Study On Physical,chemical And Electrical Properties Of Nano-modified Epoxy Under Voltage In Condensation Environment

With the power industry,the requirement of power system operation security and stability is becoming higher and higher.As one of the key components in the distribution network of power system,the switch cabinet is directly connected with the power users,and its safe and stable operation affects the reliability of power users.The southwest of our country has the high temperature and high humidity climate characteristic,the high humidity environment contains the massive water vapor,when the switch cabinet lower temperature component surface meets the high humidity air,condensation occurs on the surface of components.If the components in the switchgear are exposed to moisture and dew for a long time,the insulation components will deteriorate and the electrical insulation performance will be reduced.As a solid insulating material in the switchgear,the epoxy insulation performance affects the safe and stable operation of the switchgear.In order to improve the electrical insulation performance of epoxy in the condensation environment,a modified epoxy made of nano-alumina added to the epoxy matrix was investigated.In this paper,the nano-alumina was firstly treated in two parts,using coupling agent KH570 for surface modification and styrene grafting to treat the nano-alumina.After using E51 as epoxy resin matrix with curing agent methyl tetrahydrophthalic anhydride(MTHPA)prepared into epoxy resin samples.Modified epoxy resin samples were prepared by adding content of 1%,3% and 5% of nano alumina in epoxy resin matrix.The test platform was also constructed using air compressor,cold compressor,ultrasonic fog generator and temperature and humidity controller to simulate the condensation environment.In this paper,nano-alumina was firstly treated in two parts,using coupling agent KH570 to modify the surface,styrene grafting nano-alumina.A epoxy sample was prepared by curing the epoxy with the curing agent methyl tetrahydrophthalic anhydride(MTHPA)using E51 as the matrix.The modified epoxy samples were prepared by adding 1%,3% and 5%nano-alumina into the epoxy matrix,respectively.The epoxy quality,surface condensation state and flashover voltage of the samples in the condensation environment formed under different temperature difference conditions,the insulation performance of each sample was tested under different charge duration.Research shows:(1)the nano-alumina treated with coupling agent KH570 and styrene can be dispersed evenly in the epoxy matrix,and the agglomeration of the nano-particles is obviously reduced.(2)compared with the unmodified sample,the modified sample reduced the water absorption and improved the hydrophobicity of the sample to some extent,and the condensation state of the sample surface was significantly improved The water absorption,hydrophobicity,condensation mass and condensation state of the modified samples with different nanodoping amount are similar to those of the unmodified samples,and the modified samples still have good loss performance The flashover voltages of the modified samples in the condensation environment were measured under different temperature differences.Compared with the modified samples,the flashover voltages of the three modified samples were significantly increased,the effective value of leakage current decreased to a certain extent,and the best performance was obtained when the content of nano-alumina was 3%.(3)In the condensation environment after aging charged,the surface condensation state of the unmodified epoxy sample increases with the increase of the charged time,forming multiple water films,and under the action of an electric field,forming a large area of water films,the hydrophobicity of the sample surface gradually decreased.The hydrophobicity of the modified sample decreased slowly because of the absence of water film.With the increase of charged time,the unmodified sample has serious defects and begins to degrade.The electrical resistivity,flashover voltage and static contact angle drop sharply,and the insulation performance is seriously damaged.When the charge time increases to 7h36 min,the sample flashover occurs.The internal materials of the three samples after modification did not deteriorate seriously,and no water film and conductive channel were formed on the surface of the samples,which greatly improved the water molecules produced by condensation into the defective samples,there was only skin shedding,no chemical degradation occurred in the material,the internal structure of the material was relatively intact,and the surface of the sample still maintained good insulation performance,the resistivity,hydrophobicity,flashover voltage,loss performance and the effective value of leakage current decreased slightly,and the effective value of leakage current increased to a certain extent.But the change degree is lower,and the modification effect to the sample is remarkable,among which the modified sample with nano-alumina content of 3% has the best performance.