The thermal conductive and insulating composite material with polymer matrix and high thermal conductive filler is an ideal solution to settle insulation protection of live working equipment and heat dissipation problem of electrical and electronic equipment. In this study, micron alumina (Al₂O₃), surface modified by silane coupling agent KH550, mixed with high thermal conductive carbon nanotubes (CNT) as thermal conductive filler, silicone rubber (SR) with wide temperature range resistant and corrosion resistant was selected as polymer matrix, an SR composite material was prepared, and its performance was tested. The results show that when the total content of Al₂O₃/CNT mixed filler is 10%, the proportion of carbon nanotubes is 0.2%, the thermal conductivity of the SR composite is as high as 0.268 W/(m·K), which is improved by 103.1% compared with SR, the resistivity is 10.5×10¹² Ω·cm, the relative dielectric constant is almost unchanged, and the Shore hardness A and Young’s modulus increase slightly .

Taking the UHV DC transmission line insulators under four typical climatic conditions such as extremely arid, semi-arid, semi humid, and humid as research objects, we conducted natural pollution accumulation tests on insulators. The pollution accumulation characteristics of UHV DC insulators under different environmental conditions were obtained, and the pollution accumulation characteristics of insulators with different umbrella types and hydrophobic surface were described. The results show that from the extremely arid region to humid region, both the ratio of ESDD to NSDD and uneven pollution coefficient of the insulators decrease. The ESDD ratio of bell-type insulator to outer umbrella insulator in humid area is 0.82, and the ESDD ratio of composite surface insulator to hydrophilic surface insulator of tension string in extremely arid and semi-arid areas is 1.64 and 1.85, respectively. The research results can provide a reference for the differential design of external insulation for UHV DC transmission lines at different environmental areas.

In order to study the effect of micron particle fillers on the thermal conductivity of filled type high thermal conductive composites, we constructed a finite element model of composites with randomly distributed particle fillers in this study. The effects of filling ratio, particle size, thermal conductivity, particle shape of filler on the thermal conductivity of the composites were calculated and discussed, respectively. The results show that with the increase of filling ratio and length-to-diameter ratio of filler particle, the thermal conductivity of the composites increases significantly. The particle filler size has little effect on the thermal conductivity without considering the interface thermal resistance and particle agglomeration. The thermal conductivity of filler has little effect on the thermal conductivity of the composites. Without considering the interface thermal resistance, whether the heat conduction channel can be formed effectively is the key to determine the thermal conductivity of the filled type composites.

A series of accelerated thermal ageing tests were conducted on some nuclear cables. On the basis of Arrhenius model, the apparent activation energy of nuclear cable materials was obtained using the elongation at break method and the dielectric loss spectrum method, and the effect of activation energy variation on the ageing life evaluation of nuclear cable materials was studied. Then the thermal ageing reference curves of nuclear cable materials were developed on the basis of fixed activation energy and varying activation energy, respectively, and verified by experiments. The results show that the apparent activation energy decreases gradually with the ageing of cable materials. A small change of apparent activation energy will have great impact on the life evaluation of cable materials. The thermal ageing reference curve on the basis of varying activation energy is more consistent with the actual ageing trend of cable materials, which can be used for the ageing life evaluation of nuclear cable materials.

In order to expand the new energy vehicle market and improve the power transmission efficiency of new energy vehicles, it is necessary to improve the current-carrying capacity of its internal cables. But at the same time, with the increase of load current, the heat dissipation problem of vehicle cable has become prominent. In this study, a finite element simulation model of vehicle cable considering electric field and thermal field was established by COMSOL software, the ampacity was solved by the Nelder-Mead method, and then the effectiveness of Nelder-Mead method was verified by the analytical methods. The improvement effect of the increase of insulation material thermal conductivity on the current-carrying capacity and heat dissipation of the vehicle cable was simulated analyzed. The results show that when a silicone rubber/boron nitride nanosheets (20%) composites with 0.833 W/(m·K) of thermal conductivity was used in vehicle cable, the ampacity of vehicle cable obtained by simulation increases by 5.12%, which can promote heat dissipation more significantly at overload, but it would increase the critical radius of insulation, resulting in a slight increase of conductor temperature when the insulation thickness decreases within the critical radius of insulation.

