Search Results (62)

Stainless steel, due to its exceptional comprehensive properties, has been widely adopted as the primary material for liquid cargo tank containment systems and pipelines in liquefied natural gas (LNG) carriers. However, challenges such as hot cracking, excessive deformation, and the deterioration of welded joint performance during stainless steel welding significantly constrain the construction quality and safety of LNG carriers. While conventional tungsten inert gas (TIG) welding can produce high-integrity welds, it is inherently limited by shallow penetration depth and low efficiency. Magnetic field-assisted TIG welding technology addresses these limitations by introducing an external magnetic field, which effectively modifies arc morphology, refines grain structure, enhances penetration depth, and improves corrosion resistance. In this study, TIG bead-on-plate welding was performed on 304 stainless steel plates, with a systematic investigation into the dynamic arc behavior during welding, as well as the microstructure and anti-corrosion properties of the deposited metal. The experimental results demonstrate that, in the absence of a magnetic field, the welding arc remains stable without deflection. As the intensity of the alternating magnetic field intensity increases, the arc exhibits pronounced periodic oscillations. At an applied magnetic field intensity of 30 mT, the maximum arc deflection angle reaches 76°. With increasing alternating magnetic field intensity, the weld penetration depth gradually decreases, while the weld width progressively expands. Specifically, at 30 mT, the penetration depth reaches a minimum value of 1.8 mm, representing a 44% reduction compared to the non-magnetic condition, whereas the weld width peaks at 9.3 mm, corresponding to a 9.4% increase. Furthermore, the ferrite grains in the weld metal are significantly refined at higher alternating magnetic field intensities. The weld metal subjected to a 30 mT alternating magnetic field exhibits the highest breakdown potential, the lowest corrosion rate, and the most protective passive film, indicating superior corrosion resistance compared to other tested conditions. Full article

To address the impact of insulation medium degradation in the arc quenching chambers of ultra-high-voltage SF₆ circuit breakers on phase-controlled switching accuracy caused by multiple operations throughout the service life, this paper proposes an adaptive switching algorithm. First, a modified formula for the breakdown voltage of mixed gases is derived based on the synergistic effect. Considering the influence of contact gap on electric field distortion, an adaptive switching strategy is designed to quantify the dynamic relationship among operation times, insulation strength degradation, and electric field distortion. Then, multi-round switching-on and switching-off tests are carried out under the condition of fixed single-arc ablation amount, and the laws of voltage–current, gas decomposition products, and pre-breakdown time are obtained. The test data are processed by the least squares method, adaptive switching algorithm, and machine learning method. The results show that the coincidence degree of the pre-breakdown time obtained by the adaptive switching algorithm and the test value reaches 90%. Compared with the least squares fitting, this algorithm achieves a reasonable balance between goodness of fit and complexity, with prediction deviations tending to be randomly distributed, no obvious systematic offset, and low dispersion degree. It can also explain the physical mechanism of the decay of insulation degradation rate with the number of operations. Compared with the machine learning method, this algorithm has stronger generalization ability, effectively overcoming the defects of difficult interpretation of physical causes and the poor engineering adaptability of the black box model. Full article

This article presents a method that uses a spark plug as a sensor to monitor an internal combustion engine. In addition, the voltage sensors measured the high voltage at the spark plugs using a non-contact method. Monitoring can now be performed in a simple way in real time, along with data processing. This method can be effectively used for the monitoring of all cylinders in an internal combustion engine as well as supplementing other measurement methods to optimize engine maintenance and enable correct diagnostic decisions to be made. Experimental analysis focused on the effect of the spark plug gap on the arc duration, flashover voltage, and high-voltage waveforms. It was found that with an increasing gap, the arc duration is shortened, and the breakdown voltage increases linearly, indicating wear of the spark gap. With increasing temperature, the breakdown voltage value decreased. Non-contact measurements at different frequencies showed a relationship between the magnitude of the electric field and the spark plug gap. Full article

Recurrent catastrophic inverter failures significantly undermine the reliability and economic viability of utility-scale photovoltaic (PV) power plants. This paper presents a comprehensive investigation of severe inverter destruction incidents at the Kopli Solar Power Plant, Estonia, by integrating controlled laboratory simulations with extensive field monitoring. Initially, detailed laboratory experiments were conducted to replicate critical DC-side short-circuit scenarios, particularly focusing on negative DC input terminal faults. The results consistently showed these faults rapidly escalating into multi-phase short-circuits and sustained ground-fault arcs due to inadequate internal protection mechanisms, semiconductor breakdown, and delayed relay response. Subsequently, extensive field-based waveform analyses of multiple inverter failure events captured identical fault signatures, thereby conclusively validating laboratory-identified failure mechanisms. Critical vulnerabilities were explicitly identified, including insufficient isolation relay responsiveness, inadequate semiconductor transient ratings, and ineffective internal insulation leading to prolonged arc conditions. Based on the validated findings, the paper proposes targeted inverter design enhancements—particularly advanced DC-side protective schemes, rapid fault-isolation mechanisms, and improved internal insulation practices. Additionally, robust operational and monitoring guidelines are recommended for industry-wide adoption to proactively mitigate future inverter failures. The presented integrated methodological framework and actionable recommendations significantly contribute toward enhancing inverter reliability standards and operational stability within grid-connected photovoltaic installations. Full article

