The dry and cold environment of the Qinghai-Tibet Plateau is easy to make the insulators of railway catenary ice-coated, causing serious ice flash accidents. To study the operating status of ice-coated insulators in catenary, a two-dimensional ice-coated model of cantilever insulators was established according to the winter environmental characteristics of Golmud station on the Qinghai-Tibet railway, and the porcelain insulator XP-160 and composite insulator FXBW-110/100 were used as contrast. The spatial electric field distribution and surface temperature distribution characteristics of different types of ice-coated insulators were analyzed by electrostatic field and Joule heat field simulation. Finally, the shed structure of the insulator was optimized. The results show that as the thickness of ice layer and the length of ice crystal increase, the field intensity of each insulator increases gradually, and the surface temperature continues to rise. When the insulator is bridged by the ice crystal, the field intensity decreases, which is slightly lower than the field intensity of clean insulator. The increase of arrangement angle for the cantilever insulator will lead to the increase of electric field, but it has little effect on the temperature. Therefore, the arrangement angle of cantilever insulator should decrease during installation. The insulators with one large and two small shed structure can effectively reduce the increase of field intensity and suppress the temperature rise.

Composite insulators have been widely used in power transmission lines. In recent years, there are many grid accidents caused by insulator core rod deterioration. It is urgent to find out the influence factors and rules of composite insulator core rod deterioration. In order to study the influences of different voltage applied time and environmental humidity on the core rod deterioration of composite insulator under uniform electric field, the electric field distribution generated by the dielectric barrier discharge method was simulated and analyzed. An electrical ageing experiment platform was designed and built, and the core rod samples were conducted 200 h, 400 h, and 800 h of electrical ageing tests at power frequency under dry and humid environments. The physical and chemical properties of new sample and the aged samples were tested, and the corresponding influence laws were analyzed. The results show that after electrical ageing, the epoxy resin content in the core rod decreases. When the ageing time is less than 400 h, the epoxy resin content under humid and dry environments has little difference. When the ageing time increases to 800 h, the epoxy resin content under humid environment is significantly lower than that under dry environment.

In order to clarify the electric strength test conditions of arc-extinguishing nozzle materials, an electric strength test model of nozzle materials was established by using COMSOL finite element analysis software, and the electrostatic field distribution of the test model were calculated under different electrode shapes, environmental media, and sample thicknesses. The results show that the spherical electrodes and equal-diameter electrodes are better than non-equal-diameter electrodes, the best environmental media is transformer oil, and the sample thickness of 1 mm is better. By comparing the electric strength test results of the nozzle material samples with 1 mm of thickness in transformer oil measured with spherical electrodes and equal-diameter electrodes, it is found that the electric strength of the samples measured with spherical electrodes is higher, and the dispersion is smaller, the standard deviation is only 1.172 kV/mm. The research results provide a theoretical basis for the selection of electric strength test conditions for nozzle materials.

The boron nitride nanosheets (BNNS) was surface modified by γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560), and then epoxy resin/functionalized BNNS (EP/BNNS-KH560) composites were prepared by doping BNNS-KH560 into epoxy resin matrix. The structure and morphology of the functionalized BNNS were measured, and the properties of EP/BNNS-KH560 composites were studied. The results show that the surface of BNNS is grafted with KH560 successfully, which exhibits a transparent thin layer structure under transmission electron microscope. The addition of BNNS-KH560 with a wide energy level gap can maintain the high insulating properties, excellent dielectric properties, and mechanical properties of the composites, and improve their thermal stability. Additionally, the BNNS-KH560 can form a good heat conduction channel in epoxy resin matrix, and improve the thermal conductivity of the composites effectively. When the mass fraction of BNNS-KH560 in composites is 20%, the thermal conductivity of the composites can reach 0.51 W/(m·K).

Under repetitive impulse voltage, tests of the growth characteristics of electrical tree were conducted on laminar composite insulation consist of impregnating resin and insulating tape for wind turbine generator. The effect of impulse voltage repetitive rates on the electrical tree initiation characteristics, morphological features, and growth curve of the insulation composited by epoxy modified unsaturated polyester resin with polyimide film reinforced mica tape was studied. The growth characteristics of electrical tree extending feature along the interface of insulating tape was analyzed. The results show that under the bipolar square wave impulse voltage with the peak voltage of 7 kV and the repetitive rates of 500 Hz, 1 000 Hz and 2 000 Hz, respectively, the electrical trees in samples are all branch-shaped and the branches are relatively sparse. The electrical tree extends laterally along the interface when it grows to the insulating tape, hindering the radial growth of the electrical tree, increasing the breakdown time of the sample.With the increase of the repetitive rate of the impulse, the initiation time of the electrical tree is shortened, the initiation rate is promoted, the branches increases and its discharge channels becomes thinner, the fractal dimension is almost unchanged, and the average radial growth rate increases.

