Composite insulators with a large heating area in a 220 kV operation and maintenance AC line were taken as a sample, the impact of different environmental parameters on the heating and operating performance of the composite insulator was analyzed by conducting power frequency withstand voltage and infrared tests on the heating insulator, as well as physical and chemical property tests on the silicone rubber of the composite insulator. The results show that the abnormal heating of the aged and damp composite insulator sheath is located at the high voltage end. The higher the environmental humidity and the lower the wind speed, the larger the heating range and amplitude. After being dampened, the dielectric constant and dielectric loss of silicone rubber increase significantly, and the heat generation comes from the dielectric loss of the aged sheath on the surface. There are obvious signs of deterioration on the surface silicone rubber of the sheath at the heating point, and the interior of the sheath and the core rod are not affected by the surface heating. The operational performance of the insulator is not affected. In addition, based on the above results, suggestions for on-site maintenance of sheath ageing, moisture, and heat defects were proposed.

The differential bipolar repetitive impulsive voltage was used to simulate the impulse width modulated electrical stress environment of inverter-fed motor. The effects of impulse width, dead zoon time, and impulse frequency on the partial discharge inception voltage (PDIV) test results of enameled twisted pair wires and random wound inverter-fed motor stator winding were studied. Based on the electric field distribution of insulation under bipolar impulsive voltage and gas discharge theory, the influence mechanism of impulse voltage parameters on PDIV was analyzed. The results show that the impulse width is correlated with the generation of initial electrons, leading to a negative correlation between PDIV test results and impulse width. The changes in residual charges and spatial electric field distribution on the insulation surface caused by short dead time may be a reason for the positive correlation between PDIV and dead time. Due to the weak influence of impulse frequency on initial electron generation and electric field distribution, the correlation between PDIV and impulse frequency is low.

Cellulose insulation paper affects the reliability of transformer operation due to the long-term action of temperature and electric fields. The existing research mainly focuses on the modification effect of nano-particles on insulation paper under a single physical field, while the modification research under the combined effect of electric-thermal ageing is not yet perfect. This research prepared cellulose insulation papers modified by nano-TiO₂ particle with mass fractions of 0, 1%, 3%, 5%, and 7%, and established corresponding molecular models based on molecular dynamics simulation. Combined with macroscopic electric-thermal combined ageing tests, the influence of electric field and temperature field on the electrical properties of modified cellulose insulation papers was studied, and the optimal modification content of nano-TiO₂ was explored. The results show that the electrical properties of cellulose insulation paper are mainly affected by temperature, and the introduction of electric field accelerates the ageing of cellulose. After adding nano-TiO₂ particles, the number of hydrogen bonds in the cellulose molecular model increases, the relative dielectric constant of the modified cellulose insulation paper decreases, and the electric strength increases. There is a threshold for the improvement of cellulose modification effect by the content of nano-TiO₂, and the best modification effect on cellulose samples is achieved when the mass fraction of nano-TiO₂ is 5%.

Basin insulators in GIS are prone to surface electric field distortion due to charge accumulation, which can lead to surface flashover. To improve the surface voltage resistance performance of insulators, this paper refers to the design concept of surface functional gradient materials and utilizes the uniform treatment characteristics of titanium deposition by atmospheric pressure plasma jet (APPJ). By controlling the treatment time at different radial distances, a basin insulator with continuous conductivity gradient were prepared. At the same time, a fast electric field calculation method based on surface conductivity was established by coupling DC electric field simulation calculations with an attention mechanism-enhanced long short-term memory network (LSTM). The surface conductivity of the basin insulator was continuously gradient optimized using the artificial bee colony (ABC) algorithm. And the electrical performance of the insulator before and after optimization was evaluated and compared using simulation models and flashover tests. The result show that the density and bonding structure of the plasma titanium deposition layer are related to the treatment time, and the optimal treatment time is 3 minutes, at which the surface conductivity of the insulator is the highest. The surface functional gradient modification significantly improves the uniformity of the electric field distribution on the insulator surface. The maximum field strength on the lower surface of the insulator decreases by 70.3%, the electric field distortion rate decreases by 24.69%, and the flashover voltage is 31.34 kV, which is 14.3% higher than that of unmodified insulators.

