Influence of material volume conductivity on electric field and surface charge of RIP valve-side bushing core under DC electro-thermal coupling stress

Modifying the volume conductivity of resin impregnated paper (RIP) material is a promising way to eliminate the electric field and the surface charge along the RIP valve-side bushing core surface. In this paper, an electro-thermal coupling model is established based on the geometry of a +/- 200 kV RIP valve-side bushing and the conductivity of RIP material taken from cuts of an actual bushing core. The influence of volume conductivity of RIP material on the surface charge, the duration of capacitive-resistive field transition, and the tangential electric field along the core surface are studied. Results indicate that decreasing the volume conductivity of RIP material can help reduce the positive surface charge and the tangential electric field along the core surface. On the contrary, it increases the duration of capacitive-resistive field transition. To meet the requirements of polarity reversal test, the volume conductivity of RIP material should be decreased by two orders of existing material's volume conductivity to reduce surface charge and tangential electric field. The results are valuable for the design of RIP converter valve-side bushings.