1. GAS INSULATED TRANSMISSION
LINES(GIL)

2. INTRODUCTION TO GIL
 Gil are composed of pipes that houses conductors in SF6 gas.
 Gil are good alternative for transmission of extra high voltage(EHV).
 Gil are used for both underground and overhead transmissions.

3. WHY ONLY SF6 RATHER THAN AIR?
 Electronegativity.
 Dielectric strength.
 Arc quenching ability.

4. N2-SF6 MIXTURE.
 Ecological factors.
 Maintenance.

5. STRUCTURE OF
GIL
• Conductors & enclosures.
• Insulators.
• Enclosure joint.

6. GIL VS CONVENTIONAL LINES
 Magnetic fields.
 Noise.
 Space.
 Life span.

7. RATINGS OF GIL(2nd generation)
 Rated voltage: 230 kV – 550 kV
 Rated current: 2500 A – 4000 A
 Transmission capacity: 1000 MVA – 3800 MVA
 Rated short-time current: 63 kA/3s
 Rated Frequency: 50/60Hz
 Capacitance: 55pF/m
 Inductance: 220nH/m
 Resistance: 10mW/km (typical)
 Insulation gas: N2-SF6 mixture
 Pipe materials: Aluminum alloys

8. LAYOUT METHODS FOR INSTALLATIONS
OF GIL
1. Aboveground installation.
2. Direct burial installation.
3. Vertical installation.
4. Tunnel installation.

9. 1.ABOVE GROUND INSTALLATION
• Gil are unaffected by high
ambient temperature ,
intensive solar radiation or
severe atmospheric
pollution.
• Corrosion protection is not
required.

10. 2.DIRECT BURIAL INSTALLATION
• These systems are coted with
continuous polyethylene to
safeguard corrosion resistant
aluminum alloy.
• The land can be used for
irrigation with minor
restrictions.

11. 3.VERTICAL INSTALLATION
• Gas insulated tubular
conductors can be installed
without a problem at any
gradient ,even vertically.
• These are top solution
especially for cavern
hydropower plant.

12. 4.TUNNEL INSTALLATION
• The system stays accessible
for easy inspection and high
transmission capacity is
ensured.
• They can installed in a
tunnel or shaft.

13. ADVANTAGES
• High transmission capacity
• Low transmission losses
• Low capacitance
• High reliability
• High operational safety (no fire risk, no external impact in case of internal failures).
• No practical ageing of components
• Very low external magnetic field
• No interference with the communication systems

14. DISADVANTAGES
• Length of each GIL section is limited.
• Earthquake resistant design must be considered.
• SF6 gas is harmful to ozone.

15. APPLICATIONS
• Most of the installations are in tunnels.
• Ideal for environments that are sensitive to electro-magnetic fields.
• Suitable for metropolitan areas where high energy rate is required.
• Well suited for high power transmission.

16. Future applications
• Long Distance AC-GIL.
• Trans European Networks.
• Offshore Wind farms.
• Improved Reliability of Electric Power.

17. CONCLUSION

18. Thank you
PRESENTED BY
S.SUJAY
UNDER THE GUIDANCE OF
MRS.V.SUDHA RANI