In order to explore the ageing resistance of nitrile rubber products, such as high-temperature resistance, transformer oil resistance, and heat-compression resistance, we conducted accelerated ageing tests on nitrile rubber (NBR) under high temperature conditions of 90, 120, and 135℃ in hot air, hot oil, hot air compression, and hot oil compression, respectively. The effects of ageing temperature, ageing time, and ageing environment on the mechanical properties of NBR were researched, and compression set was used as an evaluation index to predict the actual service life of NBR. The results show that the ageing rate of NBR increases with the increase of temperature. During the ageing process, with the increase of ageing time, the Shore hardness and compression set of NBR increase, while the elongation at break decreases. 25^# transformer oil can slow down the decrease in Shore hardness and compression set performance of NBR, while it slows down the decrease at first and then accelerates the decrease in fracture elongation. Based on the Arrhenius law, the predicted service life of NBR in hot oil compression environment at temperatures of 40, 50, 60, 70, and 80℃ is 3.726, 1.877, 0.985, 0.542, and 0.303 years, respectively.

In recent years, buffer layer ablation failure occurs frequently in high voltage cables with corrugated aluminum sheathed structure, but there is a lack of effective method to determine the severity of ablation defects in cable buffer layer. In order to explore the evolution law of gas product concentration during buffer layer ablation, and use it to diagnose the severity of ablation defects, a simulated experimental platform for buffer layer ablation was established in this paper. The law of ablative characteristic gas concentration of buffer layer with different water contents changing with ablation time was investigated,and the variation law was quantitatively analyzed by using a negative exponential function n=-Aexp(-t/τ)+n₀. The results show that the concentration of C₂H4, C₂H₆, and H₂ increases in a negative exponential relationship with the increase of ablation time. With the increase of water content, the concentration of C₂H₄ and C₂H₆ decreases slightly, while that of H₂ increases. The generation rate coefficient(A/τ) of C₂H₄ and C₂H₆ can reflect that whether the buffer layer is damp, and the A/τ of H₂ increases gradually with the increase of water content in buffer layer, which is expected to be one of the bases for judging the degree of damp of buffer layer.

Cable joint is a key accessory of high-voltage DC cable, its insulation performance determines the stability of high-voltage DC transmission system. To verify the effectiveness of the charge transport model in calculating the electric field distribution of cable joints, we calculated the mobility of injected charge carriers and the conductivity of ionized charges through blocking experiments, and proposed a charge transport model that simultaneously considered the effects of injected and ionized charges, the undetermined parameters in the transport model were simplified. Then the electric field distribution of the XLPE-EPDM double-layer structure was simulated and calculated by using a simulation model, and the results were compared with the experimental results. The results show that with the increase of electric field intensity, the polarity of charge on the interfacial of the XLPE-EPDM double-layer structure is reversed. The simulation results calculated by the simulation model are in good consistency with the experimental results, which proves the effectiveness of the simulation model.

Epoxy resin and its composite materials play a major insulation role in electrical apparatus due to their excellent thermodynamic and electrical insulating properties. With the gradual development of electrical apparatus towards high voltage and high power, as well as the continuous rise of voltage levels, the performance requirements for epoxy insulating materials inside electrical apparatus are increasingly increasing. This paper focused on epoxy resin insulating materials for high-voltage electrical apparatus, and reviewed the current research and application progress from three aspects: formulation composition, curing process, and performance improvement of insulation systems. It was aimed to establish the relationship between the composition, structure, and macroscopic properties of epoxy insulation systems, provide suggestions and prospects for the development direction of domestic epoxy resin insulating materials in the future, and accelerate the localization development of epoxy resin materials for high-voltage insulation.

To investigate the influence law and mechanism of polyethylene glycol diglycidyl ether (PEGDGE) on the mechanical and thermal properties of epoxy materials for insulated pull rods, molecular dynamics simulations were used to calculate and analyze the macroscopic properties and microscopic structural parameters of epoxy resin cross-linked systems with PEGDGE mass fractions of 0, 5%, 10%, 15%, and 20% (percentage of epoxy resin mass), respectively. The effect of PEGDGE content on the mechanical and thermal properties of epoxy materials for insulated pull rods was summarized, the influence mechanism was elucidated from the perspective of system structure, and the calculation results were verified through experiments. The results show that with the introduction of PEGDGE, the glass transition temperature, tensile strength, and bending strength of epoxy resin, as well as the viscosity of castable decrease, while the impact strength of epoxy resin increases. When the mass fraction of PEGDGE is 5%, the material shows the best comprehensive performance. PEGDGE molecules with high flexibility increases the free volume fraction, mean square displacement, and the ratio of bulk modulus to shear modulus (K/G) of the epoxy resin system, which enhances the mobility of molecular segments, and leads to the increase of toughness and the decrease of rigidity of the epoxy resin material.

