In order to research the influence of processing temperature of master-batch on the properties of HVDC cable insulation, three kinds of master-batch were prepared at different processing temperatures, and then the insulating properties of HVDC cable insulation manufactured by the master-batch were studied. Impurity detection was carried out at first, and then the chemical structure of crystal points detected by impurity detection was analyzed by attenuated total reflectance infrared spectroscopy (ATR-IR). At last, the electrical and mechanical properties of three HVDC cable insulation were compared. The results show that there are more crystal points detected in the HVDC cable insulation prepared by the master-batch under an excessive processing temperature, and part crystal points are light yellow. Compared with semitransparent crystal points, there is no strong absorption peaks in the infrared spectra of light yellow crystal points, but the excessive processing temperature has a greater negative effect on the electrical properties of HVDC cable insulation, while has a smaller effect on its mechanical properties.

According to the structure characteristics of HX_D1 locomotive high voltage wall bushing, the electric fields of an imported high voltage wall bushing and the domestic high voltage wall bushing were analyzed by COMSOL finite element method. Then a domestic high voltage wall bushing was produced by the automatic pressure gel (APG) forming technology combining with the application situation of the imported high voltage wall bushing, its electrical properties were compared, and environmental tolerance tests of thermal-cold oil cycling, vibration impact, and high and low temperature alternating were conducted. The results show that the domestic high voltage wall bushing has reasonable structure and good environmental adaptability, which is suitable for the traction transformer field of HX_D1 locomotive.

The interface of thermal conductive polymer composite matrix and filler can affect the overall thermal conductivity of the composite. However, limited by traditional testing technologies, it is difficult to study the interface thermal conduction mechanism from microscopic view. In this paper, the interface thermal conduction mechanism of boron nitride (BN)/low density polyethylene (LDPE) composites was studied by scanning thermal microscope (SThM), and the interface thermal properties of the BN/LDPE composites were analyzed quantitatively. The test process of SThM was simulated by finite element analysis, and the interface thermal conduction process at the inorganic-organic interface was revealed. The results show that with the increase of BN content, the thermal conductivity of the composite increases. When the mass fraction of the BN reaches 20%, the thermal conductivity of the composite increases by 22%. The sample morphology in micro-nano scale and the voltage distribution image reflecting the thermal properties were obtained by SThM, it is found that the thermal conductivity interface width of the BN/LDPE composite is 150–200 nm. At the area that two BN particles are in contact with each other, the high thermal conductivity area increases, and the thermal conductivity interface width changes little. The fitting curve between thermal conductivity and the square of output voltage is obtained by testing the standard samples, and the interface thermal conductivity of the BN/LDPE composites is calculated to be 0.33–39.81 W/(m·K). The simulation results show that the probe tip can distinguish the filler, interface, and matrix, and the thermal conductivity of the composite increases with the increase of the interface width and thermal conductivity.

With the development of advanced electronics and high frequency communication technology, polyimide (PI) film faces more and more high thermal conductivity requirements as an important polymer insulating material. The intrinsic thermal conductivity of traditional PI film is smaller, which cannot meet the rapid cooling requirement of electronic components. In recent years, researchers had carried out a lot of researches on thermally conductive PI films and a series of polyimide-based composite films were prepared by adding inorganic thermally conductive fillers. In this paper, we summarized the latest research progress in thermally conductive PI-based insulating films and discussed the relevant thermal conduction behavior. The key factors influencing the thermal conductivity of films, which include fillers types, particle sizes, addition amount, and the interface interaction between fillers and polyimide matrix, were described systematically. In addition, the technical challenges of high performance polyimide-based thermally conductive insulating film materials were summarized and proposed.

The most important component of high thermal conductivity main insulation material for large generators is high thermal conductive epoxy adhesive. As an important component of high thermal conductive epoxy adhesive, BN powder can improve the thermal conductivity of epoxy resin, but it would affect other properties. In this paper, the researches of high thermal conductivity main insulation materials were analyzed and summarized. It was found that BN powder can inhibit the generation and aggregation of space charge in BN/epoxy composites effectively, and reduce the threshold electric field of space charge in BN/epoxy composites. The addition of BN powder could reduce the electric strength of BN/epoxy composites, under the same BN mass fraction, the electric strength of micron BN/epoxy composites was lower, and the conductivity of the composites could be reduced more effectively by nano BN than by micro BN. The surface flashover voltage of the composite decreased after charging on its surface. Then the research direction of high thermal conductivity adhesives in the main insulation materials for large generators in China was proposed.

The conventional properties, viscosity characteristics, gel characteristics, storage stability of YD319G3 epoxy modified unsaturated polyester impregnating varnish and its application in the partial model product of direct drive permanent magnet synchronous wind turbine generator were studied. The results show that the YD319G3 impregnating varnish has low toxicity and low volatility characteristics, which can meet the requirements of VPI insulation treatment process for large wind turbines, and the impregnated model and product have good insulating properties. It is a suitable impregnating resin for the VPI treatment of wind turbines.

