In this paper, a finite element model of ±400 kV DC wall bushing was firstly established, and the electric field and potential distributions of the DC wall bushing were simulated by COMSOL software. Then the effects of ice edge length, ice cover thickness, and rainfall on the surface electric field of the bushing umbrella skirt were studied. The results show that when the ice edge length increases to bridge the umbrella skirt, the electric field distorts seriously. The increase of ice thickness has little influence on the maximum surface electric field of the umbrella skirt. When the rainfall reaches 10 mm, the maximum surface electric field of the umbrella skirt increases sharply, and the electric field distortion points increase. The research results can provide reference for the development and design of UHV and EHV DC wall bushing.

The buffer layer of high-voltage cable will generate gas products during the ablation process. However, the correlation between the gas product concentrations and conductive property of buffer layer during the ablation process is still unclear at present. Therefore, we conducted a simulated ablation experiment on cable buffer layer and studied the evolution law of current density and gas product concentrations during the ablation process of buffer layer. The results show that under both the dry and wet conditions, the current density of buffer layer exhibits a bi-exponential function decay law with the increase of ablation time, and the decay rate of current density shows a trend of decrease rapidly at first and then unchanged basically with the increase of ablation time, only the wet sample exhibits peak current density during the initial stage of ablation. The gas chromatographic test results show that under the wet condition, the gas products during the ablation process of buffer layers are CO₂, H₂, CO, CH₄, C₂H₄, C₂H₆, and C₂H₂. Under both the dry and wet conditions, the gas product concentrations increase rapidly at first and then tend to a stable value with the increase of ablation time, and the increase time of gas concentration is consistent with the decrease time of current density, which indicates the change laws of current density and gas concentration with the ablation time is closely related. It is analyzed that there is a correlative relationship between the current density decay rate and the gas products generation rate during the ablation process of buffer layer, and the variation of gas product concentration can reflect the severity of buffer layer ablation.

Light weight and high insulation composite cross-arm has excellent properties of light weight and excellent insulating properties, which has been widely used in power lines in recent years. In this paper, a composite cross-arm with light weight and high insulation of foam core was prepared, and the cross-arm was conducted water absorption, dye penetration, water diffusion leakage current, electric strength, thermal induction, and vibration ageing tests. The results show that the volume water absorption of the composite cross-arm with light weight and high insulation of core is 0.036%, the water diffusion leakage current is less than 75 μA, the AC electric strength is greater than 71 kV/cm, the vibration ageing resistance is good, and the comprehensive performance is better than that of the cross-arm with traditional solid core, which can meet the need of practical engineering application.

On the basis of surface discharge tests and finite element electric field simulation methods, the surface discharge and electric field characteristics of GIS basin insulators with metal ball or wire particle defects were studied. The results show that under different metal particle defects, both the pulse voltage and ultraviolet photon number increase with the increase of voltage. The surface discharge of basin insulators with metal wire defects is more severe, compared to the situation where there are metal ball defects on the high-voltage side, the discharge is more intense when there are metal ball defects on the low-voltage side, and the change trends of simulation results are consistent with the experimental results. When there are metal particle defects on the surface of GIS basin insulators, the surface discharge intensity is positively correlated with the distortion degree of electric field, and the correlation between the distortion degree of electric field and the average pulse amplitude is significant.

A novel low dielectric loss toughening agent (Si-DABPA) was designed and synthesized, and its structure was characterized, then its toughening effect on bismaleimide (DFE950) was studied. The results show that the Si-DABPA and diallyl bisphenol A (DABPA) have the same reactivity to DFE950. Compared with the DFE950/DABPA cured material, the Thermal degradation resistance of the DFE950/Si-DABPA cured material increases, and the dielectric constant (D_k) and dielectric loss factor (D_f) decrease at 10 GHz. Compared with the DFE950/DABPA/PPE cured material, the tensile strenght of the DFE950/Si-DABPA/PPE cured material increases, while the bending strength and impact strength change little.

To evaluate the environmental adaptability of insulation system for offshore wind turbine, multi-factor cycling tests including high and low temperature test, humid heat test, salt spray test, and vibration test, were conducted on insulating resin and simulation winding, and their electrical performance changes before and after tests were characterized and compared. The result show that after ageing tests, the performance of the epoxy modified unsaturated polyester impregnating resin does not deteriorate significantly, the normal insulating performance of simulation winding just deteriorate slightly, its residual breakdown voltage is almost no attenuation, and both the key materials and simulation winding exhibit good resistance to marine environments. The insulation system of offshore direct-drive wind turbine still retains stable and excellent dielectric performance after long-term offshore multi-factor cyclic ageing tests, which can meet the requirements of marine environment.

With the rapid development of microelectronics industry, flexible printed circuit board (FPCB) has proposed higher requirements on the dielectric properties of polyimide (PI) films, which is the interlayer insulating materialof FPCB. The conventional PI film cannot meet the requirements of 5G high-frequency communication because of its high dielectric constant. In this paper, the research progress of PI film materials with low dielectric constant in recent years were reviewed from two aspects of changing the intrinsic structure of PI and introducing porous structure, and the development prospect of low dielectric constant PI film materials were proposed.

In this paper, the main ageing forms and influencing factors of oil-paper insulation for traction transformer were analyzed. The ageing mechanism of oil-paper insulation was studied, the current characteristic parameters characterizing the ageing degree of oil-paper insulation and the main residual life prediction methods were summarized, and the advantages and disadvantages of each characteristic parameter and residual life prediction method and the applicable conditions were analyzed. On this basis, the existing main problems in the ageing state assessment and residual life prediction of oil-paper insulation, as well as the future research directions were discussed.

It is found that ablative white spots are often attached to the buffer layer by disassembling high-voltage XLPE fault cables. To study the ablation characteristics of buffer layer, the chemical elements of white spot at different positions of buffer layer were analyzed by using energy dispersive spectrometer (EDS), and the conductivity of the white spots buffer layer were measured. Then on the basis of the measurement results of conductivity, an electrothermal coupling simulation model of high voltage XLPE cable was established, and the heat production characteristics of white spot buffer layer under the action of high frequency overvoltage were calculated. The results show that the white spots in the ablative area of buffer layer are the water-blocking powder precipitated by the buffer layer, and the conductivity of the buffer layer decreases obviously after the white spots are precipitated. Under the action of high frequency overvoltage, the higher the overvoltage frequency, the greater the resistance heat generated in the local periphery of buffer layer white spot, and the higher the temperature rise, which may eventually cause overheating and erosion of the buffer layer.

The general properties, viscosity-temperature relationship, storage stability, and heat resistance of ELAN 3322-300 HV1 epoxy impregnating resin were systematically studied. Winding bar and coil samples were made to simulate the insulation structure of high voltage motor, and their electrical performance was tested. The class H insulation structure was conducted thermal ageing tests. The results show that the ELAN 3322-300 HV1 epoxy impregnating resin has low curing volatile and good storage stability, its temperature index is 211, and its temperature classification is class H. The winding bar and coil samples after impregnating have excellent electrical insulation performance and thermal ageing resistance, and the temperature index of class H insulation structure is 182. The ELAN 3322-300 HV1 epoxy impregnating resin is suitable for VPI insulation treatment of class F and H high voltage motor.