CB/LDPE复合介质抑制空间电荷机制及电导特性对电场分布的影响

Suppression Mechanism of Space Charge in CB/LDPE Composite and the Influence of Conduction Characteristic on Electrical Field Distribution

为研究低剂量炭黑(carbon black,CB)对低密度聚乙烯(low density polyethylene,LDPE)空间电荷和电导特性的影响,该文采用熔融共混法制备了CB/LDPE复合介质,利用电声脉冲法测试LDPE和CB/LDPE复合介质的空间电荷分布,并在不同温度下测试了其直流电导特性。采用量子化学分子动力学模拟等手段对CB/LDPE复合介质的陷阱特性进行研究。另外采用多物理场耦合软件COMSOL Multiphysics分别仿真研究了以LDPE和CB/LDPE复合介质为绝缘的直流电缆绝缘层内电场分布。结果表明:CB/LDPE复合介质具有较强的空间电荷抑制能力、较低的电导率和电导温度依赖特性;CB颗粒作为陷阱具有较强的捕获电子能力;CB/LDPE复合介质在较大温度梯度下可有效地抑制绝缘层外侧场强的显著增加。分析认为CB颗粒的陷阱作用是改善CB/LDPE复合介质空间电荷和电导特性的主要原因,而CB/LDPE复合介在较大温度梯度下抑制场强畸变则归因于其合理的电导特性。

To investigate the influence of low content carbon black （CB） on the space charge and DC conduction characteristics of low density polyethylene （LDPE）, the blending method was employed to prepare CB/LDPE composites. The space charge distributions of LDPE and the CB/LDPE composites were obtained by the pulsed electro-acoustic （PEA） method, and the DC electrical conductivity was also measured at different temperatures. The quantum chemical molecular dynamics simulation method was adopted to research the trap characteristic of CB/LDPE composite. In addition, the physical field coupling software, COMSOL Multiphysics, was used to simulate the electrical field distribution of the DC cable insulation layer with LDPE and the CB/LDPE composites, respectively. The results show that the CB/LDPE composites have a strong ability to suppress the space charge accumulation, less DC conductivity and weak conductivity dependence on the temperature compared with LDPE. CB particles as traps can capture electrons effectively. The CB/LDPE composites can limit the electrical field strength increase outside the insulation layer under a large temperature gradient. It is deduced that the improvement of space charge and DC conduction properties are attributed to the effect of the trap, and the inhibition of the electric field distortion under a large temperature gradient is attributed to the reasonable conductivity features of the CB/LDPE composites.