Overview of development, design, testing and application of compact gas-insulated DC systems up to ±550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.

温度对直流GIL绝缘子电荷积聚特性的影响

研究直流电压下绝缘子表面电荷积聚问题对于推进直流气体绝缘金属封闭输电线路(gas insulated metal-enclosed transmission line,GIL)的发展至关重要。现有试验研究中均未考虑温度对电荷积聚的影响,难以获得用于实际工程中的直流GIL绝缘子电荷积聚情况。而仿真计算仅从理论上分析了温度对电荷积聚的影响规律,尚缺乏有效的实验验证。为了解决上述问题,该文设计了可模拟直流GIL导杆发热现象的绝缘子表面电位测量试验平台,并设计了同轴圆柱结构试验模型。研制了紧凑型静电位测量系统对不同温度下绝缘子的表面电位进行了测量,掌握了直流GIL导杆温度对绝缘子电荷积聚特性的影响。试验结果表明:当中心电极温度由室温升高至70℃时,在正极性电压作用下,绝缘子平均表面电位由278V增大至1670V(501%);在负极性电压作用下,绝缘子平均表面电位为负,绝对值由460V增大至1507V(228%)。因此,在进行绝缘优化设计时,需要考虑温度的影响,该研究可为直流GIL绝缘优化设计提供参考。