Hermann Koch

Introduction and applications of gas insulated substation (GIS)

This tutorial is meant to present and teach about all the improvements done in the design of GIS technology and to report about the excellent experiences with GIS in other countries.

Insulation co-ordination for gas-insulated transmission lines (GIL)

In this paper focus is given to the insulation co-ordination of a closed system with integrated surge arresters. The calculations of transient overvoltages are made with typical applications of the integration of GIL in the 400 kV net of overhead lines. The overvoltages in the system are calculated and discussed for system lengths of 1 km and 10 km. Recommendations for such applications for the insulation levels are given. The GIL design configuration, the lightning overvoltages of overhead lines, and the overvoltages in the GIL are discussed under respect of overvoltage protection measures. Together with the use of surge arresters the insulation levels due to overvoltages are discussed. The insulation co-ordination is a very important measure for system optimization. Calculated values found for the insulation level of the GIL were proven with type tests and long duration test set-ups. Some test results are also explained in this paper.

Connecting large offshore wind farms to the transmission network

Wind over the sea is more constant and undisturbed than on land. There are no hills, mountains or valleys in the way to slow wind or redirect wind. This ends in a more constant wind flow and with less direction changes. This improves the energy efficiency of the installed wind turbines. From experiences made in Europe mainly in Germany, the impact of the location of a wind farm can make large differences in annually wind energy generation. Efficiency can differ from 10 – 20 % on land to 70 – 80 % at sea. This high efficiency range is driving the exploration to offshore wind farms, even when the connection to the grid has some very specific requirements: Building offshore and maintaining in an unpleasant ambience with salty air. Especially in Europe where governmental goals are fixed for each member state of the European Union (EU) the development of offshore wind farms is strongly proceeding.

Future needs of high power interconnections solved with gas-insulated transmission lines (GIL)

GIL technology is world-wide in use for more than 30 years, mainly as bus ducts of gas-insulated substations, or as an underground connection in power plants, or as a replacement of an overhead line. The reason for the use of GIL in the past always was high power transmission capability. Now a second generation of GIL is available and has firstly been installed in Switzerland at the Geneva airport and in Bangkok, Thailand, within a substation. This second generation GIL is made for the use over long distances as an alternative to overhead lines and in fields of transmission ratings too high for solid insulated cables. Two main features are shown with the second generation GIL. In this paper the GIL technology is described. Special focus is given on possible applications in China.

Gas insulated transmission lines for high power transmission over long distances

The gas-insulated transmission line (GIL) has been optimised for the needs of the 21st Century, where high-power transmission lines are needed and overhead lines are often not suitable. It will be used as a power feeder into huge metropolitan areas because energy resources are usually far away from the load centre. Also, underground power transmission over long distances is economical with GIL if overhead line installations face technical or acceptance difficulties. The technology is based on over 30 years of experience with gas-insulated systems. The GIL exhibits the following differences in comparison with conventional cables: high power ratings (transmission capacity of 3000 MVA and more per system); and suitability for long distances (100 km and more without compensation of reactive power). The aim of the latest Siemens GIL development was to considerably reduce costs and to optimise the laying technique for long lines.

Basic information on Gas Insulated Transmission lines (GIL)

The GIL is a transmission system for the transmission of high power levels over long distances, to solve specific routing or access problems, or as connections in power plants, and substations. Current ratings of 4000 Amps or more per circuit and distances of several kilometers are possible. As a gas-insulated system, the GIL has the advantage of having electrical behavior similar to an overhead line. GIL capacitance is very low allowing long lines to be constructed without reactive compensation. When life cycle costs are considered, the low losses, minimal maintenance costs, high reliability and long life of GIL make it an attractive solution to transmission line installations.

Gas Insulated Switchgear GIS - State of the Art

Gas insulated switchgear (GIS) is a world-wide used technology to solve the needs and requirements coming from modern power transmission and distribution systems. In this paper the development of the GIL technology is presented, design features are explained and a focus is given to the manufacturing process to show the high quality of the production of GIS.

Turbulent natural convection and thermal behaviour of cylindrical gas-insulated transmission lines (GIL)

This paper presents a numerical study of the natural convection of gases in a horizontal annulus of gas-insulated transmission lines (GIL). It consist of thermal analysis of high voltage power gas insulated transmission lines. In different case studies, the inner cylinder is heated at a constant heat or kept at a constant temperature, whilst the outer cylinder is maintained at constant temperature. The cylinders are long and the flow is assumed to have axially independent properties. The two dimensional analyses of the heat transfer and fluid motion are performed for Rayleigh number ranging from 10/sup 5/ to 10/sup 10/, the radius ratio is at 2,5. Comparisons are made with experimental test set up and measurements.

Basic information on Gas Insulated Substation (GIS)

This paper gives an overview about design of GIS, technologies, and worldwide experiences. The steps of technical development, stages of technical design, state of the art in the production, and quality insurance are explained with practical examples. Focus is given to applications worldwide with typical projects shown, including on-site works, sequences of erection, testing, and civil works. Explanations are given about the operational primary equipment (switching, grounding, disconnecting), secondary system, gas handling, maintenance, and monitoring. All requirements are met to have a safe handling of SF6 even under the assumption of an increasing demand for the use in the electrical power supply.

Long term test of buried gas-insulated transmission lines (GIL)

In order to prove the electrical, thermal and mechanical layout of directly buried gas-insulated transmission lines (GIL), a long term test was carried out at the test field of IPH in Berlin, Germany. A single phase was buried and subjected to the cycles of higher current of 4000 A and higher operation voltage of 480 kV to simulate 50 years of life time. Electrical, thermal and mechanical measurements have been carried out and compared with the numerical simulation. In this article some comparisons of measured and calculated values are presented.