Gis Versus Non-Gis — A Value Based Comparison

Abstract

SF6 gas insulated high voltage switchgear (GIS) has been installed in an increasing number over the last three decades. GIS covering the voltage range from 72,5kV to 800kV are now in service worldwide. The driving forces for installing GIS instead of traditional air insulated switchgear (AIS) were, among other the needs to cope with space limitation in densely populated urban areas (installations in buildings and underground) to increase availability in areas exposed to high atmospheric stress (pollution, extreme climatic conditions) to improve safety of operation in earthquake areas to meet special requirements of hydroelectric plants. Economic considerations and the progress in GIS technology have reduced the gap in the overall cost relationship between AIS and GIS and thus increased the application range of this technology. Besides the economic aspects such issues as the space saving potential, improved safety and reliability, favourable maintenance, increased service availability, and insensitivity to external disturbances have played a key role. This paper comparatively presents the major layout and design features of GIS and AIS and the related performance characteristics. These allow to determine functional advantages, to carry out life cycle cost (LCC) comparisons, and to assess environmental issues (LCA - life cycle assessment). For the value based comparison exemplified LCC has been given the main impact followed by performance issues and environmental impact. As a result GIS and AIS technology achieve similar ranking values, depending on the specific assessment. The optimisation of GIS technology with respect to lowest life cycle cost, highest availability and zero-maintenance has made GIS competitive with AIS not only at special application fields.