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.

PI nano composite films were conducted long-term multiple ageing at 270℃, 70℃ and 90%RH, and 320℃, and their thickness, dielectric spectra, conductivity, partial discharge initiation voltage, and insulation life at different ageing stages were tested. The results show that the insulating properties of the PI film has no obvious change after ageing at 270℃. The high humidity environment has a significant impact on the dielectric spectra, conductivity, and partial discharge initiation voltage of the PI film, but it does not shorten its insulation life. The internal structure of PI film would change under the high temperature of 320℃, which will shorten its insulation life by about 30%.

The epoxy resin samples for dry type insulation equipment were conducted ageing test. The electric strength and dielectric spectrum of the samples with different ageing degree were tested, and their activation energy were calculated. It is found that with the increase of ageing degree, the activation energy of the epoxy resin shows a change trend of decreasing-increasing-slightly decreasing-increasing, and the electric strength shows a zigzag downward trend. The accelerated ageing time at high temperature can be converted into operating time at working temperature by the accelerated ageing factor (AF) obtained by Arrhenius equation. Taking that the electric strength decreases to 50% of the initial value as a sign of life end for material, we could obtain the activation energy corresponding to the life end of epoxy resin material, which is 209.7 kJ/mol. The judging method of the insulation state and life for epoxy resin dry type insulation based on activation energy is established, and the connection mode and test method of dielectric spectrum measurement for dry type insulation equipment are proposed by taking dry type transformer as an example. The life prediction method is applied to an actual dry type transformer in the project, it is obtained that the activation energy of the dry-type transformer is 69.4 kJ/mol, and the its minimum residual life is predicted to be 36.5 years.

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.

The discharge characteristics of column-plate electrode structure under high frequency excitation were studied by combining experiment and simulation under different solution concentrations. The discharge characteristics of gas-liquid two-phase dielectric barrier discharge (DBD) were measured through experiment, and the electrical and luminescent characteristics under different solution concentrations and applied voltage amplitudes were obtained. On this basis, the equivalent circuit model corresponding to this experiment was established by combining with the physical process of gas-liquid two-phase discharge. The model parameters were determined by combining the experiment with the electric field simulation, and the circuit simulation model was established in Simulink. The voltage and current waveform, and Lissajous graph under different concentration and voltage amplitude were obtained through simulation. The correctness of the simulation model was verified by comparing simulation and experimental results. The discharge parameters, such as air gap voltage, liquid phase voltage, discharge channel current, and energy ratio, which could not be obtained in the experiment directly, were further extracted by the above model. The results show that the solution concentration has no significant influence on the voltage and current waveform and luminescence characteristics of the loop obtained by experiment. However, it is found through simulation that the proportion of energy consumed by gas phase and liquid phase are affected by it greatly. With the increase of solution concentration, although both liquid power and gas power increase, the liquid power increases faster, resulting in that the energy ratio of liquid phase increases obviously. The energy ratio of gas phase can be improved by increasing the excitation source voltage, which can inhibit the energy obtained by liquid phase to a certain extent.

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 develop a high thermal conductive epoxy potting adhesive for dry-type transformer, we prepared a potting adhesive by adding self-made modified silica to epoxy anhydride system. The thermal conductivity and electrical insulation performance were tested, and the suitable pouring temperature and best curing process of the potting adhesive were studied. The results show that when the filling content is 75%, the potting adhesive has high thermal conductivity and excellent electrical insulation performance, the thermal conductivity is 1.494 W/(m·K), the dielectric loss factor is only 0.41%. When the pouring temperature is 70℃, the potting adhesive has good pouring process, the viscosity is low than 2 800 MPa·s within 2 h. The best pouring process for potting adhesive is 80℃ vacuum/0.5 h + 80℃/4 h + 90℃/3 h + 110℃/2 h + 140℃/5 h. Under the condition, the deposition of powder in potting adhesive is small, and the cured product has the best comprehensive performance.

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.

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.

With the miniaturization and lightweight of electronic equipment, graphite film materials with high thermal conductivity were widely concerned recently. In this paper, the preparation of polyimide (PI) based graphite film was reviewed, and the influence factors of their performance, which included molecular structure, molecular orientation, and the inducement of other materials, were introduced in detail. The research and patent situation of graphite film composite materials were summarized, and the future research and development direction were suggested and prospected.