基于双极性载流子输运模型的高压直流电缆附件绝缘EPDM/LDPE界面电荷的数值模拟

Numerical Simulation of Interface Charge Behaviors Between LDPE/EPDM for HVDC Cable Accessory Insulation Based on the Bipolar Charge Transport Model

高压直流塑料电缆是直流输电系统的关键装备,作为其重要连接环节的直流电缆附件由于介质的不连续性,容易产生界面电荷积聚,威胁电缆输电系统安全。为此,通过设置界面特性相关的表面态、界面势垒和载流子迁移率等参数,利用双极性载流子输运模型仿真研究了不同界面条件下空间电荷在乙丙橡胶（EPDM）/低密度聚乙烯（LDPE）双层介质中的注入和输运特性,并分析了界面电荷累积对复合绝缘系统电场分布的影响。仿真与实验结果证明材料表层的深陷阱能级、较高的界面势垒以及两种介质间较大的载流子迁移率差异均能造成界面电荷密度的增大,同时界面电荷积累也使电场分布畸变更加严重。因此可以从改善材料表面态分布,降低界面势垒和提高载流子迁移率匹配程度等方法出发,以解决高压直流电缆附件绝缘界面电荷积累问题。

HVDC extruded cable is the key equipment of flexible DC transmission technology. However, the interface charge between different dielectrics is easy to accumulate in the HVDC cable accessories due to the discontinuity of conductivity and permittivity, which will threaten the safety of the HVDC cable system. So, the injection and transportation behaviors of space charge in ethylene propylene diene monomer（EPDM）/low-density polyethylene（LDPE） bi-layer dielectrics were simulated by using a bipolar charge transport model with different interface characteristics including the surface states, interface barrier and carrier mobility. Furthermore, the influence of interface charge accumulation on the electrical field distribution in HVDC cable accessory was analyzed. The simulation and test results show that the interface charge density in HVDC cable accessory is increased by the deep surface trap energy level, high interface barrier and large carrier mobility difference. The accumulation of interface charge makes the electrical field distribution more distorted. Therefore, interface charge accumulation in the HVDC cable accessory can be suppressed by improving the surface state distribution and matching degree of carrier mobilities and decreasing the interface barrier.