CO) with the high-performance synthetic ester 'MIDEL 7131' fluid. In this study, the AC breakdown characteristics of various CO and MIDEL 7131 blends were analyzed, and it was determined that the most optimized AC breakdown performance under both new and aged conditions was achieved with a 40% volume of MIDEL 7131. [ABSTRACT FROM AUTHOR]

This paper characterizes and develops life models for two different wire insulating materials: Poly-ether-ketone (PEEK) and nanofilled enamel (Allotherm wire). The article focuses on predicting the lifespan of PEEK and Allotherm wire insulating materials, specifically for use in low-voltage electrical machines. The study investigates the effects of thermal ageing in terms of dissipation factor, insulation capacitance, and partial discharge inception voltage (PDIV). Delamination of the insulation layer is observed in both wires during the ageing process, resulting in an increase in the differential dissipation factor and insulation capacitance. With respect to its unaged condition, Allotherm wire exhibits faster degradation, showing 2.4- and 4.5-times higher changes in the differential dissipation factor and insulation capacitance respectively compared to PEEK wire after the 16th ageing cycle. In addition, Allotherm wire experiences faster deterioration of the PDIV, with a 42% reduction compared to 32% in PEEK after the same ageing cycle. Using a single-stress Arrhenius life model, the study estimates the relative thermal index (RTI) for both materials as 245°C for PEEK and 226.25°C for Allotherm wire. These results indicate a 72.1% decrease in the lifetime of PEEK and a 25.5% decrease in the lifetime of Allotherm wire when compared to the manufacturer’s RTI specification.

Warp knitting is a highly productive textile manufacturing process and method of choice for many products. With the current generation of machines running up to 4400 min−1, dynamics become a limit for the production. Resonance effects of yarn-guiding elements and oscillations of the yarn lead to load peaks, resulting in breakage or mismatches. This limits material choice to highly elastic materials for high speeds, which compensate for these effects through their intrinsic properties. To allow the processing of high-performance fibers, a better understanding of the viscoelastic yarn behavior is necessary. The present paper shows a method to achieve this in longitudinal yarn direction using a dynamic mechanical analysis approach. Samples of high tenacity polyester and aramid are investigated. The test setup resembles the warp knitting process in terms of similar geometrical conditions, pre-loads, and occurring frequencies. By recording the mechanical load resulting from an applied strain, it is possible to calculate the phase shift and the dissipation factor, which is a key indicator for the damping behavior. It shows that the dissipation factor rises with rising frequency. The results allow for a simulation of the warp knitting process, including a detailed yarn model and representation of stitch-formation process.

Porcelain have been widely utilized in electrical power system. The enhancement of its properties has positively influenced its behavior thence on overall power system. Nano/Micro technologies are influential field used for developing different characteristics of porcelain insulators. In this work, three weight percentages of fly ash micro-particles were admixed to neat porcelain. Characterization and morphological features for prepared samples were scrutinized using XRD and SEM. BDV, relative permittivity, and dissipation factor were measured. Moreover, porosity, bulk density, and water absorption were measured. COMSOL Software was used to simulate the electric field distribution on the samples. This study indicated, fly ash promoted the electrical characteristics of porcelain. Inclusion of 6 % fly ash along the porcelain sample increases BDV from 22.5 kV to 56.7 kV. The presence of fly ash inside porcelain not only decreased relative permittivity but also dissipation factor. The optimum sintering temperature gives lowest porosity and highest bulk density was 1200 °C.

Impedance measurements play a critical role in analyzing the electrical behavior of piezoelectric biosensors in general. Antenna analyzers are engineered to measure the specific case of input impedance for antenna systems. In this study small form factor antenna analyzer is repurposed to work as driving circuit for a Quartz Crystal Microbalance (QCM) biosensor in combination with a single board computer as an indication of how small and portable an impedance measuring system can be made, while allowing monitoring of important parameters of series and parallel resonance frequencies together with dissipation factor. A QCM crystal with a 10 MHz fundamental resonance frequency is employed to determine the limit of detection of the system in Bovine Serum Albumin (BSA) and glycerol solutions. Dissipation factor and phase angle were monitored during the experiments. Limit of detection is 20 µg/ml BSA in phosphate buffer saline (PBS) and 250 µl of glycerol in 100 ml of deionized water. [ABSTRACT FROM AUTHOR]

