A silicon carbide/organic montmorillonite/epoxy resin micro-nano non-linear corona resistant composite material was prepared. The influence of silicon carbide and organic montmorillonite content on the dielectric properties of the corona resistant material was studied. Bars were prepared using the corona resistant material, and their corona resistance and surface temperature were tested. The results show that the addition of a certain amount of nano organic montmorillonite could effectively improve the non-linear characteristic of the corona resistant composite, reduce the surface temperature of anti-corona area, and improve the corona resistance of bars.

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.

In order to deeply grasp the breakdown characteristics of AC 500 kV cross-linked polyethylene (XLPE) submarine cable insulation materials under electrical-thermal stress and establish an electrical-thermal combined lifetime model, we conducted electrical-thermal breakdown experiments on the XLPE material at 25, 40, 55, 70℃ under step stress firstly. The AC electric strength and voltage duration time were analyzed by Weibull distribution to obtain the equivalent AC electric strength and voltage duration time at different temperatures. Then the FALLOU, SIMONI, CRINE models were established by multiple linear regression method, and their error was analyzed. Finally, an E-T lifetime model for the AC 500 kV XLPE material was constructed. The results show that at the same temperature, the equivalent electric strength decreases with the increase of voltage duration time of each voltage stage. At the same voltage duration time of each stage, with the increase of temperature, the equivalent AC electric strength and voltage duration time both firstly increase and then decrease. The analysis on the electrical-thermal lifetime models indicate that the fitting error of FALLOU, SIMONI, CRINE models is large, and their fitting goodness do not meet the accuracy requirements. An improved electric-thermal combined ageing lifetime model is obtained by using stepwise regression to calculate the significance and correlation between electric-thermal variables and lifetime, and the error analysis show that it has better fitting accuracy.

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.

To investigate the key factors of design for thermo-expandable sheets, we made thermo-expandable sheets from two types of glass mat with different fiber diameter and PA thermoplastic film. Different thermo-expandable sheets were prepared by changing the fiber diameter, resin content and density, and their thermal expansion rate and effect were studied. The results show that the thermal expansion effect of thermo-expandable sheets is codetermined by the elastic potential energy of fiber and the viscous resistance of melting resin. Under the same composition and density condition, the thermal expansion rate of thermo-expandable sheets increases with the increase of fiber diameter. There is a critical resin content for thermo-expandable sheets. When the resin content is below the critical value, the thermal expansion rate increases with the increases of resin content. When the resin content is above the critical value, the thermal expansion rate decreases with the increase of resin content. The critical resin content decreases with the increase of fiber diameter. When the single fiber diameter and resin content is unchanged, the higher the density of thermo-expandable sheets, the greater the thermal expansion rate.

Using ethyl acrylate (EA) and butyl acrylate (BA) as soft monomers, methyl methacrylate (MMA), styrene (St), and acrylonitrile as hard monomers, methyl Hydroxyethyl acrylate (HEMA) and methacrylic acid (MAA) as crosslinking monomers, sodium dodecyl sulfate (SDS) as emulsifiers, and ammonium persulfate (APS) as initiators, an acrylate base emulsion was prepared through semi-continuous seed emulsion polymerization. And then a modified acrylate adhesive for FPC was prepared by adding suitable amount of curing agent and vulcanizing agent to emulsion. The optimal formulation of the acrylate base emulsion was obtained by simple variable method and orthogonal experiment, that is as follow: m(soft monomer) : m(hard monomer) : m(crosslinking agent) : m(emulsifiers): m(initiators)= 65:30:4:3:0.3, w(SDS)=2%, w(APS)=0.3%. With this formulation, the peel strength of the encapsulation sample is 0.92 N/mm, the peel strength of the single panel is 2.15 N/mm, and the soldering resistance pass rate is 100%, the moisture absorption rate of the film is 3.11%, which can all meet the performance requirements of adhesivein the FPC substrate.

Vegetable insulating oil is easy to oxidate during operation and it will affect the service life of transformer. In this study, 2,6-di-tert-butyl-p-cresol (BHT) was chosen as antioxidant, and the characteristic parameters of the vegetable insulating oil were compared by the ageing tests. The effect of BHT antioxidant was analyzed by measuring the acid value, peroxide value, and moisture content. The effect of BTH antioxidant on the insulating properties was studied by detecting the dielectric loss factor, breakdown voltage, and FDS curves. The results show that BHT antioxidant can effectively improve the dielectric constant of vegetable insulating oil. Through the molecular formula analysis on the reaction mechanism between BHT reagent and unsaturated oil in natural ester insulating oil, the oxidation resistance process of BHT in natural ester insulating oil can be reflected more intuitively. When the addition amount of BHT is 0.20%, it has a better effect on improving the insulation performance of vegetable insulating oil.

A kind of porous adsorbent was developed by low temperature hydrothermal method, and it was compared with 801 adsorbent, silica gel, activated aluminum oxide, and 13X molecular sieve through the regeneration tests of degraded mineral transformer oil. The composition change of oil after regenerated by the adsorbent were analyzed by infrared spectrum. The results show that the adsorbent has the characteristic diffraction peak of β zeolite, the aperture of the adsorbent is 0.8-1 nm, the particle size is mainly 0.7-0.9 μm, the specific surface area reaches up to 680 m²/g, the molar ratio of Si and Al is 3:1-5:1, and it has strong polarity and selective adsorption. The adsorptive capacity of the porous adsorbent is stronger than 801 adsorbent, silica gel, activated aluminum oxide, and 13X molecular sieve. It can efficiently adsorb the unsaturated hydrocarbons from degradation transformer oil without damaging the basic components of the oil.

In order to find out the effect of adding nano-SiO₂ on the relative permittivity and conduction characteristic of ethylene propylene diene monomer (EPDM) insulation, we prepared EPDM composite dielectrics with different mass fractions of nano-SiO₂ by melt-blending method. The dispersion of nanoparticles in the EPDM matrix and the bonding properties between nanoparticles and EPDM matrix were analyzed. The relative permittivity and the steady-state current of the EPDM nanocomposite dielectrics at different temperatures and electric fields were measured, and the conductance characteristic were analyzed. The results show that when the mass fraction of nano-SiO₂ is 0.5%, the dispersion of nano-SiO₂ is the best in EPDM. The steric hindrance, which formed by doping of low content, reduces the mobility of the EPDM molecular segments and its side groups, and the interface effect is obvious in the nanocomposite dielectrics, making the relative permittivity and conductance decrease, the threshold electric field strength of space charge injection enhance, the insulating performance improve significantly. With the increase of the mass fraction, the interface effect between nanoparticles and EPDM matrix is weakened. When the mass fraction of nano-SiO₂ is 2.5% or 5.0%, the agglomeration caused by doping makes the relative permittivity and the conductance increase, and the threshold electric field strength of space charge injection decreases. The interface effect caused by the addition of nano-SiO₂ is a key factor affecting the properties of EPDM nanocomposite dielectrics.

In order to improve the mechanical properties and thermal stability of cellulose insulating paper, the nano-SiO₂, surface modified by KH550, was doped into cellulose insulating paper. The nano-SiO₂/cellulose composite models with different grafting density were established through molecular simulation, and their mechanical properties, mean square displacement, cohesive energy density, solubility parameter, and radial distribution function were calculated and analyzed. The results show that when the grafting density of KH550 is 12.5%, the nano-SiO₂/cellulose composite system has optimum deformation resistance, large cohesive energy density and solubility parameter.