With the large-scale application of flexible DC transmission and other power electronic equipment in the new power system

the harmonic problem in the system has become increasingly prominent. Especially

the influence of high-frequency harmonics is more significant. However

no current study has calculated the dielectric heating characteristics of insulating materials in bushings when AC/DC voltages are superimposed with high-frequency harmonic voltages based on their actual dielectric loss characteristics at high frequencies and high temperatures

which makes it possible that the actual temperature and electric field distribution in the equipment under the action of harmonic voltage may differ significantly from the designed values. This poses a threat to the long-term operational safety of the equipment. Therefore

the dielectric properties of the impregnated paper material at high frequencies are measured and obtained in the paper. On this basis

a calculation model for the electric field and temperature distribution of the valve side bushing under the superimposed high-frequency harmonics is established. The electrical and thermal stress distribution characteristics of the bushing under different harmonic frequencies

contents and different insulating material properties are obtained. The calculation results show that high-frequency harmonics can cause more severe dielectric loss heating in the insulating medium inside the bushing. Thus

a higher temperature gradient is formed in the parallel direction of the electric field of the insulating layer of the equipment

triggering a higher gradient distribution of the material's resistivity. And more severe electric field distortion is formed under direct current voltage. The research of this paper provides an important reference for the design of bushings under the action of high frequency and the optimization of insulating materials.