GAS INSULATED TRANSMISSION LINE

Prepared by:Rahul Tyagi

Electrical Engg.3rd Year

1104320036

CONTENTS GAS INSULATED LINE (GIL) BASIC LAYOUT OF GIL MAIN COMPONENTS GENERATIONS OF GIL INSTALLATION OF GIL TECHNICAL DATA COMPARISON OF LOSSES ADVANTAGES DISADVANTAGES APPLICATIONS SUMMARY REFERENCES

GAS INSULATED LINE

Gas Insulated Line invented in 1965 by Massachusetts Institute of Technology

GIL consists Aluminium conductor surrounded by mixture of N2 and SF6 inside the enclosure.

GIL system first installation in Black Forest as long ago as 1975 of about 4km. length.

GIL system can be used both in above & below ground

BASIC LAYOUT OF GIL

MAIN COMPONENTSConductors & enclosuresInsulators & particle trapsPlug in contactsAluminum bellowsEnclosure joints

GENERTIONS OF GIL

1st Generation 2nd Generation pure SF6

Aluminium pipes with straight beads

9m long transport units

Hand welding

Application of disc spacers

N2-SF6 gas mixture Spiral welded aluminium pipes Transportation units between

11.5m and 13.5m Automated Orbital welding Bending of the whole tube

possible to radii > 400 m

Application of support insulators

INSTALLATION OF GIL

1. Aboveground Installation

GIL are unaffected by high ambient temperatures, intensive solar radiation or severe atmospheric pollution.

High transmission power can be achieved with aboveground installation.

Corrosion protection is not required.

2. Tunnel Installation

With this method of installation the land above the tunnel can be fully restored to agricultural use.

The system stays accessible for easy inspection and high transmission capacity is ensured.

3. Vertical Installation

Top solution especially for cavern hydropower plants.

GIL systems pose no fire risk, they can be installed in a tunnel

4. Direct burial Installation

These systems are coated with a continuous polyethylene to safeguard corrosion resistant Aluminium alloy.

The land can be returned to agricultural use with very minor restrictions.

TECHNICAL DATA OF GILSpecifications Rating

Rated Voltage 400-500 kV

Impulse withstand voltage 1425-1675kV

Rated Current 2000-4500kA

Rated short-circuit current 63kA/3s

Rated Transmission Load 2200-3900 MVA

Capacitance 55 nF/km

Overload Capability 100 % depends on design & requirements

Insulating Gas mixture 80 % N2 & 20 % SF6

Typical system length 100 m to 100 km

Electromagnetic Field strength 1 µT

Outer Diameter 375 to 500 mm

Weight per phase 50 kg/m

COMPARISON OF LOSSES

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

DISADVANTAGES

Length of each GIL section is limited. Particle contamination lower the insulating reliability of

GIL. Breakdown of insulator. Earthquake resistant design must be considered. SF6 gas is harmful to ozone.

Installation 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.

APPLICATIONS

SUMMARY

Sealed for lifetime Continous welded High capacity Low losses Long lifetime through particle trap No reactive compensation (1000km) No ageing of insulation Automatic reclosure functionality Low external electromagnetic fields No fire hazard

REFERENCES[1]. Koch H.,Kumar A., Christl N., Lei X., Povh D., Retzmann D., Advanced Technologies for Power Transmission and Distribution – Benefits and Impact of Innovations, Siemens Brochure, 2010.

[2]. Hillers T., Koch H., Gas-Insulated Transmission Lines (GIL): The solution for high power transmission underground, IEEE, PES Power Delivery Conference, Madrid, Spain, 08/1999.

[3]. Giebel G., Nielson H., Hurley B., Bigger transmission distance with lower load factors: the European dilemma, Modern Power System, 10/2005. [4]. IEC 62271-203 High-voltage switchgear and control gear – Part 203: Gas-insulated metal-enclosed switchgear for rated voltages above 52 kV, IEC and Geneva, Switzerland, 2003-11.

[5]. Benato R., Fellin L, Marzenta D., Paolucci A., Gas-Insulated Transmission Lines: excellent performance and low environmental impact, Vol.1 pp. 385–405, Napoli, Italia, 12.–18. May 2000.

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