In order to obtain superhydrophobic film by simple and mold free method, on the basis of the transformation of 3D printer transmission system, we filled hydrophobic silica nanoparticles in thermoplastic elastomer solution material to prepare printing ink. Then ordered porous superhydrophobic film was prepared using the ink by 3D printing technology. The printability of ink and the wettability, wear resistance, insulating property, and oil-water separation of the film were investigated. The results show that the porous structure film prepared by this method shows well super-hydrophobicity, high oil-water separation efficiency, good insulating property and mechanical properties such as wear resistance and durability.

Aiming at the problerm of seleting energy in the intrinsic conductivity measurement by charge decay method,the intrinsic conductivity of polyimide was measured by charge decay method under the electron irradiation energy range from 5 keV to 20 keV. The influence of irradiated electron energy on the test results was studied, and the fitted method of surface potential decay data was improved by adding a polarization decay time constant. The results show that a higher irradiated electron energy causes a higher charged balance potential on the surface of insulating material, resulting in more serious polarization inside the dielectric, which affects the test results of the conductivity in charge decay method. The surface potential decay data can be fitted and interpreted well by the improved method, which provides an basis for the selection of irradiated electron energy.

The high frequency repetitive impulse generated by the inverter can lead to uneven overvoltage with high amplitude along the stator windings, which will accelerate the ageing of insulation system and even cause faults. On the basis of the transient analysis software PSCAD/EMTDC, the equivalent circuit model for three-phase stator windings of 2.5 MW permanent magnet direct-drive generator was established, and the parameters of corresponding equivalent circuit were calculated by finite element method. Moreover, the experimental platform was built for verifying the validity of the calculation results. The results show that under the effect of three-phase pulse width modulation (PWM) pulse voltage, the amplitudes of the overvoltage to ground, coil to coil overvoltage, and turn to turn overvoltage of the stator winding for permanent magnet direct-drive wind generator show a decreasing trend from the connecting terminal of motor to the neutral point of winding. The experimental results further verify the accuracy of the equivalent circuit model of three-phase stator winding.

Vegetable insulating oil is a kind of environment-friendly insulating oil with high ignition point, its electrical performance is similar with that of mineral insulating oil, but the kinematic viscosity is higher than that of mineral insulating oil. In this paper, the process conditions for preparing insulating oil with low viscosity by transesterification reaction using vegetable insulating oil as raw material and NaOH and ethanol as catalyst were discussed. And the effect of transesterification reaction conditions on the kinematic viscosity of vegetable insulating oil was investigated. The results show that when the molar ratio of alcohol to oil is 6∶1, the reaction time is 1h, the reaction temperature is 70℃, and the mass fraction of NaOH is 0.5%, the kinematic viscosity of the product can reach to 5.81 mm²/s, which is close to that of mineral oil. When the mass fraction of catalyst is no more than 0.5%, the kinematic viscosity of the product is inversely proportional to the amount of catalyst, and vegetable insulating oils with different kinematic viscosity can be prepared by controlling the amount of catalyst.

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.

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.

Accelerated thermal ageing test was conducted on mineral oil-paper, natural ester-paper, mineral oil, and natural ester at 140℃ for 1 640 h. The change law of acid value and dielectric dissipation factor of the four oil samples in different ageing stage were emphatically analyzed, and the appearance changes of aged oil and paper were compared. According to that, the influence of the participation of insulating paper on the properties of different insulating oils during the ageing process was comprehensively compared. The results show that the acid value, dielectric dissipation factor, and ageing degree of the aged oil samples without insulating paper are higher than those with insulating paper. The ageing difference of natural esters with and without insulating paper is smaller than that of mineral oil, and the holding capacity for acidic substances is better than that of mineral oil, which can delay the ageing of insulating paper to a certain extent.

The surface flashover of insulating material is affected by many factors, such as surface roughness, nano fillers, and chemical functional groups. In this study, polyamide mesh was used as support and hydrophobic nano silica particles were used as modified materials. Nano fillers were embedded into polyamide mesh by the treatment method of dissolution and resolidification. The microstructure was determined by changing the mesh size, and the chemical groups on the composite surface were changed by fluorinated nanoparticles. The coupling effect of microstructure/nano filler on surface flashover was studied, and the material was endowed with superhydrophobic properties. The results show that with the polyamide mesh of 300 mesh, the composite has the best anti flashover performance, and the flashover voltage was increased by 20%.

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.

The corona accelerated ageing was conducted on silicone rubber, the insulation characteristic parameters of silicone rubber under different ageing time were measured, and the ageing mechanism of silicone rubber was deeply discussed according to the parameters. The results show that corona ageing causes serious damage to the surface structure of silicone rubber, and obvious holes and cracks are formed on its surface, resulting in serious pulverization. Corona ageing makes the long molecular chain of silicone rubber break into small molecular chain, reduces the flexibility of silicone rubber molecular chain, forms various defects, which leads to the decrease of the insulation performance of silicone rubber. With the increase of corona ageing time, the energy level centers of electron and hole traps decrease slowly at first and then decrease fast. Corona ageing leads to the gradual development of deep traps into shallow traps, reduces the binding effect on electrons, and finally leads to the occurrence of surface flashover of silicone rubber.