Aiming at the lack of metal passivator in oil for 22 transformers in a power grid company, a self-developed metal passivator adding device was used to add metal passivator, and the adding effect of metal passivator was verified by sampling and detecting the metal passivator content and corrosive sulfur regularly. The results show that adding metal passivator can alleviate the corrosion of corrosive sulfur to transformer effectively, and the key problems during the adding process of metal passivator are pointed out, which are preventing oil leakage, preventing air mixing in, controlling injection flow, and preventing pollutants mixing in.

A polyacrylonitrile (PAN)/styrene-isoprene-styrene (SIS) composite fiber membrane was prepared by electrospinning method. The effects of different PAN/SIS ratios on its porosity, liquid absorption, thermal stability, mechanical properties were studied. The results show that when the ratio of PAN to SIS is 8∶2, the SIS/PAN composite membrane fiber prepared has the most cross-linked structures, uniform size, and the best mechanical properties. The tensile strength is 20.29 MPa, the porosity and absorption rate reach 47.8% and 310.7%, respectively, and the ionic conductivity is 2.03×10^-4 mS/cm. Under the condition of 0.2 C multiplier, the initial discharge specific capacity of Li-ion battery assembled by the composite fiber membrane is 146.4 mAh/g, the discharge specific capacity fluctuates little after 50 cycles, and the capacity retention rate is as high as 98.02%, showing good cycle stability.

Within tens of meters of offshore area in Fujian, a large number of insulation layer is ablated and even on fire for 10 kV overhead insulation line, which causes great security risks to line operation and social security. The ablation location and regional distribution characteristics of the insulation line were investigated, and the main cause was that the offshore lines occurred pollution flashover discharge. Then according to the ablated line samples obtained in the field, the insulating property variation of the line before and after ablation was analyzed. Taking a 10 kV overhead insulation line model as an example, the phenomena and mechanisms of pollution flashover discharge and insulation layer ablation were simulated by finite element analysis and artificial pollution test. At last, according to the mechanism of ablation phenomenon, some specific preventive measures were proposed.

Polyethylene cables would generate crack defects inevitably during long-term operation, which will cause partial discharge faults and threaten the normal operation of power grid. Polyethylene composite materials doped with microcapsules could realize the self-healing of cracks. In order to study the effect of microcapsules on the insulating properties of polyethylene materials before repair, we prepared pure polyethylene samples and polyethylene composite samples doped with different concentrations (0, 0.5%, 1%, 5%, 10%) of microcapsules, and their basic performance, volume resistivity, and AC electric strength were measured. The results show that the volume resistivity of composite samples doped with a small amount of microcapsules (≤1%) is significantly higher than that of pure polyethylene samples. But when the concentration is larger (>1%), the volume resistivity decreases. Compared with the pure polyethylene sample, the AC electric strength of the composite materials decreases, but when the concentration is no greater than 1%, the decrease amplitude is smaller, which could meet the normal operation requirements of cable. This is mainly related to the crystallinity of material, the interface effect between microcapsule and polyethylene, and the characteristics of microcapsule itself. In general, when the doping concentration of microcapsules is no greater than 1%, the insulating properties of the polyethylene composite material can meet the requirements of normal operation for cable.

In order to study the radial temperature field distribution of overhead conductor, firstly, on the basis of heat transfer theory, a 3D model of finite element simulation was established according to the physical structure of conductor, and a simulation experiment was designed. Then the simulation and experimental results were compared. The results show that under natural convection conditions, the maximum radial temperature difference of the conductor can reach 10.4℃, and the maximum surface temperature difference of different position on conductor is 3.4℃. The simulation results coincide with the measured values under natural convection conditions basically, and the relative error between each layer temperature of the conductor is within ±5%, which verifies the reliability of the simulation model. Under forced convection conditions, there are obvious difference between simulation results and measured values, which indicates that the axial heat transfer of the conductor caused by different heat dissipation conditions has significant effect on the radial temperature field distribution of the conductor. For conservative consideration, in practical applications, the core temperature of conductor can be calculated by multiplying the maximum surface temperature of conductor measured from different position of conductor with correction coefficient of 1.05‒1.10.