Experience with gas insulated substations in the USA

This paper summarises investigations on the reliability of GIS in the USA, including a primary pilot survey of US utility experience over a 20 year period. The early years of GIS introduction were associated with problems with first generation technology, and the resultant service data shows that such difficulties may have contributed to overall perceptions on GIS reliability. A review of the design features of early GIS is thus presented and related to the design and processing approaches adopted for proven modern technology. In order to relate these observations to experience, the paper includes comparative analyses with the broader based reliability data acquired from a large number of operational GIS around the world supporting the very high reliability that can be expected from modern GIS. Implications for GIS design and advantages for modern practical application are summarized