When the power converter connected to the high-frequency transformer breaks through the bottleneck and reaches a frequency of 100kHz or even higher, the high-frequency transformer's inter-turn insulation faces more serious high-frequency discharge and high temperature problems. In order to improve the service performance of oil-immersed high-frequency transformer insulation paper, composite K-BNNSs particles are prepared by ultrasonic stripping, heat treatment and thermomagnetic stirring. Then, K-BNNSs particles are mixed with PMIA slurry to produce composite aramid paper. And the effects of K-BNNSs particles with different contents on the thermal conductivity, dielectric properties, partial discharge properties and mechanical properties of aramid paper are explored. It can be found that when the addition of composite particles (K-BNNSs) is 10%, the comprehensive performance of composite aramid paper is the best. Compared with Nomex paper, the in-plane and through-plane thermal conductivity of composite insulating paper F-10 is increased by 668.33% and 760.66% respectively. Besides, the high-frequency breakdown voltage is increased by 48.73% and the tensile strength is increased by 2.49%. The main reason is that the composite particles form a complete thermal conductive network in the aramid paper matrix and a large number of hydrogen bonds with the matrix, which enhances the internal interface bonding force of the material and changes the charge transport mechanism.
