Gas-Insulated Transmission Line – GIL
 

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Gas-Insulated Transmissi** Line – GIL


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The gas-insulated transmissi** line (GIL) is a system for the transmissi** of electricity at high power ratings over l**g distances. In cases where overhead lines are not possible, the GIL is a viable technical soluti** to bring the power transmitted by an overhead line underground without a reducti** of power transmissi** capacity.
As a gas-insulated system, the GIL has the advantage of electrical behavior similar to that of an overhead line, which is important to the operati** of the complete network. Because of the large cross secti** of the c**ductor, the GIL has low electrical losses compared with other transmissi** systems (overhead lines and cables).
This reduces the operating and transmissi** costs, and it c**tributes to reducti** of global warming because less power needs to be generated.


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Safety of pers**nel in the vicinity of a GIL is very high because the solid ****llic enclosure provides reliable protecti**. Even in the rare case of an internal failure, the ****llic enclosure is str**g enough to withstand damage. This allows the use of GILs in street and railway tunnels and under bridges with public traffic. No flammable materials are used to build a GIL. The use of GILs in traffic tunnels makes the tunnels **** ec**omical and can solve some envir**mental problems.
If GIL is added to a traffic tunnel, the cost can be shared between the electric power supply company and the owner of the traffic part (train, vehicles).
The envir**mental advantage is that no additi**al overhead line needs to be built parallel to the tunnel. Because of the low capacitive load of the GIL, l**g lengths of 100 km and **** can be built. Where overhead lines are not suitable due to envir**mental factors or where they would spoil a particular landscape, the GIL is a viable alternative because it is invisible and does not disturb the landscape.
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GIL C**structi**

The GIL c**sists of three single-phase encapsulated aluminum tubes that can be directly buried in the ground or laid in a tunnel. The outer aluminum enclosure is at ground potential.



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The interior, the annular space between the c**ductor pipe and the enclosure, is filled with a mixture of gas, mainly nitrogen (80%) with some SF6 (20%) to provide electrical insulati**. A reverse current, **** than 99% of the c**ductor current value, is induced in the enclosure. Because of this reverse current, the outer magnetic field is very low.
GIL combines reliability with high transmissi** capacity, low losses, and low emissi** of magnetic fields. Because it is laid in the ground, GIL also satisfies the requirements for power transmissi** lines without any visual impact ** the envir**ment or the landscape. Of course, the system can also be used to supply power to meet the high energy demands of c**urbati**s and their surroundings.
The directly buried GIL combines the advantage of underground laying with a transmissi** capacity equivalent to that of an overhead power line.
SOURCE: Hermann Koch, Siemens

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