At present, there is a lack of effective liquid repair materials for ablation defects in the buffer layer of high-voltage cables, resulting in the inability to timely and effectively eliminate the hidden dangers of ablation defects in high-voltage cable lines. In this paper, acrylic based buffer layer ablation defect liquid repair materials were prepared and repair experiments were conducted on actual ablation defects in cable buffer layer. The repair effect of carbon black content in repair solution on the electrical properties of the buffer layer was studied. The results show that when the mass fraction of carbon black in the repair solution coating is 20%, the volume resistivity of the repaired buffer layer decreases to the level of new buffer layer and basiclly remains unchange with temperature. Based on the characterization of micro morphology, it is analyzed that the repair solution forms a carbon black coating on the fiber surface of the buffer layer, covering the original uneven coating and non-conductive particles. At the same time, the continuous water blocking powder layer formed by ablation on the inner side of the non-woven fabric is repacked by the carbon black coating, rebuilding the electrical connection of the buffer layer, thus effectively repairs the erosion defects of the buffer layer.

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 investigate the application of laser-induced breakdown spectroscopy (LIBS) technology in rapid quantitative detection of insulator contamination, and improve the accuracy and speed of insulator contamination detection, a detection platform based on LIBS technology was established to test artificial and natural contamination samples. The artificial contamination samples were formulated by mixing NaCl, CaSO₄, CaCO₃, and kaolin, while the natural contamination samples were taken from silicone rubber insulators which had been in operation for two and four years in a regional power grid in southern China. The rapid quantitative detection of insulator contamination was carried out by means of the calibration-free LIBS method. The results show that there are 9 kinds of elements with different proportions in the two artificially contaminated samples, while the two naturally contaminated samples contain 9 and 11 distinct elements, respectively. After self-absorption correction, the contaminant elements of the insulators are presented as neatly arranged distribution points on the Boltzmann plot, with consistent regression line slopes, and high fitting degrees, and the spectral line intensities of each element enhances significantly. This effectively mitigates the impact of self-absorption on rapid quantitative detection of insulator contamination, and improves the detection accuracy.

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℃.

In the study of damage mechanisms of composite materials, acoustic emission (AE), as a nondestructive testing technique, has gained excellent application results due to its high accuracy, real-time performance, insensitivity to geometry, and wide application prospects. In this paper, the analytical methods and application status of acoustic emission technology on damage mechanism of composite materials were summarized, the advantages and disadvantages of acoustic emission technology in the study of damage mechanism of composite materials were comprehensively elaborated, and the key technologies that need to be solved urgently were also explored, and the prospects of its application in the field of composite materials were envisioned.

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 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.

Under high thermal fault, the internal state change and gas production mechanism of insulation system in super/ultra-high voltage transformer is unclear, which seriously restricts the state analysis and diagnosis of transformer. In view of this problem, the generation path of characteristic gas and decomposition mechanism of oil-paper insulation system in super/ultra-high voltage transformer were studied under high thermal fault by enthalpy theory and simulation method. The gas generation mechanism was obtained according to the enthalpy theory, and the gas generation mechanism and path proposed in this paper were verified by simulation. The results show that the chain alkanes in the oil-paper insulation system are more likely to crack than the cycloalkanes and bicyclic aromatic hydrocarbons under high thermal fault. The generation rate of cracking characteristic gas of various materials in descending order is cellulose, chain alkanes, cycloalkanes, and bicyclic aromatic hydrocarbons. According to the gas generation energy, the characteristic gases CH₄ and C₂H₆ are the easiest to generate, while C₂H₂ is the most difficult to generate. The generation rate of characteristic gases in oil-paper insulation system can be used to judge the severity of high thermal fault.

In order to study the feasibility of using sapium sebiferum seed oil as the natural ester insulating oil for transformers, sapium sebiferum seed oil was subjected to refining treatments including degumming, deacidification, decolorization, and dehydration, to prepare a sapium sebiferum seed insulating oil. Its physicochemical and electrical properties were compared with those of mineral insulating oil, and accelerated thermal ageing test was carried out on it under 130℃ to study its thermal ageing characteristic. The results show that the main fatty acid component of sapium sebiferum seed insulating oil is polyunsaturated fatty acid, its physicochemical and electrical properties can meet the requirements of relevant standards, and its kinematic viscosity and dielectric loss factor are greater than those of mineral insulating oil, but the ignition point is much higher than that of mineral insulating oil. After thermal ageing at 130℃ for 250 h, 500 h, 750 h, and 1 000 h, the sapium sebiferum seed insulating oil has less color change and higher breakdown voltage than mineral insulating oil, but its increase amplitude of dielectric loss factor is great.

An interturn insulation test platform was constructed, and the voltage-withstand tests were conducted on vegetable insulating oil-paper insulation and mineral insulating oil-paper insulation under lightning impulse voltage, switching impulse voltage, and power frequency voltage. The results show that under power frequency voltage, the breakdown voltage of vegetable oil-paper insulation is higher than that of mineral oil-paper insulation. Under switching impulse voltage, the breakdown voltage of vegetable oil-paper insulation is slightly higher than that of mineral oil-paper insulation. Under negative lightning impulse voltage, the breakdown voltage of vegetable oil-paper insulation is significantly lower than that of mineral oil-paper insulation. Considering the differences in breakdown voltage of interturn insulation with different specification of wires, on the basis of test results, the field strength of mineral oil-paper interturn insulation and vegetable oil-paper interturn insulation were simulated and calculated by finite element method so as to guide the design of interturn insulation for vegetable insulating oil transformer. The simulation results show that the maximum field strength of mineral oil-paper interturn insulation is higher than that of vegetable oil-paper interturn insulation under the breakdown voltage.