Investigation On Effects Of Type And Microstructure Of Nanoparticles On The Insulating Property Of Transformer Oil-pressboard System

At present,the modification effects of nanoparticles on transformer oil and oil-paper has been found.However,effects of Material type,size,micro-morphology of nanoparticles on oil-paper insulation have not been systemic researched;in addition,investigations of thermal ageing properties of nano modified oil-pressboard have not been reported.Therefore,in this article,we focus on TiO₂ nanoparticles,Fe₃O₄ nanoparticles and Al₂O₃ nanoparticles,investigating effects of material type and microstructure of nanoparticles on transformer oil-pressboard system and effects of nanoparticles on thermal ageing properties of oil-pressboard.In this article,the effects of the material type（conductor,semiconductor,insulator）,size（5nm,10 nm,15nm,30nm）and morphology（sphere,rod）of nanoparticles on creepage characteristics of oil-impregnated paperboard were systematically studied.The experimental results showed that the creepage characteristics of oil-pressboard can be modified by semiconductor（TiO₂）nanoparticles and conductor（Fe₃O₄）nanoparticles,but can’t be modified by insulator（Al₂O₃）nanoparticles;smaller nanopaticles have better modifying effect on oil-pressboard interfacial creepage properties.;ball-shaped nanoparticles have better modification on oil-pressboard interfacial creepage properties than rod-shaped nanoparticles.Dielectric constant,charge transport characteristics in oil-paper interface,thermally stimulated depolarization current（TSDC）were tested to analyze the reason for material,size,microtopography of nanoparticle influencing oil-pressboard interfacial creepage properties.Semiconductor（TiO₂）nanoparticles and conductor（Fe₃O₄）nanoparticles improve dielectric constant of oil and charge dissipation rate of oil-pressboard interface.Insulator（Al₂O₃）nanoparticles on the other hand,have little effect on dielectric constant of oil and charge dissipation rate of oil-pressboard interface.Nanoparticles with different sizes and morphologies have different specific area.Nanoparticles with smaller specific area have more defect dipole that can be polarized on the surface,which is good for increasing of dielectric constant and thus weakening electric field in oil.Besides,improvement of specific area of nanoparticle improve shallow trap density,which speeding up charge dissipation rate thereby reducing electric field distortion and improving the creepage performance of oil-pressboard interface.In order to study the effect of nanoparticles on the aging of oil-paper,the pure oil-impregnated paperboard and nanofluid-impregnated paperboard were subjected to accelerated thermal aging test at 130 ℃ for 36 days.The results showed that nanofluid had lower acid value and higher AC breakdown voltage than pure oil during the whole process of aging.In the early phase of ageing,nanofluid-pressboard have better creepage performance,but in the later phase of ageing,creepage performance of nanofluid-pressboard and pure oil pressboard were equal.