Search Results (2,534)

To elucidate the scale-dependent response and interfacial evolution of liquid capillary rise in glass capillaries under an electric field, capillaries with different inner diameters were used as model channels. The equilibrium capillary-rise behavior of NaCl solutions without an electric field was investigated, and the coupled effects of capillary diameter, temperature, and concentration were analyzed using response surface methodology. The additional rise of the liquid column under a direct-current electric field was examined, and the interfacial evolution mechanism was explored through meniscus visualization. The results show that, without an electric field, the equilibrium capillary height is governed mainly by capillary inner diameter, followed by temperature, whereas concentration has a relatively weak effect. The developed quadratic regression model shows high fitting accuracy. Under the applied electric field, the electrocapillary response exhibits clear scale selectivity. No significant additional rise was observed in the 0.1 mm and 0.3 mm capillaries, whereas the liquid-column height increased markedly in the 0.5 mm capillary. At 30 °C and 0.75 kV, the additional rise reached 8.2 mm, corresponding to a relative increase of 15.30%. The enhancement at 0.75 kV was stronger than that at 1.5 kV, indicating a non-monotonic voltage response. Meniscus experiments further show that 0.32% NaCl and 5% ethanol solutions respond more evidently to the electric field, with stronger interfacial restructuring for NaCl solution at 0.75 kV. These results indicate that the electric field modifies capillary pressure by altering the force balance near the three-phase contact region and the meniscus curvature, thereby inducing additional liquid-column rise. Full article

The tree-contact single-phase-to-ground fault (TSF) in 10 kV distribution networks has high transition resistance, weak fault currents, and nonlinear steady-state waveforms. As existing high-impedance fault models cannot accurately describe its complete physical evolution, this paper proposes a novel modeling and parameter identification algorithm for TSF. First, based on recorded data from full-scale experiments, the initiation and development processes of TSF are studied, revealing the main factors affecting fault electrical characteristics—such as moisture evaporation, pyrolysis carbonization, air gap breakdown, and tree body current dissipation. Then, a dynamic resistance series model for TSF is constructed, with parameters identified and calibrated using experimental data, objective functions, and physical constraints. Finally, a 10 kV TSF simulation model is built and verified. Furthermore, a cross-condition predictive validation is performed using different voltage and geometric boundaries. Results demonstrate that the proposed physics-constrained model can effectively reproduce the RMS fault current envelope with asymmetric moisture evaporation characteristics. It also accurately predicts steady-state nonlinear waveform features without parameter re-tuning, providing more physically consistent data support for future TSF identification studies. Full article

Multi-terminal voltage-source-converter-based HVDC (VSC-MTDC) systems are increasingly used to integrate renewable energy and interconnect asynchronous AC grids, but conventional fixed-coefficient droop control cannot simultaneously limit DC-voltage deviations, reduce operating losses, and preserve converter power margins during operating-point switching. This paper hypothesizes that a rule-based fuzzy adjustment of the droop slope can provide smooth multi-objective coordination without inter-station communication. A dual Mamdani fuzzy controller is developed: one controller adjusts the weighting between loss-oriented and power-margin-oriented droop coefficients according to converter power margin, while the other introduces a voltage-deviation correction according to DC-bus voltage. The controller is implemented and verified in a five-terminal MMC-based VSC-MTDC model built in PSCAD/EMTDC, where simulation data are generated under heavy-load, light-load, and power-reference switching scenarios using specified line and converter parameters. Compared with conventional droop control, the proposed strategy improves power-margin utilization, reduces operating-point discontinuities, and raises the minimum DC voltage from 370.2 kV to 381.4 kV in the severe switching case. The results confirm that fuzzy-slope droop control can achieve smoother operating-point switching and better coordinated optimization among voltage stability, operating loss, and converter reserve margin. Full article

Natural polysaccharides from Siegesbeckia orientalis L. have been reported to exhibit promising bioactivities. To enhance extraction efficiency, low-temperature plasma-assisted extraction was optimized for S. orientalis L. polysaccharides using single-factor experiments and response surface methodology. Column chromatography purified a homogeneous SIE-III fraction, followed by structural characterization. Optimal parameters were 80 kV discharge voltage, 153 Hz frequency, and 109 s treatment time, under which the polysaccharide yield reached 15.68%, significantly higher than that of the conventional hot water extraction method. Plasma treatment loosened the raw material’s surface, potentially facilitating polysaccharide release. SIE-III had a molecular weight of 20.831 kDa and comprised mainly galactose (51.7%), rhamnose (19.1%), arabinose (11.3%), and galacturonic acid (9.9%). It featured typical rhamnogalacturonan-I (RG-I) domains and a triple-helix conformation. Fourier transform infrared spectroscopy and nuclear magnetic resonance confirmed both α- and β- glycosidic linkages, and methylation analysis revealed a highly branched →3,4)-Galp-(1→ structure. This study provides an effective extraction method for plant polysaccharides and valuable insights into their potential applications in the food and other industries. Full article

