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Besides managing accruing data in production systems, Digital Twins provide additional services like the simulation or control of production systems. The Digital Twin and its real-world physical counterpart need to be interconnected using sensors and actuators to enable such services. This article proposes a simulation-based method to design and evaluate such an interface. Applying concepts from the area of software-in-the-loop, it proposes the use of a so-called Physical Twin: a simulation model which mimics the abilities of the physical system but allows simulation-based experiments to optimise the interface. After presenting the general approach, the article provides an application example of the proposed procedure. A Digital and a Physical Twin are implemented for an application scenario and connected using a simple TCP/IP interface. By varying the number of sensors as well as considering component breakdowns in the Physical Twin, this setup allows evaluating different configurations in terms of production performance. The evaluation confirms that configurations with more sensors result in higher production performance of the system. However, a saturation of the performance gain is also observable when exceeding a certain number of sensors. Therefore, determining the optimal configuration is vital to optimise the interface from a financial point of view. [ABSTRACT FROM AUTHOR]

Abstract Environmental protection is the future trend of power equipment development, and is also a research hotspot in the field of power cable insulation in recent years. Due to the excellent electrical properties and recyclability, polypropylene (PP) based composites are regarded as promising insulating materials for eco‐friendly next‐generation power cables. However, the high modulus and hardness of pure PP make it difficult to be directly employed as cable insulations, which needs to be further optimised. General methods of mechanical performance regulation often result in the deterioration of electrical performance, such as breakdown strength, space charge and so on. Therefore, it is recognised that the major challenge impeding practical applications of PP power cable insulation arises from the synergetic regulation of multi‐performances. The multi‐level structures influencing the multi‐performances of PP are introduced by the authors and the researches on the performance enhancement of PP through nanoscale structure regulation in recent years are reviewed in detail. Seven kinds of modification methods including nano‐doping, chemical grafting, in‐suit copolymerisation, heat treatment, nucleating agent, voltage stabiliser and elastomer blending are paid special attention. Based on the full understanding of the research status, the challenges and issues of future research are put forward for eco‐friendly PP power cable insulation.

Abstract Polymer dielectrics with excellent thermal resistance and superior energy storage behaviour are extensively demanded with the increasing development of film capacitors applied in hostile environments. In this study, novel diamine with sulfonyl‐containing side chain was designed and synthesised. The corresponding polyimide (PI) dielectrics derived from the sulfonyl‐containing diamine were prepared, so were the polyimides possessing the same backbone but without side chains. Consequently, superior thermal resistance of glass transition temperature ranged from 162–208°C was obtained. Moreover, the polyimides presented permittivity of 3.34–5.89 at 1 kHz, Weibull breakdown strength of 377–538 MV/m and discharged energy density of 3.82–5.85 J/cm3. In particular, sulfonyl‐containing polyimide of SPI‐2 with flexible backbone and sulfonyl side chain indicates the highest discharged energy density and charge‐discharge efficiency simultaneously. The introduction of the strong polar sulfonyl group in the side chain enhances dielectric and energy storage properties effectively. In addition, it is found that the dipolar moment density (μ/Vvdw) calculated from molecular simulation is closely correlated to permittivity measured from experiments. The combined method of molecular simulation and experiments would offer an effective approach to assist in molecular design of high‐performance polymer dielectrics.

Abstract Dielectric energy storage capacitors with excellent high temperature resistance are essential in fields such as aerospace and pulse power. However, common high‐temperature resistant polymers such as polyimide (PI) and polyether sulfone have low energy storage densities and energy efficiencies at high temperature, which are greatly limited in practical applications. The polymer nanocomposites prepared by doping modification can regulate the charge injection and transport process, and improve the high‐temperature energy storage performance. However, the quantitative relationship between charge injection and charge trapping and the energy storage performance of linear polymer nanocomposites still needs further study. An energy storage and release model considering the charge trapping effects is constructed by the authors. We simulate the high‐temperature energy storage properties of polyimide nanocomposite dielectrics (PI PNCs) with different charge injection barriers and trap parameters at 150°C. A triangular voltage is applied to the electrodes at both sides of the PI PNCs, the electric displacement‐electric field loop is simulated, and the discharged energy densities and energy efficiencies are calculated. The simulation results are consistent with the experimental results. Increasing the charge injection barrier, deep trap energy and deep trap density can effectively reduce the charge injection and the carrier mobility, thereby improving the discharged energy densities and energy efficiencies of dielectric capacitors. In the case of low charge injection barrier (1.3 eV), with the increase of deep trap energy (0.7–1.5 eV) and deep trap density (1 × 1021–1 × 1025 m−3), the discharged energy density changes from 0.20 to 1.44 Jcm−3, the energy efficiency changes from 9.0% to 99.9%, and the high‐temperature energy storage performance improves significantly. This research provides theoretical and model support for the improvement of the high‐temperature energy storage performance of nanocomposites.

Abstract The significant progresses of polymer‐based nanocomposites with improved dielectric performances are urgently calling for an effect way to realise commercial production. Up to now, the biaxial stretching technology is still a powerful method to produce the high‐performance dielectric films applied in the film capacitors due to its full‐blown applications. In this work, a classical composite system of BaTiO3/polypropylene was applied to reveal the connection between the microstructure changes and dielectric properties of the corresponding nanocomposite films in the biaxial stretching process. The permittivity of BT‐30 wt% nanocomposite reached 2.8 at 103 Hz after stretching, and its breakdown strength reached 340 MV/m. In addition, the breakdown strength of BT‐10 wt% nanocomposite could even be promoted to 452 MV/m, which was 1.3 times higher than that before stretching. The microstructure test demonstrated that the rearrangement of nanofillers, high crystallinity and the oriented polypropylene crystals were advantageous to the improvement of breakdown strength for the stretched nanocomposite films. Therefore, the application of biaxial stretching technology into the preparation of nanocomposite dielectric film is an enormous potential way for the energy storage film capacitors.

