The accumulation of space charge distorts the local electric field of the polymer insulation layer, inducing the generation of electric branches, accelerating the aging process in HVDC cables. It is essential to suppress the space charge in the insulating layer for the development of HVDC cables. The important role of semiconductive shielding compound is now becoming recognized. In this paper an approach is presented to decrease carrier injection from the semiconductive layer to the insulating layer, by using adding BaTiO₃ into semiconductive shielding compound. BaTiO₃ particles were prepared by sol-gel method. The synthesized BaTiO₃ was doped into the CB/EVA/LDPE base material, squeezed, molded, and vulcanized to obtain the BaTiO₃/CB/EVA/LDPE shielding compound with different BaTiO₃ concentrations. The resistance-temperature curve of shielding material was measured by four electrode method. The space charge accumulation of polyethylene insulating layer with BaTiO₃/CB/EVA/LDPE shielding compound as electrode was measured by thermal stimulation current method. The dispersion of BaTiO₃ in the matrix was uniform. When the amount of BaTiO₃ is 2wt%, the addition of BaTiO₃ can significantly inhibit the PTC effect of semi-conductive shielding compound. When the doping amount of BaTiO₃ is 2wt%, the resistivity of shielding compound is 50 Ω ▪ cm at 90 degrees。 Compared with the shielding material without BaTiO3, its resistivity is reduced by 55.7%. When the amount of BaTiO₃ is 2wt%, the addition of BaTiO₃ significantly reduces the accumulation of space charge in the polyethylene insulating layer with the doped shielding compound as the electrode.
 

BaTiO3,semiconductive compound,HVDC cable,space charge,electron emission