A graphene oxide (GO) was synthesized by modified Hummers’ method, and a graphene oxide/polyimide (GO/PI) composite film was prepared by solution blending method. The structure and the properties of the composite film were analyzed by XRD, TMA, TGA. The results show that compared with the PI film without GO, when the mass fraction of GO in composite film is 0.2%, the mechanical properties of the composite film increase obviously, the tensile strength increases by 26.77%, the elongation at break increases by 76.47%, and the elastic modulus changes little basically. When the mass fraction of GO is 0.1%, the maximum value of T₅ and T₁₀ of the composite film are 587.3℃ and 603.3℃, which increase by 2.44% and 1.69% compared with that of the PI film without GO, respectively. It is indicated that the addition of GO with appropriate amount can enhance the mechanical properties and thermal properties of PI films.

LDHNSs dispersion was obtained by ultrasonic stripping of hydrotalcite assisted with intercalation agent. PI/LDHNSS composite films were prepared by in-situ polymerization, and their electrical properties were studied. The results show that the LDHNSs disperse uniformly in PI matrix without obvious agglomeration and stacking, which show good interfacial compatibility with the matrix. Compared with pure PI film, the volume resistivity and electric strength of the composite films decrease slightly to some extent with the addition of LDHNSs. However, it should be note that the corona resistance life of the composite film is improved significantly. When the mass fraction of LDHNSs is 0.5%, the corona resistance life of the composite film is the longest, which is about 8 times longer than that of pure PI, realizing the maximum improvement of corona resistance performance for composite at a relatively low addition amount.

Under different environmental relative humidity (RH), the corona resistance of polyimide film presents significant differences. In order to understand the effects of RH on the surface corona characteristics and ageing process of film, we monitored the corona discharge process, electrical properties, and surface morphology of the film under different RH, and obtained the effects of RH on the corona ageing of film. The results show that with the increase of RH, the changing trends of the discharge activity at positive and negative half cycle are opposite. When the RH is equal or less than 69%, both the discharge quantity and discharge frequency show rapid growth stage, stationary stage, and secondary development stage with corona time, and when the RH attains 84%, both of them increase linearly with time. The changing rate of moisture content (Δwt%) of the film increases significantly at the beginning of corona ageing and tends to be stable at the middle and later periods, and when the RH attains 84%, the Δwt% increases linearly with the ageing time. It is analyzed that the surface electrothermal damage of film caused by corona discharge is the main cause of the rapid decrease of surface resistivity (ρ_s). With the corona erosion, water penetrate into the film gradually, eventually leading to the sharp decrease of ρ_v till breakdown.

Optical fiber sensing technology has the advantages of anti-electromagnetic interference, small volume, multiplexing, etc. Intelligent on-line monitoring for power equipment by optical fiber sensing technology has become a new trend of power grid development. In this paper, the research progress of several optical fiber sensing technologies in the field of power equipment monitoring were reviewed, including fiber grating sensing technology, scattering distributed optical fiber sensing technology, fluorescent optical fiber sensing technology, and interferometric optical fiber sensing technology. From the aspects of temperature monitoring, strain monitoring, partial discharge monitoring, fiber-optic current sensor, pollution monitoring, and hydrogen monitoring, the application as well as the advantages and disadvantages of different sensing technologies in different power equipment were explained. At last, the development direction of the engineering and networking application of optical fiber sensing technology was proposed.

This article started from the composition and classification of silicone grease to get access to the performance requirements according to the demand of cable accessories. And then the two typical common grease used in cable accessories was described, including normal silicone grease and silicone fluoride grease. At last, the research status of coated silicone grease used for cable accessories and the selecting method of silicone grease were summarized.

Alkylbenzene insulating oil, represented by dodecylbenzene, is a kind of liquid medium that widely used in oil-filled submarine cables. Due to the stagnation of the development of oil-filled cable technology in China, the application and research of this type of insulating oil is relatively scarce. This paper introduced the physical and chemical, electrical, ageing, and biological toxicity of dodecylbenzene insulating oil for submarine cables.

