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.

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 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.

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.

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.

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 study the fiber characteristics of insulating wood pulp during the beating process and their impact on the properties of electrolytic capacitor separator, fibers with different beating degree were prepared using a Valley beater to prepare electrolytic capacitor separators, and their mechanical properties and electrical properties were tested. The results show that with the increase of beating time, the beating degree of the insulating wood pulp increase, leading to the decrease of fiber length and the increase of brooming degree. With the increase of beating degree, the surface pore structure of the prepared separators significantly decreases, while the density, tensile strength, and electric strength of the separators increase. In addition, with the increase of beating degree, the liquid absorption performance of the separators decreases, and the equivalent series resistance (ESR) per unit thickness increases.

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.

In this paper, different types of polyurethane potting materials were developed successfully by taking propylene epoxide-tetrahydrofuran polyether or polytetrahydrofurane glycol as polymer polyols, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI) as curing agents, and adding an appropriate amount of silica aerogel. The mechanical property, proccessability, low temperature resisitance, high temperature resistance, resistance to high and low temperature shock, and insulting property of the polyurethane potting materials were analyzed systematically. The results show that the polyurethane potting material formulated with propylene oxide-tetrahydrofuran copolymer and TODI as primary components, supplemented with silica aerogel with the mass fraction of 0.5%, exhibits outstanding processability, mechanical strength, and electrical insulation. It also demonstrates exceptional tolerance to extreme temperature fluctuations. This material achieves a glass transition temperature as low as -69.3°C and maintains a compression cold resistance coefficient of 0.54 at -60°C. Its 5% weight loss temperature reaches 302.3°C. After enduring 20 cycles of thermal shock between -65°C and 125°C, the material retains 93.5% of its tensile strength with a dimensional change rate of merely -0.6%, while preserving excellent insulation properties: volume resistivity of 4.2×10¹² Ω·cm and dielectric strength of 25 kV/mm.

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.

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%.

The compatibility of cable termination structural materials with insulating fluids has an important impact on the safe and stable operation of cables. In this paper, the compatibility of cable termination materials with polyisobutylene is studied by analyzing the changes in morphology, swelling and mechanical properties of silicone rubber, ethylene-propylene insulating self-adhesive tape, and halogenated butyl + ethylene-propylene waterproof insulating tape before and after the compatibility test, as well as the changes in the physicochemical and dielectric properties of polyisobutylene before and after the compatibility test, and combined with the attenuated total reflectance Fourier transform infrared spectroscopy and thermogravimetric analysis with other means. The results show that the compatibility of the stress cone material silicone rubber with polyisobutylene is good, the compatibilities of ethylene-propylene insulating self-adhesive tape and halogenated butyl + ethylene-propylene waterproof insulating tape with polyisobutylene are not good, and the physicochemical and dielectric properties of the polyisobutylene impregnated insulating tape are also degraded after compatibility test.

To investigate the thermal ageing mechanism of dry air core reactor encapsulated insulating materials at the molecular level, this study conducted 336-hour accelerated thermal ageing tests on epoxy/glass fiber composites at 180℃. The evolutionary characteristics of functional groups, molecular chain segment motions, activation energies, and AC electric strength of the epoxy/glass fiber composites after ageing were characterized by infrared spectroscopy, dielectric spectroscopy, and AC electric strength test. The effect of the decrease in activation energy caused by the changes in chemical structure and the evolution of molecular chain segment movement properties during ageing on the AC electric strength was investigated. The results show that a lot of carbonyl groups and small molecular chains dominated by ester and ketone groups generate during the ageing process. These small molecule chains and polar groups greatly increase the free volume and the number of free electrons inside the epoxy matrix, so that the chain segment movement is gradually enhanced and the activation energy is reduced, which ultimately leads to a significant reduction in insulation capacity.

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.

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.

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.