A review of some critical aspects of insulation design of GIS/GIL systems

The electrical power industry worldwide has some 35 years of manufacturing and field experience with compressed gas, SF₆ or SF₆/N₂ mixtures, switchgear and transmission lines (GIS/GIL). Such equipment is in use for distribution as well as the highest transmission voltages, and a 1000 kV GIS is currently being tested and evaluated. Several power utility and manufacturing industry surveys, especially for GIS installations, and many of the areas of operation focus on insulation design of such systems. Amongst these there are at least two areas of insulation design that are considered critical, namely, metallic particle contamination and support spacer reliability. The management and control of particle contamination and quality assurance of spacers are crucial considerations as the industry moves forward to higher voltage GIS and long GIL designs using SF₆ in some components and SF₆/N₂ mixtures in others. The paper reviews the current technology of particle control and quality assurance of support spacers. Partial discharge monitoring plays an important diagnostic role in ensuring insulation integrity of GIS/GIL installations