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

随着距离电力消费中心较远的可再生能源装置数量的增加，高压直流（HVDC）电力传输的使用也在增加。与高压交流电（HVAC）系统相比，HVDC技术在长距离电能传输中表现出更小的损耗。现代高压直流电缆系统采用高分子绝缘材料，具有良好的电气特性。绝缘材料的一个缺点是可能积聚空间电荷，这可能导致局部场应力的增加。这些可能会损坏绝缘材料，导致高压直流电缆传输系统的故障。本研究计划的重点是发展绝缘材料中电荷动力学的计算模拟模型，特别是用于高压直流电缆和电缆终端系统。建立可靠的空间电荷分布的计算模拟，扩展高压直流电缆绝缘性能的数学模型。基于先前与电场和空间电荷分布的径向对称准静态模型相关的工作，将开发一个扩展的绝缘材料电导率模型，以包括界面和表面的影响。该模型将考虑不同介电材料界面上的空间电荷行为。此外，将模拟最终叠加直流电压的瞬态电压，并分析由此产生的空间电荷行为。将开发三维模拟，以考虑沿电缆几何形状的温度或压力梯度的影响。此外，还将模拟和分析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，高压直流电缆系统可以计算出高度真实的环境场景。最后，对数值计算技术进行改进，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公差不确定性输入参数相关的随机不确定性量化分析，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.