The temperature rise characteristics of gas-insulated transmission lines (GIL) determine their current-carrying capacity. To investigate the temperature rise characteristics of two typical environmental friendly insulating gases — perfluoroisobutyronitrile (C₄F₇N) mixed gas and dry air, the temperature rise process of a 126 kV three-phase common-tank GIL was simulated, and based on the simulation results, a temperature rise test platform was established. Then the temperature rise tests were carried out under conditions such as different gas dielectrics and current magnitudes. The results show that under the identical current conditions, the temperature rises of both C₄F₇N/CO₂ mixed gas and dry air under typical application parameters are similar, yet both exceed that of SF₆ gas. When the current loading is 3 150 A, both C₄F₇N/CO₂ mixed gas-filled and dry air-filled equipment can meet the requirement of temperature rise not exceeding 75 K, but when the current loading is 3 465 A, neither filling with C₄F₇N/CO₂ mixed gas nor filling with dry air can satisfy this requirement. It is also found that when the three gases were filled respectively, the temperature rise of phase B is higher than that of phase A and phase C, aligning with simulation results and thermal convection processes, indicating that the maximum temperature rise of phase B conductors requires special consideration in the temperature rise design of 126 kV three-phase common-tank GIL.

Room temperature vulcanized silicone rubber (RTV-SiR) is an important polymer coating material for high voltage insulators. The ageing behavior of RTV-SiR under long-term exposure to environmental stimuli is an essential consideration for its field applications. In this study, composite coatings were prepared by incorporating nanometer-scale silicon dioxide (SiO₂) and aluminum trihydrate (ATH) into RTV-SiR. Then the composite coating samples were conducted accelerated ageing for 9 000 h, and their micro-morphology, hydrophobicity class (HC), leakage current, Fourier transform infrared spectroscopy (FTIR), electrical strength, and mechanical strength were tested to investigate the ageing characteristics of SiO₂/ATH-filled RTV-SiR. The results show that the addition of SiO₂ and ATH fillers to RTV-SiR enhances the anti-degradation capability and environmental stress resistance of the composite coatings during ageing, preserving the samples' hydrophobicity. After ageing, compared with RTV-SiR, the composite samples exhibit a relatively smaller increase in leakage current and maintain higher electrical strength. According to FTIR analysis, the loss rates of several important absorption peak intensities of RTV-SiR are higher during ageing, and almost none of them can be restored, whereas those of the samples filled with SiO₂/ATH demonstrate a loss-recovery characteristics. Additionally, compared with RTV-SiR, the SiO₂/ATH-filled samples exhibit significantly lower reductions in tensile strength, elongation at break, and hardness after ageing treatment, indicating superior ageing resistance.

The interfacial characteristic between the shielding layer and insulation layer is a key factor determining the service life and operational reliability of the high-voltage cables. This study focused on the regulation of the dispersion of conductive carbon black (CB), and investigated the impact of interfacial characteristics between the shielding layer and cross-linked polyethylene (XLPE) insulation layer. The semi-conductive shielding materials with two different formulations were prepared, and an imported semi-conductive shielding material was selected as a comparison sample, then the mechanical, thermal, and electrical compatibility between the shielding materials and insulation layer were comprehensively evaluated. The results show that the introduction of polymer dispersant polyvinylpyrrolidone (PVP) into the matrix resin significantly improves the dispersibility of CB. The mechanical compatibility between the shielding layer and insulation layer is predominantly influenced by crosslinking, and an optimal crosslinking compatibility can enhance the interfacial adhesion and prevent delamination. The PVP-modified shielding layers exhibit better thermal compatibility with the insulation layer in terms of the coefficient of thermal expansion, and show superior thermal conductivity compared to the imported shielding material. Furthermore, the improved CB dispersion optimizes electrical compatibility between shielding layer and insulation layer, elevating the AC electrical strength at the shield-insulation interface.

To solve the ageing problem of transformer insulation oil after the long-term operation, three composite materials, including glucose attapulgite (GLU-APT), starch attapulgite (AL-APT), and polydopamine attapulgite (PDA-APT), were designed and prepared. The structures of the composite materials were characterized by X-ray diffractor, field emission scanning electron microscopy, Raman spectrometer, Fourier transform infrared spectrometer, and N₂ adsorption-desorption test. The results show that the decolorization and acid value reduction effects of the three composite materials on retired oil improves significantly compared to APT, among which the GLU-APT shows the best regeneration effect to retired oil. When the mass ratio of GLU-APT adsorbent and retired transformer oil is 1:2, the adsorption time is 2 h, and the adsorption temperature is 90℃, the decolorization rate of regenerated oil can reach 88.2%, and the acid value is reduced to 0.010 mgKOH/g, the adsorption efficiency can maintain 90% after 5 cycles of regeneration.

In order to suppress surface charge accumulation on the insulation in HVDC wall bushings and improve their flashover performance, the epoxy resins used for the supporting insulator and the tube body were surface fluorinated under the same conditions using a fluorine/nitrogen mixture. The results show that fluorine atoms are introduced into the surface layers of two types of epoxy resins by the substitution for hydrogen atoms and the addition to carbon-carbon double bonds, forming C-F bonds. The fluorination is accompanied by chain breaking, which mainly occurs at the crosslinking sites. Due to the difference in epoxy value, two types of epoxy resins show different crosslinking densities. SEM imaging shows that they have different thicknesses of the fluorinated layer and surface morphologies. Surface potential decay and surface conductivity measurements reveal that the fluorination increases surface conductivity of two types of epoxy resins and inhibits their surface charge accumulation to different degrees. Flashover tests show that their DC flashover voltages are significantly increased by the fluorination to almost the same degree.

