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。封装气体绝缘系统在很大程度上同时满足高可靠性、不受环境条件影响以及适用于海上使用和人口密集地区的紧凑系统的要求。这些气体-固体绝缘系统的可靠性会由于组装时的局部放电或操作相关缺陷而显著降低。与交流电压应力相比，直流操作迫使局部放电行为发生根本变化。因此，众所周知的放电过程的物理强烈影响的附加效应。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。出于这个原因，这些过程的影响的基础研究缺陷为基础的气体-固体绝缘系统的局部放电成为强制性的。为此，在模型布置中研究了绝缘气体压力、电场强度和电压极性的影响下的随时间变化的放电行为。具体而言，空间电荷的局部放电的起始，放电的稳定性和充电和放电行为的气-固界面的影响将被研究。此外，在时间和频率域中的传导和场约束的光学和电学参数的放电类型的表征计划。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进行，而且还将使用合成空气作为天然替代品。因此，新的基本模型的局部放电形成下的绝缘气体直流电压应力，这有利于加速发展的混合电源基础设施，包括AC和DC组件。预计调查的结果将允许可靠的局部放电特性的结论，这将使直流电压应力下的缺陷识别。此外，调查提供了一个重要组成部分的瞬态过程的计算尺寸和进一步发展的气-固绝缘系统。由于长期行为的考虑，完成了对目前缺少的直流设备测试程序标准化的重要贡献。总体而言，这些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.