Search Results (1,741)

To improve the accuracy of the icing prediction model for overhead transmission lines, a physics-guided Fast-Slow Transformer icing prediction model for overhead transmission lines is proposed, which is based on the icing prediction model with meteorological input characteristics. First, the ice cover data is segmented into different time resolutions through Fourier transform; a transformer model based on Fourier transform is constructed to capture the local and global correlations of the ice cover data; then, according to the calculation model of the comprehensive load on the conductor and the conductor state equation, the variation law of ice thickness, temperature, wind speed, and tension is analyzed, and the model loss function is constructed according to the variation law to guide the training process of the model. Finally, the sample mixing enhancement algorithm is used to reduce the overfitting problem and improve the generalization performance of the prediction model. The results show that the proposed prediction model can consider the mechanical constraints in the ice growth process and accurately capture the dependence between ice cover and meteorology. Compared with traditional prediction models such as LSTM (Long Short-Term Memory) networks, its mean square error, mean absolute error, and mean absolute percentage error are reduced by 0.464–0.674, 0.41–0.53, and 8.87–11.5%, respectively, while the coefficient of determination (R²) is increased by 0.2–0.29. Full article

Portuguese civil wind bands have operated as voluntary, non-profit organisations since the 19th century and serve as presentational and communal platforms for amateur music-making. Their core mission centres on providing music instruction and practical training for amateur musicians. This study examines the motivational factors driving adult musicians’ participation in civil wind bands. The research involved 617 adult wind band musicians nationwide who completed an online questionnaire. The findings indicate that fellowship consistently ranks as the primary motivator for participation, regardless of gender, age, and formal music education level. Musicianship emerged as the second most influential factor, with younger and older musicians placing substantial value on personal musical growth. Conversely, conductor leadership was the least important motivator, particularly among older musicians and those with higher levels of formal music training. These findings highlight the multidimensional nature of motivations for sustained participation in civil wind bands. The implications suggest that music directors and organisational managers can leverage insights from motivational studies to foster inclusive, self-rewarding, and intergenerational participation. Full article

Solid-state lithium batteries are considered ideal due to the safety of solid-state electrolytes. The Na superionic conductor-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a solid electrolyte with high ionic conductivity, low cost, and stability. However, LATP is reduced upon contact with metallic lithium, leading to lithium dendrite growth on the anode during charging. In this study, LATP was synthesized, and the relationship between crystallinity and ionic conductivity was investigated at different heat treatment temperatures. Optimal sintering conditions and ionic conductivity were analyzed for sintering temperatures from 800 to 1000 °C. To suppress reactions with Li metal, 50 nm thick Ag and 10 nm thick Al₂O₃ layers were deposited on LATP via DC sputtering and plasma-enhanced atomic layer deposition. The electrochemical stability was tested under three conditions: uncoated LATP, Al₂O₃-coated LATP, and Ag+Al₂O₃-coated LATP. The stability improved in the following order: uncoated < Al₂O₃-coated < Ag+Al₂O₃-coated. The Al₂O₃ coating suppressed secondary phase formation by preventing direct contact between LATP and Li, while Ag coating mitigated charge concentration, inhibiting dendrite growth. These findings demonstrate that Ag and Al₂O₃ nano-layers enhance electrolyte stability, advancing solid-state battery reliability and commercialization. Full article

High-speed rotating flywheel bearings, designed for space applications, generate a high-resistance hydrodynamic lubrication film, which isolates the rotor, transforming it into a conductor. This phenomenon introduces a novel failure mode—flywheel bearing electrical damage caused by space charging effects. This paper first reviews the sources of common shaft voltages in flywheels and the mechanisms of electrical damage and improves the principle of deep charge causing shaft voltages in flywheel bearings, proposing that surface charge is another source of shaft voltages. The quantified analysis model of flywheel bearing electrical damage in relation to rotational speed and high-energy electron flux is derived, indicating that the damage caused by space charge–discharge to the bearing is of small magnitude and only becomes apparent after long-term accumulation, thus being easily overlooked. Based on the causal chain of electrical damage, a correlation analysis model consistent with physical principles is constructed, and the correlation between on-orbit anomalies of the flywheel and high-energy electron flux is confirmed through the use of big data. Preliminary experiments are conducted to validate all of the research results. Finally, suggestions are given for the reliable design, application, and testing of flywheels. Full article