Voltage-gated ion channels (VGICs) are traditionally associated with electrically excitable cells; however, increasing evidence indicates that they are also expressed in non-excitable cells, including vascular endothelial cells. This review aims to summarize the current knowledge on the expression, regulation, and functional role of VGICs in the vascular endothelium, and to highlight their potential contribution to endothelial signaling. We examined the molecular structure, biophysical properties, and functional roles of voltage-gated Na⁺ (Na_V), Ca²⁺ (Ca_V), and K⁺ (K_V) channels in vascular endothelial cells. Particular attention was given to studies investigating VGIC activity in native endothelium and to emerging mechanisms regulating their activation. Endothelial cells express multiple VGIC subtypes at low densities, which are insufficient to generate action potentials but can modulate membrane potential (V_M) and Ca²⁺-dependent signaling. The dynamic regulation of the endothelial V_M, through the interplay between hyperpolarizing and depolarizing conductances, emerges as a key determinant of VGIC availability and activation. VGICs contribute to essential endothelial functions, including angiogenesis, vasomotor responses, blood–brain barrier permeability, and inflammation. Dysregulated VGIC expression and/or activity may be implicated in several pathological conditions, such as atherosclerosis, calcific aortic stenosis, and tumor vascularization. VGICs represent an unexpected but functionally relevant component of endothelial signaling. Elucidating their role in native vascular beds and disease contexts may uncover novel mechanisms of endothelial regulation and identify new therapeutic targets in cardiovascular and cancer biology. Full article

Non-contact magnetic sensing technology is widely adopted in transmission line online monitoring scenarios including current measurement and fault location for its non-contact measurement capability, strong environmental robustness and low deployment cost. However, existing magnetic-sensing-based galloping monitoring methods suffer from two critical limitations: no theoretical guidance is provided for sensor placement, and a high false detection rate is observed under current fluctuation conditions. To address these issues, a novel transmission line galloping monitoring method based on spatial magnetic field distribution features is proposed in this paper. A conductor galloping-power frequency magnetic field coupling model is first established to derive the optimal magnetic sensor array arrangement strategy. Subsequently, a galloping detection algorithm fusing multi-node frequency-domain features and phase difference information is proposed to eliminate current fluctuation induced false detection. Simulations conducted based on actual 500 kV transmission line parameters and verification tests carried out on a scaled-down laboratory platform confirm that reliable galloping detection can be realized by the proposed method under both current low-frequency oscillation and random fluctuation scenarios. With advantages of non-contact deployment, high anti-interference performance and detection accuracy, the proposed method has promising application potential in engineering-oriented high-voltage transmission line monitoring. Full article

With increasingly stringent restrictions on SF₆ greenhouse gas emissions, C₄F₇N-based gas mixtures have attracted considerable attention as promising alternatives for high-voltage circuit breakers; however, their relatively weaker arc-quenching capability poses significant challenges for interruption chamber design at high voltage levels. In this study, a 3.5% C₄F₇N/83.5% CO₂/13% O₂ gas mixture was used as the arc-extinguishing medium in a 550 kV environmentally friendly gas circuit breaker. Based on a magnetohydrodynamic (MHD) model considering PTFE nozzle ablation effects, systematic optimization studies were conducted on key structural parameters of the puffer-type interruption chamber, including the exhaust hole diameter, nozzle throat diameter and length, arcing contact diameter, and downstream expansion angle. Simulations under arcing times of 9.9 ms and 11.4 ms were performed to evaluate chamber pressure, axial temperature, extinction peak voltage, and post-arc conductance characteristics. The results indicate that extending the nozzle throat straight section to 70 mm, enlarging the exhaust hole, and increasing the moving contact radius can effectively enhance pressure buildup, reduce arc-core temperature, and improve dielectric recovery capability. Under the 11.4 ms arcing condition, the optimized structure achieved an extinction peak voltage of 6972.4 V and a G200 value of 0.731 ms, demonstrating substantially improved interruption performance. These findings reveal the synergistic relationship between arcing time and structural parameters and provide theoretical guidance for the engineering design of environmentally friendly high-voltage gas circuit breakers. Full article