At present, most of the researches on SF₆ substitute gas rely on experimental selection, with high cost, heavy workload, and low efficiency. Studying the theoretical relationship between molecular structure parameters and insulation performance of SF₆ can provide direction for the molecular design and selection of SF₆ substitute gas, and improve the researching efficiency. Firstly, we focused on the current quantitative structure-activity relationship model with development potential, especially a new type model involving molecular electrical parameters, force parameters, and geometric parameters. Then the molecular design method based on the new quantitative structure-activity relationship model was introduced. Finally, the problems and development directions to be further studied of the new quantitative structure-activity relationship model in the research of SF₆ substitute gases were discussed from the three aspects of gas insulation performance database, the diversification of predictive properties, and the improvement of molecular design methods.

Outdoor oil-filled cable terminals are key accessories in high-voltage transmission and transformation lines. However, high-voltage cable terminal failures have occurred continuously under cold weather in China, which seriously affects the safety of power grid operation. For this reason, an equivalent experimental device for the cable main insulation-stress cone interface insulation of the oil-filled cable terminal was designed, and the effect of the silicone rubber/XLPE interface coating silicone oil on the partial discharge activity under 10℃ and -30℃ was tested. Moreover, the failure mechanism was studied according to microscopic observations and electric field simulation. The results show that under 10℃, coating silicone oil on the interface can effectively improve the compatibility and insulation strength of the cable terminal interface. When there is no scratch, the partial discharge initial voltage of the interface coating with silicone oil is about 17.2% and 200% higher than that without coating silicone oil. However, under -30℃, silicone oil has a solidification shrinkage effect, resulting in the generation of air gap or the re-exposure of inherent blemish, and the partial discharge initial voltage decreases significantly, which is even slightly lower than that without coating silicone oil. The electric field simulation results show that the maximum field strength distortion value under very cold environment is 6.26 kV/mm, which is higher than the electric strength of air, and it is easy to cause discharge breakdown.

In this paper, five kinds of epoxy resin samples with different ratios of acid anhydride curing agent were prepared by hot pressing method. The thermal and dielectric properties of the samples were tested, and then the best anhydride curing agent ratios were selected, and the steric effects caused by methyl substitution were analyzed. The results show that the mixed anhydride curing sample with the molar ratio of methylhexahydrophthalic anhydride and hexahydrophthalic anhydride of 8∶2 shows the highest glass transition temperature, and the electrical strength is improved, while the dielectric loss remains unchanged, which is closely related to the increased rigidity of the system.

The liquid crystal epoxy monomer was cured to obtain liquid crystal epoxy resin prepolymer, and liquid crystal epoxy resin fiber films with different fiber diameters were obtained by electrospinning technique. The birefringence of the samples was observed by polarizing microscopy and removable hot stage, and the mechanical properties, dielectric properties, and insulation properties of the liquid crystal epoxy resin fiber films with different fiber diameters were systematically evaluated. The results show that the liquid crystal epoxy resin prepared by electrospinning method can form and maintain an ordered liquid crystal phase. The finer the fiber diameter, the higher the degree of orientation arrangement, and when the fiber diameter is 280 nm, the tensile strength (7.53 MPa) of the liquid crystal epoxy resin fiber film is the largest. Under the test frequency ranging from 10^-1 Hz to 10⁶ Hz, the dielectric constant of the liquid crystal epoxy resin reaches to the highest value of 2.34, and the dissipation factor is only 0.002 at industrial frequency. In addition, the liquid crystal epoxy resin fiber film has high resistivity, and when the fiber diameter is 280 nm, the volume resistivity of the liquid crystal epoxy resin fiber film can reach to 5.49×10¹⁵ Ω·cm.

In this paper, the compatibility of four kinds of insulation materials, including enamelled round wire, enamelled rectangular wire, impregnated resin, and rubber gasket materials, with automatic transmission fluid (ATF) for oil-cooled electric vehicle motor was studied. Deionized water was added to ATF and the volume fraction was 0.5%, the compatibility experiments of four insulation materials with ATF were conducted at 155℃ according to the thermal class. The results show that the enamelled round wire, enamelled rectangular wire, and the impregnated resin has good compatibility with ATF. The performance of acrylic rubber was degraded obviously during the experiment, which does not meet the performance requirements of sealing materials.