This paper presents the manufacturing and testing methods of 30kV and 33nF high voltage filter capacitors. One of the biggest advantages of small companies is that they are able to produce a high diversity of capacitors in small quantities. One of the prices of this flexibility is a higher level of manual manufacturing process in production. But this higher level of manual manufacturing does not mean lower quality in the final product. For high quality products in the high voltage industry, it is necessary to do routine tests in all of the products. For high voltage capacitors the following three tests must be done to ensure quality: voltage strength test, partial discharge test, capacitance and dissipation factor test. The capacitance and dissipation factor test have to be done at different voltage levels. The voltage strength test has to be done at least 20% higher than the rated voltage. This kind of test gives us information not only about the quality of the product itself, but about distribution of the capacitance for example, or about the strength of the production process, and about the quality management system of the company. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are getting great interest due to their large applications in modern electronics technology such as memory devices, pyroelectric detectors, modulators, and so on, rubidium dihydrogen phosphate (RDP) is a member of Potassium dihydrogen phosphate family of ferroelectric crystals. In De Gennes–Kobayashi pseudospin model few extra terms like phonon anharmonic terms, extra spin phonon interaction terms, four body interaction terms and electric field terms are included. Dielectric properties have been investigated. Statistical Green function method of Zubarev is employed to derive excitation frequency, capacittivity, and dissipation factor for RDP. Theoretical data are compared to experimental data of other workers for RDP. [ABSTRACT FROM AUTHOR]

This paper reports the critical investigation on the streaming current of ester fluids towards power transformer. The spinning disc methodology is adopted for measuring the streaming current at the liquid and pressboard interface. Based on the measurement of the streaming current, the optimization of the benzotriazole (BTA) additive is evaluated, considering its impact with and without temperature. According to the experimental findings, a negative streaming current is observed when BTA concentrations reaches 130 ppm in the ester fluids, and the effect of temperature is found to enhance the magnitude of streaming current. Only a minimal change is noticed in the viscosity of ester fluids with the addition of BTA but to the contradictory, an increased dissipation factor is observed. The diffusion of BTA additive in ester fluids towards reduction in streaming phenomenon can impact the other dielectric properties inside the power transformers. Thus, it is required to identify the optimal concentration of BTA in ester fluids before implementing to real-time applications. In the present research work, the response surface methodology (RSM) is being utilized as an optimization technique with central composite design (CCD) as a tool to identify the permissible level of BTA under transformer standstill and normal operating temperature conditions. During transformer standstill conditions, the optimal concentration level of BTA provided by RSM-CCD towards lower streaming current is 106.863 ppm with its permissible disc velocity of 300 rpm. A quadratic model is being followed for standstill conditions with its R2 value equivalent to 0.9889. Considering this BTA concentration as a base input to RSM-CCD during transformer operating conditions, the optimal concentration of BTA is found to be 104.265 ppm with temperature limit of 65 °C resulting in magnitude of streaming current, viscosity, and dissipation factor to 1145.33 pA, 18.43 mPa.s and 0.0159, respectively. [ABSTRACT FROM AUTHOR]

This study focuses on the dielectric relaxation response of insulating liquids based on mineral oil and synthetic ester in a thermal field.The research also offers the dielectric relaxation response of the magnetic nanofluid based on the investigated synthetic ester. The reason for investigating the synthetic ester-based nanofluid is that the temperature characteristics of the mineral oil-based magnetic nanofluid have already been investigated in several studies. Nanofluid based on synthetic ester is not sufficiently explored in this regard. The behavior of insulating liquids in the thermal field is divided into two parts. The first one points to the effect of temperature on the dielectric properties of the insulating liquids in the range from 293.15 K to 363.15 K. The insulating liquids show relaxation processes in the investigated frequency spectrum (1 mHz–3 kHz), which are dependent on temperature. The logarithm of the relaxation frequency decreases linearly with decreasing temperature according to Arrhenius' law. Mineral oil has the highest value of activation energy. In the second part, the results are focused on the influence of the rate of temperature increase on the dielectric parameters and moisture content of the investigated fluids. A slower increase in temperature causes an increase in polarization losses and a reduction in the distribution of relaxation times. In the case of base oils, also a reduction in activation energy. The change in the heating rate of the investigated liquids does not affect their moisture. Changes in dielectric parameters are not caused by changes in the moisture of insulating liquids, but by thermal aging.