Biaxially oriented polypropylene (BOPP) is the most favorable commercial dielectric energy storage film due to its low dielectric loss and high electric breakdown strength. However, its low dielectric constant always leads to relatively low energy storage density. In this study, we propose an efficient strategy to increase the dielectric constant of BOPP films by laminating with high dielectric polyvinylidene fluoride (PVDF). Utilizing the high dielectric constant of PVDF and optimizing its thickness and layers, the high‐temperature energy storage density at low‐electric field is significantly improved. When the thickness of interlayer PVDF is 5 μm and the total number of stacked layers is 7, the BOPP/PVDF multilayer films deliver excellent high‐temperature energy storage performance. The dielectric constant of BOPP/PVDF multilayer films increases to 3.54, 1.74 times higher than pure BOPP films. At a low electric field of 200 kV/mm, the discharged energy storage density of BOPP/PVDF multilayer films increases to 1.02 and 0.99 J/cm3 at 100 and 125°C. (BOPP ~0.50 and 0.48 J/cm3@200 kV/mm). This work provides an efficient way to improve the high‐temperature energy storage density of BOPP films by constructing all‐organic multilayer structure. [ABSTRACT FROM AUTHOR]

Due to the advantages of fewer energy conversion stages and a simple structure, direct current (DC) microgrids are being increasingly studied and applied. To minimize distribution loss in DC microgrids, a systematic optimal control framework is proposed in this paper. By considering conduction loss, switching loss, reverse recovery loss, and ohmic loss, the general loss model of a DC microgrid is formulated as a multi-variable convex function. To solve the objective function, a top-layer distributed integral convex optimization algorithm (DICOA) is designed to optimize the current-sharing coefficients by exchanging the gradients of loss functions. Then, the injection currents of distributed energy resources (DERs) are allocated by the distributed adaptive control in the secondary control layer and local voltage–current control in the primary layer. Based on the DICOA, a three-layer control strategy is constructed to achieve loss minimization. By adopting a peer-to-peer data-exchange strategy, the robustness and scalability of the proposed systematic control are enhanced. Finally, the proposed distribution current dispatch control is implemented and verified by simulations and experimental results under different operating scenarios, including power limitation, communication failure, and plug-in-and-out of DERs. [ABSTRACT FROM AUTHOR]

Power electronics are becoming increasingly more important, as electrical energy constitutes 40% of the total primary energy usage in the USA and is expected to grow rapidly with the emergence of electric vehicles, renewable energy generation, and energy storage. New materials that are better suited for high-power applications are needed as the Si material limit is reached. Beta-phase gallium oxide (β-Ga2O3) is a promising ultra-wide-bandgap (UWBG) semiconductor for high-power and RF electronics due to its bandgap of 4.9 eV, large theoretical breakdown electric field of 8 MV cm−1, and Baliga figure of merit of 3300, 3–10 times larger than that of SiC and GaN. Moreover, β-Ga2O3 is the only WBG material that can be grown from melt, making large, high-quality, dopable substrates at low costs feasible. Significant efforts in the high-quality epitaxial growth of β-Ga2O3 and β-(AlxGa1−x)2O3 heterostructures has led to high-performance devices for high-power and RF applications. In this report, we provide a comprehensive summary of the progress in β-Ga2O3 field-effect transistors (FETs) including a variety of transistor designs, channel materials, ohmic contact formations and improvements, gate dielectrics, and fabrication processes. Additionally, novel structures proposed through simulations and not yet realized in β-Ga2O3 are presented. Main issues such as defect characterization methods and relevant material preparation, thermal studies and management, and the lack of p-type doping with investigated alternatives are also discussed. Finally, major strategies and outlooks for commercial use will be outlined. [ABSTRACT FROM AUTHOR]

The objective of this paper is to determine the transient characteristics and sites of the pre‐breakdown (pre‐BD) in the spark conditioning under power frequency voltage (PFV) in vacuum. A multi‐angle optical path system was designed and made the determination of the pre‐BD sites in spark conditioning possible, through one camera at two viewing angles. The experimental results indicate that, in the spark conditioning under PFV, the pre‐BDs continuously occurred at a random moment. Within several half‐waves, the number of the pre‐BDs could reach dozens of times, which was the key for the treatment of the electrode surface in conditioning. Under the application of PFV, the single pre‐BD occurred at a random moment, in which it would last for several microseconds and the peak value of the current would reach several amperes. Moreover, the pre‐BD sites randomly distributed in the surface of the electrode and almost covered the whole surface of the electrode. The pre‐BDs took place independently in both time and space, in which there should be no effect between each other of two sequential pre‐BDs. To sum up, the transient characteristics and the sites of the pre‐BDs determined in this paper could reveal the physical mechanism of the pre‐BD on the treatment of electrode surface in the conditioning process, which is quite significant to improve the BD voltage of vacuum interrupter. [ABSTRACT FROM AUTHOR]

Improvement techniques aimed at enhancing the dielectric strength and minimizing the dielectric loss of insulation materials have piqued the interest of many researchers. It is worth noting that the electrical breakdown traits of insulation material are determined by their electrochemical and mechanical performance. Possible good mechanical, electrical, and chemical properties of new materials are considered during the generation process. Thermoplastic polyurethane (TPU) is often used as a high-voltage insulator due to its favorable mechanical properties, high insulation resistance, lightweight qualities, recovery, large actuation strain, and cost-effectiveness. The elastomer structure of thermoplastic polyurethane (TPU) enables its application in a broad range of high-voltage (HV) insulation systems. This study aims to evaluate the feasibility of using TPU on transformer windings as a solid insulator instead of pressboards. The investigation conducted through experiments sheds light on the potential of TPU in expanding the range of insulating materials for HV transformers. Transformers play a crucial role in HV systems, hence the selection of suitable materials like cellulose and polyurethane is of utmost importance. This study involved the preparation of an experimental setup in the laboratory. Breakdown tests were conducted by generating a non-uniform electric field using a needle–plane electrode configuration in a test chamber filled with mineral oil. Various voltages ranging from 14.4 kV to 25.2 kV were applied to induce electric field stress with a step rise of 3.6 kV. The partial discharges and peak numbers were measured based on the predetermined threshold values. The study investigated and compared the behaviors of two solid insulating materials under differing non-electric field stress conditions. Harmonic component analysis was utilized to observe the differences between the two materials. Notably, at 21.6 kV and 25.2 kV, polyurethane demonstrated superior performance compared to pressboard with regards to the threshold value of leakage current. [ABSTRACT FROM AUTHOR]

To avoid early stage failure of rolling bearings as components of train drives of electrical engines, the bearings must be protected. As state of the art, alumina coatings are applied by atmospheric plasma spraying and subsequently an organic sealer is used to enhance the service life of these bearings under harsh conditions. This includes high applied frequencies and high ambient air humidity. For further improvement, mullite coatings and a newly developed an epoxy‐ and silicon‐based sealer applied by different sealing techniques are investigated to further enhance the electrical insulation of the bearing coatings. Impedance measurements under dry and wet conditions are conducted to analyze the capacitive behavior of the coatings. X‐ray diffraction measurements are used to correlate the influence of the present crystallographic phases of the ceramic coating on the capacitive behavior. In a following step, selected coating systems are applied onto bearings and tested in demonstrator tests. For higher currents of roughly IBearing ≥ 0.6 A, all newly developed coatings exhibit a decreased number of electrical breakdowns compared to the reference. Consequently, choosing this coating system as electrical protection coating for bearings in electrical engines can reduce the damage occurring from electrical current breakdowns. [ABSTRACT FROM AUTHOR]

