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.

High-voltage cross-linked polyethylene (XLPE) cables constitute the core power transmission and distribution channels of urban power grids. Buffer layer failure caused by ablation has become a major hidden danger threatening the safety of cable body and the stability of power grid operation. This paper systematically summarized the research status of defect detection technologies for high-voltage cable buffer layers. Three mainstream methods, including electrical detection methods (broadband impedance spectroscopy, partial discharge detection), chemical gas detection methods (characteristic gas analysis), and imaging detection methods (X-ray, CT detection), were reviewed and compared in terms of their detection principles, effectiveness, applicable scenarios, and advantages and disadvantages. Finally, the challenges faced by existing technologies and future development directions were pointed out.

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.

To improve the dielectric properties of polypropylene (PP), different mass fractions of β-nucleating agent and nano-montmorillonite (MMT) were added into a PP matrix in this paper to construct various ternary composite systems β-MMT-PP, and the synergistic effect of the two on the microstructure and dielectric properties of PP was investigated. The modified PP materials were characterized by means of X-ray diffractometry (XRD), differential scanning calorimetry (DSC), polarizing optical microscopy, pulsed electro-acoustic (PEA) method, conduction current, and DC breakdown tests. The results indicate that the addition of an appropriate amount of β-nucleating agent and MMT can effectively improve the microstructure of PP. When the mass fractions of β-nucleating agent and MMT are 0.5% and 1.0%, the β-crystal content and crystallinity in the composite system reach their peak values of 84.01% and 55.4%, respectively. With the addition of β-nucleating agent and MMT, both the space charge injection threshold field strength and the breakdown strength of PP are improved, reaching maximum values of 19.73 kV/mm and 94.99 kV/mm, respectively. An appropriate amount of β-nucleating agent can induce the transformation from α-crystal form to β-crystal form and refine the spherulites, thereby better improving the dielectric properties of the material.

This study aims to clarify the effects of the crystallization characteristics of domestically washed polypropylene resin and the casting process on the microstructure of cast films and the comprehensive properties of biaxially oriented polypropylene (BOPP) films. Using domestically washed polypropylene resin as the research object, the effects of crystallization characteristics of the domestic resin and casting process on the regulation of the cast film microstructure and the resulting effects on the comprehensive properties of BOPP films were systematically investigated by means of characterization techniques such as polarizing optical microscopy (POM) and wide-angle X-ray diffractometry (WAXD). The results show that the domestic resin can form β-crystals of relatively small size during slow cooling. Increasing the chill roll temperature can increase the crystallinity, β-crystal content, and spherulite size of the cast film, while the β-crystals on the cast film surface directly influence the size and distribution morphology of the crater rings on the surface of the domestic BOPP film. The comprehensive properties of the domestic BOPP film have approached those of imported products of the same specification.

To prepare epoxy resin-based composites with excellent comprehensive properties, this study synthesized dendritic nanosilica (DSiO₂) via a dual-template method and applied them to modify epoxy resin (EP). The relationship between structure and property of the composites was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption-desorption tests. The results indicate that after modification with the silane coupling agent Z-6040, DSiO₂ exhibits excellent dispersibility in epoxy resin. As the mass fraction of DSiO₂ increases from 0 to 0.9%, the onset curing temperature of the composite decreases from 160.7℃ to 111.3, and the peak temperature decreases from 196.3℃ to 159.6℃; the tensile strength increases from 24.2 MPa to 53.6 MPa, the elongation at break increases from 10.5% to 13.5%, and the Rockwell hardness increases from 85.1 to 91.5. Compared with the unmodified EP, the DSiO₂/EP composites exhibit significantly increased storage modulus, a glass transition temperature (T_g) that shifts toward higher temperature, and enhanced thermal stability.

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.

To develop composite separator materials with excellent flame retardancy, electrical properties, and mechanical properties to meet the safety requirements of power battery systems for new energy vehicles, we prepared a series of ATO/PS composites by adding different mass fractions of nano antimony tin oxide (ATO) to polystyrene (PS). The micromorphology, mechanical properties, flame retardancy, electrical properties, and corrosion resistance of PS and ATO/PS composites were systematically compared. The results show that when the ATO mass fraction is 4%, the ATO/PS composite achieves the best comprehensive performance. Compared with pure PS, its tensile strength, elongation at break, flexural strength, and impact strength increase by 27.75%, 36.71%, 20.31%, and 26.54%, respectively; the flame retardancy is significantly improved, with the limiting oxygen index increasing by 23.7% and the UL-94 rating upgrading from NR to V-0; in terms of electrical properties, the volume resistivity decreases by 77.5% and the dielectric loss factor decreases by 51.5%. When the ATO mass fraction is 5%, excessive ATO leads to a decline in mechanical properties due to the agglomeration effect, and the improvements in flame retardancy and electrical properties slow down.

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 address the key problems in ultra-high voltage flexible DC transmission system that the core biaxially oriented polypropylene (BOPP) films for dry-type DC capacitors rely on imports, and the high ash content of domestic polypropylene resins leads to insufficient insulation and ageing resistance of the films, we selected imported electrical-grade, domestic continuously washed low-ash, and domestic unwashed high-ash polypropylene resins to prepare BOPP films. The microscopic morphology, crystal structure and electrical properties of the films were characterized systematically, and the combined electro-thermal ageing tests under AC-DC superimposed conditions were conducted. The results show that BOPP films prepared from low-ash domestic washed polypropylene resin have higher electric strength and more stable high-temperature dielectric performance. Moreover, the crystal structure of the films has no significant changes after ageing, and their electrical properties are close to those of the imported BOPP films.

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.

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.

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.

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.

Porcelain insulators are critical components of transmission lines, and their defects will directly threaten the safe and stable operation of power systems. Taking XP-160 porcelain insulators as the research object, we proposed a numerical simulation method for microwave detection of porcelain insulator defects. The variation patterns of the reflection coefficient and transmission coefficient under crack and metal inclusion defects were analyzed and compared, the optimal detection method and detection frequency were obtained, and the detection mechanism was analyzed. The results show that at a frequency of 20 GHz, the microwave reflection method with the antenna placed horizontally achieves the best detection performance for both types of defects, and defect orientation can be identified through rotational detection. Internal defects cause changes in the nearby electromagnetic field distribution, which in turn leads to variations in the characteristic parameters.

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.