Modelling and Simulation of Electo-quasistatic Fields in Insulator Materials of High-Voltage Direct Current Cables and Cable Terminations with Nonlinear Effects due to Temperature and Space Charge Distributions and Nonlinear Field Grading Materials

随着越来越多的可再生能源安装在距离用电中心很远的地方，高压直流输电的使用也越来越多。与高压交流输电系统相比，高压直流输电技术在电能远距离传输方面具有更小的损耗。现代高压直流电缆系统采用聚合物绝缘材料，具有良好的电气特性。绝缘材料的一个缺点是可能积累电子空间电荷，这可能导致局部场应力增加。这些都有可能破坏绝缘材料，导致高压直流电缆输电系统的故障。本研究方案的重点是开发绝缘材料中电荷动力学的计算仿真模型，特别是用于高压直流电缆和电缆终端系统。空间电荷分布的可靠计算模拟高压直流电缆绝缘特性的扩展数学模型有待发展。在前人关于电场和空间电荷分布的径向对称电性准静态模型的基础上，建立了考虑界面和表面效应的绝缘材料电导率的扩展模型。该模型可以考虑不同介电材料界面的空间电荷行为。此外，要模拟最终叠加直流电压的暂态电压，并分析由此产生的空间电荷行为。将开发三维模拟来考虑沿电缆几何形状的温度或压力梯度的影响。此外，还模拟和分析了电场分级材料的可能使用及其对空间电荷分布的影响。在三维仿真模型中，可以用非常逼真的环境场景来计算高压直流电缆系统。最后，需要改进数值计算技术，以减少计算时间，提高数值效率。如果这些模拟方案要用于参数优化或与具有容差不确定性的输入参数相关的随机不确定性量化分析，则这是强制性的。

With a growing number of installations of renewable energy sources with long distances to the centers of electric power consumption the use of high voltage direct current (HVDC) electric power transmission increases. The HVDC technology exhibits less loss for long distances of electric energy transport in comparison to high voltage alternating current (HVAC) systems. Modern HVDC cable systems feature polymeric insulation materials, which have good electrical characteristics. A disadvantage of the insulating materials is the possible accumulation of electric space charges which may result in increased local field stresses. These can possibly damage the insulation material and result in a failure of the HVDC cable transmission system.This research proposal focusses on the development of computational simulation models for the electric charge dynamics in insulation materials, especially used in high voltage direct current cables and cable termination systems. Reliable computational simulations of space charge distributions extended mathematical models of HVDC cable insulation properties are to be developed. Based on previous work related to radial symmetric electro-quasistatic models of electric field and space charge distributions, an extended model for the electric conductivity of the insulation material is to be developed to include effects at interfaces and surfaces. This model will allow to consider space charge behavior at interfaces of different dielectric materials. Further, transient voltages, which eventually superimpose the DC voltage, are to be simulated and the resulting space charge behavior is to be analyzed. Three dimensional simulations will be developped to consider effects of temperature or pressure gradient along the cable geometry. In addition, the possible use of electric field grading materials and their effects on space charges distributions will simulated and analysed. Within three dimensional simulation models the HVDC cable system can be computed with highly realistic environment scenarios. Finally, the numerical computation techniques are to be improved to reduce the computation time and increase numerical efficiency. This is mandatory if these simulation schemes are to be used for parameter optimization or for stochastic uncertainty quantification analysis related to input parameters with tolerance uncertainties.