The new environmentally friendly insulating medium C₄F₇N gas mixture will decompose under long-term overheating and partial discharge conditions, and some of the decomposition products will not only affect the stable operation of gas-insulated switchgear, but also cause personal safety hazards. Therefore, the internal of equipment need equip with adsorption materials to adsorb the decomposition products. Molecular sieves, with wide variety and ionic modification space, are regarded as the most promising adsorbent materials for the treatment of C₄F₇N decomposition products. In this paper, the adsorption isotherms and adsorption sites of 11 kinds of pure silica-type molecular sieves (three kinds with cage structure characteristics and eight kinds with pore structure characteristics) on C₄F₇N and its decomposition products were investigated by molecular dynamics calculations. Then the adsorption energy, electron transfer, and density of states parameters of ZSM molecular sieves modified by the cation (H⁺, Na⁺, Mn²⁺, and Fe²⁺) on C₄F₇N and its decomposition products were obtained based on density functional theory (DFT). The molecular dynamics results reveal that the molecular sieve topology and the window size between gas molecules and molecular sieve are important factors affecting the adsorption process. The density functional calculations show that the modification of Mn²⁺ and Fe²⁺ ions could effectively enhance the adsorption effect of ZSM molecular sieves on the decomposition products of C₄F₇N, and the adsorption process is chemisorption. During the adsorption, the main action site of C₄F₇N is C≡N bond, the main action site of C₂F₆ is C=C double bond and F atom, and the main action site of C₃F₈, C₂F₆, and CF₄ is F atom.

In cable accessories, the interface between cable body insulation and accessory insulation often coat with insulating oil for cable to enhance the sealing and insulating properties between the interfaces of cable accessories. In order to investigate the compatibility and applicability of cable body insulation and insulating oil, and to provide a reference for the selection of insulating oil for cables, the adsorption compatibility of PP and XLPE on three typical insulating oils (silicone oil, silicone grease, and polyisobutylene) at 25℃ and 75℃ was studied. The results show that affected by the molecular structure, PP and XLPE have limited adsorption capacity on silicone oil and silicone grease, and they can easily adsorb polyisobutylene, resulting in a significant increase of quality. PP coordinating with silicone grease have the best properties, which can improve the mechanical properties and electric strength of PP. XLPE exhibits close properties in silicone oil and silicone grease, among which silicone grease impregnation maintains good mechanical properties, while silicone oil impregnation maintains good insulating properties. Through analysis it is found that appropriate amount of adsorption improves the surface roughness, fills the internal defects of the insulation, and improves the insulating properties of material. By studying the influence of different types of coating materials on the main insulating material at different temperatures, the adaptability results of insulating medium and cable main insulation are obtained, which can provide a reference for standardizing the selection of insulating oils for cable terminals and improving the operating reliability of cable terminals.

In view of the problem of uneven electric field distribution and severe local electric field distortion in insulation partitions of high-voltage switchgear, dielectric functional gradient materials were introduced into the preparation of insulation partitions, and two optimization schemes, which are internal insulation structure optimization and surface insulation structure optimization, were proposed. By changing the upper limit of dielectric constant of material, the thickness of insulation partition, and the thickness of surface coating, electric field and temperature field simulation calculations were carried out to compare and analyze their effects on the optimization of electric field distribution. Finally, simulations and dielectric loss characteristics tests were conducted to compare the two optimization schemes. The results show that compared to the traditional homogeneous insulation partitions, changing the internal insulation structure and adding surface coatings can reduce the maximum field strength along the surface without considering the influence of internal operating environmental factors in the switchgear. When the thickness of insulation partition increases to 12 mm, the electric field optimization effect is optimal, and the maximum field strength along the surface can be reduced by 69.8%. When the surface coating thickness is 1 mm, the electric field optimization effect is optimal, and the maximum field strength along the surface can be reduced by 62.9%. Through simulation and experimental comparison, it is proved that the partition with optimized internal insulation structure has better electric field control effect and insulation performance.

Polyethylene-based non-crosslinked cable insulation materials have better electrical and mechanical properties, simpler processing, lower energy consumption than XLPE, and can recycle, which are one of the most promising new environmentally friendly cable insulation materials. In this paper, LLDPE/HDPE blending insulating materials with different ratios were prepared using domestically produced base materials, and their electrical, mechanical, rheological, and thermal and oxygen aging resistance properties were tested and compared with the blending materials prepared by imported base materials. The results show that both the domestic and imported blending materials have the best electrical properties and mechanical properties when the mass ratio of LLDPE and HDPE is 7:3. The electrical properties of the domestic blending materials are similar to those of the imported blending materials at the optimal ratio, but the tensile strength is lower. There is a significant difference between domestic and imported blending materials in thermal and oxygen ageing resistance. Through the molecular weight and its distribution test, infrared spectroscopy analysis, it is found that the branching degree of domestic LLDPE is similar to that of imported LLDPE, but its molecular weight distribution range is wider and there is an obvious long-tailed distribution in the direction of low molecules, which may be one of the reasons for the lower tensile strength and antioxidant properties of domestic blending materials.