The intermediate joint of high-voltage cables, as a critical component in the power transmission system, plays a direct role in the stable operation of the entire electrical system. In recent years, frequent explosions of intermediate joints in high-voltage cables have led to significant economic losses and safety risks. Therefore, studying the explosion mechanisms and explosion prevention measures of high-voltage cable intermediate joints is particularly important. This article provides a systematic review of the explosion mechanisms and explosion prevention measures for high-voltage cable intermediate joints. It begins by introducing the composition of cable systems and the structural features of the 220 kV prefabricated cable joint. Next, the article elaborates on the spatiotemporal evolution process of cable joint explosions. Typically, a cable joint explosion undergoes several stages: partial discharge, arc breakdown, and insulation material decomposition, which ultimately leads to explosion and ignition. Subsequently, the article reviews each of these dynamic stages in detail. Finally, the article discusses the existing explosion prevention measures and their shortcomings, and proposes future directions for the development of explosion prevention measures. This article can provide a theoretical foundation and technical reference for the research on the explosion mechanisms of high-voltage cable joints, as well as for the development of explosion prevention measures. Full article

This study investigates the arc performance of Ag-Cr₂AlC composite materials. Spark plasma sintering method was employed to prepare the Ag-Cr₂AlC composite material. A self-made arc erosion device was utilized to erode the material with different times of arc. The surface of the material was categorized into three distinct areas: the eroded center area, the eroded edge area, and the heat-affected area. After one time of arc erosion, the material exhibits a relatively flat surface with a small erosion area. However, after one hundred arc erosions, the eroded area has significantly increased, accompanied by numerous splashes, protrusions, and pores. The action of the arc leads to the decomposition and oxidation of the Ag-Cr₂AlC composite material, resulting in the formation of Ag₂O, Al₂O₃, and Cr₂O₃ on the surface. During the process of 100 arc erosions, the breakdown current value remains relatively stable, ranging from 20 to 35 A. From the first to the 70th arc erosion, the breakdown strength consistently varies between 3 × 10⁶ V/m and 6 × 10⁶ V/m. Subsequently, there is an observed enhancement in breakdown strength, leading to the appearance of ageing. These findings establish a theoretical foundation for the application of silver-based electrical contact materials. Full article

In order to solve the problem of slow dielectric recovery caused by large arc energy when interrupting a high rising rate fault current in a fast DC current-limiting circuit breaker (FDCCLCB), a new contact structure with multi-point static contacts in parallel is proposed. Based on the principle of parallel multi-point contacts, the new structure can form the arc mode during multi-point arcing when the contacts are separated, reduce the arc energy of each finger contact, effectively reduce the ablation effect of the arc on the contact, and improve dielectric recovery ability after the arcing of the contact. Using high-speed camera technology to photograph the arc shape of the new contact, the assumption of multi-point arcing is verified, and a dielectric recovery experimental platform is built to study the dielectric recovery characteristics of the new contact structure. The experimental results show that, when the arc energy is 3.6 J and the dielectric recovery time is 60 µs, the critical field strength reaches 1.5 V/µm; when the arc energy is increased to 22 J, the critical field strength is 0.6 V/µm under the same dielectric recovery time. It can be seen that reducing the arc energy of the contact can effectively improve the dielectric recovery ability of the contact. Due to the magnetic field coupling between each finger contact, the current and arc energy on each contact are different, resulting in a weak point of breakdown and finger contacts at two ends. Finally, in order to solve the problem of large contact current at two ends, a solution to adjust the spacing among contacts is proposed. A genetic algorithm is used to optimize the spacing parameters. The optimization results show that the maximum arc energy of the finger contact is only 19.07% of the total arc energy, which greatly reduces the arc energy of the contact and improves the post-arc recovery ability of the contact. Full article

