Space Charge Suppression Method of Insulation Layer of HVDC Cable Based on Semi-Conductive Shielding Layer Modified by Nitrogen-Doped Graphene

Space charge accumulation in the cable insulation will cause local electric field distortion, and accelerate the aging of the material. The inner semi-conductive layer as an important structure of cable will affect the charge injection characteristics in the insulation layer. This work intended to explore the method of modifying the semi-conductive layer with the Nitrogen-doped graphene (NG) to suppress the charge accumulation utilizing the super-smoothness of graphene and electron adsorption of N element. First, the NG is prepared using N-modified graphene, and the semi-conductive layer with different NG content is fabricated. Second, the physical and chemical properties of the semi-conductive composite are carried out, then the charge accumulation characteristics in the insulation layer under the effect of the semi-conductive layer are characterized. The results showed that an appropriate amount of NG doping can significantly inhibit the charge accumulation in the insulation layer. The surface roughness decreased by about 32.13% when the doped NG content is 0.5 phr. With the increase of NG content from 0 to 1 phr, the accumulation charges inside the insulation layer decreased by about 36.84%. This research provided a new approach for suppressing space charge accumulation in the insulation material of high voltage cable.