The present paper is dedicated to the search for an alternative material based on an aluminum (Al)—few-layer graphene (FLG) composite for use in electrical applications. Due to its excellent properties, graphene has the potential for use in many applications, especially in electronics, electrical engineering, aerospace, and the automotive industry. One area where the properties of graphene can be exploited is in overhead power transmission, where the main challenge at the moment is to reduce transmission losses. The utilization of conductors that exhibit superior electrical conductivity is instrumental in ensuring the mitigation of transmission losses. The utilization of graphene or other carbon allotropes is appealing due to their elevated electrical conductivity, substantial mechanical strength, and considerable heat resistance, which can enhance the properties of the composite, thereby increasing its resistance to operational conditions, particularly long-term exposure to temperature, a parameter closely related to the current carrying capacity of the OHL. This article presents the findings of research on the production of a composite based on aluminum powder and graphene, as well as the identification of its electrical and mechanical properties. The primary challenge in this research lies in the development of a method to synthesize carbon materials with aluminum using powder metallurgy, with particular attention paid to the mixing and compacting process, which is of significant importance in ensuring the appropriate distribution of carbon material in the composite. The research carried out has determined the influence of the graphene content (0.1–1 wt.%) on the electrical conductivity (max. 35.4 MS/m) and mechanical properties of Al-FLG composites (UTS = 156 MPa). Full article

This article examines contacting by means of ultrasonic welding between a cast aluminum winding and a copper conductor of a wheel hub drive for a passenger car. The effect of thermal stress on the formation and growth of intermetallic phases (IMC) in the contact is analyzed. By using microscopy, the growth constant under the specific load conditions can be identified with the help of the parabolic time law and offer a possibility for predicting the service life of the corresponding contacts. As a result, it can be stated that the increase in electrical resistance of the present contact at load temperatures of 120 °C, 150 °C, and 180 °C does not reach a critical value. The growth rates of the IMC also show no critical tendencies at the usual operating temperatures (120 °C and 150 °C, e.g., at 150 °C = 4.59 × 10⁻⁷ μm²/s). The activation energy calculated using the Arrhenius plot of 155 kJ/mol (1.61 eV) can be classified as high in comparison to similar studies. In addition, it was found that future investigations of the IMC growth of corresponding electrical contacts should rather be carried out with electric current. The 180 °C sample series were carried out in the oven and with electric current; the samples in the oven did not show clear IMC, while the samples exposed to electric current already showed IMC under the microscope. Full article

In overhead wire transmission systems, the presence of AC resistance results in increased energy dissipation, adversely affecting the lines’ capacity to conduct current. This paper employs a finite element aluminum conductor steel-reinforced (ACSR) model, combined with electrical measurement techniques, to investigate AC resistance. By applying varying levels of AC current, the model is employed to determine the AC resistance which closely aligns with theoretical values estimated using the Morgan algorithm. The trends observed in the parameters are consistent, thereby validating the accuracy of the model. Following simulations and analyses regarding both AC resistance and temperature variations within the conductors—and incorporating empirical measurement results—it is demonstrated that, when environmental factors are not considered, any increase in the conductor temperature can be integrated into a revised model. This updated model is subsequently compared against test results obtained from an experimental platform; the findings confirm that the estimation errors remain within an acceptable range. Overall, this simulation model serves as a valuable reference for assessing AC losses in existing conductors, as well as contributing to reduced experimental costs while mitigating the associated risks and challenges. In summary, this simulation model serves as an essential reference for assessing AC losses in current conductors and aids in reducing experimental costs while addressing the associated risks and challenges. Full article

This article focuses on the analysis of a direct air-cooled rotor winding of a wound field synchronous machine, the innovation of which lies in the increase in the internal cooling surface, the cooling of the winding compared to the conventional inter-pole cooling, and the development of a CHT evaluation model accordingly. Conjugate heat transfer (CHT) analysis is used to explore the cooling efficacy of a parallel-cooled hollow-conductor winding of a salient-pole rotor and to identify a cooling performance map. The use of high current densities of 15–20 Arms/mm² in directly cooled windings requires high cooling intensity, which in the case of air cooling results not only in flow velocities above 15 m/s to ensure permissible operating temperatures, but also the need for coolant distribution and heat transfer studies. The experiments and calculations are based on a non-rotating machine and a wind tunnel using the same rotor coil(s). CHT-based thermal calculations provide not only reliable results compared to experimental work and lumped parameter thermal circuits with adjusted aggregate parameters, but also insight related to pressure and cooling flow distribution, thermal loads, and cooling integration issues that are necessary for the development of high power density and reliable electrical machines. The results of the air-cooling integration show that the desired high current density is achievable at the expense of high cooling intensity, where the air velocity ranges from 15 to 30 m/s and 30 to 55 m/s, distinguishing the air velocity of the hollow conductor and bypass channel, compared to the same coil in an electric machine and a wind tunnel at the similar thermal load and limit. Since the hot spot location depends on cooling integration and cooling intensity, modeling and estimating the cooling flow is essential in the development of wound-field synchronous machines. Full article

