The unique three-dimensional network structure, which is formed following the curing process, endows the epoxy resin composite with excellent properties. However, this structure also makes the epoxy resin difficult to degrade or recycle effectively. The present study employs a grinding-reconstruction strategy, utilizing physical grinding to transform epoxy resin waste into micron-sized powders. These powders are subsequently reintroduced into the epoxy resin matrix to prepare samples with varying filler contents. The results demonstrate that the incorporation of fillers does not compromise the overall performance of the composite material. When the filler mass fraction is 3%, the composite material’s volume resistivity and breakdown strength are improved by 9.68% and 28.5%, respectively, compared to pure epoxy. Concurrently, its glass transition temperature, tensile strength, and elongation at break are analogous to those of pure epoxy. This work investigates the impact of epoxy powder obtained through physical grinding as a filler on the performance of epoxy resin, providing new insights and references for the recycling of epoxy resin composites.

Thermoplastic resins have been demonstrated to enhance the toughness of epoxy resins (EP) without compromising their heat resistance and modulus. Moreover, thermoplastic/EP composites exhibit excellent electrical properties. As a filler, however, thermoplastic resins often increase the viscosity of the castables, which has always plagued its application in the field of power equipment casting. In this paper, 1,4-butanediol diglycidyl ether (BDDE) was utilized to dilute the hydroxyl-terminated polyethersulfone (PES)/EP system with the objective of enhancing its processability and enabling its application in the field of casting of electrical equipment. It was found that the introduction of this reactive diluent reduced the viscosity of the castables. When 5 wt

The circuit breaker for a 750 kV alternating current filter (ACF) field is different from the line circuit breaker. It must be switched frequently due to changes in operation mode and daily load. In addition, it is subjected to mixed alternating current (AC) and direct current (DC) voltages, which leads to more frequent pre-insertion resistor faults. In this paper, pre-insertion resistor specimens were collected from a worksite, and the ability of the pre-insertion resistors to resist impact loads was assessed using a falling weighing impact test. When the impact energy applied to the pre-insertion resistors exceeded 7.5 J and the transient impact force reached 90 kN, the pre-insertion resistors cracked and broke. The simulation results showed that under impact load, an increase in the flatness tolerance of the pre-insertion resistors produces significant stress concentration. The stress exceeds the maximum allowable value, which causes breakage at the outer edges. The defective outer edge breakage distorts the circumferential field strength of the resistor stack and increases the maximum field strength by 30

Vanadium doping effectively modulates carrier transport and enhances breakdown voltage in 4H-SiC, yet its underlying microscopic mechanisms remain incompletely understood. The lack of clarity regarding doping-induced carrier behavior in both conducting and blocking states impedes rational carrier selection and limits device performance optimization. This study employs a multiscale simulation framework integrating first-principles calculations with Boltzmann transport theory, incorporating electro-thermal coupling effects, to systematically investigate the influence of vanadium doping on the electrical and thermal properties of 4H-SiC. Results demonstrate that vanadium introduces new defect energy levels, enhances carrier-phonon scattering, and significantly lowers carrier mobility, which is identified as the dominant contribution to the improved breakdown voltage. Meanwhile, the doping-induced lattice distortion markedly suppresses phonon transport and reduces thermal conductivity. The combined effect of these competing electrical-thermal processes ultimately strengthens the material's voltage withstand capability. This work establishes a comprehensive defect-carrier-phonon coupling model, providing critical theoretical guidance for the performance optimization of high-power 4H-SiC devices through defect engineering.

