Ultra high-voltage gas-insulated switchgear - a technology milestone

China is in urgent need of electrical power. Huge power plants are built all over the country and the enormous flow of electrical power to the large megacities has to cross several thousand kilometres from the source to the end user. At those dimensions, losses of the power lines can be significant. The State Grid Corporation of China (SGCC) is thus aiming for 1100 kV as the voltage level for AC transmission to keep losses as low as possible, a step into a new area of electrical grids. Asea Brown Boveri (ABB), together with its partners and suppliers, has developed the heart of such a system a gas-insulated switchgear (GIS) design that could pass all the tests with this groundbreaking technology. Many years of experience at voltage levels of up to 800 kV are available as the basis for developing GIS for 1100 kV. Nevertheless, the individual components such as circuit-breakers (CB) and disconnectors differ greatly from the known designs. As regards the CB, for instance, it emerges that a design with the closing resistor in a parallel tank is advantageous. The very fast transient overvoltages become more important for the disconnector design. Copyright (C) 2011 John Wiley & Sons, Ltd.