| Epoxy resin has a low shrinkage rate during the curing process,is easy to be molded,and has good heat resistance,high mechanical and electrical strength,and has become a widely used insulating material in electrical equipment.Epoxy resin can be used for gas-insulated substation busbar support pads,transformers,reactors,high-voltage motors,cast circuit breakers,epoxy cast dry-type transformers,indoor and outdoor insulators and electronic packaging.With the development of society,the improvement of the voltage level of the power grid imposes higher requirements on the electrical performance of electrical equipment,at the same time,it also faces severe challenges——the problem of aging of epoxy resin is becoming more and more prominent.In this paper,epoxy resin as the main research object,nano-silica as a filler,the characteristics of the electrical tree growth and breakdown characteristics of pure epoxy resin and its nano-composites were studied in detail.In order to study the initiation,growth characteristics and structural characteristics of the electric tree branches in the epoxy resin composites with different nano-filler concentration,the effects of the electric tree branch at thepower frequency of 20 kV were carried out by using the localized buck transformer and the real-time microscopic observation device.The mass fraction of nanosized silica in nano-materials was 0.5%,1% and 2.5%,respectively.It was found that the initiation time of the electric tree branches was significantly prolonged at the mass fraction of 0.5%,and the growth rate of the electric tree branches decreased significantly.When the mass fraction is 1%,the growth resistance of epoxy resin is the best and the structure of the electric tree branches is more complex plexus-branch type,compared with the pure epoxy resin,the main color of the electric tree branches should be shallow,the development mechanism is also quite different;When the mass fraction was 2.5%,the growth rate of electric tree branches was faster than that of 1%,and the shape was complex stick-plexiform.Finally,the mechanism of the growth of nanoparticles was analyzed by the interface between the nanoparticles and the epoxy resin matrix.In order to study the initiation,growth characteristics and structural characteristics of the electrical branches in epoxy resin and its composite materials at different ambient temperatures,the power frequency voltage of15 kV was selected and the temperature was 25°C,40°C,60°C,80°C,and100°C.Silicon dioxide mass fractions of 0.5% and 1% were used to initiate the induction and culture experiments.The study found that with the increase of temperature,the voltage of the branches of the trees is obviously decreased,the growth rate is obviously accelerated,and the shape and structure of the branchesof the electric branches are also different.For pure epoxy resin,the dendrite branches from branch to branch-cluster to plexiform;the mass fraction of nano-silica is 0.5%,and the dendrite is dendritic-arborate-plexiform-pine-sparate-sparse Dendritic;nano-silica mass fraction of 1%,electrical branches from the arbuscular-plexiform-pine-like-dendritic-sparse dendritic.In order to study the breakdown performance of epoxy resin,the breakdown test of epoxy resin was carried out under different voltage conditions under different ambient temperatures and different nano-SiO2 mass fractions.The study found that with the increase of temperature,the breakdown strength of epoxy resin decreases rapidly;under the strength of AC field,the mass fraction of nano-silica is 0.5%;the performance is the best;under the strong DC field,the pure epoxy resin.The best breakdown performance,0.5% of the worst breakdown performance;finally analyze the breakdown of epoxy resin under AC-DC field strength. |
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