As reactive network modifiers in epoxy resin systems participate directly in the curing and crosslinking process, they inevitably affect the stoichiometric balance, crosslinked network structure, and insulation performance of the material. By constructing BDGE and HDGE bisphenol A epoxy/anhydride systems with different modifier contents and epoxy to anhydride equivalent ratios, the effects of network structure regulation on the thermal and electrical properties of the systems are systematically investigated through glass transition temperature, dielectric spectra, volume resistivity, and dielectric breakdown strength measurements, together with molecular dynamics and density functional theory calculations. The results show that increasing modifier content and chain length promotes network loosening and leads to decreases in glass transition temperature, volume resistivity, and dielectric breakdown strength. Molecular dynamics and density functional theory results further indicate that the observed deterioration in insulation-related properties is more closely associated with increased free volume and weakened electron confinement, whereas the HOMO-LUMO bandgap differences among the representative segments are relatively small. These results provide a basis for understanding the structure property relationship and for optimizing the formulation design of epoxy insulating materials.

When high-voltage DC equipment is subjected to polarity-reversing voltage, the insulation performance of its internal insulation material, epoxy resin-impregnated paper (RIP), is significantly affected by low-frequency polarization. To clarify the underlying mechanisms, this study analyzes the impact of the relationship between low-frequency dielectric relaxation time and polarity-reversing time on the dynamic changes of space charges at different temperatures based on the pulsed electro-acoustic (PEA) method. Furthermore, the influence of traps at the epoxy resin (EP)/RIP interface on interfacial charge accumulation is considered. By improving the existing bipolar carrier transport model, the dynamic characteristics of interfacial space charges in RIP under different polarity-reversing times are explored. The results show that at 313K, due to the low-frequency dielectric relaxation time constant exceeding 60s, the charge distribution is not significantly affected by the reversal time; At 333K and 353K, the reduction in dielectric relaxation time leads to a decrease in interfacial charge density and maximum field strength, with the peak field strength shifting towards the epoxy layer; At 373K, influenced by space charge dissipation and enhanced relaxation effect, the electrode surface charges and the maximum field strength in the epoxy layer initially decrease and then increase with increasing reversal time. The simulation results more explicitly characterize the interfacial polarization process between EP and RIP, and together with the experimental results, elucidate the mechanism of low-frequency polarization on the dynamic characteristics of space charges in RIP under polarity-reversing voltage. The research results may provide a theoretical basis and reference for the insulation design and optimization of high-voltage DC equipment.

Dry-type bushing are widely employed in extra-high-voltage transmission systems, however, residual stresses tend to develop in their capacitor cores during the curing process, potentially compromising insulation performance. This study investigates the curing kinetics of epoxy-impregnated paper, develops a simulation model to analyze the residual stress distribution during the curing of dry-type bushing, and constructs an electric field distribution model by introducing internal defects into regions of high residual stress within the capacitor core. The results reveal a non-uniform distribution of internal residual stresses during the curing process. Significant stress accumulation is observed near the interface between the aluminum conductor and the epoxy-impregnated paper. The maximum residual stress of 27.43 MPa occurs at the lower end of the interface. Moreover, air gaps and microcracks caused by residual stresses can lead to a non-uniform electric field distribution on both sides of the capacitor core. The findings of this paper provide a theoretical basis for enhancing the insulation reliability of dry-type bushings.

During the vacuum interruption process, the anode undergoes significant erosion due to the arc column, significantly affecting the interruption performance. In this study, experimental and simulation investigations were carried out to explore the erosion behavior and microstructural evolution of the CuCr alloy anode under vacuum arc conditions. Based on arc erosion experiments combined with scanning electron microscopy (SEM) characterization, the results show that the size of the eroded Cr particles decreases by approximately two to three orders of magnitude compared with that of the original Cr particles, while the particle shape becomes more irregular. Meanwhile, the eroded CuCr alloy exhibits a distinct particle-layered structure along the axial direction. The upper Region 1 contains only fine Cr particles generated after arc erosion, the middle Region 2 consists of both fine and original coarse Cr particles, and the lower Region 3 retains the original coarse Cr particle structure. To clarify the formation mechanism, thermodynamic simulations were conducted. The results indicate that the difference in melting points between Cu and Cr is the dominant factor responsible for the layered structure. In addition, this study indirectly reveals the temperature distribution characteristics inside the anode during the erosion process.