The 2D Janus transition‐metal dichalcogenides (TMDs) and alloyed TMDs are a widely studied emerging class of 2D materials that have been extensively used in electronic devices because of their excellent electronic, optical, and mechanical properties. The properties and behaviors of 2D‐materials‐based devices, such as the electrical breakdown caused by structural failure, are significant issues that have drawn considerable attention. In this study, the electrical behavior of polymorphic molybdenum sulfide selenide (MoSSe) devices is studied via in situ biasing experiments and recorded using transmission electron microscopy (TEM) at the atomic scale. The selenization temperature is a key factor in the phase transition of the material, which further affects the electrical and mechanical properties of MoSSe. The effects of electron‐beam irradiation and bias voltage are also discussed through a combination of experiments and theory. Quantifying the defect coverage and defect size also helps us to understand the behavior of material degradation. Furthermore, Cs‐corrected scanning TEM is utilized to identify the evolution of the morphology. The fracture morphology of the synthesized structure also varies with the application of high voltage. The cracks and defects caused by Joule heating are studied in terms of fracture type and size. [ABSTRACT FROM AUTHOR]

In this article we present the results of time-of-flight mass spectrometry of volatile products formed during the electrical breakdown of polyethylene terephthalate and polypropylene polymer films in high vacuum. During the breakdown of films, all the substance emitted from the breakdown channel is a gas of low-molecular products of destruction of macromolecules. The breakdown mass spectra do not contain lines of carbon molecules, the presence of which could indicate carbonation of the channel. To explain the formation of charge carriers, the ionization mechanism of destruction of macromolecules in an electric field is used without the involvement of impact ionization. The final stage of electrical breakdown (the flow of a high-density conduction current) occurs when the critical concentration of traps and electrons ≈1024 m–3 is reached. [ABSTRACT FROM AUTHOR]

High‐dielectric and low‐loss materials hold potential for various electronic devices. A prevalent approach to producing high‐dielectric and low‐loss dielectrics is incorporating inorganic ceramic materials with high dielectric constants into a polymeric matrix. However, doping of inorganic ceramic materials results in agglomeration of the inorganic materials and poor interfacial compatibility between the matrix and the dopant, thus limiting their range of application. In this study, sulfonated poly(arylene ether nitrile) (SPEN) functionalized copper calcium titanate (CCTO) (SPEN@CCTO) was synthesized by modifying hydroxylated CCTO with SPEN and then introduced into the PEN matrix offering SPEN@CCTO/PEN. The successful encapsulation of SPEN at CCTO was confirmed through FT‐IR, XRD, and XPS. SEM observation revealed that SPEN@CCTO nanomaterials not only prevented agglomeration of CCTO but also significantly improved interfacial adhesion between the matrix and filler, highlighting the importance of SPEN@CCTO in enhancing the mechanical properties of resulting nanocomposites. Electrostatic permittivity of SPEN@CCTO/PEN and CCTO/PEN composite dielectric materials were evaluated in the frequency range spanning 10 Hz to 1 MHz. In comparison with CCTO/PEN composite dielectric materials, SPEN@CCTO/PEN composites show superior dielectric characteristics, characterized by higher dielectric constants and lower losses in dielectric. The SPEN@CCTO/PEN film's dielectric constant at 10 Hz and electric breakdown strength with 15 wt% SPEN@CCTO were found to be 5.9 and 178.8 kV/mm, respectively. Thereby, the energy storage density of SPEN@CCTO/PEN composite film was calculated to be 0.83 J/cm3. In addition, the excellent mechanical properties of SPEN@CCTO/PEN ensured it as promising flexible dielectric materials in the future. [ABSTRACT FROM AUTHOR]

The glow of a nanosecond diffuse discharge between two tips with high spatial resolution has been studied. At atmospheric air pressure, as well as at pressures of 300, 100, and 30 Torr, a large number of thin luminous tracks, starting from the region of bright spots on the electrodes, have been discovered. It is shown that the shape of the tracks changes from straight lines to winding ones, and the direction of their movement in some cases changes to the opposite. It is shown that, under conditions of the formation of thin luminous tracks, the bands of the second positive nitrogen system dominate in the emission spectrum of diffuse plasma with a sharply inhomogeneous electric field and nanosecond duration of the voltage pulse. Using an ICCD camera, it has been shown that no emission of the tracks is detected during the first tens of nanoseconds against the background of wide streamers and a diffuse discharge. A hypothesis has been put forward to explain the appearance of numerous tracks during air breakdown in a nonuniform electric field. [ABSTRACT FROM AUTHOR]

Electrical breakdown is an important physical phenomenon in power equipment and electronic devices. Recently, the mechanism of AC and DC breakdown has been preliminarily revealed as electrode–dielectric interface breakdown and bulk breakdown, respectively, based on space charge dynamics through numerical calculations. However, the AC breakdown mechanism still lacks enough direct experimental support, which restricts further understanding and the design and development of electrical structures. Here, in this study, LDPE films with various thicknesses ranging from 33 μm to 230 μm were surface modified with ozone for different durations to experimentally investigate DC and AC breakdown mechanism. The results indicate that carbonyl groups (C=O) were introduced onto the film surface, forming shallow surface traps and leading to a decreased average trap depth and an increased trap density. Such a surface oxidation modulated trap distribution led to enhanced space charge injection and bulk electrical field distortion, which decreased DC breakdown strength as the oxidation duration went longer, in all film thicknesses. However, such decreases in breakdown strength occurred only in films below 55 μm under AC stresses, as the enhanced electrical field distortion at the electrode–dielectric interface was more obvious and dominating in thin films. These experimental results further confirm the proposed electrode–dielectric interface breakdown of dielectric films and provide new understandings of space charge modulated electrical breakdown, which fulfills dielectric breakdown theory and benefits the miniaturization of power equipment and electronic devices. [ABSTRACT FROM AUTHOR]

The dielectric performance of pressboards impregnated with mineral oil is one of the key points in regard to the quality of the transformer's working life. Partial discharges (PDs) occurring in the pressboard can cause some insulation defects which might be one of the major reasons for an electrical breakdown. Detection of the PDs in pressboards gives a chance to understand the dielectric behavior of the insulators, hence major defects can be prevented just in early stage. The main point of the study is to investigate the differences in dielectric performance of layered and non-layered pressboards in the presence of PDs. For this purpose, the PD behavior of a layered pressboard with three layers (each with a thickness of 0.5 mm) and of a non-layered (solid) pressboard (with a thickness of 1.5 mm) is examined for two different high voltage levels (20 and 30 kV). To detect the PDs, Hall Effect Sensors are employed, considering that PDs cause fluctuations in the magnetic field. To analyze the magnetic field measurements from a statistical point of view, the Kaplan–Meier method and the Weibull analysis are used. [ABSTRACT FROM AUTHOR]