Nickel doped magnesium-manganese spinel ferrites with nominal composition Mg0.5Mn0.5Fe2-xNixO4 (x ​= ​0.0, 0.15, 0.20, 0.25) nanoparticles are synthesized using WOWS sol gel method. Initially, the mixture is heated along with continuous stirring to dissolve all precursors and then, precursors' mixture is converted it into gel, and finally a fluffy powder is obtained. Powder and some prepared pellets of all samples are annealed at 700 ​°C in a furnace for 1 ​h. The x-ray diffraction (XRD) spectra revealed that all samples are of single-phase spinal crystal structure and possess a good crystallinity. The crystallite size obtained from XRD data decreases with the increase in doping concentration. The lattice parameter has values from 8.35 to 8.38 ​Å. Surface morphology observed by scanning electron micrographs (SEM) reveals that most of the particles are of almost spherical shape and size distribution of the particles varies in the range of 71–84 ​nm. Dielectric constant and dissipation factor decreases sharply at low frequencies and becomes almost constant at higher frequencies. Dielectric constant and dissipation factor decreases from 8.82 to 1 and 0.18 to 0.01 respectively with the increase in doping concentration. Results obtained from vibrating sample magnetometer (VSM), reveals the increasing trend in both saturation magnetization and coercivity with the increase in nickel concentration. The synthesized material could find its application data storing cards and magnetic recording media. [ABSTRACT FROM AUTHOR]

The principal objective of this paper is to investigate the propagation behaviour of SH-type waves incurred due to a point source in a porous piezoelectric layer resting over a heterogeneous viscoelastic substrate. The Green’s function technique is used to determine the frequency equation which ultimately reduces to the classical Love wave equation as a special case of the present problem. Further, expressions for the particle displacement in the layer and substrate have been obtained. Some numerical computations and comparative analysis have been performed to demonstrate the behavioural characteristics of SH-type wave propagation under the influence of some of the critical factors such as heterogeneity parameter associated with rigidity, internal friction and, density. Other affecting factors include dissipation factor, attenuation coefficient, piezoelectric constant, the width of the PPM layer and dielectric constants, which have been unravelled and displayed graphically. [ABSTRACT FROM AUTHOR]

Recently, Polarization Depolarization current (PDC) measurement is widely accepted time domain spectroscopy-based method for assessing the insulation condition. Various performance parameters like Dissipation factor (%tan $\delta $ ), Paper Moisture (%pm), Dielectric Adsorption Ratio (DAR), Polarization index (PI) etc. can be estimated by analyzing the PDC data. During field measurement various factors influences the recorded PDC data. As per existing literature, presence of low frequency noise, effect of temperature variation and influence of residual charge are common during field measurement. These factors significantly affect recorded polarization current and hence estimated performance parameters. Hence, analysis using recorded polarization current data may provide misleading information regarding insulation condition. Under such practical situation where polarization current is affected by above mentioned factors that generally observed during field measurement, depolarization current should be used for analysis of insulation condition. The depolarization current does not influence by such external factors. The present work shows the importance of depolarization current where polarization current is influenced by external low frequency noise and residual charge. The analysis firstly applied on sample prepared in the laboratory and then on data collected from real life in-situ transformers. The results obtained from the analysis shows that the data obtained from depolarization current is more reliable.