Epoxy resins (EPs) form three-dimensional network polymers upon curing, endowing them with excellent properties while rendering their waste resistant to degradation and recycling. In this study, ground EP micron-sized powder was fluorinated via plasma technology and subsequently incorporated as functional filler for composite reconstruction. Microscopic morphology, chemical composition, and insulating properties of both pristine and modified EP powders/composites were systematically characterized. The experimental results show that after plasma fluorination for 30 min, the agglomeration of small-sized particles of the filler is improved, the crack distribution of the specimen is diversified, and the degree of brittleness is reduced. Compared to the specimens before fluorination, the dielectric constant and volume resistivity decreased, while the breakdown voltage increased significantly. Two-parameter Weibull analysis further confirmed reduced dispersion in breakdown voltage distribution. These findings demonstrate the feasibility of plasma-assisted filler treatment for enhancing EP’s insulation performance while establishing a sustainable recycling paradigm for EP-based composites.

The reduction of sulfur hexafluoride utilization constitutes a pressing global challenge in the development of eco-sustainable power apparatuses. Developing vacuum circuit breakers for transmission-level applications represents a strategic solution to this challenge. This development requires upscaling contact diameters, making it imperative to understand arc behavior under these expanded contact conditions. However, systematically obtaining arc parameters through experimental approaches currently poses significant challenges. The objective of this study is to numerically obtain the vacuum arc plasma parameters under five large contact diameters of 80, 100, 120, 140, and 160 mm. A two temperature magnetohydrodynamic model was built to simulate vacuum arcs. The results show that as the contact diameter increases, the temperature, number density, and pressure exhibit progressive reductions. The current density exhibits a sharp decline with increasing contact diameter. Under larger contact diameters, the axial magnetic field demonstrates enhanced effectiveness in suppressing current constriction compared to smaller diameters. Using anode input heat flux density as the critical criterion, interruption risks were evaluated for each contact size. For a typical discharge condition for a high voltage level vacuum switch with 40 kArms short-circuit current, 3.6 m/s opening velocity, and 200 mT axial magnetic field, the recommended contact diameter range of 120–140 mm balances interruption reliability and practical application requirements.

During high-current vacuum arcing, asymmetric arcing with off-center plasma columns may occur due to stochastic discharge initiation and mechanical motion, receiving less research attention than symmetric arcing. The objective of this paper is to numerically analyze the influence law of asymmetric arc ignition on arc parameters. For 60 mm diameter contacts, three arc conditions of symmetric arcing, 33% arc offset, and 67% arc offset were modeled. The results show that the arc offset causes asymmetry in the arc’s distribution. For 33% offset, the pressure and number density on the side away from the root of the arc is about 50% of root values, while these parameters fall below 20% for the 67% offset. Simultaneously, arc offset elevates peak parameter values: under 33% offset, maxima for ion pressure, ion density, ion temperature, electron temperature, and current density rise 12%, 11%, 6%, 6%, and 14% versus symmetric arcing; during 67% offset, these escalate significantly to 67%, 61%, 12%, 18%, and 47%. This study contributes to providing reference for the analysis of vacuum interruption processes under asymmetric arcing conditions.

Epoxy resin serves as a critical insulating component in ultra-high voltage dry direct current bushings. However, the accumulation of space charges within the epoxy resin, a byproduct of charge mobility, poses a significant risk to the reliability and operational safety of bushings. Conventional space charge attenuation models, especially after voltage removal, have limited use in simulations aimed at understanding this phenomenon. This study introduces an improved model integrating the bipolar charge transport mechanism with space charge decay based on the hopping conduction mechanism and Schottky's theorem, establishes a theoretical framework for predicting the space charge behavior following voltage removal, and conducts a simulation to investigate the decay process within the internal structure of epoxy resin and measure the residual charges after voltage removal using the pulsed electro-acoustic method. The experimental data validate the accuracy of the proposed model and theoretical assumptions. The findings show that the remaining negative charges after voltage removal are not enhanced by the field enhancement; the anodic positive and cathodic positive charges are distributed in two-segment discontinuous traps, whereas the negative charges are distributed in one-segment traps. The model identifies two distinct trapping sites for anodic and cathodic positive charges, and one trapping site for negative charges. After voltage removal, when the field strength exceeded 40 kV mm(-1), positive charges exist near the upper and lower electrodes, and negative charges exist near the center of the specimen. The consistency between the simulated predictions and experimental data proves the effectiveness of the proposed model in accurately simulating the space charge decay in epoxy materials after voltage removal.