Ag-Nb₂AlC composite materials with a Nb₂AlC volume percentage ranging from 10% to 40% were prepared using the spark plasma sintering method. The composite with 10% Nb₂AlC achieved a high density of 99.2%. The microhardness exhibited a peak value of 84.8 HV at a Nb₂AlC content of 30%. The conductivity of the composite material decreases linearly with an increase in Nb₂AlC content, ranging from 0.134 MS·cm⁻¹ to 0.086 MS·cm⁻¹. A three-dimensional laser scanning microscope was employed to characterize the morphology following arc erosion, and the erosion area was subsequently measured. Results indicated that arc erosion was concentrated on the Ag-20 vol.% Nb₂AlC composite material, resulting in a smaller circular erosion area. As Nb₂AlC content increased to 30% and 40%, the arc shifted, leading to an expansion of the erosion area. Notably, the Ag-30 vol.% Nb₂AlC composite material exhibited the highest arc energy (3.401 kJ). The eroded surface displayed spattered particles and a convex morphology. Additionally, EDS and Raman spectroscopic analyses revealed the formation of Nb₂O₅, Ag₂O, and Al₂O₃ on the surface. The arc erosion mechanism was analyzed from an electrical perspective, indicating that the formation of the arc is attributed to the development of a positive streamer and air breakdown within a strongly nonuniform field. Consequently, the surface atoms of Ag-Nb₂AlC absorb energy, leading to the formation of metal ions that combine with the ionized air to create oxides. This research lays a theoretical foundation for the application of silver-based electrical contact materials. 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

This study explores the use of a high-temperature arc generated during tungsten inert gas (TIG) welding to enhance the mechanical properties of the surface of AISI 1020 steel. An innovative two-step process involves using the high-temperature arc as an energy source to fuse a previously electrodeposited Ni/TiO₂ coating to the surface of the substrate. The cladded surface is characterised by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), an optical microscope (O.M.) equipped with laser-induced breakdown spectroscopy (LIBS), Vicker’s microhardness testing, and pin-on-plate wear testing. The treated surface exhibits a unique amalgamation of hardening mechanisms, including nanoparticle dispersion strengthening, grain size reduction, and solid solution strengthening. The thickness of the electrodeposited layer appears to strongly influence the hardness variation across the width of the treated layer. The hardness of the treated layer when the Ni coating contains 30 nm TiO₂ particles was found to be 451 VHN, validating an impressive 2.7-fold increase in material hardness compared to the untreated substrate (165 VHN). Similarly, the treated surface exhibits a twofold improvement in wear resistance (9.0 × 10² µm³/s), making it substantially more durable in abrasive environments than the untreated surface. Microstructural and EDS analysis reveal a significant reduction in grain size and the presence of high concentrations of Ni and TiO₂ within the treated region, providing clear evidence for the activation of several strengthening mechanisms. Full article

Background: Alterations in glycolipid and glycosphingolipid pathways lead to compromised cell membranes and may be involved in cataract formation. However, the exact role of glycolipids in lens opacification is not completely understood. The aim of the current study is to investigate proteome complexity and the role of glycolipid and glycosphingolipid pathways in cataract formation. Methods: The anterior capsule and phacoemulsification (phaco) cassette contents were collected during cataract surgery from eleven participants with diabetic cataract (DC), twelve participants with age-related cataract (ARC), and seven participants with post-vitrectomy cataract (PVC). Liquid chromatography–mass spectrometry with data-independent acquisition (DIA) was used for the identification and quantification of proteins. Results: The results of this study revealed that the main significantly differentially expressed pathways in the ARC group compared to the DC and PVC groups in phaco cassette samples included the glycolipid metabolic, glycosphingolipid biosynthetic, and glycosphingolipid metabolic processes, with GLA being among the most significant proteins in the ARC group. Similarly, in the anterior capsule samples, the main significantly differentially expressed pathways in the ARC group compared to the DC and PVC groups were the glycolipid metabolic, glycosphingolipid biosynthetic, and glycosphingolipid metabolic processes, with ST3GAL5 being among the most significant proteins in the ARC group. Conclusion: Glycolipid and glycosphingolipid metabolic processes may be involved in cataract formation. ST3GAL5 may modify the cell-to-cell interaction induced by cell surface sugar chains, leading to the formation and progression of cataract. GLA, associated with the breakdown of glycolipids, may lead to cataract formation when a certain threshold is surpassed, secondary to increased glycolipid metabolism. Full article

