A high phosphorus content epoxy resin (DPOEP) was synthesized by using 2,5-dihydroxybenzyl(diphenyl)phosphine oxide (DPOHQ) and epichlorohydrin (ECH) as reactants, and then the structure of DPOEP was characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The curing reaction characteristics of DPOEP with the curing agent of active ester resin DFE617 was studied, and the effects of DPOEP content and phosphorus-containing epoxy resin structure on the flame-retardant performance, dielectric properties, and thermal stability of dicyclopentadiene (DCPD) epoxy resin curing system were investigated. The results show that the curing process of DPOEP/DFE617 system follows a first-order reaction. DPOEP can promote the carbonization of condensed phase in the DCPD epoxy resin/DFE617 system, and the limiting oxygen index of cured resin reaches 36.6%-38%, achieving V-0 rating in the UL94 test. The dielectric loss factor of the epoxy resin curing system decreases with the increase of DPOEP content. At a lower content of DPOEP, the epoxy resin cured material is halogen-free and flame retardant while maintaining good thermal properties.

Large generators are affected by factors such as thermal stress during operation, resulting in deterioration or even failure of stator bar insulation, which affects the safe and stable operation of the generator. In order to clarify the effectiveness of the polarization and depolarization current (PDC) method for evaluating the main insulation performance of stator bars, at first, PDC method was used to evaluate the main insulation performance of stator bars in the thermal ageing state. According to the PDC test results, the basic characteristic parameters such as the steady-state conductance current, 0.1 Hz polarization/depolarization loss, and asymmetry coefficient were extracted. Then, singular value decomposition (SVD) algorithm was used to analyze the PDC data of the bar sample with the extended Debye model, and the branch number and branch parameters of its analog circuit were obtained. Through analysis, the change regulation of the above characteristic parameters during ageing was clarified. Finally, Fourier transform infrared spectrum (FTIR) analysis was conducted on samples with different thermal ageing durations to further clarify the mechanism of post-insulation curing and degradation from a microscopic perspective. The results show that as the degree of insulation ageing intensified, the steady-state conductivity current and 0.1 Hz polarization/depolarization loss increases, the degree of asymmetry coefficient deviation from 1 intensifies, and the interface polarization time constant τ₂ decreases.

In order to develop a safe and eco-friendly accelerator, the differences between zinc neodecanoate and zinc naphthenate were studied from the three aspects of volatility characteristic, Zn²⁺ ion content, and the promoting curing characteristics of epoxy anhydride resin. Using high purity bisphenol A epoxy and methyl hexahydrophthalic anhydride as resin matrix, zinc neodecanoate and zinc naphthenate accelerators was added to the resin matrix,respectively. And then resin cured samples were prepared through the same process, and the glass transition temperature (T_g) and thermogravimetric curves of the samples were tested. The results show that due to the characteristic of single molecular structure, high Zn²⁺ content, and very low volatile organic compounds (VOCs), zinc neodecanoate is environmentally friendly. Comparing to zinc naphthenate, zinc neodecanoate requires a higher temperature to ensure complete curing of the epoxy anhydride resin. But under the same existing process conditions, the T_g of cured sample accelerated by zinc neodecanoate can reach 152℃, which is 11℃ higher than that of zinc naphthenate (141℃), indicating that the cured product accelerated by zinc neodecanoate has better thermomechanical properties.

In order to study the insulating material characteristics of MgO cable and its ampacity evaluation method, in this paper, morphology observation and composition analysis were conducted on MgO powder to determine its purity and inclusions at first. And then the dielectric and thermal characteristic parameters of MgO powder were measured, and the influence of moisture on the dielectric parameters was analyzed. Finally, an equivalent thermal curcuit model for MgO insulated multi-core cables and a simplified analytical algorithm for ampacity were proposed, which was validated by a two-dimensional numerical simulation model. The results show that the volume resistivity of dry MgO samples is higher than 10¹² Ω·m, which can decrease by more than 1 order of magnitude under the effect of moisture. In the frequency range of 10^-1‒10⁴ Hz, the dielectric constant of the dry MgO sample is about 7.9, and the dielectric loss factor is about 5×10^-4‒5×10^-3, which increases significantly after being moisture exposed, especially in the low frequency range. The electric strength of the dry MgO is 3.5‒4.8 kV/mm, and the data measured by different methods have a certain degree of dispersion. The rated ampacity of MgO insulated multi-core cable can be evaluated accurently by using the simplified analytical algorithm, which is beneficial to practical engineering applications.

In order to identify the potential risk of enamelled wire quality degradation, the influence of surface conductivity on the electrical insulation performance of enamelled wire was studied, and the electrical breakdown law of enamelled wire was also observed and analyzed. The results show that with the increase of surface conductivity of enamelled wire, the partial discharge (PD) inception voltage decreases significantly. Most of the electrical breakdown does not occur at the bonding position of enamelled wire, but randomly occurs at the weak points of electrical insulation at two adjacent enamelled wire. In the process of production, transportation, and assembly of enameled wire, it is necessary to avoid surface contact with salt substances, and control the environmental humidity during the assembly process， and avoid the surface charge transfer of insulating materials affecting the overall insulation performance of the motor.