Analyzing the dielectric relaxation process is essential for further optimization and application of the formulated system. To clarify the impact of two excellent second-phase toughening fillers, liquid rubber and polyethersulfone (PES), on the dielectric relaxation process of epoxy resins (EPs), we measured the broadband dielectric spectroscopy of the composite material from - 40 degrees C to 200 degrees C. Various dielectric relaxation models (HavriliakNegami (HN) model, complex ac conductivity, and complex electric modulus) are rationally used to analyze through the in-depth understanding of the dielectric spectrum information in each temperature range. The results indicate that incorporating hydroxyl-terminated liquid nitrile rubber (HTBN) introduces the alpha relaxation process in the low-temperature region and the interfacial polarization process in the medium-temperature region. In contrast, the hydroxyl-terminated PES, which has a strong interfacial bonding ability with EP, does not introduce any new relaxation process. Further analysis and fitting of the dielectric spectrum data across the full-temperature range were performed. In the low-temperature region, the beta relaxation intensity decreased with the introduction of PES. In the medium-temperature region, both the relaxation time and activation energy of the interfacial polarization increase with higher PES doping, owing to the introduction of the highly polar sulfone group. In the high-temperature region, the introduction of fillers increases the contribution of electrode polarization. In addition, the carrier transport process is suppressed as PES content increases in the ternary formulation system. This study investigates the dielectric relaxation process of ternary composites, which may facilitate the application of this formulation system in electrotechnical equipment.

This study focuses on the thermal curing process of epoxy resin/alumina composites, aiming to reduce residual strain and manufacturing costs while improving overall performance in basin-type insulator production through optimized curing parameters. Experimental and simulation studies indicate that residual strain typically arises at the interface in basin-type insulators during both the cooling and curing phases, with the curing process exerting a more substantial influence on the final strain. To reduce strain, we propose a method that combines Radial Basis Function (RBF) neural networks with a genetic algorithm for the multi-objective optimization of the curing process of basin-type insulators. Utilizing the dataset derived from the basin-type insulator simulation model, we constructed an RBF neural network model and optimized the curing process parameters through the Non-dominated Sorting Genetic Algorithm (NSGA-II). Optimization results demonstrate a 7.6 % reduction in residual strain, a 62.41 % decrease in the maximum difference in degree of cure, and a 26.01 % reduction in economic costs compared to the original scheme. The method described in this study provides reference value for practical engineering problems.

Due to silicon carbide (SiC) power devices' superior performance in terms of switching frequency, loss, and so on, they are widely used in high-power and high-frequency electronics. While SiC devices are in blocking mode, the transport and accumulation of charge carriers in SiC may lead to significant degradation and failure of semiconductor materials, which is the primary factor limiting their application in high-voltage and large-current fields. In addition, transition metal vanadium is often used to compensate for the defect levels in SiC, leading to more complex carrier transport dynamics behaviors. In this research, the effect of vanadium doping on the withstand voltage properties of SiC was explored. Firstly, characterization experiments, including x-ray diffraction, Raman spectroscopy, and Kelvin probe force microscopy on SiC before and after vanadium doping, were performed. Secondly, the transport dynamics of charge carriers in SiC were studied. Based on the influence of vanadium on the trap characteristics, the effect mechanism of vanadium doping on carrier transport dynamic behaviors was elucidated. Finally, the relationship between microscopic carrier transport and macroscopic dielectric properties was discussed. The results show that vanadium doped SiC introduces deep energy level traps, which are able to capture carriers and cause charge accumulation, inhibit carrier migration. This can also affect conductance current. Therefore, vanadium doping can effectively improve the voltage withstand capability of SiC in blocking mode by regulating the trap characteristics and carrier transport behaviors.