Air discharge results from the interaction between electric field and atmospheric environment, therefore the air gap switching impulse discharge voltage is affected by the interelectrode electric field distribution and the atmospheric parameters. In order to calculate the discharge voltage of rod-plane long air gaps at high altitude areas, we construct an insulation prediction model based on k-nearest neighbor (KNN) algorithm with air pressure, temperature, humidity, altitude, and electric field characteristic parameters as feature set. The KNN algorithm was trained by the test data in the altitude range of 55-4 300 m to establish the mapping relationship between air gap features and the insulation strength, and then discharge voltage prediction of rod-plane air gaps at the high altitude of 5 000 m with different gap distances was realized. The maximum relative error and the mean absolute percentage error are 8.58% and 3.78%, respectively, which verifies the effectiveness of the proposed method. When the model was extrapolated to the rod-plane air gaps in plain area under different atmospheric parameters, the predicted discharge voltages also had good agreement with the experimental values. This study results can provide references for the calculation of air gap insulation strength in different atmospheric environment.

This paper focuses on the effect of melt radical graft modification of hindered phenolic antioxidant (AO3052) on the space charge and breakdown properties of polypropylene (PP) insulation. The DC conductivity, space charge distribution, and DC breakdown characteristics of grafted polypropylene with different antioxidant contents were tested and compared with the unmodified polypropylene. The results show that the antioxidants grafting can increase the sensitivity of conductivity to temperature and improve the conductivity activation energy of the samples. The 0.5% antioxidant grafting is effective in improving the space charge accumulation problem and reducing the degree of electric field distortion of PP. The DC electric strength of PP at 90℃ increases by 31.3%, and the ageing electric strength of PP at 90℃ increases by 36.1%, which is attributed to the ability of 0.5% antioxidant grafting in inhibiting the space charge accumulation. The energy band structure analysis suggests that the antioxidant grafting modification can introduce more local energy levels and potential traps in the forbidden bands of PP, which inhibits the charge transport. Meanwhile, the phenolic hydroxyl groups in the hindered phenolic antioxidants can scavenge the free radicals in PP, and the combined effect of the two enhances the breakdown performance of PP.

To address the limitations of traditional methods in accurately detecting micro-defects in epoxy-based insulation, we proposed a novel defect detection method based on photon emission counting analysis under different defect influence. Insulation rod and insulation spacer samples with scratches, surface protrusions, and metal particles were prepared, and their photon counting before partial discharge inception was tested under AC voltage excitation. The results indicate that the average photon counting of samples with severe defects is 12 times higher than that of samples without defects. The photon counting results are significantly influenced by defect types, sizes, position, and insulation gas, and the average photo counting is positively correlated with the defect severity. Therefore, the photon counting can be as a promising tool for early detection of defects in epoxy-based insulation materials.

Silicone rubber has excellent mechanical and electrical properties and excellent resistance to high and low temperatures, which is widely used in the field of electrical insulation. In this paper, the effects of extreme ambient temperature on the mechanical and electrical properties of silicone rubber (SR) were reviewed. The crystallization behavior of silicone rubber at low temperature and the methods to improve the thermal stability of silicone rubber were introduced. Finally, the future development trend of silicone rubber was prospected.

Silicone rubber composites are widely used in wire and cable, electronic packaging and other fields due to their excellent weather resistance, electrically insulating properties, high chemical stability and other advantages. In this paper, the research progress of filled thermal conductive and electrically insulating silicone rubber composites was reviewed from the aspects of thermal conductive mechanism, influencing factors of thermal conductivity, and strategies to improve the thermal conductivity of silicone rubber composites, and the research prospects of filled thermal conductive and electrically insulating silicone rubber composites were prospected.

In recent years, attentions on smooth aluminium sheathed cables has continued to increase in China, but at present, the researches on the laying of smooth aluminium sheathed cables are still insufficient. Conductor heating caused by thermo-mechanical stress during laying process of cable may cause safety problems. In this paper, a finite element model of smooth aluminium sheathed cable under vertical serpentine laying was established, and the thermo-mechanical effect of the cable was calculated and analyzed. The results show that the vertical serpentine laying of cable would generate serpentine arc lateral slip, making the axial force induced by thermal effect much smaller than that of the straight laying of cable, which meet the long-term safe operation conditions of cable. With the increase of temperature, the lateral slip of vertical serpentine laying gradually increase, the increase trend is consistent with the theoretical calculation results, and the axial force changes from tensile force to compressive force and then gradually increase. By appropriately increasing the arc width and semi-serpentine pitch of vertical serpentine laying of cable, the axial force of cable can be reduced.