The paper presents a study on the effects of thermal aging on a low-voltage cable. Cable samples with a length of 50 cm were subjected to thermal cycling from +140 °C to −20 °C in a climate chamber with controlled temperature. This treatment compares the short-term failure or the emergency overload of some cables under real operating conditions at low temperatures. The effect of the temperature cycle is investigated through electrical measurements such as dielectric spectroscopy, voltage response measurements, and mechanical measurements such as Shore D hardness investigation. The results revealed that the thermal cycles of accelerated aging caused the plasticizer to diffuse into the jacket and then be released into the environment. At the same time, the thermal shocks produced microcracks in the cable jacket, accelerating the removal of the plasticizer. [ABSTRACT FROM AUTHOR]

This study presents the experimental results of the effects on base oils after thermal and electrical aging to determine key parameters of next-generation fluids for thermal management in electric vehicles. The test fluids selected were a mineral base oil API G-III, an API G-IV Polyalphaolefin (PAO), a diester, and a polyolester, all of which had similar kinematic viscosity (KV100 = 4 cSt). All were initially characterized with measurements of density, viscosity, thermal conductivity, specific heat capacity, breakdown voltage, resistivity, and dissipation factor. They underwent two separate aging processes, one thermal, heating the test fluid at 150 °C for 120 h with a copper strip as a catalyst; and the second one an electrical aging process, with the application of 1000 breakdown voltage discharges. The same properties were measured again after each aging process and compared to the initial ones. It was found that the thermal properties ranged with similar values and did not suffer major changes after the aging processes, unlike electrical properties, which vary between samples and after thermal and electrical stress. The insights gained from this study have implications for both the development of next-generation e-thermal fluids and the future standardization of these fluids for EV thermal management applications. The findings of this study underscore the significance of formulating and selecting a suitable dielectric fluid for EV thermal management. By leveraging the insights provided, researchers and engineers can advance in the development of efficient and reliable e-thermal fluids while working towards future standardization to enhance the performance and safety of EV battery systems. [ABSTRACT FROM AUTHOR]

Recently, due to the intensive and fast progress of the high frequency wireless communication environment, including 5th generation (5G) wireless communication, more robust substrate for printed circuit board (PCB) application, especially with less power consumption, is required. In this study, modified resins based on styrene-maleic anhydride (SMA) copolymer were prepared and evaluated as binder resin to accomplish a low dielectric constant or relative permittivity (εr: <3.0) substrate for the PCB application under ultrahigh frequencies (UHF; 1 GHz~9.4 GHz). The low εr dielectric characteristics of the modified SMA copolymer could be correlated with effects from the stereo-structure of carbon chains or conformational orientation, where the degree of crystallization was analyzed by X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopies. Prepreg films of the low εr modified SMA copolymers and their compounds with epoxy resins were also characterized in terms of dielectric loss or dissipation factor (Df), which have shown more noticeable relation with their stereo-structures as well. [ABSTRACT FROM AUTHOR]

An explicit relation between half‐width at half‐maximum ΔT in a dissipation factor of dipolar molecular rotors in a solid phase and rotational barrier height Ub was derived within the Debye relaxation model. The formula for Ub is simply expressed as Ub≈1.317kT*2ΔT. Here, T* is the temperature at the peak position in the dissipation factor, and k is the Boltzmann constant. The formula is an alternative to the familiar Arrhenius equation, from which Ub has so far been estimated in various dielectric experiments. The distinction of the proposed formula is the determination of Ub from a single peak in a dissipation factor induced by an electric field, while the Arrhenius equation needs data for the magnitudes of the dissipation factor and temperatures at several peaks. By applying the proposed formula to dipole molecular rotors (ROT‐2F) in a single crystalline and polycrystalline, for which Ub values were reported (Horansky et al., Phys. Rev. B 74, 054306 [2006]), the calculated values of Ub were quantitatively reproduced. This indicates the validity of the proposed formula, and the formula is expected to be applied to the analysis of dielectric spectra of 2D dipolar molecular rotor systems. [ABSTRACT FROM AUTHOR]

There are materials that could serve useful purpose(s) in many fields, but they are left unutilized due to lack of both the knowledge on their useful properties and availability of values as per such properties. Notably, the knowledge of dielectric properties of some materials of plant origin is lacking whereas such is necessary for industrial, agricultural, electrical, electronics, biophysical and medical applications as well as other uses of a material. In this research, Raphia Vinifera is a material of choice. The experimental determination and computation of some dielectric properties of Raphia fiber from epidemis of young leaflets of Raphia Vinifera is explored. The properties considered for determination were dielectric permittivity, loss angle and dissipation factor. A Schering Bridge arrangement was employed, with a fixed thickness and varying areas of sample at various select frequencies. The values of the investigated properties recorded for our research sample trended towards being dependent of frequency. At frequency values above 1 kHz, the values of the properties determined decreased with increase in frequency. The values compared favorably with those of the already known and commonly used dielectric materials. The preliminary investigation showed that Raphia Vinifera would have usefulness in the electrical and electronic industries as raw material for the production of capacitor among other uses.