In this paper, a modified Shooting and Bouncing Ray (SBR) method based on high-order impedance boundary conditions (HOIBCs) is proposed to analyze the electromagnetic (EM) scattering from electrically large three-dimensional (3D) conducting targets coated with radar-absorbing material (RAM). In addition, the edge diffraction field of coated targets is included in the calculation to improve the accuracy of the calculation. Firstly, the SBR method based on the bidirectional tracing technique is presented. It is concluded that the calculation of the scattered field of the coated targets requires the determination of the reflection coefficients on the coated surface. The reflection coefficients of the coated targets are then derived using HOIBC theory. Finally, the equivalent edge current (EEC) of the impedance wedge is derived by integrating the UTD solutions for the impedance wedge diffraction with the impedance boundary conditions. The simulation results show that the proposed method improves computational efficiency compared to MLFMA while maintaining accuracy. Furthermore, the RCS characteristics of targets coated with different RAMs, different coating thicknesses and with different angles of incidence were compared, as well as the RCS results of coated targets with those of conventional perfect electrical conductor (PEC) targets. Full article

To study the aerodynamic and vibration characteristics of iced conductors under the influence of wind fluctuations, a harmonic superposition method is used to simulate nonuniform wind speeds. A user-defined function is written on the basis of the secondary development function of the Fluent 2021 R1 software to determine the displacement and velocity of the conductor at each time step, and a two-way fluid–structure interaction (FSI) numerical simulation of an iced conductor under a nonuniform wind field is performed via an overset mesh method. In the analysis, the aerodynamic coefficients and galloping characteristics of iced conductors under different degrees of freedom (DOFs) are investigated by considering different combinations of quasi-steady theory, unsteady theory, a uniform wind field, and a nonuniform wind field. The results show that in a nonuniform wind field, the mean, standard deviation (SD), and peak values of the drag and torsion coefficients of the conductors calculated via unsteady theory are significantly larger than those calculated via quasi-steady theory, indicating that the obtained aerodynamic coefficients of the latter (the mean values are typically used) conceal the characteristics of the iced conductors in an actual wind environment and ignore the adverse effects of the variability. Full article

In light of the issues associated with the laying process of transmission line cables, including concealed security risks and contact collisions between pulleys and cables, which primarily stem from reliance on drawings, this paper introduces a simulation methodology for the cable laying construction process utilizing Building Information Modeling (BIM) technology. Initially, two-dimensional DWG graphic data are employed to develop a model of the target equipment and construction environment using BIM software (Solid works 2020). Subsequently, the cable is accurately modeled by applying ADAMS virtual prototype technology, the bushing force connection method, and the macro command language. This allows for the construction of a three-dimensional real cable laying system for transmission lines, enabling the simulation of the dynamic cable laying process in the field. Subsequently, an error analysis is conducted to compare the axial tension and laying speed of the cable with theoretical calculation values. The study then proceeds to analyze tension fluctuations during the cable laying process and assess the load-bearing capacity of the pulleys, thus facilitating effective control of the construction process and enhancing safety measures. The findings indicate that the proposed method can accurately and efficiently simulate the on-site cable laying construction process, with numerical errors maintained below 5%, thereby validating the integrity of the model. Furthermore, the traction overload safety protection amplification coefficient is determined to be α = 1.5. It is highlighted that the bearing capacity of the block must exceed 60% of the load carried by the conductor at constant speed. This research provides a theoretical foundation for addressing safety hazards in cable laying engineering and holds certain engineering value. Full article