In order to improve the dielectric properties, insulating properties, and thermal conductivity of polymer composites comprehensively, on the basis of boron nitride nanoplates (BNNS) modified polyvinylidene fluoride hexafluoropropylene(P(VDF-HFP)), we prepared a three-layer (P(VDF-HFP)/P(VDF-HFP)-BNNS/P(VDF-HFP)) composite by layer by layer solution casting method, the bottom and top layer were the P(VDF-HFP) film, and the middle layer was the modified P(VDF-HFP) film with 0, 1%, 3%, 5% volume fraction of BNNS, respectively. The properties of the composites were analyzed. The results show that compared with the pure P(VDF-HFP) and the single layer composite films modified with 1% BNNS, the dielectric properties of the three-layer polymer material modified with 1% BNNS is improved obviously, its dielectric constant and dielectric loss factor is 8.52 and 0.022 at 1 000 Hz, respectively. Its electrical breakdown property and thermal conductivity are more excellent, the electric strength is 452.6 MV/m, which is 17.3% and 24.9% higher than that of the pure P(VDF-HFP) and the single layer composite films modified with 1% BNNS, respectively, and its thermal diffusion rate is 0.04 mm²/s, which is 25% and 5.3% higher than that of the pure P(VDF-HFP) and the single layer composite films modified with 1% BNNS, respectively.

The ageing characteristics of composite insulators are often obtained by the accelerated ageing test at laboratory, but this method is difficult to simulate the actual complex environment, and the equivalence between accelerated ageing and natural ageing need further verification. In view of this, we selected 153 composite insulators in operation with different operating years and operation environments in Ningxia area to conduct multiple tests, and studied their natural ageing characteristics from three aspects, including the physical and chemical properties of silicone rubber material, the electrical properties and mechanical properties of insulator. The results show that the operating years, pollution degree, and pollution composition are the main factors affecting the ageing of silicone rubber material, and the chemical pollution can accelerate the ageing of materials. Under the same operating years, the ageing degrees of electrical and mechanical properties of insulator are lower than that of the electrical and mechanical properties of silicone rubber material. The mandrel of insulators operating for more than 15 years in heavy pollution areas can still maintain good performance. The junctions of mandrel and sheath, mandrel and hardware are the weak points of the electrical and mechanical properties of insulator, respectively. The manufacturer formulation and process are the important factors affecting the natural ageing, and there will be agglomeration performance degradation in low-quality batches. In the operation and maintenance sampling inspection of composite insulators, it is necessary to pay attention to the insulators with long service life in the heavy pollution area or chemical pollution area, and the composite insulators in operation with performance aggregation degradation from the same manufacturer batch need to conduct supplementary sampling inspection.

The composite insulation cross arm has the characteristics of light weight and high strength, which can play an important role in reducing the area of the line corridor and strengthening the insulation capacity of the power grid. The electrical insulation performance of the internal insulation interface is related to the safe and stable operation of the power system. In this study, based on IEC 62217:2012, a 144-hour water diffusion test was carried out on the interface specimens of the inner-filled composite crossarm, and the leakage current and breakdown at different stages were measured. Combined with the test results, the insulation crossarm samples were analyzed. Interface ageing characteristics under water diffusion test conditions. The results show that when the water diffusion time is 144 h, the leakage current of the sample is as high as 20 mA, which is 1000 times that of the sample without the water diffusion test, and the interface breakdown time is faster than that of the sample without the water diffusion test. 65%, water molecules have a destructive effect on the interface under the action of high temperature diffusion, and the longer the water diffusion time, the greater the damage to the polyurethane/glass fiber reinforced plastic interface.

When we design and optimize the insulation structure of a DC cable, its electric field distribution characteristics is an important reference basis. A simplified model of 320 kV DC cable was established by COMSOL simulation software, and its steady-state and transient electrical characteristics were studied. Then the reliability of the simulation model was verified by experiments. The result shows that the maximum temperature of conductor and the maximum temperature difference between inner and outer surfaces of insulating layer were used as the constraint conditions, when the ambient temperature is lower than 12℃, the decisive factor of DC cable ampacity is the tem-perature difference between inner and outer surface of the insulating layer (20℃). When the ambient temperature is higher than 12℃, the decisive factor of DC cable ampacity is the maximum operating temperature of conductor (70℃). In the process of simulated switching impulse test, lightning impulse test, and load cycle test under 30℃ of insulation temperature difference, the maximum transi-ent and steady-state breakdown field strength are 58 kV/mm and 25 kV/mm, respectively. According to the performance parameters of DC insulating material, the DC cable structure can meet the design requirements. The test results indicate that the COMSOL multi-physical field simulation has important guiding significance for the structure design of DC cable.