Porous polyimide hybrid films with ultralow dielectric constant and dissipation loss were synthesized during chemical imidization and rapid evaporation of polymer solutions. Polyimide (PI) of bis(4-aminophenyl)-1,4-diisopropylbenzene (BISP) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) were synthesized in N-methylpyrrolidinone (NMP) to yield the corresponding poly(amic acid)s (PAA)s, which were then chemically imidized. To reduce the dielectric properties of the porous PI films, amine-functionalized, surface-modified hollow silica nanoparticles (AHNS) with various sizes from 100 nm to 1 μm, prepared via sol-gel process, were added with PAA at 3, 5, or 10 % weight content, followed by chemical imidization to produce the porous PI/AHNS films. To avoid the high-volume shrinkage of wet gels and maintain the high porosity of the PI with low polarizability, AHNS nanoparticles were added to the porous structure of the PI xerogels as a physical crosslinker. The polyimide hybrid film with 10 nm AHNS nanoparticles at 10 % weight content showed a dielectric constant of 1.151 and a dissipation rate of 0.001 at a frequency of 10 GHz. [Display omitted] • Preparation of composite thin film with ultralow dielectric constant and dissipation loss. • Porous composite thin film with excellent thermal stability and low polarizability. • Prevention of the high-volume shrinkage of wet gels. [ABSTRACT FROM AUTHOR]

According to the latest research, nanofluids as a possible future substitution for high-voltage equipment insulation have the potential to enhance the heat transfer and insulation properties of their base fluids. Dielectric properties are represented by breakdown strength (AC, DC, lightning) and dielectric performance as a set of quantities including dissipation factor, permittivity, and volume resistivity. In this study, natural and synthetic esters were mixed with C60 nanoparticles. Samples were examined for dissipation factor, relative permittivity, and volume resistivity at temperatures between 25 °C and 140 °C to monitor changes in dielectric performance with rising temperature, in accordance with IEC 60247. In addition, the samples were tested for AC breakdown voltage (using mushroom-like electrodes with a gap distance of 1 mm) and evaluated using the Weibull distribution statistical method. These measurements allowed complex evaluation of the examined mixtures and the determination of optimal concentration for each ester-based nanofluid. [ABSTRACT FROM AUTHOR]

In recent years, due to the increasing use of nonlinear loads, the level of harmonics deteriorating the power quality has also increased in the distribution system. The harmonics have a negative effect on the behavior of equipment and materials, as they distort voltage and current waveforms of the system it is connected to. This leads to heating problems due to additional losses for the distribution system components. Due to the multitude of technical, environmental and social causes, the use of power cables, especially cross-linked polyethylene (XLPE) power cables, is increasing rapidly. In this context the problem of power system harmonics and using of XLPE power cables in distribution systems are spreading simultaneously. In this study, 60 kV overvoltage (5·U0) aging process was performed on 12/20.8 kV XLPE power cable samples at Yıldız Technical University High Voltage Laboratory. The dielectric parameters (PK, tanδ and C) of the aged cable samples were measured. By using OMICRON CPC100/CP-TD1 measuring device, the effects of harmonics with different measurement voltages have been examined on underground cables. The performance of aged cables is analyzed under harmonic voltages and the results are presented. The disruptive effects created by the 3rd–5th and 7th order harmonics have been revealed. [ABSTRACT FROM AUTHOR]

In this work, Aluminum doped Zinc oxide thin films were sputtered on glass substrate by the direct current (DC) magnetron sputtering method. The influence of Ar gas pressure on the structural and optical properties was measured. The optical parameters were calculated by UV–Visible spectroscopy, the nature of transition reveals direct allowed transition for the prepared films. Also, some physical quantities such as the strength of electron–phonon interaction, dissipation factor (tanδ) in the visible region and the lattice dielectric constant were presented for these thin films. The AFM analysis extracts surface parameters of the AZO thin films that help us to quantitively investigate the surface analysis. The band gap energy and transition index without any presumption about transition natural were calculated from Derivation Ineffective Thickness Method (DITM) and it was found that the reaction of Ar gas pressure plays an essential part in controlling the physical quantities of AZO thin films. [ABSTRACT FROM AUTHOR]

