Effect of Nano-doping on the Interface Charge Characteristics of SIR/XLPE Composite Insulation

In the accessories of the HVDC cables, cross-linked polyethylene (XLPE) as the main insulation and silicone rubber (SIR) as the accessory insulation form a composite insulation structure. Due to the mismatch of the conductivity and permittivity of the two materials, interface charges will accumulate and affect the electrical properties of the composite insulation under DC voltage. Nano-doping of SIR is one of the means to improve its electrical properties. This paper compares the space charge distribution of the composite insulation composed of nano-TiO2 doped SIR and XLPE and the composite insulation composed of pure SIR and XLPE under different DC electric fields. The experiment results show that nano-doping of SIR can reduce the accumulation of the interface charge in the composite insulation structure when the electric field strength is high, while the interface between pure SIR and XLPE accumulates more charges when electric field strength increases.