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors in next-generation pulse devices. In this work, Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT)-based lead-free ceramics with an ultrahigh recoverable energy storage density (W rec) were designed and fabricated by introducing the relaxor end-member of Bi(Zn 2/3 Ta 1/3)O 3 (BZT). The addition of BZT disrupted the ferroelectric (FE) long-range order and triggered an FE-to-relaxor FE (RFE) phase, leading to the formation of locally polar nano-regions (PNRs) and significantly inhibiting grain growth. Meanwhile, the presence of PNRs with good thermal stability improved the temperature stability of both the dielectric constant (ε ') and W rec. More importantly, the breakdown electric field strength was significantly improved up to ∼640 kV/cm, resulting in an ultrahigh W rec of ∼7.11 J/cm3 for the 8%BZT doped BCZT (BCZT-BZT8) ceramic. Furthermore, the BCZT-BZT8 ceramic exhibited excellent charge/discharge performances (C D ∼ 458.4 A/cm2, P D ∼ 50.4 MW/cm3, W D ∼ 1.354 J/cm3, t 0.9 ∼ 320 ns) with good thermal stability in the temperature range of 298–373 K. The defect chemistry of the BCZT-BZT8 was explored using electron paramagnetic resonance (EPR) spectroscopy which revealed an EPR signal (g ∼ 1.955), associated with oxygen vacancies. The above findings indicate that the novel composition of BCZT-BZT8 has great prospects in energy storage capacitor applications. [ABSTRACT FROM AUTHOR]

The process of distributing electricity from the substation to the consumers often occurs interference, electrical interference at the station caused by two factors that are internal factors and external factors. Internal factors such as lack of good equipment, while external factors such as human error and natural disturbances such as lightning, earthquakes, flood, wind and others. Safety protection system on electrical equipment of Pandu substation. Surge arresters play an important role in Pandu substations to limit switching overvoltages and lightning strikes, followed by overvoltages from lightning current to earth. the efficiency of the arrester is a function of the distance from its location to the protected equipment, the maximum system voltage achieved is 165 kilo vot, the arrester`s rated voltage is 132 kilo volt line impedance /conductor 475,764 ohms, air insulation breakdown voltage 1515.8 kilo voltv, arrester discharge current 4.27 kilo ampers and an optimal distance between arrester and transformer 10.96 meters. [ABSTRACT FROM AUTHOR]

Class II ceramics are a material with high permittivity but low reliability of their capacitance and bias voltage due to high the temperature sensitivity of their dielectric permittivity. In this work, a BST-based (Ba0.9−xSrxCa0.1)TiO3·0.03(Bi2O3·3TiO2) (x = 0.2, 0.25, 0.3, 0.35, 0.4) composition with Y5U characteristics was investigated through compositional control to develop high-permittivity and voltage-stable ceramic compositions. Sr doping can increase the breakdown strength (Eb) but decreases the Curie temperature (Tc). The composition at x = 0.3 can obtain optimal comprehensive electrical properties, with high permittivity of 4206, low dielectric loss of ~0.009, and moderate breakdown strength (Eb) of 77.6 kV/cm, which meets Y5U specifications. Typically, a low bias-voltage dependence of capacitance is confirmed with a variation rate of 7.64% under 20 kV/cm. This strategy provides a promising candidate for high-permittivity Class II ceramic dielectrics that can be used in this field. [ABSTRACT FROM AUTHOR]

High‐dielectric and low‐loss materials hold potential for various electronic devices. A prevalent approach to producing high‐dielectric and low‐loss dielectrics is incorporating inorganic ceramic materials with high dielectric constants into a polymeric matrix. However, doping of inorganic ceramic materials results in agglomeration of the inorganic materials and poor interfacial compatibility between the matrix and the dopant, thus limiting their range of application. In this study, sulfonated poly(arylene ether nitrile) (SPEN) functionalized copper calcium titanate (CCTO) (SPEN@CCTO) was synthesized by modifying hydroxylated CCTO with SPEN and then introduced into the PEN matrix offering SPEN@CCTO/PEN. The successful encapsulation of SPEN at CCTO was confirmed through FT‐IR, XRD, and XPS. SEM observation revealed that SPEN@CCTO nanomaterials not only prevented agglomeration of CCTO but also significantly improved interfacial adhesion between the matrix and filler, highlighting the importance of SPEN@CCTO in enhancing the mechanical properties of resulting nanocomposites. Electrostatic permittivity of SPEN@CCTO/PEN and CCTO/PEN composite dielectric materials were evaluated in the frequency range spanning 10 Hz to 1 MHz. In comparison with CCTO/PEN composite dielectric materials, SPEN@CCTO/PEN composites show superior dielectric characteristics, characterized by higher dielectric constants and lower losses in dielectric. The SPEN@CCTO/PEN film's dielectric constant at 10 Hz and electric breakdown strength with 15 wt% SPEN@CCTO were found to be 5.9 and 178.8 kV/mm, respectively. Thereby, the energy storage density of SPEN@CCTO/PEN composite film was calculated to be 0.83 J/cm3. In addition, the excellent mechanical properties of SPEN@CCTO/PEN ensured it as promising flexible dielectric materials in the future. [ABSTRACT FROM AUTHOR]

Tellurium oxides of the ATeO3 form typically do not crystallize in perovskite structures. Here, we show that perovskite-like ATeO3 (A = Ca, Sr, Ba) thin films can be grown on perovskite single-crystal substrates via epitaxial stabilization. These films are stable with high optical bandgaps, low dielectric losses, and a high electric breakdown strength. Hysteretic dielectric behavior found in SrTeO3 and BaTeO3 strongly suggests the presence of antiferroelectricity and ferroelectricity, respectively. These properties make perovskite tellurium oxides possibly appealing candidates for thin film coating or insulator materials in advanced microelectronics. Tellurium oxides constitute a largely unexplored class of materials that might show new and interesting functionalities in epitaxial thin-films. Our work encourages new work within this field. [ABSTRACT FROM AUTHOR]

Dielectric elastomers are widely used as electroactive polymer materials due to their high energy density, high strain, and low loss. However, the practical applications are limited sometimes by their low electromechanical strain ability due to relatively low dielectric permittivity for polymers. Herein, multiwalled carbon nanotube (MWCNT) filled silicone rubber (SR) composites with a five‐layered structure are prepared with the outer two layers of neat SR while the middle three layers are MWCNT filled SR, in which the former functions as insulating layers while the latter acts as the dielectric permittivity enhancement layers. Further, by differing the MWCNT content within the middle three layers, we find that as the concentration distribution increases from 1:1:1 to 1:2:1 and 1:3:1, both Young's modulus and dielectric permittivity gradually improve while dielectric loss remains extremely low even though the total MWCNT content reaches 1.6 wt%. With the combined effects of dielectric permittivity and modulus, the composite with evenly distributed MWCNT content (1:1:1) shows the highest actuation strain under a given electric field strength. Meanwhile, the electric breakdown strength of the composite 1:1:1 is also the highest, leading ultimately to a maximum actuation strain of 10.87% at the breakdown strength of 14.6 kV/mm. [ABSTRACT FROM AUTHOR]

