Investigating the relationship between microstructure and macroscopic properties of epoxy resin (EP) materials for high-voltage insulation at the molecular level can provide theoretical guidance for the synthetic design of EP. Here, using diglycidyl ether (DGEBA) as the resin matrix and methyl tetrahydrophthalic anhydride (MTHPA) as the curing agent, a set of crosslinked EP molecular models at different curing stages were constructed based on the proposed crosslinking method. We studied the influences of crosslinking density on micro-parameters and macro-properties employing molecular dynamics (MD) simulations. The results indicate that crosslinking of DGEBA/MTHPA is a contraction and exothermic process. The structural parameters and macroscopic properties are closely related to the degree of crosslinking. With the increase of crosslinking density, the mean square displacement (MSD) of the system decreases, and the segment motion in the models is weakened gradually, while, the fractional free volume (FFV) first decreases and then increases. In addition, the thermal and mechanical properties of DGEBA/MTHPA have a significant dependence on the crosslinking density. Increasing crosslinking density can improve the glass transition temperature (T_g), reduce the coefficient of thermal expansion (CTE), and enhances the static mechanical properties of DGEBA/MTHPA system. Furthermore, the relationship between microparameters and properties has been fully investigated. Free volume is an important factor that causes thermal expansion of DGEBA/MTHPA. Moreover, there is a negative correlation between MSD and mechanical moduli. By elevating temperature, the decline in mechanical moduli may be due to the exacerbated thermal motion of the molecules and the increasing MSD values.

In view of the threat of metal particles to the insulation performance of AC GIL (Gas insulated transmission line), this paper uses aluminum powder to simulate the metal particles which are closer to the engineering practice, A scaled-down model similar to the actual GIL structure was built to study the movement characteristics of aluminum powder in GIL. The discharge, movement and distribution characteristics of aluminum powder was recorded in experiment. The research shows that the particles from spacer to the part below the shielding should be prevented. The particles with particle size of about 150 mesh move more violently. At the same time, the movement of powder particle in GIL is affected by Van der Waals force. According to the characteristics of particle motion distribution, grid-shaped trap and strip-shaped trap were designed and compared in this paper, and the trap capture coefficient was proposed. Finally, the suggestion of particle trap arrangement is put forward, that is, grid-shaped trap can be set near the spacer, and strip-shaped trap can be selected for the rest of the GIL.

Epoxy resin samples were processed by one direction and multi-directions polishing methods in this research. The contact angles of the samples, the AC/DC flashover voltage in C₄F₇N/CO₂ gas mixtures and the charge dissipation rate of the polished samples were measured. The results show that the contact angle of the polished epoxy resin sample increases. In the gas mixtures, the surface roughness modification of the epoxy resin under different voltage types is proposed. According to the charge dissipation rate, the development mechanism of creeping flashovers under different voltage is revealed. Different dissipative properties ultimately enhance the creeping discharge voltage of the samples by suppressing electron secondary electron emission. This paper offers a basis for insulation design in the C₄F₇N/CO₂ gas mixture.

Epoxy resin is the main material of spacer in a gas insulated transmission line and other gas-insulated equipment. During long-term operation, the charge accumulates on the surface of the epoxy resin, which will distort the electric field and thus accelerate the failure of the insulation. In this paper, the surface of the epoxy resin was fluorinated by dielectric barrier discharge at different times. The surface physical, chemical, and flashover properties of the samples before and after modification were measured. The results show that the method used in this paper can graft fluorine on the surface of the sample, change the surface roughness, and make the electron trap shallower and the hole trap deeper. The appropriate modification time can reduce the charge accumulation on the surface, hinder the formation of flashover channels, and improve the surface flashover voltage, showing potential for use in the improvement of the insulating performance of insulating materials.

Bushing is an indispensable component in high voltage direct current (HVDC) transmission project. As the main insulating material possesses poor thermal conductivity and negative temperature coefficient (NTC) electrical resistivity, HVDC bushing suffers from the distortion of electro-thermal-coupled fields. Therefore, it is urgent to reveal the influence of electrical resistivity-temperature characteristic and thermal conductivity on the DC electric field distribution within bushing insulation, guiding the design and application advanced insulating materials. Here, the simulation of temperature and DC electric field distribution within a 400 kV bushing are carried out. The results show that the optimization of NTC effect and thermal conductivity of an insulating material is able to obtain a more uniform electric field distribution through homogenizing the electric resistivity distribution within bushing insulation. The activation energy of the insulating material has a similar variation trend with the maximum electric field within bushing insulation, which has a potential to represent the temperature dependence of electrical resistivity of insulating materials. It also shows that the reduction of DC electric field by increasing the thermal conductivity has a saturation feature. As a result, the suppression of the NTC effect should be considered together to obtain a smaller electric field within HVDC bushing. The research study provides a new idea to regulate the DC electric field distribution, which is beneficial to the design of advanced insulating materials.

Gas insulated transmission lines (GIL) have a wide application prospect in special occasions such as cross terrain power transmission. Metal particle pollution is an important reason for the low insulation performance of GIL. When micron metal particles (MMPs), which are the most common metal particles in engineering, adhere to insulators or high-voltage electrodes, the insulation performance will be reduced. Based on that, this paper mainly studied the static adhesion characteristics of MMPs. Firstly, the static adhesion models and their applicable conditions were introduced. Then, through the atomic force microscope (AFM) test, the adhesion force of MMP-electrode and MMP-insulator was obtained. The test results show that MD model should be used to calculate the adhesion force of MMP-electrode and MMP-insulator. In addition, the adhesion force presents the characteristics of random distribution due to the surface asperities of MMPs and samples. Therefore, according to the test results, this paper introduced the equivalent adhesion work, which is a random variable, and obtained the probability distribution model of equivalent adhesion work. Finally, the distribution of adhesion force was obtained. The above research results provide guidance for inhibiting the adhesion of metal particles in GIL.