In order to study the effect of crepe paper on the curing characteristics of epoxy resin, we analyzed the curing process of epoxy resin and epoxy impregnated paper system by differential scanning calorimetry (DSC). The kinetic model parameters of curing reaction were calculated by Flynn-Wall-Ozawa and Malek methods. The results show that both the curing reaction of epoxy resin and epoxy impregnated paper system conform to the autocatalytic kinetic model. The hydroxyl group in the crepe paper has a catalytic effect on the curing reaction, which leads to the decrease of the activation energy of the curing reaction. The restraint of crepe paper leads to the decrease of the frequency factor and reaction order, so that the curing rate of epoxy impregnated paper system is slower than that of epoxy resin. At the same temperature, the curing process of epoxy impregnated paper requires more time.

A triethoxyacetylenic silane (TEOAS) was synthesized to treat the surface of hydroxylated multiwalled carbon nanotubes (MWCNTs), and then the MWCNTs-T was obtained and characterized. PSA/MWCNTs and PSA/MWCNTs-T composite resins were prepared using solution method by mixing silicon-containing polyarylacetylene (PSA) with MWCNTs and MWCNTs-T, respectively. The thermal conductivity, thermal stability, electric insulation, and bending properties of the PSA/MWCNTs and PSA/MWCNTs-T composites were investigated. The results show that TEOAS was grafted on the surface of MWCNTs successfully, and MWCNTs-T is compatible with PSA matrix. The thermal conductivity of the composites increases with the increase of the mass fraction of MWCNTs and MWCNTs-T. The effect of MWCNTs-T is more obvious, with the mass fraction of 2%, the thermal conductivity of PSA/MWCNTs-T reaches 0.62 W/(m·K), which is 3 times as higher as that of PSA. The introduction of MWCNTs and MWCNTs-T can decrease the thermal stability and bending properties of PSA, the effect of MWCNTs-T is smaller than that of MWCNTs. The glass transition temperature of the PSA/MWCNTs is higher than 500℃, the electrical resistivity of the composite resin decreases linearly with the increase of frequency, while is still higher than 10⁸ Ω·cm at 10⁶ Hz.

It is one of the important methods to obtain the ZnO varistor ceramics with high-performance by improving the distribution uniformity of grain. In this paper, ZnO varistor ceramics samples doping with different contents of Sb₂O₃ were studied from several aspects such as the average grain size, distribution uniformity of grain size, and shape of grain. In addition, the non-uniform coefficient of grain size and the shape parameter were applied for quantification. The results show that with the increase of the doping content of Sb₂O₃, the average grain sizes, the non-uniform coefficients of grain size, and the shape parameters of the samples decrease generally. It suggests that the distribution uniformity of grain size is improved, and the grain shapes develop from slender to regular, which can also explain the enhance of the electrical properties of the samples. According to the analysis, the spinel phase formed after doping Sb₂O₃ inhibits the anisotropic growth of the crystal grains, which decreases the grain size and improves the uniform distribution and the shape of the grains. In addition, the inhibiting effect of spinel phase on the growth of grains in the large-grain region is weaker than that in the little-grain region.

A kind of composite foam material was prepared by adding hollow polymer microbeads to the organosilicon modified resin, and then the composite foam material was used as the internal filling material for the composite insulating cross-arm. The influence rule of the microbead type and filling content on the density, hydrophobicity, dielectric loss factor, and electric strength of the composite foam material was analyzed. The results show that the filling of organic microbeads can effectively reduce the density of the composite foam, and the density of the sample filled with 920DET40d25 microbeads can be reduced to 0.5538 g/cm³. Because there are more hydrophobic groups in the microbeads, the hydrophobicity of the composite foam material is enhanced. With the increase of the microbead content, the electric strength of composite foam material shows a downward trend, but the insulation strength of all the samples still meets the requirements of the internal insulation material for composite cross-arms. Considering the requirements of the density and insulation strength of the composite foam material, the sample filled with 920DET40d25 microbeads with a mass fraction of 2.5% meets the application requirements.