This chapter introduces the subject of gaseous insulation and provides information relating to the application of gaseous insulants to high-voltage systems. It examines atmospheric air and compressed gases and illustrates how, by linking available experimental test data from such sources with a knowledge of the 'effectiveness' of various practical gas-gap clearances, the designer can achieve reliable insulation design. The chapter also briefly discusses the need for extra high-voltage (EHV) and ultra high-voltage (UHV) test areas or laboratories. Evidence is presented of how laboratory studies, on representative insulation systems and electrode arrangements, provide the designer with choices relating to electrical stresses, clearance levels, service performance and testing procedures. Gas-insulated substations (GIS) using sulphur hexafluoride (SF6) gaseous insulation have been used in transmission systems worldwide for more than 45 years. The service reliability of this class of equipment is of paramount importance. In addition, the chapter presents a large amount of experimental breakdown information on SF6 and briefly reviews the application of field computation strategies in support of GIS and other equipment designs. Several of the major factors influencing the insulation design and in-service behaviour and reliability of SF6 gaseous and epoxy resin support insulations, as used in GIS equipment, will also be considered.

Chapter Contents:

• 3.1 Introduction
• 3.2 Atmospheric air clearances
• 3.2.1 Test areas
• 3.2.2 Sphere gaps
• 3.2.3 Spark gaps
• 3.2.4 Overhead lines and conductor bundles
• 3.2.5 Guidelines for live working
• 3.3 Other gases
• 3.4 Switchgear and GIS
• 3.4.1 Introduction
• 3.4.2 Arc extinction media
• 3.4.3 General dielectric considerations
• 3.4.4 Performance under contaminated conditions
• 3.4.5 GIS service reliability
• 3.4.6 Gas-insulated transmission lines (GIL)
• 3.4.7 Vacuum switches
• 3.5 System modelling for switchgear design applications
• 3.5.1 Field analysis techniques
• 3.5.2 Prediction of breakdown voltages
• 3.6 Summary
• Acknowledgements
• References

Inspec keywords: epoxy insulation; gas insulated switchgear; substations; electrochemical electrodes

Other keywords: transmission systems; representative insulation systems; electrical stresses; epoxy resin support insulations; service reliability; compressed gases; extra high-voltage test area; clearance levels; gas-insulated substations; GIS; service performance; gaseous insulants; gas-gap clearances; electrode arrangements; testing procedures; ultra high-voltage test area; atmospheric air gases; hexafluoride gaseous insulation; switchgear

Subjects: Switchgear; Reliability; Organic insulation; Substations; Electrochemical conversion and storage