The object of research is the mechanisms of synthesis of nanocarbon structures in the process of electric high-voltage breakdown of hydrocarbons. The problem to be solved is the purposeful synthesis of various types of nanocarbon with small losses of raw materials. Mechanisms of nanocarbon formation in the process of high-voltage electric breakdown of hydrocarbons have been established. It is shown that a high-voltage breakdown leads to a cascade of chemical transformations. As a result of transformations, lower gaseous hydrocarbons are formed due to the destruction of molecules and higher ones – as a result of polymerization, and as a result of dehydrocyclization and polymerization with the participation of metal catalysts – various carbon nanostructures. The possibility of targeted synthesis of fullerene-like structures, nanotubes with diameters from 10 to 50 nm, nanofibers, and films is demonstrated. Experimental studies have confirmed that the qualitative and quantitative composition of nanocarbon can be varied in a wide range. With an increase in the number of carbon atoms or the number of C–C bonds in the raw material molecules, other things being equal, the practical yield of solid nanocarbon increases. It was determined that the synthesis of structured nanocarbon from a mixture of hydrocarbon gases, formed as a result of high-voltage breakdown of liquid hydrocarbons, actively occurs on the nickel-chromium catalytic surface. An increase in the area of the catalytic deposition surface leads to an increase in the yield of nanocarbon. The study of the ability of the obtained nanocarbon samples to absorb electromagnetic radiation confirmed the potential of the method of high-voltage breakdown of hydrocarbons for the synthesis of materials that weaken electromagnetic radiation at a frequency of 25 to 38 GHz. The greatest weakening is observed for samples consisting mainly of carbon nanotubes and nickel nanoparticles [ABSTRACT FROM AUTHOR]

Energy conversion and storage devices are highly desirable for the sustainable development of human society. Hybrid organic–inorganic perovskites have shown great potential in energy conversion devices including solar cells and photodetectors. However, its potential in energy storage has seldom been explored. Here the crystal structure and electrical properties of the 2D hybrid perovskite (benzylammonium)2PbBr4 (PVK‐Br) are investigated, and the consecutive ferroelectric‐I (FE1) to ferroelectric‐II (FE2) then to antiferroelectric (AFE) transitions that are driven by the orderly alignment of benzylamine and the distortion of [PbBr6] octahedra are found. Furthermore, accompanied by field‐induced AFE to FE transition near room temperature, a large energy storage density of ≈1.7 J cm−3 and a wide working temperature span of ≈70 K are obtained; both of which are among the best in hybrid AFEs. This good energy storage performance is attributed to the large polarization of ≈7.6 µC cm−2 and the high maximum electric field of over 1000 kV cm−1, which, as revealed by theoretical calculations, originate from the cooperative coupling between the [PbBr6] octahedral framework and the benzylamine molecules. The research clarifies the discrepancy in the phase transition character of PVK‐Br and shed light on developing high‐performance energy storage devices based on 2D hybrid perovskite. [ABSTRACT FROM AUTHOR]

PDMS-based composites such as silicone elastomers are commonly found in high-voltage engineering, especially in outdoor insulation as coatings or structural elements or at interfaces between network elements, such as cable sealing ends (CSE). They are also promising prospects for dielectric elastomer generators (DEG), which are retrieving electrostatic energy from large strain amplitudes. The upper limit of energy conversion from these transducers is determined by the dielectric breakdown strength (DBS). Therefore, developing reliable systems that operate under high electric fields and variable repeated strains requires a thorough understanding of the mechanisms behind electrical breakdown and its coupling to mechanical cycling. In this study, the effect of Mullins damage and mechanical fatigue on silicone elastomers has been investigated. An electro-mechanical instability model that considers cyclic softening allows for predicting the evolution of the breakdown strength depending on the loading history. The results highlight the importance of the "first cycle," where up to a 30% reduction in the mean DBS was measured. However, subsequent mechanical fatigue only marginally contributes to the degradation, which is a promising perspective for the long-term performance of any silicone elastomer as long as the precise impact of the first cycle is known. [ABSTRACT FROM AUTHOR]

In this study, a novel lead‐free high‐entropy ceramic (HEC) system, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(1–3x/2)LaxTiO3 (0 ≤ x ≤ 0.15) (abbreviated as BNCBST‐xLa), was designed to enhance energy storage performance through La substitution and prepared via a hydrothermal method. Results indicate that La doping at A site in BNCBST induces lattice distortion and further improves dielectric relaxation. Moreover, grain growth is inhibited by the La content, which results in an increase in the insulation resistance and thus significant enhancement in the electric breakdown strength (Eb). Accordingly, the system with x = 0.03 exhibits an excellent recoverable energy density (Wrec) of 2.43 J/cm3 and a high energy storage efficiency (η) of 85.5% under a great Eb of 245 kV/cm, together with wide temperature stability (Wrec and η vary within ± 8.3% and ± 1.1% at 30–150°C). The findings of this study suggest that the obtained La‐modified BNBCST HECs are promising for energy storage applications. [ABSTRACT FROM AUTHOR]

This work is a maiden attempt to investigate the role of fluorinated boron nitride nanosheets (f-BNNs) in monitoring electrical properties of transformer oil (TO). Ultrathin (~5 nm) f-BNNs of 100–500 nm width were obtained by exfoliating pristine h-BN using NH4F. The exfoliation resulted in attaching few electronegative fluorine (F) to boron atoms and converted h-BN from insulator to semiconductor. TO nanofluids (NFs) at 0.005 wt. % of f-BNNs showed ~27 % surge in AC breakdown voltage (BDV) (validated by Weibull statistics), high volume resistivity and excellent stability, superior than h-BN nanosheets or BN nanoparticle. The leap in the electrical insulation was explained due to the fluorination assisted reduction in charge relaxation time from 60 ms–30 s in h-BN to 63 μs–0.6 s in f-BNNs, higher degree of streamer charge scavenging in the electrical double layers (EDLs) and interfacial polarization at the large oil-nanofiller interface. A theoretical calculation yielded in a potential depth of 13.8 V and 19.5 V at h-BN and f-BNNs surface, respectively, which implied f-BNNs provided a huge potential barrier and propagation delay to the streamer charges. Finally, the superior stability of f-BNNs in TO with time and temperature was observed from multiple tests and was explained owing to its 2D morphology, lipophilicity, and F induced large natural electrostatic repulsion between the nanosheets. Such excellent responses at low filler fractions recommends f-BNNs as a better alternative among all reported BN brothers for future TO applications. [ABSTRACT FROM AUTHOR]