Using styrene-butadiene-styrene (SBS) as the resin matrix and SiO₂ as the filler, SiO₂/hydrocarbon high frequency hydrocarbon copper clad laminate with low dielectric loss were prepared by hot-pressing method using a double-roll open mill and a flat vulcanizing machine. The resin film forming method and the influence of different contents and morphologies of SiO₂ under the open mill film on the dielectric performance, peel strength, thermal conductivity, tensile performance, and water absorption rate of high frequency hydrocarbon copper clad laminate were explored. The results show that compared with the traditional solvent-based resin film method, the solvent-free film production using an open mill has obvious advantages in the molding of composite resins and material properties. With the increase of SiO₂ content, the dielectric constant and dielectric loss of the high frequency hydrocarbon copper clad laminate increase, while the peel strength and water absorption rate decrease. Under the same particle size and filling content of SiO₂, the dielectric constant, dielectric loss factor, and water absorption rate of spherical SiO₂/hydrocarbon high frequency hydrocarbon copper clad laminate are lower than those of angular SiO₂/hydrocarbon high frequency hydrocarbon copper clad laminate. When the mass fraction of spherical SiO₂ is 75%, the comprehensive performance of the carbon-hydrogen high-frequency board is relatively superior, with a dielectric constant lower than 3.3, a dielectric loss factor of 0.002 2, and a water absorption rate lower than 0.040%.

Thick-film heating has become a key thermal-management solution for new-energy vehicles. To meet the relevant application demands, it is necessary to develop dielectric slurries for aluminum-based thick-film heating elements. This study utilized the built-in machine learning model of the Inorganic Glass Engineer System for property prediction to assist in the development of dielectric insulating glass formulations for aluminum-based thick-film heating elements, and conducted experimental verification. The results show that the insulating glass prepared by the optimal formula can be sintered at 580℃, with a thermal expansion coefficient of 18.8×10^-⁶℃^-1. When the dielectric-layer thickness exceeds 110 μm, it has a breakdown voltage over 1.29 kV and a leakage current less than 0.21 mA, which can meet the usage requirements of the medium layer of aluminum-based thick-film heating elements.

Epoxy resin/micron-alumina composites are widely employed as supporting and insulating components in electrical power equipment, and their glass transition temperature and thermal expansion coefficient critically influence the long-term performance of electrical power equipment. Epoxy resin composite dielectrics containing 0%, 20%, 40%, and 60% mass fractions of micron-alumina fillers were prepared in this paper. Their thermal expansion coefficients and glass transition temperatures were calculated through numerical fitting of dielectric constant measurements at high-temperature and high-frequency. The results demonstrate that with the increase of the mass fraction of micron-alumina fillers, the thermal expansion coefficient of composite dielectrics reduces significantly, and the glass transition temperature also showing a decreasing trend. Comparative analysis between calculated values and existing experimental data reveals that the calculated value is consistent with the experimental value, confirming the scientific validity and effectiveness of dielectric spectroscopy as a methodology for evaluating the thermal properties of epoxy composite dielectrics. This approach can serves as an effective supplementary technique to conventional experimental methods for investigating the thermal characteristic of polymer.

A series of resins with ≥30% of solid content and about 4 000 mPa·s of viscosity and their polyimide films were prepared by introducing flexible 4,4′-oxobisphthalic anhydride (ODPA) or twisted non-coplanar structure 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) into the molecular structure of homophthalic tetracarboxylic acid dianhydride-4,4′-diaminodiphenyl ether (PMDA-ODA), and capped with a capping agent. The properties of the films were characterized by tensile testing machine, breakdown voltage tester, TMA, DMA, TGA, and cross-cut tester. The results show that when the solid content of the semi-rigid structure PMDA-ODA resin increases to 30% and the viscosity reduces to about 4 000 mPa·s, the film could not be formed due to the low molecular weight, and the PI film with good electromechanical properties can be prepared through introducing flexible monomer to improve the the polymer flexibility and using norbornene diacetic anhydride (NA) for capping. When continuing to increase the resin solid content and increase the proportion of flexible monomers, the electromechanical properties, heat resistance, ahd the adhesion on the copper sheet of the film decrease. The films with 30% of solid content, about 4 000 mPa·s of viscosity, 30% mole fraction of ODPA, and end-capped with NA show better electromechanical properties, heat resistance, and adhesion, which can be used as a impregnating varnish for insulation protection on the surface of substrate.

Photosensitive polyimide (PSPI) has a unique role in semiconductor packaging, among them, ester-type PSPIs containing acrylic acid derivatives are widely used in industry. Generally, the PSPIs are synthesized by the well-established chloride method, but chloride ions are introduced during the synthesis process, which negatively affects the reaction apparatus, resin purification, and the environment. For the development of green and reliable synthesis methods, we explored the reaction process for the preparation of hydroxyethyl methacrylate PSPI by polyisoimide using 4,4′-diaminodiphenyl ether (ODA) and 4,4′-biphenyl ether dianhydride (ODPA) as the polymerized monomers. The effect of solid content, solvent, and reaction temperature on the gel formation during the synthesis process of PSPI was discussed. The photolithographic and thermo-mechanical properties of PSPI prepared by the polyisoimide method were investigated. The results demonstrate that the PSPI prepared by this method has good photolithographic patterning ability (for a film with thickness of 4.5 μm, circular holes can be opened at a diameter of 15 μm, and the film retention rate is ≥90%) and excellent thermal properties and mechanical properties (T_d5%=471℃, T_g=297℃, and tensile strength is 127.5 MPa). There are no Cl-ions introduction during synthsis process, and the process is green and friendly, and simplified with a short reaction cycle. The method was extended to the preparation of other four PSPI systems, and the isomerization method is found to be universal, and this efficient and green synthesis method provides theoretical guidance for the preparation of high-performance PSPI photoresists in laboratories and enterprises.