Analysis of insulation breakdown of the wall bushing in a flexible DC converter station and modification mechanism research on the material

Abstract

Epoxy resin-impregnated insulating paper （RIP）， the main insulation of wall bushings， is characterized by its uneven electric field distribution. The causes of insulation breakdown of the wall bushing in a flexible DC converter station are analyzed. Furthermore， the method of adding nano-SiO2 （silicon dioxide） to modify epoxy resin is adopted to improve the electrical and thermal properties of the bushing in view of the material characteristics of the epoxy resin core. The experiments show that the relative dielectric constant of the cured epoxy resin decreases to 4.23 （at 50 Hz）， the dielectric loss factor is 0.002 （at 50 Hz）， the breakdown field strength reaches 31 kV/mm， and the volume resistivity is 3.7×1013 Ω·m when the nano-SiO2 is added with a mass fraction of 4%. The effects of nano-SiO2 on the basic physical characteristics and main electrothermal characteristics of epoxy resin are summarized to further improve the electrical insulation properties of the wall bushing material.

Keywords

• flexible dc transmission
• wall bushing
• epoxy resin
• nanoparticles