Gas Insulated Transmission Lines – Bulk Power Transmission Today and in the Future

摘要

In Asia the need of high power underground transmission systems is mainly driven by the rapid growth of the electrical power supply. In large cities (Mega Cities) the power ratings are constantly increasing, in some cases in the city centres by more ten 10% per year, and in the same time available space is constantly reduced. The reliability of the power supply of such Mega Cities is linked to the possibility of strong power transmission connections into the load centres. With the sizes of Mega Cities underground transmission length of 10, 20 or more kilometres will be normal applications in the future. The gas insulated line (GIL) offers a solution for such requirements: High Power Ratings, underground and across long distances. Gas insulated lines offer a suitable solution as they fit in the service scheme of transmission lines as well as they are capable to carry currents up to 4000 A. The second generation GIL also is used to connect different parts of the substation or power generation plant with a strong, high power transmission line. The advantage of the second generation technology is that the insulating gas is a gas mixture with only 20% SF6 and a majority of 80% N2 to reduce the total amount of SF6. The second advantage is that the GIL of the second generation is completely welded with an automated orbital welding machine, including a 100% quality control of the welding. Based on this new technology the enclosure is practically gas tight so that no refill is needed during lifetime.In this publication the focus is given to the future application of GIL under the special aspect of power transmission in densely populated areas. Additionally, the main primary and secondary components are being discussed as well operational issues such as maintenance and monitoring.