Solid‐state lithium‐metal batteries (SSLMBs) are considered as the next‐generation energy storage systems due to their high theoretical energy density and safety. However, the practical deployment of SSLMBs has been impeded by the failure of solid‐state electrolytes (SSEs) which is indicated by the increased impedance, elevated polarization, and capacity degradation. The failure is commonly a result of lithium (Li) dendrite growth and propagation, inactive Li generation, unstable interface formation, void and pore formation, and crack infiltration. The failure processes can be divided into electric failure, (electro)chemical failure, and mechanical failure based on the different mechanisms. The systematical understanding of SSEs failure is crucial for the development of SSEs. Therefore, this review comprehensively summarizes the details of the three SSEs failure to provide new insights for future studies, shedding light on the design of SSLMBs with high energy density, safety, and cycling stability. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the structural, microstructural, dielectric, and energy storage properties of Nd and Mn co-doped Ba0.7Sr0.3TiO3 [(Ba0.7Sr0.3)1−xNdxTi1−yMnyO3 (BSNTM) ceramics (x = 0, 0.005, and y = 0, 0.0025, 0.005, and 0.01)] via a defect dipole engineering method. The complex defect dipoles (M n T i " − V O ∙ ∙ ) ∙ and (M n T i " − V O ∙ ∙) between acceptor ions and oxygen vacancies capture electrons, enhancing the breakdown electric field and energy storage performances. XRD, Raman, spectroscopy, XPS, and microscopic investigations of BSNTM ceramics revealed the formation of a tetragonal phase, oxygen vacancies, and a reduction in grain size with Mn dopant. The BSNTM ceramics with x = 0.005 and y = 0 exhibit a relative dielectric constant of 2058 and a loss tangent of 0.026 at 1 kHz. These values gradually decreased to 1876 and 0.019 for x = 0.005 and y = 0.01 due to the Mn2+ ions at the Ti4+- site, which facilitates the formation of oxygen vacancies, and prevents a decrease in Ti4+. In addition, the defect dipoles act as a driving force for depolarization to tailor the domain formation energy and domain wall energy, which provides a high difference between the maximum polarization of Pmax and remnant polarization of Pr (ΔP = 10.39 µC/cm2). Moreover, the complex defect dipoles with optimum oxygen vacancies in BSNTM ceramics can provide not only a high ΔP but also reduce grain size, which together improve the breakdown strength from 60.4 to 110.6 kV/cm, giving rise to a high energy storage density of 0.41 J/cm3 and high efficiency of 84.6% for x = 0.005 and y = 0.01. These findings demonstrate that defect dipole engineering is an effective method to enhance the energy storage performance of dielectrics for capacitor applications. [ABSTRACT FROM AUTHOR]

Dielectric Elastomer Actuators (DEAs) enable the realization of energy-efficient and compact actuator systems. DEAs operate at the kilovolt range with typically microampere-level currents and hence minimize thermal losses in comparison to low voltage/high current actuators such as shape memory alloys or solenoids. The main limiting factor for reaching high energy density in high voltage applications is dielectric breakdown. In previous investigations on silicone-based thin films, we reported that not only do environmental conditions and film parameters such as pre-stretch play an important role but that electrode composition also has a significant impact on the breakdown behavior. In this paper, we present a comprehensive study of electrical breakdown on thin silicone films coated with electrodes manufactured by five different methods: screen printing, inkjet printing, pad printing, gold sputtering, and nickel sputtering. For each method, breakdown was studied under environmental conditions ranging from 1 °C to 80 °C and 10% to 90% relative humidity. The effect of different manufacturing methods was analyzed as was the influence of parameters such as solvents, silicone content, and the particle processing method. The breakdown field increases with increasing temperature and decreases with increasing humidity for all electrode types. The stiffer metal electrodes have a higher breakdown field than the carbon-based electrodes, for which particle size also plays a large role. [ABSTRACT FROM AUTHOR]

Desired ratio of relative permittivity and elastic modulus limits the application of silicone rubbers as flexible electromechanical actuators. The relative permittivity can be improved by incorporating varieties of high‐k (high dielectric constant) particles and polymer reagents as plasticizers and crosslinkers into elastomer matrix. The present work investigates the effect of polyethylene glycol (PEG) flakes, as a soft filler, and titanium diborides (TB) particles, as a hard filler, on electromechanical actuation performance of polydimethylsiloxane elastomer for soft actuator. Elastomer composites with various concentrations of fillers are prepared to compare the influences on optical, dielectric, and mechanical properties. Uniform dispersion of fillers is confirmed by field emission scanning electron microscopy, energy dispersive x‐ray spectrometer, and Fourier transform‐infrared spectroscopy analysis. Results show that the elastic modulus and relative permittivity are significantly influenced by filler contents. The elastic modulus increases with lower concentrations of PEG fillers, and at 8 wt%, it becomes comparable to the base material. Soft fillers aid in maintaining low elastic modulus, whereas hard fillers increase electrical breakdown strength as well as dielectric loss with almost equal changes in relative permittivity for both composites. The maximum actuation strain of 30.8% and 26.2% is attained for an in‐house fabricated linear actuator with 8 wt% of PEG and TB particles, respectively. [ABSTRACT FROM AUTHOR]

The voltage endurance coefficient n of cross‐linked polyethylene (XLPE) insulation is an important indicator for the analysis of insulation failure mechanism. Accurately obtaining the value of n can provide technical support for the reliability evaluation of cable operation. The constant stress method and the step stress method are used to obtain the values of n, but the test parameters can influence the accuracy of the obtained n values. Two methods for selecting test parameters are proposed. The equivalence between the two methods is established, providing theoretical support for the accurate evaluation of the n value of solid insulation materials by using the step stress method. The accuracy of the evaluation results is verified by analyzing the test data. The test results show that the nstep = 13.04 evaluated by the step stress test with the proposed parameter selection method is consistent with the test result of constant stress nconstant = 12.83. [ABSTRACT FROM AUTHOR]

Even though BiFeO3–BaTiO3 (BF–BT) with high Curie temperature and excellent piezoelectric properties is very suitable for high‐temperature applications, its rapid reduction in resistivity with temperature limits its further application. So far, there is no effective method to improve the resistivity of BF–BT at a high‐temperature state. In this work, hot‐press sintering combined with an oxygen atmosphere was used to prepare (1 − x)BF–xBT (x = 0.2–0.33) ceramics for the first time, which reduced the sintering temperature from 1000 to 920°C. The controllable grain size can be achieved by adjusting the sintering temperature and the applied pressure. The X‐ray photoelectron spectroscopy results confirmed that using hot‐press sintering effectively avoided the generation of heterovalent Fe ions, and the resistivity of BF–BT ceramics at the high‐temperature stage was improved by two orders of magnitude. It was found that hot‐press sintering can cause the oriented growth of the sample along the (1 1 0) direction, and further refined X‐ray diffraction was used to accurately analyze the changes in the lattice structure. The hot‐press sintered samples obtained larger polarization strength, especially the electro‐induced strain showed excellent temperature stability in the wide temperature range of 30–170°C. Hot‐pressing sintering combined with an oxygen atmosphere is more suitable for preparing high insulation and electrical breakdown resistance ceramics. [ABSTRACT FROM AUTHOR]

