Post insulator is an important supporting component in gas insulated metal enclosed switchgear (GIS), its insulating properties affects the reliability and stability of GIS. Taking the post insulator for engineering GIS as research object, we selected the surface tangential electric field strength of the insulator as the insulating properties index, and analyzed the influence of the umbrella skirts number, starting position, root radius, top radius parameters of the insulator as well as the shrinkage umbrella skirt structure on the insulating properties. The results show that the tangential electric field of insulator shows wave peaks and troughs oscillation distribution by increasing the umbrella skirt number, which is conducive to hinder the development of insulator surface discharge. The maximum tangential electric field strength increases with the increase of umbrella skirts number, and decreases with the increase of the distance between the starting position of umbrella skirt and the high-voltage electrode. The location of the maximum tangential electric field value shifts with the radius at the base of umbrella skirt. Compared with the original structure, the maximum tangential electric field strength along the surface of optimized structure decreases from 12.66 kV/mm to 9.69 kV/mm, and the decrease rate is 23.5%. It is found that the insulation margin is more than 1.3 times through the negative lightning impulse voltage test and margin test.

In this paper, the general rules and characteristics of the failure damage of basin insulators in recent years were firstly summarized. Then, the typical failure area of sample was extracted to analyze the matrix microstructure morphology and the failure fracture surface morphology. Finally, the micro mechanical properties of the heterogeneous interface in composite materials were characterized and analyzed by nanoindentation mechanics technology, and the crack initiation and failure fracture mechanism of Al₂O₃/epoxy resin composite materials were expounded. The results show that the fracture toughness value of the epoxy resin matrix is about 0.55 MPa·m^1/2, and the cracks originate from the epoxy resin matrix under the action of load and continuously expand. When encountering high-strength Al₂O₃ particles, the cracks deflect due to the retardation and rapidly expand along the interface between the particles and matrix.

With the rapid development in the field of microelectronics and microelectronics processing technology, manufacturing microelectronic devices using inkjet printing technology has become a popular direction in additive manufacturing. In this paper, an UV-curable vinyl-terminated polyarylether prepolymer was prepared by nucleophilic substitution reaction with twisted non-coplanar phthalazinone and hexafluoroisopropyl as structural units. A new low dielectric ink system for 3D printing was constructed by using diacrylate reactive diluents and free radical fast initiators into the prepolymer. The results show that the viscosity of the ink system before curing is lower than 300 mPa·s,indicating good processability. After UV and thermal curing, the infrared testing shows that the curing degree can reach over 87%, and the curing is basically complete. The minimum volume shrinkage is only 2.4%, which indicate the ink has excellent dimensional stability. The glass transition temperature of the material can reach up to 210℃, and the thermal decomposition temperature can reach up to 370℃, which indicate the ink has the potential of long-term use at 150℃. At 10 GHz, the dielectric constant of the material can reach 2.61, and the dielectric loss factor is only 0.014, which indicate the ink has excellent dielectric properties. The ink system prepared in this study is applicable to the additive manufacturing process of large curvature conformal circuit and has good application prospect in the field of microelectronics.

To reduce the errors of the ageing state evaluation method based on the extended Debye model in describing the degradation process and explaining the ageing mechanism of oil-paper insulation, the polarization-depolarization (PDC) curves of oil-paper insulation samples with different ageing degrees were tested and analyzed in this paper. A distributed Debye model considering the relaxation branches with probability distribution was established, and an accurate evaluation method for the ageing state of oil-paper insulation bushing was finally proposed by solving through regularization method. The results show that with the increase of ageing degree, the polarization current overall shifts towards the direction of increasing the depolarization current and decreasing the relaxation time, and the time for the curve to reach a stable value is shortened. The distributed Debye model can effectively describe the multiple relaxation processes of the aged oil-paper insulation samples, and the regularization method can effectively solve the system ill-posed problems encountered when solving ill-conditioned linear equation. As the ageing degree increases, the probability density of the relaxation time distribution function corresponding to the main relaxation peak of sample increases, and the most probable relaxation time constant gradually decreases. The ageing state evaluation model constructed in this paper has high evaluation accuracy, whose error is less than 1.37%.

The "thermal expansion and contraction" behavior of the internal atoms in epoxy resin and the intrinsic issue of low thermal conductivity seriously restrict the application of epoxy resin in dry-type DC sleeve insulation. To address this, we introduced boron nitride whiskers with low thermal expansion coefficient into epoxy resin to prepare a new boron nitride whisker/epoxy (BNw/EP) composite dielectric, and its microstructure, thermal expansion coefficient, thermal conductivity, electrical properties, thermal stability, and mechanical properties were tested and analyzed. The results show that within the temperature range of 20-100℃, the thermal expansion coefficient of the composite dielectric with 10% mass fraction of boron nitride whisker is reduced by 15% compared to pure epoxy resin, while the thermal conductivity increases to 0.28 W/(m·K), which is 33.33% higher than that of pure epoxy resin. In addition, its dielectric constant is below 5.28 and the dielectric loss is below 0.02 in the frequency range of 10²-10⁶ Hz, the volume resistivity is 10¹⁴ Ω·cm, and the tensile strength is maintained at about 49.5 MPa. This study proves that on the basis of ensuring the insulation, dielectric and mechanical properties of the composite dielectric be not damaged, filling the epoxy resin matrix with boron nitride whiskers can effectively reduce the thermal expansion coefficient of the material and improve the thermal conductivity.

