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 invasion of moisture at the insulation interface of cable accessories is the main cause of electrical breakdown and insulation failure. However, the effect mechanism of moisture on interface discharge and breakdown remained unclear. Therefore, this paper conducted experiments and simulations to analyze and study the causes of breakdown failure at the insulation interface of cable accessories under the influence of moisture. First, the discharge evolution characteristics during the breakdown process at dry and humid interfaces were described through experiments. Subsequently, by combining discharge products with electric field analysis, the effect mechanism of moisture on the breakdown development at the interface was explained. Finally, a field case was presented to confirm the validity of the proposed breakdown mechanism of the insulation interface under the influence of moisture. The results show that the discharge process during the interface breakdown of insulation interface develops in stages, accompanied by gas generation. The bubbles regions formed by the generated gases lead to severe electric field distortion, which reduces the electric strength of the interface. The dynamic motion of the bubbles also increases the randomness of interfacial discharge, causing the interfacial breakdown process to be accompanied by multiple discrete arc discharges along random path.

To investigate the rejuvenation effect and enhancement mechanism of the voltage stabilizer-containing rejuvenation fluid on moisture-affected XLPE/SiR interface, XLPE was sanded by sandpapers with different granularities to prepare XLPE/SiR interface samples. At first, the surface roughness of the samples was measured using a profilometer, and interfacial breakdown tests were conducted. Then, the samples were subjected to moisture tests. After that, the antioxidant 300 and ferrocene were selected as voltage stabilizers, and five rejuvenation fluids with different stabilizer content were prepared to rejuvenate the moisture-affected interfaces. The interface samples before and after rejuvenation were further analyzed by surface profilometry, Fourier transform infrared spectroscopy (FTIR), polarization-depolarization current (PDC), and interface breakdown tests. The results show that the interfacial breakdown voltage decreases with the increase of surface roughness, while the moisture exposure elevates the interfacial DC conductivity and dielectric loss factor and decreases the interfacial breakdown voltage. After the rejuvenation, the interface roughness, DC conductivity, and dielectric loss factor of the samples decrease, and the rejuvenated product can homogenize the electric field distribution between the cavity and the solid dielectrics, and significantly increase the interfacial breakdown voltage. Moreover, the addition of antioxidant 300 and ferrocene can enhance the interfacial breakdown voltage, and ferrocene has a better improvement effect on the insulation performance of the moisture-exposed interface.

Mastering the distribution pattern of surface charges during DC pre-flashover is essential for clarifying the intrinsic mechanism of charge-induced flashover. This paper investigated the surface charge distribution characteristics of epoxy resin at DC pre-flashover moment and their influences on flashover voltage magnitude based on a plate-type insulation structure. Under two testing conditions—with and without pre-deposited charges on specimen surfaces—the dynamic distribution of surface charges was captured during the process of applied voltage escalation leading to flashover. By introducing SiC-epoxy composite coatings to modify specimen surface states, the dominant charge accumulation patterns during flashover triggering and the charge accumulation modes preceding flashover occurrence were comparatively analyzed. The results show that homopolar charge accumulation predominates on specimen surfaces during voltage escalation toward flashover. The charge accumulation mode exhibites a transition phenomenon shifting from the micro-charge zone to the charge surge zone during flashover triggering. Immediately before flashover, homopolar charges nearly coveres the entire specimen surface, while the pre-deposited charges primarily influence the flashover voltage magnitude by altering the homopolar charge accumulation quantity at the pre-flashover moment.