In order to improve the electrical tree resistance of epoxy resin, composites were prepared using dihydroxydiphenylsilane and a novel silicone modifier modified epoxy resin and micron silica, and the composites were subjected to accelerated thermal aging test and electrical tree test and recorded the growth process of electrical trees to further obtain the characteristic parameters of electrical trees in the experimental samples. The results show that the silicone‐modified epoxy resin/silica composite has better thermal stability and electrical tree resistance than the unmodified epoxy resin/silica composite and pure epoxy resin. Analysis of the scanning electron microscope (SEM) and breakdown field strength results show that the introduction of the modifier enhanced interfacial properties between the epoxy resin and silica. At the end of the electrical tree test, the length of the electrical tree in the silicone‐modified epoxy resin/silica composite was at a minimum 25.31% of the length of the electrical tree in the unmodified epoxy resin/silica composite with the same silica filling ratio, and 9.19% of the length of the electrical tree in the pure epoxy, while the electrical trees in the silicone‐modified epoxy resin/silica composite have lower expansion factors, as well as higher fractal dimensions, compared to those in the resin without added silica. [ABSTRACT FROM AUTHOR]

The restrike of vacuum circuit breaker during the breaking process causes overvoltage and intensifies the insulation deterioration of high‐voltage equipment. To solve this problem, the vacuum breaker aging test method and the restrike characteristics are researched. A withstand voltage test platform of 40.5‐kV vacuum circuit breaker was established to obtain the effects of the contact spacing and loop and inrush currents of vacuum circuit breaker on the number of restrike, the wavefront steepness of the breakdown voltage, and the breakdown duration. The number of restrike during the breaking of vacuum circuit breaker decreased and the duration of the repeated‐breakdown arc increased with the increased contact spacing of vacuum circuit breaker. As the loop current of the test system increased, the number of restrike during the breaking of vacuum circuit breaker, the wavefront steepness of the breakdown voltage, and the duration of the restrike arc increased. As the inrush current amplitude increased during the closing of vacuum circuit breaker, the number of restrike and the duration of the repeated‐breakdown arc during the breaking of vacuum circuit breaker increased. The results provide a theoretical basis and data support for the preventive test of 40.5‐kV vacuum circuit breaker and the optimization of the withstand voltage test. [ABSTRACT FROM AUTHOR]

This study characterizes low-resistance regions in a locally degraded multilayered ceramic capacitor (MLCC) using scanning spreading resistivity microscopy, scanning electron microscopy, and transmission electron microscopy. The MLCC consists of a core–shell structure that degrades before electrical breakdown in highly accelerated lifetime tests. Areas of local insulation degradation in the MLCC are revealed by Dy-containing solid solution grains. The characteristic grains within the low-resistance region show the resistance distribution. Degraded grains around the anode, which are assumed to strongly reflect the front-line insulation degradation, suggest that the shell and grain boundaries strongly repress insulation degradation. These results show that improved material uniformity and microstructure design are vital for achieving highly reliable MLCCs. [ABSTRACT FROM AUTHOR]

Memristors (elements of nonvolatile electrically reprogrammable memory) based on electroformed open sandwich-metal–dielectric–metal (MDM) structures are fabricated using thin-film technology. Studies of the electroforming process and the features of the current–voltage characteristics (CVCs) after it was carried out for structures with various electrode materials showed that in the case of a tungsten anode, it was possible to minimize the probability of electrical breakdown during electroforming and subsequent operation of the memory elements. This is valid for any position of the anode in the MDM structure: both upper and lower. However, it is experimentally shown that tungsten is not the optimal material. The production of the anode from molybdenum retains all the advantages of the design with tungsten, and in addition, it leads to a noticeable decrease in the electroforming voltage, which can increase the reliability of this process. The results obtained can be used to optimize the design of the memory element. [ABSTRACT FROM AUTHOR]

The process of formation of anodic electrical breakdown in the crystal structure of ice and liquid water is considered within the framework of the mechanism of generation of free charge carriers through interatomic Auger transitions in the valence band of the dielectric. [ABSTRACT FROM AUTHOR]

The discharge energy determines the machining resolution, minimum processable feature size, and surface roughness, which makes it a hot research topic in the microelectrical discharge machining (EDM) field. In this paper, a kind of novel discharge-energy-generation method in micro-EDM is investigated. In this method, the opposite induced charges on the electrolyte jet and workpiece serve as the source of the discharge energy. The operating mechanism of this discharge energy is revealed by analyzing the equivalent discharge circuit. The unique discharge current and voltage between the electrolyte jet and the workpiece are sampled and investigated. In contrast with the pulsating energy in conventional EDM, this study shows that the direct current (DC) voltage source can automatically generate a continuously periodical pulsating discharge in the electrostatic-field-induced electrolyte jet (E-Jet) EDM process. After further analyzing the electric signals in a single discharge process, it can be found that the interelectrode voltage experienced a continuous sharp electric breakdown, a nearly unchanging process, and a fast exponential recharging process. The discharge frequency increases as the electrolyte concentration and interelectrode voltage increase but decreases as the interelectrode distance increases. The discharge energy per pulse increases with the increasing interelectrode distance and electrolyte concentration but with the decreasing interelectrode voltage. Finally, the electrostatic-field-induced discharge-energy generation and change mechanisms are revealed, which provides a feasible method for micro-EDM with continuous tiny pulsed energy only using the DC power supply. [ABSTRACT FROM AUTHOR]

The dense plasma focus (DPF) can be an intense source of x rays, wherein the insulator sleeve strongly dictates the electrical breakdown, which subsequently affects the formation of a plasma sheath and a collapse phase. Experiments on a 25 kJ DPF (operated at 4.4 kJ) are carried out to demonstrate the influence of insulator surface morphology on the pinch structure, dynamics, and x-ray yield using a Ne fill. Two borosilicate insulators are directly compared, one with a smooth finish and the other machined with four circumferential grooves traversing the perimeter of the exterior insulator surface. Comparisons are made through same-shot imaging diagnostics of the evolving plasma sheath during breakdown, rundown, and at the pinch in addition to the time-resolved measurements of emitted x rays via filtered photodiodes. The presence of structures on the insulator sleeve reduces x-ray production across all fill pressures by a factor of 2.8 ± 2.4 on average and reduces the highest x ray producing shots by a factor of 5.5 ± 1.8. Observations of sheath asymmetry and inhomogeneity at lift-off are observed and correlated with subsequent observations of off-axis radial collapse. Taken together, this suggests that local variations in the insulator surface decrease the spatial uniformity of the sheath, leading to an azimuthally asymmetric focus, reduced electron densities, and, ultimately, degraded x-ray production. [ABSTRACT FROM AUTHOR]