The disadvantages of poor thermal conductivity and mechanical properties severely restrict the further application of epoxy resin in electrical equipment insulation. Therefore, Epoxy composite dielectrics (EP/BNNS) with different BNNS contents were prepared by using nitride nanosheets (BNNS) as fillers. The phonon transport, stress distribution, polarization relaxation, trap distribution, and other conditions inside the epoxy composites dielectric were analyzed, and then the mechanisms of BNNS improving the thermal, mechanical, and electrical properties of the epoxy composite dielectric were systematically explored. The results show that when the BNNS filling mass fraction is 5.0%, the thermal conductivity of the epoxy composite dielectric reaches 0.36 W/(m·K), the bending strength and tensile strength reach 120 MPa and 57.4 MPa, respectively, and the electric strength reaches 96.9 kV/mm, while the composites dielectric also have good dielectric properties. The introduction of BNNS can optimize the thermal and mechanical properties of the epoxy composite dielectric without compromising their electrical performance.

To achieve the healability and reprocessability of silicone rubber insulating materials, it is feasible to introduce healable functional groups into the structural network of silicone rubber to extend its service life and reduce the safety hazards of power system operation. This paper used silane coupling agents to introduce amino groups into the main chain of silicone rubber, and then introduced dynamic hindered urea bonds into the silicone rubber network through the reversible reaction of isocyanates and hindered amines. A healable silicone rubber material was prepared, and the mechanical, electrical, healable, and reprocessable properties of silicone rubber were studied. The results show that the insulation performance of silicone rubber containing dynamically hindered urea bonds meets the application standards. Under certain temperature and pressure, silicone rubber samples can heal mechanical damage and electrical breakdown damage with high healing efficiency. The sample can be reprocessed through the cutting-hot pressing process, and the reprocessed sample can still retain certain mechanical and electrical insulation properties.

In order to adapt to different on-site monitoring conditions, make full use of multimodal monitoring information, and improve the flexibility and accuracy of transformer fault diagnosis methods, a fault diagnosis method of power transformer based on dynamic multimodal fusion was proposed in this paper. The method introduced a dynamic fusion strategy, which firstly constructed a layer of modal selection network that can autonomously screen the input monitoring information and dynamically select the diagnostic modes to adapt to the different monitoring conditions on site. Secondly, it established corresponding diagnostic models for different input modes, and adopted the corresponding fusion method to diagnose under the non-single modal conditions for achieving the full utilization of the monitoring information of each modality. Finally, actual cases collected from multiple municipal bureaus were used for verification. The results show that the method proposed in this paper can effectively improve the flexibility and accuracy of transformer fault diagnosis results, and can be adapted to different monitoring conditions on site. Compared with other methods, the recognition accuracy of this method is higher, up to 97.33%, and the false alarm rate and missed alarm rate are the lowest.

A flame retardant monomer 6-(2,5-bis ((4-vinylbenzyl) oxy) phenyl) dibenzo [c,e][1,2] phosphono-6-oxide (DOPVB) was synthesized by using 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxy-10-phosphophenanthrene-10-oxide (DOPO-HQ) and 4-chloromethyl styrene (VBC) as raw materials. The DOPVB flame retardant was compounded with epoxy resin (EP) to prepare EP/DOPVB composites with different phosphorus contents, and their thermal, flame retardant, and dielectric properties were tested. The results show that the optimal synthesis conditions for DOPVB is that the molar ratio of reactants DOPO-HQ, VBC, and K₂CO₃ is 1∶2.2∶3.0, and the reaction time is 6 hours, then the yield is 74.55%. The EP/DOPVB cured material with a phosphorus content of 2.5% has the best comprehensive performance, its glass transition temperature is 130.4℃, which is 45.21% higher than that of pure EP. The dielectric constant is 2.98 and the dielectric loss factor is 0.005 03, which is 21.99% and 72.16% lower than that of pure EP, respectively. The vertical combustion test of the composite material prepared from the cured material reaches V-0 level, with a limit oxygen index of 67.4%.

Electrical laminated wood is widely used in the field of transformer insulation due to its high mechanical strength, low dielectric loss factor, and dielectric constant close to transformer oil. However, its insulation performance is lower than that of laminated paperboard, and there is a significant risk of insulation accidents when it is used in high field strength area of transformer. In this paper, the raw material selection, processing technology, and current problems of electrical laminated wood were discussed and analyzed, and the influencing factors of its insulation performance were analyzed, providing references for improving the product quality of electrical laminated wood.

There are many types of insulating oils and insulating papers with different compositions, which will have different moisture equilibrium curves when they are used in conjunction. To obtain the moisture equilibrium curves of different oil-paper insulation systems, this research constructed a moisture equilibrium curve model applicable to new oil-paper insulation systems based on the relative moisture content relationship between oil and paper at moisture equilibrium, and verified the model by combining with the measured results of moisture equilibrium experiments. The results show that under typical operating temperature of transformer, the prediction accuracy of the moisture equilibrium curve model for different oil-paper insulation systems is higher than 90%, confirming the effectiveness of the model.