The integration of distributed generation (DG) changes the fault current path, magnitude, direction, and transient characteristics of distribution networks, which increases the difficulty of fault type identification. In particular, weak fault features and high-frequency transient components may reduce the reliability of traditional feature-based diagnosis methods. To improve the representation and classification capability of fault signals, this paper proposes a fault type identification method based on wavelet packet transform and an improved CNN-BiGRU model with a channel attention mechanism. First, three-phase voltage, three-phase current, and zero-sequence voltage signals are decomposed by wavelet packet transform, and the corresponding time–frequency matrices are constructed. Then, these matrices are integrated and converted into time-frequency images, so that multi-source fault information can be represented in a unified form. On this basis, CNN is used to extract local spatial features from the time-frequency images, while BiGRU is employed to capture bidirectional dependency information of fault features. Furthermore, a channel attention mechanism is introduced to enhance informative feature channels and suppress redundant information, thereby improving the fault classification performance. Simulation results based on a 10 kV DG-integrated distribution network show that the proposed method achieves high recognition accuracy under different DG capacities and access configurations. Compared with CNN, BiGRU, and CNN-BiGRU models, the proposed CNN-BiGRU-Attention model shows better classification accuracy and adaptability, demonstrating its effectiveness for fault type identification in active distribution networks. Full article

This paper applies the comparative PCA-ANN vs. Autoencoder-ANN framework to transformer partial discharge (PD) severity classification, using a 294-sample dataset spanning four severity classes: Normal, Low PD, Medium PD, and High PD. Two raw measurements of discharge magnitude (pC) and applied voltage (kV) are expanded into a 15-dimensional physics-informed feature space. Both linear (PCA) and nonlinear (bottleneck Autoencoder) feature extraction are evaluated exhaustively across all latent dimensions k = 1–15, feeding an identical ANN classifier. PCA + ANN achieves perfect test accuracy of 100.0% at k = 9, while Autoencoder + ANN achieves 98.3% at k = 8. PCA + ANN demonstrates superior performance on this dataset, attributed to the low intrinsic dimensionality of the two-measurement PD feature space and the highly separable nature of PD severity classes in the engineered ratio feature space. The Autoencoder provides a more compact latent representation but introduces classification errors for the Normal class due to its extreme under-representation. Cross-validation confirms PCA + ANN stability (97.4 ± 0.9% vs. 97.0 ± 1.0%). These results, alongside the companion DGA study, provide the complete baseline for comparing linear and nonlinear feature extraction across two transformer diagnostic modalities. Full article

This paper focuses on 220 kV cable sheath overvoltage caused by three typical operating conditions: harmonics, short-circuits, and lightning strikes. A sheath voltage simulation model on the 220 kV side is developed in PSCAD. Through multi-parameter scanning and sensitivity analysis, the overvoltage characteristics and key influencing factors are systematically studied, and engineering optimization strategies for sheath protector configuration are proposed for different types of overvoltage. Under harmonic conditions, a suppression circuit composed of discharge capacitance and discharge resistors is proposed to attenuate high-frequency disturbances. Under high-amplitude overvoltage conditions such as short-circuits and lightning strikes, the sheath protector configuration is optimized by adjusting cable length and grounding configuration. Under large current conditions, a parallel configuration scheme for sheath protectors is proposed from the perspective of energy absorption. Multi-condition simulations are conducted, and a simulation-based case study is carried out based on the actual layout and parameters of a traction substation cable line. The results show that the proposed strategies can effectively reduce the peak value of sheath overvoltage, providing simulation-based quantitative engineering guidance for the configuration of 220 kV cable sheath protectors based on sensitivity analysis results. Full article

Surge reliability is a crucial aspect of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) reliability. This study investigates the degradation behavior and mechanisms of switching characteristics in 1.2 kV planar-gate SiC MOSFETs under repetitive surge current. A surge current test platform is established to conduct surge tests on the device, while monitoring the evolution of its switching characteristics. The results indicate that after 4000 surge current cycles, the device’s turn-on delay time (t_d(on)), rise time (t_r), and turn-on loss (E_ON) show no significant changes. In contrast, the turn-off delay time (t_d(off)), fall time (t_f), and turn-off loss (E_OFF) increase by 9%, 7.5%, and 8.3%, respectively. Switching characteristics variations are closely linked to the reduction in threshold voltage (V_TH) and the increase in gate-source capacitance (C_GS) and gate-drain capacitance (C_GD). The degradation of these parameters stems from the accumulation of positive trapped charge in the gate oxide layer above the channel and junction field-effect transistor (JFET) region. The increase in charges results from the combined effects of negative gate bias and cyclic high temperature induced by repetitive surge current. This study provides a theoretical basis for the comprehensive understanding of the impact of surge current on SiC MOSFET performance. Full article