Low frequency AC transmission systems exhibit extensive application prospects in scenarios such as long distance offshore wind power transmission and have garnered significant attention in developing eco-friendly power systems. Compared with conventional 50 Hz AC systems, low frequency systems demonstrate prolonged short-circuit current duration with distinct vacuum arc characteristics. Consequently, this study conducts numerical analyses of arc evolution dynamics and anode thermal processes in 20 Hz vacuum interrupters to evaluate the applicability of standard 50 Hz vacuum circuit breakers under low frequency conditions. Results reveal that reduced frequency alters the coordination between arc current and contact gap, intensifying arc constriction during later arcing stages for 20 Hz vacuum arc, thereby elevating the plasma parameters, including pressure, temperature, and current density. Under specified conditions, namely 60 mm contact diameter, 2.0 m/s contact opening speed, and 10 kArms short-circuit current, the peak anode heat density reaches 5.2 × 108 W/m2 for 20 Hz arcs, exceeding the maximum value of 50 Hz with 4.1 × 108 W/m2 by 26%. The 20 Hz arc anode further maintains elevated temperatures for extended duration, attaining a peak center temperature of 1795 K, which is 64% higher than the 50 Hz value of 1095 K. These findings provide theoretical guidance for designing low frequency vacuum interrupters.

In response to growing environmental concerns, this study proposes the use of dry air as an insulating gas in gas-insulated switchgear (GIS) to replace the traditional SF6 gas. To address the problem of gas leakage, the helium tracer method is employed to detect the leakage of insulating gas within the equipment, focusing on the impact of helium addition on the insulation performance of GIS. Electrodes and experimental chambers were designed to simulate the electric field conditions under actual operating circumstances. Breakdown voltage experiments at power frequency were conducted to study the insulation performance of mixed gases with three different concentrations of helium under two pressure conditions. The breakdown voltage values at power frequency were theoretically analyzed from the perspective of gas discharge. Additionally, the breakdown voltage dispersion of mixed gases with different concentrations of helium was analyzed, considering the operational stability of GIS equipment. The experimental results indicate that the addition of helium has a negligible effect on the insulation performance of dry air when compared to the pure dry air power frequency breakdown results. This confirms that the helium tracer method is an effective technique for detecting the leakage of insulating gas in environmentally friendly dry air GIS equipment.

The interfacial residual stress formed in the preparation of dry-type bushing is an important factor restricting its reliable operation. In this paper, the kinetic equation of epoxy resin impregnated paper curing is derived by using the non-isothermal DSC analysis method, and the dry-type bushing model is established by simulation software to derive the temperature, curing degree change, and interfacial residual stress distribution of dry-type bushing in the curing process. According to the results, the maximum value of the interface residual stress formed after curing occurs at the contact between the impregnated paper and the ends of the center capacitor, which is up to 10.9 Mpa. This result will be conducive to the efficient manufacturing and reliable operation of the dry-type bushing.

Epoxy resins are widely used in power equipment, and due to the material as well as process requirements, multi-layer epoxy structures inevitably exist. The interlayer interface between epoxy layers, formed via secondary curing, causes a potential weak link in the material's properties. This work experimentally measures the temperature and strain at the epoxy-epoxy interface under various conditions, including the presence or absence of epoxy and differing chemical doses of curing agent. Subsequently, an epoxy-epoxy interface strain resin simulation model is established to examine the mechanism of interface stress formation by exploring the curing kinetics of epoxy resins using the Straink method. Experimental measurements and simulation calculations reveal the presence of an interaction between interlayer interfaces during the secondary curing. Changing the dose of curing agent in the post-pouring layer can change the interaction between the layers and regulate the interlayer interface performance.