Gas Insulated Transmission Line

By Nirmal -
        Gas-insulated transmission line (GIL) are a further development of the tubular conductor intended for long distances and are especially suitable for connecting conburations to the power supply. They are also as “invisible” as ordinary powercables as well as having a number of other advantages. The first mixed-gas-insulated power transmission in the line in the world successfully completed its field trials with an endurance test in early 1999. The most important aim in the further development of tubular conductors for long-distance power transmission was to reduce cost as they can be used ecnomically over distances of upto several kilometers. This has now been achieved. The system costs of the gas-insulated transmission lines developed by Siemens are now only a factor of 8 or 10 above those of overhead power lines,down from a factor of 30. Now the GIL has reached the order of magnitude to be accepted by ultilities if an overhead line must be brought underground. The basis of this reduction in costs was : adaptation of installation techniques similar to those used in layimg pipelines;simplification and standardisation of individual components: and use of a sulfur hecafluoride (SF6) and nitrogen (N2) gas mixture. In the past, pure SF6 has been the most widely used gas tubular conductors,most of which have been incoperated into substations

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