Weak grid infrastructure and the absence of flexible storage are among the principal barriers to reliable, low-carbon energy access in sub-Saharan transmission systems. This paper proposes a hierarchical multi-objective framework for the optimal siting and sizing of battery energy storage systems (BESSs), applied to the 130-bus Mali transmission network within the EMERGE project. The upper level employs NSGA-II to simultaneously maximize daily price arbitrage revenue and minimize active power losses; the lower level solves a network-constrained DC optimal power flow with thermal branch limits enforced as hard linear inequalities via the Power Transfer Distribution Factor (PTDF) matrix. Over 500 generations, the framework identifies Bus 91 (SIRAKORO II, 150 kV) as the dominant storage location, achieving a maximum daily revenue of approximately €10,033 at a marginal loss increment of $6.7\times {10}^{-3}$ MWh. The resulting Pareto front gives Mali system planners a quantitative tool for trading off private investment returns against grid-level environmental impact, demonstrating that rigorous network-constrained BESS planning is technically tractable and economically viable in the resource-constrained context of sub-Saharan energy transitions. Full article

Non-uniform fiber deposition remains a critical limitation in electrospun poly(lactic acid) (PLA) coating systems. In the present study, experimental characterization was combined with numerical simulations to evaluate the influence of electrospinning parameters on fiber morphology, coating uniformity, and thickness distribution. A 3% PLA solution was electrospun under different processing conditions by varying the applied voltage, needle-to-collector distance, flow rate, and deposition time. The resulting coatings were further analyzed using numerical simulations performed with ANSYS Fluent 2020 R2 software. The results demonstrated that both solution-related and operational parameters strongly influence fiber morphology and spatial deposition behavior. Increasing the applied voltage promoted the formation of thinner fibers; however, excessively high voltage values generated jet instability associated with fiber fragmentation and spray formation. Furthermore, the deposited fibrous layers showed preferential accumulation in the central region of the collector, together with a gradual decrease in coating thickness toward the peripheral areas. A strong correlation was observed between the numerical simulations and the experimental results, confirming the reliability of the proposed modeling approach. Among the investigated conditions, the optimal electrospinning parameters were identified as an applied voltage of 16 kV, a needle-to-collector distance of 17 cm, and a flow rate of 2.5 mL/h. These conditions enabled the formation of homogeneous PLA nanofibers with minimal structural defects and improved substrate adhesion. The combined experimental and numerical approach provides valuable insight into the optimization of electrospinning parameters governing fiber formation and deposition behavior. Full article

Electrification of public transit is central to sustainable urban development, yet it introduces passenger exposure to extremely low-frequency magnetic fields (ELF-MFs), which the International Agency for Research on Cancer (IARC) classifies as possibly carcinogenic to humans (Group 2B). This study presents a systematic cross-platform comparison of ELF-MF exposure in direct current (DC) light rail and alternating current (AC) heavy rail systems operating under a single national regulatory framework. A total of 9100 continuous measurements were collected across 28 trips on the Tel Aviv Red Line light rail transit (1500 V DC) and the Israel Railways Tel Aviv–Binyamina corridor (25 kV, 50 Hz AC) during 23–26 November 2025, using calibrated Tenmars TM-192D gaussmeters. Mean passenger seat magnetic flux density was 0.226 ± 0.147 µT (2.26 ± 1.47 mG) for the DC system and 0.900 ± 0.606 µT (9.00 ± 6.06 mG) for the AC system. The difference was highly significant (Welch’s t = −73.06, p < 0.001). DC light rail exposure remained consistently below Israel’s precautionary 0.4 µT (4 mG) threshold for continuous public exposure, whereas AC heavy rail mean levels exceeded this threshold in every monitored trip while remaining far below ICNIRP general public reference levels. These findings highlight a “Green Dilemma” in sustainable transport policy: the environmental benefits of rail electrification must be balanced with prudent electromagnetic exposure management in jurisdictions applying strict precautionary limits. Full article

Electric-field-enhanced evaporation is an innovative approach to reducing the energy consumption of evaporation processes. To investigate the effect of an electric field on droplet heat-flux characteristics during evaporation, this study numerically simulated the evaporation of pinned sessile droplets on a solid substrate under a parallel-plate electrode configuration. The results show that increasing the plate voltage (from 2 kV to 4 kV) can significantly enhance the surface flow velocity, with the maximum increase reaching 157% in the early stage of evaporation; however, this enhancement diminishes as evaporation progresses. At higher voltages, the internal flow field of the droplet transitions from a single circulation to a double-circulation structure, and the influence of voltage on the droplet’s bulk internal temperature gradient is limited, with the maximum temperature difference remaining below 1 K. When the ambient temperature is below 308.15 K, the electric field enhancement of evaporation is most pronounced: compared with natural (no-field) evaporation, the drying time is reduced by approximately 15.5%. However, when the ambient temperature exceeds 308.15 K, the electric field enhancement decreases markedly. These findings provide a theoretical basis for electric-field-assisted evaporation technologies and inform directions for parameter optimization. Full article