Temperature compensation occupies a significant function in the insulation condition evaluation of converter transformer bushings based on the Frequency Domain Spectroscopy (FDS), which could influence the accuracy of its insulation diagnosis. In order to accurately obtain the variation law of FDS at different temperature, a Resin Impregnated Paper (RIP) insulation bushing for converter transformer was designed by the equivalence of maximum electric field, coaxial cylinder structure and RIP materials. The increment law of dielectric parameters both dissipation factor and capacitance at wideband frequency (1mHz ~ 10kHz) was measured for a quality RIP insulation samples at the temperature from 30°C to 100°C. 1) Under the uniform temperature, it was found that the value of dissipation factor was rising with the frequency from 10 Hz to 0.001Hz, while the tendency was reversed at the frequency from 100Hz to10kHz. 2) The minimum value of tan $\delta $ from 0.001Hz to 10kHz could be driven to higher frequency moving (10Hz to 10kHz) by the action of temperature rising 30°C to 100°C.3) The effect of temperature on the lower frequency 0.001Hz ~ 1Hz tan $\delta $ of RIP insulation closely conformed to the index law of Arrhenius equation, while it was in accordance with the linear decrease at higher frequency 1kHz ~ 10kHz. The effect of temperature on dissipation factor could be eliminated by curve segment shifting based the experiment equation, which it at 0.001Hz dissipation factor could be eliminated by curve shifting based the index equation originated Arrhenius equation. The method is beneficial to eliminate the influence of temperature on the dielectric spectroscopy test results, and then to eliminate the influence of temperature on the dielectric spectroscopy diagnosis of RIP bushings.

The hydrophilic nature of cellulose compromises the dielectric properties of kraft paper insulation when exposed to water and moisture. The effort to address this setback is an ongoing research enquiry. In the present work, surface-modified rutile-titanium dioxide nanoparticles (rutile-TiO2 NPs) are reinforced into cellulose pulp to fabricate a nanocomposite kraft paper insulation. Surface modification of the nanofiller particles is intended to reduce the hydrophilicity of the resultant nanocomposite kraft paper insulation. The nanoparticles (rutile-TiO2 NPs) improve other dielectric properties of the insulation. The chemicals used for the surface modification of the rutile-TiO2 NPs were the alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA). The nanofiller retention, dispersion and hydrophobic properties of the resultant reinforced kraft paper were experimentally analyzed. The results show that more than 50% of the nanofillers were retained within the reinforced kraft paper and translated to 1.5% by weight loading of the nanoparticles in the kraft paper. Scanning electron microscopy (SEM) images showed evenly distributed nanofillers, with some traces of agglomeration. The moisture absorption property of the kraft paper specimen modified with rutile-TiO2 NPs surface conditioned with 5 vol/vol% ASA improved by 74% compared to the control (reference) specimen. Water vapor transmission rate of the surface-modified nanoparticles reinforced kraft paper insulation decreased by 30%. Compared to the unfilled paper, the contact angle of water droplets on the surface of the reinforced kraft paper improved by 12%. Water absorption rate improved by being 4 times slower in paper specimens containing rutile-TiO2 NPs surface conditioned with 5 vol/vol% ASA. Dielectric dissipation factor measurement results showed that the specimen modified with rutile-TiO2 NPs surface conditioned with 5 vol/vol% ASA had 40% lower dielectric losses than the reference samples. This study, therefore, has successfully improved the hydrophobic properties of kraft paper by filling it with surface-modified rutile TiO2 using 5% ASA as the nanoparticle surfactant.

