To study the influences of metal materials of transformer on the oil-paper insulation performance

10 types of insulating samples which were constituted by two kinds of 25 naphthene base mineral oil A and B

ordinary Kraft paper

copper and silicon steel sheets were thermally aged at 120 ℃ and sampled. Some ageing indicators including the oil acidity

dielectric dissipation factor

copper and iron content

furfural content and degree polymerization of insulating paper were measured during the ageing process

and the aging characteristics of different samples were compared and analyzed. Moreover

insulating papers were tested and determined by the frequency domain spectroscopy（FDS）

scanning electron microscope（SEM） and energy dispersive spectrometer（EDS）. The following conclusions can be drawn: silicon steel sheet has a negligible effect on the deterioration of insulating. Copper can increase the dielectric dissipation factor

accelerate the production of furfural

and make the acid number of the specimens to be 2～3 times higher than that of the specimens without copper at the end of aging. The addition of metal materials can lead to a faster decrease of polymerization degree of insulating paper

and the effect of copper is more remarkable than that of silicon steel sheet. During thermal ageing process

the dielectric dissipation factor of insulating paper increases gradually and the carbon content in the element of insulating paper increases obviously. The addition of metal materials can remarkably increase the dielectric dissipation factor and carbon content of insulating paper

and the effect of copper is more remarkable than that of silicon steel sheet.The copper increases the carbon content of insulation paper to be around 80% at the end of aging. The results lay the foundation for the study of the influence of metal materials on the properties of oil-paper insulation and the accurate assessment of the aging condition of transformers.