This document provides an overview of gas insulated transformers (GITs). It discusses how GITs work, the applications of GITs such as in hospitals and power plants where fire safety is important, and their features like reduced space, high reliability, and no pollution. The document also describes the construction of GITs including the insulating gas (SF6) and cooling apparatus, as well as important accessories like pressure gauges. GITs offer advantages over oil insulated transformers.

1. CONTENTS
Introduction
SF6, An overview
Applications of Gas Insulated
Transformer
Features of GIT
Layout
Cooling apparatus of a GIT
Important accessories
Conclusion

2. INTRODUCTION
A transformer is a static piece of apparatus by means of
which electric power is transform one circuit to another at
constant frequency. It accomplished this by mutual induction.
It can raise or lower the voltage in a circuit but with a
corresponding decrease or increase of current.
Types of Transformer
According to Construction :
 Core type
 Shell type
According to Voltage :
 Step up
 Step down
According to Cooling :
 Air blast
 Oil filled self-cooled
 Oil filled water cooled
 According to Insulation :
 Oil insulated
 Gas insulated

3. SF6 AN OVERVIEW
 SF6 is Sulphur hexafluoride formed by chemical reaction
of molten sulphur and fluorine.
 It is colorless, odorless, nonflammable, non-corrosive and
chemically stable.
 High dielectric strength.
 Quenches arc effectively and has excellent cooling
properties.
 Good thermal conductivity and excellent thermal stability.
 It’s not poisonous and eco-friendly.
 It can be recycled.

4. APPLICATIONS OF SF6 GAS
INSULATED TRANSFORMER
Hospitals, underground shopping centers, substations
where a high level of fire safety is required.
Water treatment plants and hydroelectric power plants
where waterways must be kept unpolluted.
Thermal power plants, chemical plants, public works
facilities etc. where high reliability is required.
FEATURES OF A GAS INSULATED
TRANSFORMER

5. Highly flame resistant and non-explosive.
High resistance to moisture.
Reduced installation space.
High reliability.
Causes no pollution.
Explosion proof tank.
Easy inspection and maintenance work.
Pressurerise on internal fault :

6. LAYOUT

7. Construction
The construction of a GIT is basically the same as an
OIT, with the exception of insulating material and cooling
medium. Therefore, broad experience of OIT technology can be
applied to GIT design, manufacturing and maintenance.

8. Constructional Features
Constructional
Features
Oil Immersed
Transformer
(OIT)
Gas Insulated
Transformer
(GIT)
Insulation/Cooling Insulating Oil SF6 (Pressure 0.14 or
0.43MPa-g)
Solid Insulation
Material
Oil Impregnated
Paper, Pressboard
PET Film, PPS Film,
Aramide Paper,
Pressboard
Conservator Necessary Unnecessary
On Load Tap
Changer
Arcing Switching in
Oil
Vacuum Interrupter
Cooling system

9. COOLING APPATARTUS
Employs a cooling medium in liquid phase such as a
Refrigerant R113 otherwise known as
Trifluorotrichloroethane or C2F3Cl3.
SF6 gas is obviously used as the second cooling medium.

10. IMPORTANT ACCESSORIES
Fig. Dial Thermometer
Fig. Pressure Gauge
Fig. Temperature Compensating Pressure Switch

11. CONCLUSION
Incessant research and continuous developments have
made construction of large capacity gas insulated transformer
possible.
With the eco-friendly aspects of SF6 gas and
considering the huge advantages of the gas, long strides can
be made in this regard to further utilize it and increase the
efficiency of the transformer and making the power system
more reliable and safer.