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.

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.

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.

In order to realize the recycling and reuse of degraded glass fiber (d-GF), to obtain degraded glass fiber was obtained by chemical degradation method from the selected the 220 kV retired composite insulator core rod, and the mechanical, thermal, and microscopic differences between degraded glass fiber and ordinary glass fiber (GF) were compared. Then, polyethylene (PE) composite materials (d-GF/PE, GF/PF) reinforced with different contents of glass fiber were prepared to explore the reuse prospects of degraded glass fiber reinforced materials. The results show that silane coupling agent can realize the surface modification of degradable glass fiber, and the modification effect is slightly better than that of ordinary glass fiber. The surface of the degraded glass fiber is relatively rough, with scale like damage and a small amount of resin residue in some areas, but there is no obvious erosion or fracture phenomenon on the whole. The fracture stress distribution of degradable glass fiber is relatively discrete, and the average fracture stress is 1 520 MPa, which is 29.95% lower than that of ordinary glass fiber. The interface state between glass fiber and polyethylene matrix in d-GF/PE is good, under the same glass fiber content, the difference in maximum fracture stress between d-GF/PE and GF/PF is only 2.15 MPa.

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.

In order to reveal the influence of external electric field on the internal molecular structure characteristics of silicone rubber insulation materials at the micro level, this paper used molecular simulation and quantum chemistry methods to explore the changes in the microstructure and space charge characteristics of silicone rubber under the action of external electric field. The results show that with the increase of electric field strength, the total energy of the silicone rubber molecule system decreases, the dipole moment and polarizability increase, and the C-Si bond inside the molecule becomes longer when subjected to the stretching effect of external electric field, resulting in a decrease of the stability of silicone rubber structure and affecting its mechanical and electrical properties. Under a higher electric field strength , the energy gap of the frontier orbitals decreases, and the reactive active sites of the silicone rubber molecular chain change, it causes of trap energy levels for the electron traps and hole traps in the frontier orbitals of the molecular chain to form different degrees of trap energy level distribution, and enhances the ability of silicone rubber to capture free electrons or injected charges in insulating materials. When the electric field reaches the critical value of 12.75×10³ kV/mm, the molecular structure of silicone rubber is disrupted and causes changes in the infrared spectrum.

To solve the problem of poor thermal conductivity of polyimide (PI), PI was doped with hexagonal boron nitride (h-BN) modified by a surface wetting agent (F068) through in-situ polymerization, and then a series of h-BN/PI high thermal conductivity composites were prepared. The structure of h-BN/PI composites was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The thermal conductivity mechanism of h-BN/PI composites was explored by introducing the Y.Agari model, and the influence of modified h-BN filler doping content on the thermal conductivity, mechanical, heat resistance, and insulating properties of the composites was analyzed. The results show that with the increase of modified h-BN doping content, the thermal conductivity and thermal stability of h-BN/PI composites increase, while their tensile strength, elongation at break, and electric strength exhibit a significant downward trend. When the doping amount of modified h-BN is less than 30%, the influence of polymer crystal size factor on the thermal conductivity of the composites is dominant. When the doping amount of modified h-BN is higher than 30%, the influence of the free factor of the thermal chain formed by thermal conductive particles on the thermal conductivity of the composites is dominant. When the doping amount of modified h-BN is 50%, the thermal conductivity of h-BN/PI composite reaches 0.83 W/(m·K), the electric strength is 198.6 kV/mm, the 5% thermal decomposition temperature is 595℃, the tensile strength is 64.8 MPa, and the elongation at break is 10.4%.

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.

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%.

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%.