中文摘要：

聚合物绝缘材料的电导率通常是电场和温度的函数。选取低密度聚乙烯（10wdensitypolyethylene，LDPE）．纳米氧化镁（MgO）／LDPE及氧化硅（si02）／LDPE三种材料作为研究对象，对三种材料的电导率一温度和电导率一场强关系进行了实验研究。构建了表征材料电导率与场强及温度关系的数学模型，并依据此模型，针对320kV、500Mw直流电缆结构，应用COMSOL有限元分析软件，计算了绝缘内电场分布。结果表明：直流场下，电场分布具有电导率依赖关系，温度变化引起的电导率变化，将导致电场分布与温度分布有关；同时，电导率还依赖于场强的变化，这种依赖关系可在一定程度下平抑由于几何结构或温度梯度形成的绝缘层内部场强不均匀性；纳米颗粒的掺入可降低电导率，性能改善机制与纳米粒子界面层电学行为相关。

英文摘要：

The conductivity of polymeric solid dielectrics tends to be a strong function of temperature and electric field. In this paper, conductivity at different temperature and electric field for three kinds of materials, LDPE, MgO/LDPE, SiOjLDPE was investigated. Based on the measurement results, a mathematical model was established to describe the conductivity as a function of temperature and electric field. According to the model, by using COMSOL analysis software, the electric field distribution in a 320kV, 500MW DC cable geometry was calculated. Experiments results revealed that, under the DC condition, the electric field distribution is conductivity-dependent. Conductivity changes caused by the temperature, which will lead to electric field distribution is temperature-dependent. Meanwhile, conductivity and electric field strength have a nonlinear relationship, which can stabilize the distortion of the electric field caused by the geometric structure or temperature gradient. Nanocomposites can decrease conductivity effectively. Interfacial electric charge in the boundary of the nano particles and the polymer matrix was suggested to be responsible for the improvement of electrical properties.