基于分子链位移的HVDC电缆接头界面区域空间电荷分布研究

Study on Interface Region Space Charge Distribution of HVDC Cable Joints Based on Molecular Chain Dynamics

在高压直流电缆接头绝缘中,携带被深陷阱捕获电荷的分子链在库伦力作用下会发生位移,导致聚合物绝缘中深陷阱能级发生变化,进而对电荷输运造成影响。该文基于分子链动力学对传统双极性电荷输运模型进行改进,在温度梯度下分析高压直流电缆接头不同界面的深陷阱能级、空间电荷及电场分布,探讨在温度梯度下深陷阱能级变化对电缆接头绝缘界面电荷分布的影响。研究表明:基于分子链动力学改进的双极性电荷输运模型中,复合绝缘界面以及介质内部深陷阱能级增大,导致电荷在介质内部的扩散和迁移受到阻碍,大量电荷在界面积聚;界面电荷分布规律与界面深陷阱能级分布一致;相较于接头内部整体高温,接头两侧存在较大的温差更容易使接头绝缘面临更严峻的挑战,电缆接头在10K的温差下能够保持较为良好的电气绝缘和运行状态。所得结果为进一步理清电缆接头绝缘电荷输运特性提供了支撑。

In the insulation of high voltage DC(HVDC)cable joints,the molecular chains containing the trapped charges captured by the deep traps will shift under the action of the electric field,which will lead to the change of the deep trap energy level in the polymer insulation,and thus affect the charge transport.In this paper,an improved bipolar charge transport model based on molecular chain dynamics was proposed,and the deep trap energy level,space charge and electric field distribution at different interfaces of HVDC cable joints were analyzed under temperature gradient.The effects of deep trap energy level under temperature gradient on interface charge distribution of cable joint were discussed in detail.The results show that in the improved bipolar charge transport model based on molecular chain dynamics,the deep trap energy level increases at the interface and inside the medium,which hinders the charge diffusion and migration,resulting in a large number of charges accumulated at the interface.The distribution of the interface charge is consistent with the distribution of the interface deep trap energy level.Compared with the overall high temperature inside the joint,the large temperature difference on both sides of the joint is more likely to cause more severe challenges for the joint insulation,and the cable joint can maintain a good electrical performance and operating condition under a temperature difference of 10 K.The research can provide support for further clarifying the characteristics of the insulation charge transport of cable joints.