To investigate the application of anodization technology on improving the interface performance between epoxy resin and aluminum electrodes, aluminum alloys were electrolyzed for different durations to form anodized films on the substrate surface. The morphology, composition, structure, and electrical properties of the anodized films were characterized, and the effects of anodic oxide films on the adhesion and dielectric properties of the epoxy-aluminum interface were analyzed. The results show that after anodic oxidation, an amorphous anodized film with a nanoporous structure is formed. As the electrolysis time increases, the thickness of the anodized film increases linearly, while the internal defects also increase, which reduces the volume resistivity and electric strength. The film exhibits a high dielectric constant and dielectric loss factor, which remain stable at 25℃-125℃. Benefiting from the nanoporous structure and polar bonds, the adhesive shear strength between the aluminum substrate and epoxy resin increases from 6.76 MPa to 10.89 MPa, and the adhesive tensile strength increases from 6.89 MPa to 9.78 MPa after anodic oxidation. The impact toughness increases from 66.21 kJ/m² to 76.42 kJ/m², and the flexural strength increases from 147.65 MPa to 180.50 MPa. The anodized film improves the electric strength of the aluminum-epoxy composite, and the interface polarization makes the dielectric constant and dielectric loss factor of the aluminum-anodized film-epoxy composite structure slightly higher than those of the aluminum-epoxy structure. In HVDC electric fields, space charges mainly accumulate at the interface between the electrode and the dielectric, and the anodized film can inhibit the injection of charges into the dielectric. Therefore, as an effective interface modification method, anodic oxidation can enhance the mechanical and electrical properties of aluminum electrodes and epoxy resin.

To investigate the effects of hydrophobic coatings on charge accumulation characteristics of silicone rubber, this study prepared hydrophobic coatings with hydrophobic fumed silica (SiO₂) particles as fillers. The surface charge distribution on silicone rubber surface coated with hydrophobic coatings containing different amounts of SiO₂ particles was measured under both positive and negative DC corona using an electrostatic capacitance probe. Additionally, the surface micromorphology, static contact angle, surface resistivity, and DC creepage flashover voltage of silicone rubber surface coated with hydrophobic coatings containing different amounts of SiO₂ were characterized. The results show that the static contact angle of silicone rubber surfaces increases with the increase of SiO₂ content in the hydrophobic coating. However, applying hydrophobic coatings on silicone rubber will exacerbate the surface charge accumulation. When the mass fractions of SiO₂ is 2%, 6%, and 10%, the maximum surface charge density accumulated on silicone rubber surface increases by 5.03%, 20.11%, and 24.06%, respectively, which will also decrease the surface resistivity and DC creepage flashover voltage of silicone rubber. Analysis suggests that the hydrophobic coating surface will generate more gaps and holes, thereby facilitating the capture and adsorption of charges, making it difficult for the charges to dissipate.

In the development of gas insulated switchgear (GIS) and gas insulated transmission lines (GIL) towards higher voltage and larger capacity, the insulation performance at the internal insulator's gas-solid interface is recognized as a critical factor affecting the operational safety of GIS/GIL equipment. To ensure the insulation safety of GIS/GIL equipment in engineering applications, it is imperative to elucidate the insulation failure mechanisms at the gas-solid interface and explore methods to enhance its insulation performance. In this paper, first, the research progress in the field of gas-solid interface insulation was reviewed, the mechanisms of dynamic charge behavior at the gas-solid interface and its influencing factors were analyzed, and methods for charge regulation at the gas-solid interface were introduced. Subsequently, the mechanism of insulation failure influenced by metal particles at the interface was discussed, and the motion characteristics of metal particles and their mitigation measures were summarized. Following this, the insulation characteristics at the gas-solid interface in environmental-friendly insulating gases were described, and the methods for electric field regulation and flashover voltage enhancement at the interface were summarized. Finally, the research directions for gas-solid interface insulation of insulator in GIS/GIL were outlined.

Polyimide (PI) is a class of high-performance polymer materials containing π-conjugated imide ring in the main chain, and its size of the band gap is one of the main factors directly affecting the thermal stability, optoelectronic properties, dielectric properties and other properties of the material. The electrically powered diamine group and the electrically absorbing dianhydride group in the conventional PI molecular structure determine that the value of band gap is nearby 3.0 eV, which directly affects its performance in the field of high-temperature energy storage, high-frequency communication, electrical insulation, etc. Because of the excellent structural designability of PIs, the band gap of PIs can be adjusted by modulating the monomer combination/chain segment structure/space structure, and the above properties of PIs can be optimized. In this paper, based on the main research progresses of PI bandgap modulation reported in recent years, the main strategies of PI bandgap modulation were elaborated from the perspectives of polymer structure and adjusting polymerization process, respectively, and the difficult problems faced in PI bandgap modulation were discussed with the example of its application in the field of dielectric energy storage. Finally, the future development direction of PI bandgap modulation was discussed on the basis of current research status of PI bandgap modulation.

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.

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.