To address the dielectric matching problem in the oil-paper insulation system composed of cellulose insulating paper and low-permittivity insulating oil, this study employed low-temperature plasma for the surface treatment of insulating paper to improve the oil-paper insulation performance. A nanosecond pulse power supply was used to drive dielectric barrier discharge (DBD) to generate Ar/HMDSN plasma, and the effects of operating parameters such as precursor flow rate and treatment time on the properties of insulating paper and oil-paper insulation were investigated. The changes in surface physicochemical characteristics were analyzed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to explore the mechanism of property changes of the insulating paper. The results show that the insulation and mechanical properties of the insulating paper first increase and then decrease with the increase of precursor flow rate and treatment time, with the most significant improvement achieved after treated for 6 min under the flow rate of 15 mL/min. Compared with the untreated insulating paper, the relative permittivity of the insulating paper treated under these conditions decreases by 35.7%, the tensile strength increases by 23.1%, the flashover voltage and breakdown strength increase by 34.2% and 25.0%, respectively, and the flashover voltage and breakdown voltage of oil-paper insulation is correspondingly improved by 24.4% and 17.2%. During the plasma treatment process, low-polarity molecular fragments generated from the reaction precursor can penetrate the insulating paper and undergo deposition polymerization on the fiber surface, reducing molecular polarity, thereby comprehensively improving the both the surface and the bulk insulation properties of insulating paper.

Metal particles are easily generated during the installation and operation of DC gas-insulated transmission lines (GIL). Under electrodynamic forces, the particles may contact with insulators, causing electric field distortion on the insulator surface, partial discharge, or even insulation breakdown, which seriously threatens the safe operation of GIL equipment. Based on a coupled electric field-flow field mathematical model for DC GIL, combined with the motion trajectories of metal particles inside the DC GIL, the feasibility of an lifting type particle trap as a particle movement suppression scheme was investigated. The results show that after installation of particle trap, the jumping motion of most particles is suppressed. The electric field strength in the bottom area of the trap is significantly reduced, but the degree of electric field distortion increases at the top area of trap, and insulator and high-voltage conductor, indicating that a balance between the electric field shielding range and distortion risk must be considered when designing trap parameters. By optimizing trap parameters such as lifting height, grid width, baffle width, and distribution angle, the low-field-strength coverage area can be expanded, which enhances the electric field shielding effect and particle movement suppression capability of the trap, and reduces the proportion of escaped particles.

This study aimed to establish a rapid on-site detection method for the mechanical properties of cross-linked polyethylene (XLPE) cable insulation based on near-infrared spectroscopy. Considering the high light transmittance of XLPE insulation and taking into account spectral repeatability and signal-to-noise ratio, a transflective "6+1" fiber optic acquisition probe and a supporting detection device were developed. The near-infrared spectra of 60 cable samples were collected, and the influence of spectral baseline drift was eliminated by second-order derivative pretreatment. The elongation at break and tensile strength of the samples were measured according to GB/T 2951.11—2008 and used as reference values for modeling, and the repeatability of the reference data was verified. The preprocessed spectral matrix was correlated with the reference values using partial least squares (PLS) regression, and a multivariate calibration model for the mechanical properties of XLPE insulation was established. The results show that the cross-validation standard errors of the model for elongation at break and tensile strength are 12.16 and 0.55, respectively. When five blind samples were prepared by the model, the relative deviations between the predicted results and the reference values are all less than 5%, demonstrating that the model can effectively achieve rapid assessment of the mechanical properties of XLPE insulation.

Insulation interface defects are a major cause of cable terminal failure in extreme cold environments, and the stress state at the epoxy resin/silicone rubber interface directly determines the mechanical integrity and the stability of thermal and electrical properties of the cable terminal interface. In this study, a simplified model of the epoxy resin/silicone rubber interface in cable terminals was first designed based on the actual assembly process. The interface stress of this simplified model under extreme cold conditions was calculated using finite element analysis. Then, a quantitative relationship model between the interface stress and the reflection coefficient of epoxy/silicone rubber composite samples was established using an ultrasonic pulse detection system. Finally, a simplified terminal model was fabricated, and ultrasonic pulse detection experiments were carried out under extreme cold environments ranging from 20℃ to -40℃. The interface stresses at different temperatures were inverted using the quantitative model and compared with the simulation results. The results show that the ultrasonic velocity in epoxy resin increases linearly with the decrease of temperature, and the increase rate is 3.446 7 m/(s·℃). During the process of cooling from 20℃ to -40℃, the interface stress of epoxy/silicone rubber decreases significantly due to the loss of interference caused by the temperature drop.The error between the simulation and experimental results remains around 5%, confirming the reliability of the proposed interface stress back-calculation method under extreme cold environments.

Dry air is widely used as an alternative to SF₆ gas in gas-insulated switchgear (GIS). However, metallic particle contamination is a key issue that restricts the development of high-voltage GIS. In this paper, a model for predicting the cumulative breakdown probability of high-voltage air gaps was established on the basis of time-volume theory, and the influence of metallic particles on the breakdown characteristics of high-voltage dry air gaps at high voltage levels was studied. The results show that metallic particles located near the electrodes are more likely to cause gap breakdown, and those near the high-voltage electrode are more likely to cause breakdown than those near the grounded electrode. Meanwhile, particles with sharp protrusions are more likely to cause gap breakdown than round particles. Therefore, in the design of gas-insulated equipment, particle traps or barriers should be used to keep metallic particles away from the electrodes, and the occurrence of particles with sharp protrusions should be avoided as much as possible.