Summary: There is a good application prospects in improving the performance for the heat storage system with Multiple phase change materials (PCMs). This article aims to evaluate the performance of multiple PCMs with reasonable PCM proportion from the perspective of entransy. A two‐dimensional mathematical model of phase change heat storage unit is established, and verified experimentally. Two indicators, entransy dissipation rate and dissipation factor, are proposed with entransy theory to evaluate the heat storage performance. The influence of the PCM proportions, heat transfer flow (HTF) inlet temperature and flow rate on the performance are explored. Results indicate that the multiple PCMs with the PCM proportion of 2/3/4 is the most optimal. And with the increase of HTF inlet temperature and flow rate, the dissipation factor decreases at first and then increases. So there is also an optimal HTF inlet temperature and flow rate, which is 343 K and 0.0005 m/s respectively. The present research has guiding value for the performance improvement of the device using multiple PCMs. [ABSTRACT FROM AUTHOR]

The humidity role in the partial discharge (PD) inception mechanism is quite complex, and there is no widely accepted theory that can describe the humidity effect on PD. In this article, the PD activity of interturn insulation of electric motor winding is experimentally investigated for different relative humidity (RH) conditions at 30 °C ambient temperature. Since the inception of PD leads to a boost in the dissipation factor (i.e., tan $\delta$) and insulation capacitance (IC), tan $\delta $ and IC tip-up test can be adopted as an indirect measurement of PD. The test campaign is carried out employing twisted pairs as samples, and both tan $\delta $ and IC are measured under a sinusoidal voltage regime. Apart from being indirectly detected, PD activities are also directly measured through a photomultiplier, while the tip-up test is performed. The adoption of direct PD measurement is to discriminate the PD from other ionization processes (e.g., water film ionization), which cannot be distinguished by indirect measurement. The experimental findings allow stating that the change of PD inception voltage (PDIV) at higher RH is due to the different places of water film formation on the insulation surface, and Paschen’s law combined with finite element analysis is used to interpret the effect of water film on PDIV. In addition, it is verified that the tan $\delta $ and IC tip-up test is not suitable for indirect measurement of PD in high humidity conditions. In fact, the higher leakage current, due to the water condensation on the insulation surface, influences the tan $\delta $ and IC measurements causing an increment in their values regardless of the PD inception. [ABSTRACT FROM AUTHOR]

This study presents the experimental results of the effects on base oils after thermal and electrical aging to determine key parameters of next-generation fluids for thermal management in electric vehicles. The test fluids selected were a mineral base oil API G-III, an API G-IV Polyalphaolefin (PAO), a diester, and a polyolester, all of which had similar kinematic viscosity (KV100 = 4 cSt). All were initially characterized with measurements of density, viscosity, thermal conductivity, specific heat capacity, breakdown voltage, resistivity, and dissipation factor. They underwent two separate aging processes, one thermal, heating the test fluid at 150 °C for 120 h with a copper strip as a catalyst; and the second one an electrical aging process, with the application of 1000 breakdown voltage discharges. The same properties were measured again after each aging process and compared to the initial ones. It was found that the thermal properties ranged with similar values and did not suffer major changes after the aging processes, unlike electrical properties, which vary between samples and after thermal and electrical stress. The insights gained from this study have implications for both the development of next-generation e-thermal fluids and the future standardization of these fluids for EV thermal management applications. The findings of this study underscore the significance of formulating and selecting a suitable dielectric fluid for EV thermal management. By leveraging the insights provided, researchers and engineers can advance in the development of efficient and reliable e-thermal fluids while working towards future standardization to enhance the performance and safety of EV battery systems.

One of the promising and exciting avenues for developing effective and efficient dielectric materials with high energy density and low cost is the recent approach of introducing inorganic nanoparticles into polymer matrices to form dielectric polymer composites, which finds application in the electrical energy storage, electronic and power device productions. Therefore, this study explored the potential of metakaolin (prepared from kaolin sourced from Kankara, Nigeria) in influencing the polyester composite dielectric properties, being a material found to be environmentally friendly and affordable. The dielectric constants and dissipation factors were used to assess the impact of introducing metakaolin in the polyester matrices. A precision LCR meter was used at room temperature, over a frequency range of 20 Hz to 1 MHz. The metakaolin used was found to be composed of 41.54 % Al2O3 and 55.28 % SiO2. The study's outcome indicates that the dielectric constant and dissipation factor increased with the metakaolin loading due to interfacial polarization but was found to decrease with increasing frequency. However, the composite with 10 %wt metakaolin was found to have shown the highest dielectric constant, based on this study, indicating an excellent electrical property, validating its use for devices like capacitors.