With the rapid development of modern electrical equipment, higher requirements have been put forward for nanocomposite films with higher dielectric strength and mechanical properties. Therefore, we modified boron nitride nanosheets (BNN) with 3-aminopropyltrihydroxysilane to obtain modified BNN (aBNN), and then mixed aBNN with aramid nanofiber (ANF) to prepare dense ANF/aBNN nanocomposite films by high-temperature hot-pressing method. The thermal stability, mechanical properties and electrical insulating properties of films were characterized. The results show that with the increase of aBNN content, the thermal weight loss rate of the nanocomposite film decreases significantly. When the mass fraction of aBNN is 10%, the tensile strength, elongation at break, and toughness of the ANF/10%aBNN nanocomposite film reach the maximum value, which is 235 MPa, 14.0%, and 32.4 MPa·m^1/2, respectively, it is 25%, 9.4%, and 75.1% higher than that of ANF/10%BNN, respectively. The electrical strength of ANF/10%aBNN is as high as 154 kV/mm, which is about 15% and 11.6% higher than that of pure ANF and ANF/10%BNN, respectively. And the volume resistivity reaches the maximum value of 7.94×10¹⁷ Ω·cm (tested at 60℃), which is 893% and 694% higher than that of pure ANF and ANF/10%BNN, respectively.

Due to its advantages of high flash point, high ignition point, and biodegradability, natural ester insulating oil is gradually being promoted and applied in high voltage level power transformers. In order to provide basic data support for the insulation structure design of high voltage and large capacity natural ester transformer, we took mineral oil as a reference, and selected natural ester insulating oil as the test object to analyze its breakdown characteristics and gas generation law under lightning impulse voltage. The results show that the lightning impulse breakdown voltage of natural ester turn-to-turn insulation is above 200 kV, with the increase of turn-to-turn insulation thickness and insulation gap distance, it shows an upward trend and is slightly lower than the breakdown voltage of mineral oil under the same conditions. H₂ and C₂H₂ dissolved in oil are the main characteristic gases under lightning impulse voltage, and their relative percentage content increases with the increase of insulation gap. The Duval pentagon method is used for fault diagnosis of dissolved gases in oil, and the discharge at the fault points are basically diagnosed as high-energy discharge, which are consistent with the energy released by lightning impulse.

Insulating materials are prone to flashover along the surface due to their inherent properties, contamination accumulation, rain and snow, and so on. In this paper, a multifunctional nanocomposite coating (SiO₂/MWCNTs/PDMS) was prepared through a "polymer+nanofiller" method by using polydimethylsiloxane (PDMS) elastomer as the matrix, SiO₂ nanoparticles and multi-walled carbon nanotubes (MWCNTs) as fillers. The trap distribution, DC surface flashover voltage, and hydrophobicity of the nanocomposite coating were tested and analyzed. The results show that the composite coating has a high surface roughness, which hinders the development of surface discharge. The surface flashover voltage of the composite coating increases from 17.7 kV to 24.3 kV, with a growth of 37.3%. With the increase of SiO₂ and MWCNTs content, the water contact angle of the composite coating has no obvious change the maximum water contact angle reaches 150.5°, and the composite coating has good self-cleaning ability. The research results can provide reference for the engineering application of composite insulation coating materials in the future.

Polyurethane foam adhesive has good expansion filling characteristics, electrical insulation performance, and waterproofness. To achieve its application in filling the inner layer of the cable joint protective shell, at first, we tested the thermal, electrical, and mechanical properties of polyurethane foam adhesive with different foaming ratios. Then, a two-dimensional axisymmetric model of the cable joint was established, and the steady-state temperature field distribution of the cable joint under different filling adhesive conditions was simulated and analyzed. Finally, a physical model of the 110 kV intermediate joint was established, and thermal cycling tests were conducted on cable joints using different filling adhesives. The results show that all the performance test results of polyurethane foam adhesive are good. With the increase of foaming ratio, the thermal conductivity, insulation performance, and mechanical property of the foam adhesive decrease, with a foaming ratio of 3 times, the foam adhesive shows optimal comprehensive performance. The absolute error between the simulated and measured temperature values of various structure inside the joint using different filling adhesives are basically no more than 10%, which verifies the effectiveness of the simulation model. The steady-state temperature distribution of the joint filled with foam adhesive is similar to that of the joint filled with traditional waterproof adhesive.

Aiming at the refining and regeneration issues of retired transformer insulating oil, we used catalytic hydrogenation to decolorize retired transformer oil. Based on this, polyethylene glycol modified chitosan adsorption process was used to remove corrosive sulfur and heavy metal copper ions, and achieve the regeneration of retired transformer oil. The results show that when the catalytic hydrogenation temperature is 220℃, the reaction pressure is 4 MPa, and the volume ratio of hydrogen to oil is 300∶1, the retired transformer oil can achieve decolorization. The self-made modified chitosan-polyethylene glycol composite adsorbent material (CS-PEG) can quickly remove the corrosive sulfur and metal copper ions from oil samples. After being treated by this process, the retired transformer oil becomes transparent, its acid value decreases to 0.003 mg(KOH)/g, the breakdown voltage reaches 45 kV, and the dielectric loss factor drops below 0.001. This process has good potential for application.