Fundamental investigations on the partial-discharge behaviour in gas-solid insulating systems under DC voltage stress

使用低损耗高压直流输电传输大量能源考虑到可再生能源日益融入现代和可持续的电力供应。密封式气体绝缘系统在很大程度上满足了海上使用和人口稠密地区对高可靠性、不受环境条件影响和紧凑型系统的同时要求。这些气固绝缘系统的可靠性可能会由于组装时的局部放电或与操作相关的缺陷而显著降低。与交流电压应力相比，直流操作从根本上改变了局部放电行为。因此，众所周知的放电过程物理受到附加效应的强烈影响。它们包括定向电荷运动，空间电荷和表面电荷的积累，以及由于无脉冲预电流而改变的放电形成。因此，对这些过程对气固绝缘系统中基于缺陷的局部放电的影响的基础研究变得非常必要。为此，在模型装置中研究了绝缘气体压力、电场强度和电压极性对放电行为的影响。具体而言，将研究空间电荷对局部放电起始、放电稳定性以及气固界面充放电行为的影响。此外，还计划在时间域和频域中描述关于传导和场限光学和电学参数的放电类型。关于可预见的技术和政治发展，调查不仅将使用经批准的绝缘气体六氟化硫，而且还将使用合成空气作为天然替代品。因此，将开发出直流电压应力下绝缘气体局部放电形成的新的基本模型，从而促进包括交流和直流元件在内的混合电源基础设施的加速发展。预计调查结果将对局部放电特性得出可靠的结论，从而能够识别直流电压应力下的缺陷。此外，这些研究还为计算气固绝缘系统的尺寸和进一步发展的暂态过程提供了必要的组成部分。由于对长期行为的考虑，为目前缺乏直流设备测试程序的标准化做出了重要贡献。总体而言，调查将确保创新能源供应基础设施的可靠长期服务。

The transmission of large amounts of energy using low-loss high-voltage direct-current transmission takes into account the growing integration of renewable energy sources in a modern and sustainable power supply. Encapsulated gas-insulated systems satisfy to a vast extent, the simultaneous requirements of high reliability, independence from environmental conditions and compact systems for both offshore-usage and in densely populated areas. The reliability of these gas-solid insulating systems can be significantly reduced due to partial discharges at assembly or operational related defects. In comparison to AC voltage stress, DC operation forces a fundamentally changed partial discharge behaviour. Hence, the well-known physics of discharge processes are strongly influenced by additional effects. They are including an oriented charge movement, the accumulation of space and surface charges and a changed discharge formation due to pulseless pre-currents. For this reason, basic studies on the influence of these processes on defect-based partial discharges in gas-solid insulation systems become mandatory. For this purpose, the time-dependent discharge behaviour is studied in a model arrangement, under the influence of the insulation gas pressure, the electric field strength and the voltage polarity. Specifically, the influence of space charges on the partial discharge inception, the stability of the discharges and the charge and discharge behaviour of the gas-solid interface will be studied. Furthermore, a characterization of the type of the discharges with respect to conducted and field-bound optical and electrical parameters in time and frequency domain is planned. With respect to foreseeable technical and political developments, the investigations will not only be carried out with the approved insulation gas sulphur hexafluoride, but also with synthetic air as a natural alternative. Thus, new fundamental models for the partial discharge formation in insulating gases under DC voltage stress will be developed, which facilitate an accelerated development of a hybrid power supply infrastructure, including AC and DC components. It is expected that the findings of the investigations will allow reliable conclusions on partial discharge characteristics, which will enable the identification of defects under DC voltage stress. Additionally, the investigations provide an essential component for the calculation of transient processes for dimensioning and further development of gas-solid insulating systems. Due to the consideration of the long-term behaviour, an essential contribution for the currently missing standardisation of test procedures for DC equipment is accomplished. Overall, the investigations will ensure a reliable long-term service of the innovative energy supply infrastructure.