The anisotropic conductivity of resin impregnated paper (RIP) has been seldom considered in the simulation of electric field distribution and charge accumulation within the valve-side bushing of a converter transformer until now. In order to investigate both the anisotropy in the conductivity of resin impregnated paper and its temperature dependence

we established a three-electrode volume conductivity measurement platform. A simulation model based on electric-thermal-fluid multi-physical coupling was developed for a scaled model of an 800 kV DC bushing. The characteristics of electric field distribution and charge accumulation were compared between isotropic and anisotropic conductivity scenarios. It was observed that resin impregnated paper exhibits significant anisotropy in volume conductivity

with the volume conductivity along the paper being over six times greater than that across it within a temperature range of 40~100 ℃. The simulation results indicated that

when considering anisotropic conductivity

substantial negative charges accumulated at the end of the bushing under the positive DC power compared with the isotropic condition. The maximum negative charge density reached 1.28×10-5 C/m2. This led to a 20.2% decreased potential at this location and a 10.9-fold electric field intensification of SF6 side across the gas gap between the shielding electrode and the end of the bushing core. These findings reveal that the surface flashover observed in actual resin impregnated paper bushings may be attributed to discharges occurring within small gaps present in these bushings.