The research progress of epoxy resin reinforced by different types of fillers, including carbon nanomaterials, ceramics, metals, and natural fillers in recent years was reviewed. The reinforcement effects of types, dispersion, and surface modification of fillers on the mechanical properties of epoxy resin were summarized in detail. And the research and development direction of reinforced modification of epoxy resin were also prospected.

In order to study the effect of coating silicone grease on the distribution of multiple physical fields at the crosslinked polyethylene/silicone rubber composite interface under thermal ageing, the electrical-thermal-mechanical multi-physics field model of 110 kV cable terminal joints was established using COMSOL Multiphysics software. The distribution of electric field, temperature field, and stress field at the composite interface before and after coating silicone under thermal ageing was simulated. The results show that after coating with silicone grease, the sealing degree of the interface increases, which decreases the distortion degree of the electric field and leads to the slight decrease of the temperature rise of the interface, but the stress of the interface distributes unevenly. After ageing, the swelling of silicone grease on silicone rubber increases the relative dielectric constant of silicone rubber, and the interfacial charge density, and causes the electric field strength increase further. The increase of temperature promotes the penetration of silicone grease to silicone rubber, which decreases the thermal conductivity of silicone rubbe and make the interface temperature higher than that before ageing. Under thermal ageing, the elastic modulus of the silicone rubber coating with silicone grease decreases significantly and the interfacial stress decreases further.

In order to obtain polypropylene based cable insulating materials with excellent dielectric properties, polypropylene based composites adding with nano MgO modified by silane coupling agent KH570 was prepared by melt blending method. The effect of nano MgO addition on the microstructure, dielectric properties, and mechanical properties of of the composites was studied. The results show that nano MgO promotes the transformation of polypropylene from α crystallographic orientation β, the interface of polypropylene and nano MgO is well bonded after the nano MgO is modified by KH570. The addition of nano MgO can inhibit charge injection, when the mass fraction of MgO is 1%, the composite has the smallest space charge density, which is 0.6 C/m², while excessive addition of MgO can lead to local charge accumulation in the composites. When the mass fraction of nano MgO is 1%, the composite shows the highest tensile strength (24.6 MPa), while the breaking elongation decreases with the addition of MgO. The direct current breakdown strength of pure polypropylene based material is the lowest. At 100℃, the direct current breakdown strength of polypropylene based composite materials with a MgO mass fraction of 1% is the highest (302 kV/mm), which is only 28.77% lower than that at 20℃.

Epoxy resin (EP) has been widely applied in electrical insulating materials, but with a low thermal conductivity, it cannot meet the requirement of heat dissipation in modern electrical equipment with high-power density. In this paper, silver acetate (AgAc) and 2-ethyl-4-methylimidazole (2E4MI) complex was deposited on boron nitride (BN) surface to prepare imidazole-silver modified BN hybrid materials (Ag(2E4MI)₂Ac@BN), then Ag(2E4MI)₂Ac@BN was filled in EP to prepare Ag(2E4MI)₂Ac@BN/EP composites,and its thermal conductivity was studied. The results show that when the volume fraction of filler is 20%, the thermal conductivity of Ag(2E4MI)₂Ac@BN/EP composites is 1.72 W/(m·K), which is 79.2% higher than that of BN/EP composites (0.96 W/(m·K)). The results of Monte Carlo simulation show that in the EP matrix, the thermal contact resistance (R_c) of Ag(2E4MI)₂Ac@BN is 2.7×10⁶ K/W, which is lower than the that of BN (R_c=5.5×10⁶ K/W). In comparison with BN/EP composites, Ag(2E4MI)₂Ac@BN/EP composites exhibit higher tensile strength and dielectric loss tangent (tanδ), lower dielectric strength and volume resistivity, while maintain good electrical insulating properties.

In order to further explore the application potential of C₄F₇N/CO₂ mixed gas in high-voltage electrical equipment, a preparation system for C₄F₇N/CO₂ mixed gas was established and mixed gas with different volume fraction of C₄F₇N was prepared by partial pressure method. A gas chromatograph-hydrogen flame ionization detector (GC-FID) detection method was established, in view of the difficulty in controlling the testing quality during the preparation of C₄F₇N/CO₂ mixture system, the thermal driven diffusion simulation experiments of different C₄F₇N/CO₂ mixed gas was carried out based on fluid mechanics and finite element analysis. The results show that when the volume fraction of C₄F₇N is 2%, 5%, and 10%, the diffusion equilibrium time of C₄F₇N/CO₂ concentration is 4 775 s, 6 600 s, and 8 800 s, respectively; the concentration diffusion equilibrium time of C₄F₇N gas is 94 min, 122 min, and 158 min, respectively. The three C₄F₇N/CO₂ mixed gas can achieve good quality control effect in the quality detection and application after preparing for 100 min, 125 min, and 160 min, respectively.