钛酸铜钙纳米纤维/液体硅橡胶复合介质非线性电导性能

为解决直流电缆附件内因温度梯度和材料电导率差异而引起的局部电场畸变的难题，本文通过静电纺丝方法制备了钛酸铜钙（CaCu₃Ti₄O₁₂）纳米纤维，并将其分散在液体硅橡胶中合成了具有非线性电导特性的CaCu₃Ti₄O₁₂纳米纤维/液体硅橡胶复合介质。采用XRD和SEM对CaCu₃Ti₄O₁₂纳米纤维和CaCu₃Ti₄O₁₂纳米纤维/硅橡胶复合介质进行微观结构表征，并对CaCu₃Ti₄O₁₂纳米纤维/硅橡胶复合介质的介电特性、空间电荷特性及在30℃、50℃、70℃条件下电导率随电场强度变化规律和击穿强度进行测试，最后建立电缆附件模型，并对附件应力锥根部电场进行仿真。结果发现:CaCu₃Ti₄O₁₂纳米纤维/硅橡胶复合材料的介电常数和电导率都随着CaCu₃Ti₄O₁₂纳米纤维含量的增加而增大，当纳米纤维达到3vol%时复合介质的相对介电常数增加到3.27，非线性电导率也变化了近4个数量级，经过空间电荷测试发现，空间电荷的消散量与CaCu₃Ti₄O₁₂纳米纤维含量也正相关，复合材料的直流击穿强度随纳米纤维含量的增加而降低，通过对附件进行稳态电压作用下的电场分布仿真分析发现，当CaCu₃Ti₄O₁₂纳米纤维的含量为2vol%时，应力锥根部最大电场强度已经从增强绝缘中转移到电缆主绝缘中，在正、反极性雷电冲击电压作用下，3vol%含量的CaCu₃Ti₄O₁₂纳米纤维/硅橡胶复合介质作为增强绝缘材料时最大电场强度均远远低于其击穿强度。以上实验结果表明，CaCu₃Ti₄O₁₂纳米纤维作为填充相在较低的掺杂浓度实现了对液体硅橡胶的改性，满足了复合介质应用于电缆附件的电气绝缘性能需求。 

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.