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0-8493-1703-7/03/$0.00+$1.50
© 2003 by CRC Press LLC
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Gas-Insulated
Substations
2.1
SF
6
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2.2
Construction and Service Life...........................................
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Circuit Breaker • Current Transformers • Voltage
Transformers • Disconnect Switches • Ground
Switches • Bus • Air Connection • Cable
Connections • Direct Transformer Connections • Surge
Arrester • Control System • Gas Monitor System • Gas
Compartments and Zones • Electrical and Physical
Arrangement • Grounding • Testing • Installation •
Operation and Interlocks • Maintenance
2.3
Economics of GIS.............................................................
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References ....................................................................................
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A gas-insulated substation (GIS) uses a superior dielectric gas, SF
6
, at moderate pressure for phase-to-
phase and phase-to-ground insulation. The high voltage conductors, circuit breaker interrupters,
switches, current transformers, and voltage transformers are in SF
6
gas inside grounded metal enclosures.
The atmospheric air insulation used in a conventional, air-insulated substation (AIS) requires meters of
air insulation to do what SF
6
can do in centimeters. GIS can therefore be smaller than AIS by up to a
factor of 10. A GIS is mostly used where space is expensive or not available. In a GIS the active parts are
protected from the deterioration from exposure to atmospheric air, moisture, contamination, etc. As a
result, GIS is more reliable and requires less maintenance than AIS.
GIS was first developed in various countries between 1968 and 1972. After about 5 years of experience,
the use rate increased to about 20% of new substations in countries where space is limited. In other
countries with space easily available, the higher cost of GIS relative to AIS has limited use to special cases.
For example, in the U.S., only about