The gas insulated transmission line (GIL) is a technology developed for the needs of the 21st century, where huge metropolitan areas need an electrical supply for the public and industry. Natural resources of energy are often far away from metropolitan areas. The GIL, as an alternative to overhead lines and synthetic cables, will help to solve local energy supply needs. The technology developed is based on over 20 years of experience, with gas insulated systems that are in synergy with pipeline technic. (C) 1998 Elsevier Science S.A.