After long-term hygrothermal ageing, the bonding between fibers and resin in basalt fiber composites is prone to damage, making the development of hygrothermal ageing-resistant coatings become a key factor in advancing the application of basalt fibers. In this paper, the construction of hygrothermal-resistant sizing coatings was carried out through molecular dynamics simulation and first-principles molecular dynamics simulation. The effects of four types of epoxy emulsions—diglycidyl ether of bisphenol A (DGEBA), dimer acid-modified epoxy resin (DAER), hydrogenated bisphenol A epoxy resin (HBPA), and cycloaliphatic epoxy resin (CER)—used as sizing coatings for basalt fibers on the hygrothermal resistance of basalt fiber reinforced polymer (BFRP) were simulated and analyzed. The results show that owing to the low polarity and high energy gap of the primary crosslinking structure formed by CER and MHHPA, the CER-modified basalt fiber (BF-CER) imparts the best insulation performance to the composite; meanwhile, its high interfacial binding energy results in the highest flexural strength among the four types of samples. Due to its strong dielectric barrier capability and high binding energy stability, BF-CER displays the best stability in mechanical and electrical properties within 20 h of ageing. During ageing from 20 h to 120 h, the HBPA-modified basalt fiber shows the highest stability owing to its lower degree of hygrothermal degradation. In summary, BF-CER possesses the most outstanding hygrothermal ageing resistance.

Magnetic slot wedges of motors play a crucial role in improving the air gap magnetic flux density distribution, reducing motor temperature rise and noise, and enhancing efficiency. However, their detachment can lead to severe problems such as stator-rotor rubbing and insulation damage, threatening the safe operation of the motor. To address this, in this paper, the anti-detachment technologies for magnetic slot wedges were systematically reviewed. The factors influencing the detachment of magnetic slot wedges were summarized, the effects of material and structure on the anti-detachment performance of magnetic slot wedges were concluded, and the existing detection methods for slot wedge detachment were combed. Finally, the future development directions of anti-detachment research were discussed.

To address the challenge of on-site, non-destructive, and live assessment of the mechanical life of distribution cable outer sheaths, a thermal ageing platform and a hygrothermal accelerated ageing platform were established in this paper, and the evolution law of the compression modulus of PVC sheaths with ageing time and multi-stress coupling effects was systematically investigated. Based on the changing law of compression modulus, an Arrhenius single-stress ageing model and a Peck hygrothermal coupled ageing model were constructed, and the prediction errors of the two models were compared; meanwhile, an on-site sampling scheme with radial and axial multi-point sampling was proposed. The results show that the compression modulus increases exponentially with ageing time, while the elongation at break decreases rapidly. At 120℃, the degradation rate at 60% relative humidity is significantly higher than that at 40% relative humidity, and the humid environment can further accelerate the rigid-to-flexible transition process of the material. Under hygrothermal environments, the Peck hygrothermal coupled model can significantly reduce the prediction errors compared with the Arrhenius model. The error of radial and axial multi-point sampling on the cable can be reduced to 4.1% compared with the traditional specimen testing.

To systematically investigate the short-term and long-term DC voltage endurance characteristics of polypropylene (PP) materials, we took PP sheet specimens as the research object and tested their DC breakdown strength at different temperatures and thicknesses. Through linear voltage ramp and stepwise voltage ramp tests, the effects of voltage application method and ramp rate on the DC breakdown strength of the specimens were studied. On this basis, combined with the breakdown test data under constant voltage, the DC voltage endurance coefficients of the material determined by different voltage application methods were compared, and the applicability of each method was analyzed. The results show that as the temperature increases, the DC breakdown strength of the PP specimens decreases, which conforms to the Arrhenius equation. As the specimen thickness increases, the breakdown strength decreases following an inverse power law. The faster the voltage ramp rate, the higher the measured DC breakdown strength. As the voltage application time increases, the breakdown strength of the specimens decreases. The DC voltage endurance coefficient of the PP material determined by the inverse power law of electrical ageing based on the data from the constant voltage method and the stepwise voltage ramp method is approximately 13.

To investigate the effects of different accelerators and their dosage on the pre-curing and cured properties of epoxy resin/anhydride systems (EP/MTHPA), this study employed three accelerators—DMP-30, N,N-dimethylaniline, and N,N-dimethylbenzylamine—to prepare EP/MTHPA cured products at different curing agent dosages. The pre-curing behavior of the resin system and the mechanical properties, thermal stability, and electrical properties of the cured materials were studied. The results show that when the accelerator dosage is 0.75 g, the viscosity variation of the resin system is more suitable for production process control. Among them, the EP/MTHPA/DMP-30 system exhibits excellent comprehensive performance, with the lowest polymerization activation energy of 74.58 kJ/mol, a heat deflection temperature reaching 123.40℃, a flexural modulus, flexural strength, and impact strength of 123.6 MPa, 2.9 GPa, and 14.8 kJ/m², respectively, and a volume resistivity of 9.6×10¹⁶ Ω·cm.