Beating degree of cellulose insulation paper is a comprehensive reflection of the fiber being cut

swelled and fibrillated

and it has a direct impact on insulation performance of oil-paper composite insulation in power transformers. In order to study the influence of beating degree on the insulation properties of insulation paper

paper with five beating degrees was prepared and immersed with 25# mineral oil

then the mechanical properties

breakdown strength

and dielectric properties of paper were tested. The microstructure of fiber morphology was observed by SEM and the effect of beating degree on the mechanical strength was researched. By using the tape model of oil impregnated paper

the influence mechanisms of beating degree on electrical insulation properties were analyzed. The research results show that

as the beating degree increases

the fibers gradually become shorter and thinner

and the connection between fibers get enhanced

wheras the fibers are severely damaged while the beating degree is too high. Therefore

the mechanical strength and electrical strength present a trend of rise firstly and then fall with the increase of beating degree. In addition

the energy level inside paper decreases firstly and then increases

and the trends of permittivity and dielectric loss are as the same as energy level. In summary

it is considered that paper with 85 o SR beating degree has better insulation performance compared with other beating degrees.