In this paper, the positive and negative DC breakdown voltage of ester insulating oils and mineral insulating oil in extremely uneven field under small and medium gap were studied, and then compared with their lightning breakdown voltage. The results show that the DC breakdown voltage of ester liquids is lower than that of mineral insulating oil. The negative DC breakdown voltage is lower than the lightning breakdown voltage under small gaps, but it is higher than the lightning breakdown voltage under medium gaps.

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.

To realize the development of fluorescent optical fiber partial discharge detection system, according to the light radiation characteristics of insulator creeping discharge, the key performance and matching efficiency of the fluorescence photoelectric measurement system were compared and analyzed. The main components, characteristic spectral lines, and spectral statistical changing with discharge intensity of the insulator creeping discharge spectrum were obtained through experiments. Combined with the emission spectrum of insulator creeping discharge, excitation spectrum of fluorescent fiber, and capture efficiency of the fiber, the fluorescence excitation efficiency of two fluorescent fibers for partial discharge was compared and analyzed, and the excitation intensity and excitation efficiency of two typical PS fluorescent fibers were obtained. The results show that the fiber with 299-477 nm of excitation spectrum is better than the fiber with 294-410 nm of excitation spectrum. The R3896 PMT and fluorescent fiber system has better matching efficiency, and the SNR of PMT reaches a peak value of 12.45 dB under the optimal driving bias. Under the optimal bias voltage, the self-temperature drift effect of natural cooling system is approximately 7%, and the cooling recovery time is approximately 40 min.

In order to accurately evaluate the maximum impulse voltage which corona resistance enameled wire endured, the corona resistance time of enameled wire under different impulse voltage was tested respectively, and the optimal fitting relationship curve equation between them was analyzed. The results show that the corona resistance time decreases exponentially with the increase of impulse voltage. Because the corona resistance time in the fitting equation has practical physical significance, no matter how the corona resistance time changes, it is greater than zero, which can indirectly solve the maximum impulse voltage that the corona resistance enameled wire can endure.

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.

In order to research the insulation ageing characteristics of cross-linked polyethylene (XLPE) cables, it is necessary to perform ageing tests under laboratory conditions. In this paper, the current research progress on insulation ageing tests and detection techniques of XLPE cables was reviewed. Firstly, the common ageing types and phenomena of XLPE cables were introduced, and the current research results on the growth mechanism and influencing factors of water tree ageing and electrical tree ageing were elaborated. Secondly, the accelerated ageing test methods for XLPE cables under laboratory conditions and their effect on cables were introduced. Then, the current detection methods of cable insulation ageing were briefly classified, the principle, applicable conditions, and advantages and disadvantages of each methods and the characteristics and application method of each insulation detection stage were introduced. Finally, the problems related to cable insulation ageing and their future research directions were discussed.

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.

This article introduced the relevant characteristics of fungi. Fungi were cultivated under laboratory conditions and transplanted to the surface of silicone rubber insulators. Then, the static contact angle, ESDD, NSDD, and pollution flashover voltage of contaminated silicone rubber insulators were measured. The inhibition of fungi on the hydrophobicity of silicone rubber insulators and its influence on the pollution flashover voltage were analyzed. The results show that the adhesion of fungi on the surface of the silicone rubber insulator decreases the hydrophobicity of the insulator. The higher the concentration of fungus, the worse the hydrophobicity; the pollution flashover voltage on the surface of the silicone rubber insulator decreases slightly due to the adhesion of fungi; at the same time, the higher the concentration of fungi, the higher the ESDD and NSDD.

Combined with the special application environment and special structural characteristics of traction motor, the polyester imide insulation system of traction motor based on polyesterimide resin and three-in-one mica tape was studied in this paper. The heat resistance and processability of polyesterimide resin were studied by thermogravimetric analysis (TGA) and viscosity-temperature curve, on the basis of it, simulated insulation structure was prepared using the three-in-one mica tape with good compatibility with polyesterimide resin to verify the electrical ageing performance and reliability of the insulation system. The results show that the insulation system based on the selected polyesterimide resin and three-in-one mica tape has outstanding processability, mechanical properties, electrical properties, heat resistance, reliability, and low cost. The heat resistance index reaches to 215, which meets the requirements of high bonding strength, high heat resistance, and high reliability of traction motor.