Embedding stacked HTS tapes into twisted slots is one design approach for constructing fusion conductors. This paper adopts a Cable-in-Conduit Conductor (CICC) structure, utilizing commercially REBCO coated conductors. The cable framework is made of copper and features six helically twisted slots filled with 2G HTS tapes. Two 1 m long samples with twist pitches of 200 mm and 300 mm, respectively, were fabricated. In one slot, copper and superconducting tapes were alternated, while the remaining grooves were filled with copper tapes. The 90 µm thick copper-plated bare tapes provided by Shanghai Superconductor were used for testing. By measuring the critical current of tapes positioned at different locations within the grooves at 77 K, the characteristics of each tape in the stacked arrangement were individually characterized. The study obtained the current degradation patterns of tapes located at different positions within the grooves under various bending radii. This paper will present and discuss the preliminary results of the bending measurements conducted at 77 K under a self-field. Full article

We have proposed and developed a method for measuring the thermal conductivity of highly efficient thermal conductors. The measurement method was tested on pure metals with high thermal conductivity coefficients: aluminum (99.999 wt.% Al) and copper (99.990 wt.% Cu). It was demonstrated that their thermal conductivities at a temperature of T = 22 ± 1 °C were <λ_Al> = 243 ± 3 W/m·K and <λ_Cu> = 405 ± 4 W/m·K, which was in good agreement with values reported in the literature. Artificial graphite (${\rho }_{\mathrm{G}1}$ = 1.8 g/cm³) and natural graphite (${\rho }_{\mathrm{G}2}$ = 1.7 g/cm³) were used as reference carbon materials; the measured thermal conductivities were <λ_G1> = 87 ± 1 W/m·K and <λ_G2> = 145 ± 3 W/m·K, respectively. It is well established that measuring the thermal conductivity coefficient of thin flexible graphite foils is a complex metrological task. We have proposed to manufacture a solid rectangular sample formed by alternating layers of thin graphite foils connected by layers of ultra-thin polyethylene films. Computer modelling showed that, for equal thermal conductivities of solid products made of compacted thermally exfoliated graphite and products made of a composite material consisting of 100 layers of thin graphite foil and 99 layers of polyethylene, the differences in temperature fields did not exceed 1%. The obtained result substantiates our proposed approach to measuring thermal conductivity of flexible graphite foil by creating a multi-layer composite material. The thermal conductivity coefficient of such a composite at room temperature was <λ_GF> = 184 ± 6 W/m·K, which aligns well with measurements by the laser flash method. Full article

The complex terrain of China frequently leads to wildfires, which in turn pose a threat to the safe operation of power transmission lines. Studying the breakdown characteristics of air gaps under wildfire conditions is of great significance for understanding wildfire propagation mechanisms, risk assessment and management, and ecological environment protection. This paper establishes an experimental platform simulating wildfire climatic conditions and conducts experimental research on air gaps between rod–rod gaps and conductor–ground gaps. The experimental voltage types include direct current, power frequency, and standard operating waves. The impact of wildfire factors on the breakdown voltage and discharge characteristics of air gaps was obtained. The results indicate that the main factors affecting the air gap breakdown characteristics during wildfires are flame height and smoke. Flame height directly influences the gap insulation distance. Under flame bridging conditions, the maximum decrease in breakdown voltage reaches 70–80%. As the concentration of smoke increases, the degradation of insulation performance becomes more pronounced, with a reduction ranging from 20% to over 50%. Full article

Electrostatic techniques have introduced innovative approaches to devise efficient tools for pest control across various categories, encompassing pathogens, insects, and weeds. The focus on electric discharge technology has proven pivotal in establishing effective methods with simple device structures, enabling cost-effective fabrication using readily available materials. The electric discharge-generating devices can be assembled using commonplace conductor materials, such as ordinary metal nets linked to a voltage booster and a grounded electric wire. The strategic pairing of charged and grounded conductors at specific intervals generates an electric field, leading the charged conductor to initiate a corona discharge in the surrounding space. As the applied voltage increases, the corona discharge intensifies and may eventually result in an arc discharge due to the breakdown of air when the voltage surpasses the insulation resistance limit. The utilization of corona and arc discharges plays a crucial role in these techniques, with the corona-discharging stage creating (1) negative ions to stick to pests, which can then be captured with a positively charged pole, (2) ozone gas to sterilize plant hydroponic solutions, and (3) plasma streams to exterminate fungal colonies on leaves, and the arc-discharging stage projecting electric sparks to zap and kill pests. These electric discharge phenomena have been harnessed to develop reliable devices capable of managing pests across diverse classes. In this review, we elucidate past achievements and challenges in device development, providing insights into the current status of research. Additionally, we discuss the future directions of research in this field, outlining potential avenues for further exploration and improvement. Full article