The frequent disconnection of inverter power devices and load characteristics of motor can lead to high-frequency pulse overvoltage, which would lead to premature failure of generator insulation and bring challenges to the stability and reliability of system. From the failure mechanism of inverter motor insulation, the different stress failure forms of inverter motor insulation were investigated firstly, and the main factors affecting the failure of the insulation system were sorted out. Then the state detection methods of inverter motor insulation and the delay measures were comprehensively reviewed. Finally, the major challenges and future research direction currently faced by inverter motor insulation were emphasized.

Cross-linked polyethylene (XLPE) and silicone rubber (SIR) are commonly used insulation materials for high-voltage direct current cables and reinforced insulation materials for accessories at present. The composite insulation composed of the two will age under long-term thermal stress. To investigate the charge transport characteristics of XLPE/SIR composite insulation with different ageing degrees, XLPE/SIR samples with different ageing degrees were prepared and subjected to simultaneous measurement of space charge and isothermal relaxation current. At the same time, by combining Fourier transform infrared spectroscopy (FTIR) testing and quantum chemical computation (QCC), an energy band model of XLPE/SIR system before and after ageing was constructed, and the charge transport behavior of XLPE/SIR was explored. The results show that negative charges always accumulate at the XLPE/SIR interface, and the amount of charge increases with ageing time. There are always homopolar charges accumulating near the cathode and anode, and the distribution range decreases with ageing time. After ageing, the depth of charge traps in SIR does not change much, while deeper charge traps appear in XLPE. The negative charge accumulation at the interface between the unaged XLPE/SIR is mainly caused by Maxwell-Wagner polarization, while the increase of negative charge accumulation at the interface of the aged samples is mainly related to the introduction of shallow electron traps in SIR and deep electron traps in XLPE.

In order to investigate the surface discharge process and its microscopic characteristics of glass fiber reinforced epoxy resin composite insulating material, an experimental platform of slant plate electrode was constructed in this paper. Surface tracing and corrosion tests were conducted on samples by a constant tracing voltage method, and the formation mechanism of electric trace was analyzed by combining the Bernoulli equation of ideal liquid. The change of functional groups, surface roughness, and three-dimensional morphology of epoxy resin materials under different stages of tracing corrosion were tested. The results show that the damp and polluted area of insulation composite material is very easy to generate leakage current and discharge, and the most serious corrosion situation always occurs at the bottom electrode firstly. With the increase of tracing corrosion degree on the surface of sample, the epoxy group, hydroxyl group, amino group, aldehyde group in epoxy resin molecular chain gradually decompose, and the carbonyl group decompose not completely after its generation. The surface morphology of the material gradually becomes rough and irregular, the surface roughness shows an upward trend, and the roughness during the explosive period is about 2.8 times bigger than that during the starting period.

Taking the DC submarine cable in ±525 kV DC transmission project as the research object, we conducted DC voltage withstand test, impact voltage withstand test, and gradient voltage withstand test. The breakdown strength, ageing life index, Bahder's coefficient and other key parameters of the insulation material were analyzed. The insulation thickness of the ±525 kV DC cable under different voltage withstand condition was designed and calculated. The insulation design thickness was calibrated on the basis of the electric field distribution and temperature distribution of DC cable. The results show that the distortion degree of electric field distribution in DC cables is mainly determined by the temperature difference of insulation layer, and the insulation temperature difference is mainly determined by the magnitude of current passing through the cable conductor. Taking into account the research results and the long-term safety and reliability of cable, it is recommended that the insulation thickness of ±525 kV DC cables is designed to be 28 mm.

In order to investigate the effect of continuous changes in high and low temperatures on the epoxy composite insulation of cable terminals, micron Al₂O₃/epoxy composite insulation samples were prepared in this paper, and thermal-cooling cycling experiments were conducted on the samples. The changes in dielectric properties and degradation mechanism of epoxy composite insulation samples under different number of thermal-cooling cycling were analyzed through the AC breakdown, isothermal surface potential attenuation, and dielectric properties tests. The results show that during the process of thermal-cooling cycling, the cross-linked network of epoxy composite insulation deteriorates gradually under the combined action of high temperature thermal ageing and high and low temperature alternating stresses, the filler gradually separates from the matrix, microcracks and holes appear in the sample, the free volume increases, and the dielectric constant and electric strength continue to decrease. After 750 hours of thermal-cooling cycling, the AC electric strength of the sample decreases by 15.2%, the deep trap density decreases by 41%, the shallow trap density shows a fluctuating trend, and the dielectric loss factor (tanδ) firstly decreases and then slightly increases.