Nonlinear conductivity of copper calcium titanate nanofibers/liquid silicone rubber composite

To solve the problem of local electric field distortion caused by the difference in temperature gradient and material conductivity of DC cable accessory, copper calcium titanate (CaCu₃Ti₄O₁₂) nanofibers were prepared by electrospinning and dispersed in liquid silicone rubber to synthesize CaCu₃Ti₄O₁₂ nanofibers/liquid silicone rubber composites with nonlinear conductivity. The microstructures of CaCu₃Ti₄O₁₂ nanofibers and CaCu₃Ti₄O₁₂ nanofibers/liquid silicone rubber composites were characterized by XRD and SEM. The dielectric spectral characteristics, space charges characteristics and the conductivity and the breakdown strength in the environments of 30℃, 50℃ and 70℃ of the CaCu₃Ti₄O₁₂ nanofibers/liquid silicone rubber composites were investigated. The intermediate joint of cable accessory model was established, and the simulation of the electric field distribution of the accessory was performed. The results show that the dielectric constant and conductivity of the composites increase with the increase of the content of CaCu₃Ti₄O₁₂ nanofibers. When the nanofiber reaches 3vol%, the relative dielectric constant of the composite increases to 3.27 and the nonlinear conductivity has also changed by nearly 4 orders of magnitude. Then space charge test find that the dissipation of space charge is positively correlated with the content of CaCu₃Ti₄O₁₂ nanofibers. The DC breakdown strength of the composites decreases with the increase of nanofiber content. The simulation analysis of the electric field distribution under the steady-state voltage shows that when the content of CaCu₃Ti₄O₁₂ nanofiber is 2vol%, the maximum electric field strength at the root of the stress cone has been transferred from the reinforced insulation to the main insulation of the cable. Under the action of positive and negative polarity lightning impulse voltage, the maximum electric field strength of the 3vol% CaCu₃Ti₄O₁₂ nanofibers/silicone rubber composite as the reinforced insulating material is far lower than its breakdown strength. The above experimental results show that the CaCu₃Ti₄O₁₂ nanofibers as fillers have achieved the modification of the liquid silicone rubber at a lower doping concentration, which satisfies the electrical insulation performance requirement of the composite applied to the cable accessories.