We present a novel electric permittivity sensor based on Bleustein–Gulyaev (BG) waves. Toward that end, we formulate the nonlinear electromechanical partial differential equations governing a BG wave resonator. We find that the permittivity of the material-under-test changes the sensor natural frequencies, thereby enabling the implementation of a frequency-shift permittivity sensor. We also find that the sensor sensitivity is enhanced by increasing bias voltage to drive the sensor into the nonlinear regime. Bias was found to be limited by electrical breakdown. The sensor was fabricated by depositing aluminum electrodes on a shear-poled lead zirconate titanate piezoelectric substrate. Experimental measurements of the displacement on the sensor surface were in good agreement with the developed model. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) are soft, electrically powered actuators that have no discrete moving parts, yet can exhibit large strains (10%–50%) and moderate stress (∼100 kPa). This Tutorial describes the physical basis underlying the operation of DEA's, starting with a simple linear analysis, followed by nonlinear Newtonian and energy approaches necessary to describe large strain characteristics of actuators. These lead to theoretical limits on actuation strains and useful non-dimensional parameters, such as the normalized electric breakdown field. The analyses guide the selection of elastomer materials and compliant electrodes for DEAs. As DEAs operate at high electric fields, this Tutorial describes some of the factors affecting the Weibull distribution of dielectric breakdown, geometrical effects, distinguishing between permanent and "soft" breakdown, as well as "self-clearing" and its relation to proof testing to increase device reliability. New evidence for molecular alignment under an electric field is also presented. In the discussion of compliant electrodes, the rationale for carbon nanotube (CNT) electrodes is presented based on their compliance and ability to maintain their percolative conductivity even when stretched. A procedure for making complaint CNT electrodes is included for those who wish to fabricate their own. Percolative electrodes inevitably give rise to only partial surface coverage and the consequences on actuator performance are introduced. Developments in actuator geometry, including recent 3D printing, are described. The physical basis of versatile and reconfigurable shape-changing actuators, together with their analysis, is presented and illustrated with examples. Finally, prospects for achieving even higher performance DEAs will be discussed. [ABSTRACT FROM AUTHOR]

Electrical breakdown of liquid dielectrics under nanosecond pulsed high voltage has been investigated extensively in the last decade. Prior studies have focused on either experimental characterization of the breakdown process and discharge plasma or formulation/verification of the electrostrictive cavitation mechanism of the breakdown initiation. There remain knowledge gaps toward a clear physical picture of how the first plasma is generated in a region saturated by nanoscale cavities created by electrostrictive forces in inhomogeneous fields at the nanosecond timescale. Initial plasma results from the multiplication of primary electrons that gain energy collisionlessly in the cavities to cause collisional ionization of water molecules on the cavity walls. This paper quantitatively discusses the possible sources of primary electrons that seed the plasma discharge. Electron detachment from hydroxide is shown to be the most probable and sustainable electron source. Using numerical modeling, this study demonstrates the plausibility of an electron multiplication mechanism involving two neighboring cavities. The drift of hydrated electrons from one cavity to the next is the rate-limiting step and sets the minimum electric field requirement. This work will inform subsequent experimental studies and have implications in various applications such as plasma sources in biomedical applications, cavitation study, and insulation of pulsed power equipment. [ABSTRACT FROM AUTHOR]

We report results from a study on electrical breakdown in liquid helium using near-uniform-field stainless steel electrodes with a stressed area of ∼ 0.7 cm 2. The distribution of the breakdown field is obtained for temperatures between 1.7 K and 4.0 K, pressures between the saturated vapor pressure and 626 Torr, and with electrodes of different surface polishes. A data-based approach for determining the electrode-surface-area scaling of the breakdown field is presented. The dependence of the breakdown probability on the field strength as extracted from the breakdown field distribution data is used to show that breakdown is a surface phenomenon closely correlated with Fowler–Nordheim field emission from asperities on the cathode. We show that the results from this analysis provide an explanation for the supposed electrode gap-size effect and also allow for a determination of the breakdown-field distribution for arbitrary shaped electrodes. Most importantly, the analysis method presented in this work can be extended to other noble liquids to explore the dependencies for electrical breakdown in those media. [ABSTRACT FROM AUTHOR]

Cross-linked polyethylene (XLPE) has been recognized as an outstanding insulator for high-voltage power cables due to its favorable structural integrity at high temperature, low moisture sensitivity, chemical resistance, and low rates of failure due to aging. However, the roles of by-products and amorphous regions generated during the XLPE production are not clearly known at the atomistic scale. In this study, we present an eReaxFF-based molecular dynamics simulation framework with an explicit electron description verified against density functional theory data to investigate the roles of XLPE by-products and processing variables such as density and voids on the time to dielectric breakdown (TDDB) of polyethylene (PE). Our simulation results indicate that an increase in density of PE increases the TDDB; however, adding a by-product with positive electron affinity such as acetophenone can reduce the TDDB. Furthermore, during the electrical breakdown in PE, electrons tend to migrate through voids when transferring from the anode to cathode. In comparison with neutral acetophenone, we find that the acetophenone radical anion can significantly reduce the energy barrier and the reaction energy of secondary chemical reactions. [ABSTRACT FROM AUTHOR]

Reverse breakdown in Cu(In,Ga)Se2 (CIGS) solar cells can lead to defect creation and performance degradation. We present pulsed reverse-bias experiments, where we stress CIGS solar cells with a short reverse voltage pulse of ten milliseconds and detect the electrical and thermal response of the cell. This way, we limit the duration of the reverse stress, allowing us to study the initial stages of reverse-bias defect creation in CIGS solar cells and modules. Our results show that permanent damage can develop very fast in under milliseconds. Furthermore, we find the location of defect creation as well as the susceptibility to defect creation under reverse bias depends strongly on whether the cell is encapsulated or not, where encapsulated cells are generally more robust against reverse bias.

Electrical breakdown in a pulsed asymmetric dielectric barrier discharge between a glass-covered mesh electrode and a grounded metal electrode in the air at atmospheric pressure is investigated. Volume discharge forms between the metal tip and the dielectric surface and spreads over the dielectric surface. Breakdown and discharge behaviors depend on the polarity of the charged electrode covered with glass compared to the metal rod electrode. In the case of the dielectric cathode (covered mesh), volume discharge features a stronger and longer-lasting emission. Volume discharge is weaker with outstretched surface discharge developing on the opposite glass electrode sustained by the embedded mesh when the metal rod functions as a cathode. The development and spatial distribution of the surface discharge depend on the relative polarity of the dielectrics caused by the charge deposition of the preceding discharge and is independent of the polarity of the applied high voltage. The discharge emission is brighter for the metal cathode and dielectric anode than for the metal anode, with a branching discharge developing and spreading in a star-like structure along the embedded grid, while a ring-like structure was observed for the metal anode and dielectric cathode. The duty cycle influences the discharge development and properties through the effects of the gas phase and surface pre-ionization. [ABSTRACT FROM AUTHOR]