In order to investigate the characteristics and typical influential factors of wildfires caused by accidental faults in high-voltage transmission lines, a bespoke platform was constructed for the purpose of conducting simulation experiments. Discharge and ignition experiments were conducted on a variety of substrates, including kidney fern fragments, cedar needle fragments, poplar sawdust, and eucalyptus leaf fragments, to investigate the effects of different gaps on the initiation and propagation of wildfires. The results demonstrate that the discharge-inducing ignition stages can be succinctly summarized as “two phases and two points” (the discharge induction period, the gap breakdown point, the arc induction period and the fault removal point) when a suitable gap is maintained between the simulated falling lines and the vegetation surface. In the event of direct contact, the removal of the fault is not possible. The potential for ignition of the aforementioned vegetation types by the discharge is as follows: cedar needles > eucalyptus leaf fragments ≈ poplar sawdust > kidney fern fragments. As the water content increases, eucalyptus leaf fragments can still be ignited, and the breakdown voltages required for discharge-inducing ignitions gradually decrease. In the case of different forest ground vegetation types, when ignited by the discharge between the falling lines and the vegetation under conditions of proper gap and moisture content, the resulting ignition and sustained flames will promote the formation of streamer channels and further aggravate the discharges and burning processes, potentially leading to the ignition of a wildfire. Full article

High-voltage cables will continue to operate for a period of time in the event of a small current arc fault, which poses a risk of fire. Two simulated ignition methods, moving electrode and melting fuses, are proposed to analyze the ignition characteristics of low-current arcs. The ignition test was carried out, and the combustion effect was compared. The results indicate that the moving electrode ignition method can achieve long-distance arc ignition test when the current is small and is suitable for simulating the arc ignition situation of cable outer protective layer damage. By controlling the movement speed, it can be ensured that the arc will not be interrupted during the electrode movement process. However, the arc is difficult to sustain using the fuse melting method when the current is small and the distance is long. The fuse melting method is suitable for simulating insulation breakdown situations. The results show that the critical arc duration for cable ignition under five different current conditions of 2–10 A is 28 s, 21 s, 14 s, 9 s, and 4 s, respectively. The maximum height of the cable flame under 2–10 A arc current is 9–52 cm and 16–63 cm, respectively, when the arc duration is 50 s and 100 s. The self-ignition time of the cable after the arc extinguishing is 8–95 s and 14–261 s, respectively. The maximum temperature of the cable flame is positively correlated with arc current, and the maximum flame temperature of the cable under 2–10 A arc current is 540–980 °C. Based on the actual current monitoring data in cable tunnels, the research results can provide reference for the risk assessment and protection of cable tunnel fires. Full article

In this study, we explored the correlation between fluctuated waveform tails under both positive and negative impulse voltages and their corresponding spectral lines during millisecond observations of arc discharge. We examined impulse voltages in ±100, ±125, and ±150 kV across 3, 3.5, and 4 cm gaps using spectroscopic analysis focused on oxygen excitations. Six selected spectra in ±100, ±125, and ±150 kV at 3.5 cm and two negative spectra of −100 kV at 3 and 4 cm were analyzed by identifying spectral lines in the wavelength range of 200–900 nm. The results revealed a correlation between the fluctuated waveform tails and spectral lines in positive voltage discharges, which were almost similar, while in negative voltage discharges, this correlation was found only in −100 kV at 3 and 4 cm. We concluded that during the spark phase for both positive and negative voltage discharges, symmetrical fluctuation in the waveform tails was observed after breakdown time, especially above the voltage level of the recombination phase. This suggested the presence of energetic oxygen excited states in the 200–400 nm range, with higher peak intensity than the O I line at 777.417 nm, observed in most positive impulse voltage discharges and at −100 kV with 3 and 4 cm gaps, contributing to rapid breakdown. Full article

In recent years, with the continuous growth in power demand, lithium-ion batteries (LIBs) have become an indispensable component of various electronic devices, transportation vehicles, and energy systems. The safety performance of LIBs is one of the most significant issues facing their continued development. In battery systems, the presence of arcs constitutes a significant safety hazard that necessitates attention; the thermal runaway (TR) of LIBs releases a large quantity of particles with elevated temperature and high velocity, probably resulting in arc failures. Changes in the insulation structure inside battery packs and the accumulation of particulate matter resulting from the TR of battery cells are potential causes of arc-induced disasters. In this study, we utilized fully charged 71 Ah ternary LIB Li (Ni_0.8Co_0.1Mn_0.1) O₂ (NCM811) pouch cell samples and collected the vented particles in an inert atmosphere after TR. All the settled particles were classified into six groups; by conducting experiments with different particle sizes, electrode spacings, and circuit loads, the patterns of the particle-induced arcs were understood. The results indicate that as the particle size increases, the critical breakdown voltage decreases. Regarding electrode spacing and circuit load resistance, larger values require higher critical breakdown voltages. The research results provide valuable guidance for the electrical protection and safety design of battery systems. Full article