Electrothermal Characterisation and Advancements of Insulation Systems for HVDC Cable Joints by Simulation and Experiment

对于正在进行的绿色能源过渡，部署了地下高压直流(HVDC)电缆系统，而不是更传统的架空输电线路，因为它们需要的空间更少，对景观的影响更小，从而提高了公众的接受度。高压直流技术的发展是我们这个时代高压工程界面临的最大挑战之一。本研究建议通过实验和模拟相结合的方式支持这一努力，以便更深入地了解高压直流设备，并以电缆接头为突出例子。现场分级原则对电缆接头至关重要，因为它确保了在正常和不利的运行条件下的电气和热稳定性。该项目旨在对绝缘和现场分级系统进行全面的描述。主要的挑战是理解和量化材料、几何和场之间的复杂相互作用，在块体领域和材料界面上。该项目将结合电热场模拟和高压测量技术，以表征受非线性场和温度相关材料、极化和电荷积累影响的电热场分布。因此，应用现有的和新开发的在相关电热暴露下测量此类绝缘材料的方法。数据被转换为行为材料曲线，包含所有依赖关系，并考虑到正在发生的不确定性。测量活动和瞬变电热场模拟研究了电缆接头中的电场和热场效应。此外，不确定性量化和灵敏度分析有助于更好地理解磁场分级、磁场偏转和热稳定性，这些都是高压直流技术的主要原则。此外，该项目还研究了高压直流设备的慢瞬变(发热、电荷积累)和快速瞬变(极性反转、闪电)的影响，从而评估电缆接头在实际负载和危险情况下的稳健性。最后，该项目通过对包括分级材料的新型电缆接头进行尺寸标注来演示所开发的工具链。通过仿真，可以探索较大的设计参数空间，而通过对原型部件的测量，可以进行微调，从而在范围内进行创新的电缆接头设计。这项研究将显著提高对现场分级和高压直流电缆接头的理解，为面向21世纪坚固耐用的高压直流设备的模拟辅助设计战略铺平道路。

For the ongoing green energy transition, underground high-voltage direct current (HVDC) cable systems are deployed instead of more conventional overhead transmission lines, as they require less space and have less impact on the landscape, leading to greater public acceptance. The development of the HVDC technology is one of the greatest challenges of our time for the HV engineering community. This research proposal supports this endeavour by intertwining experiment and simulation towards a deeper understanding of HVDC equipment, focusing on cable joints as prominent examples. The principle of field grading is of paramount importance for cable joints, as it ensures electric and thermal stability under regular and adverse operating conditions. This project aims at a full characterisation of insulations and field grading systems. The main challenge is to understand and quantify the complex interplay between materials, geometry and fields, in bulk domains and at material interfaces. The project will combine electrothermal field simulation and HV measurement techniques in order to characterise electrothermal field distributions affected by nonlinear field- and temperature-dependent materials, polarisation and charge accumulation. Therefore, existing and newly developed procedures for measuring such insulation materials under relevant electrothermal exposure are applied. The data is converted into behavioural material curves, containing all dependencies and accounting for the occurring uncertainties. Measurement campaigns and transient electrothermal field simulations investigate electric and thermal field effects in cable joints. Furthermore, uncertainty quantification and sensitivity analyses yield an improved understanding of field grading, field deflection, and thermal robustness, being the major principles of HVDC technology. Moreover, the project studies the effect of slow (heating, charge accumulation) and fast transients (polarity reversal, lightning) of HVDC devices, thereby assessing the robustness of cable joints under realistic loads and hazards. Finally, the project demonstrates the developed tool chain by dimensioning a new cable joint including graded materials. By simulation, a large design-parameter space can be explored whereas by measurements on a prototype part, fine-tuning can be carried out, which brings an innovative cable joint design within range. The research will lead to a significantly improved understanding of field grading and HVDC cable joints, paving the way towards a simulation-aided design strategy for decisively robustified 21st century's HVDC equipment.