The greatly reduced electric and magnetic fields, combined with the superior dielectric strength of SF6 gas, enable GIL systems to provide a compact power transmission solution. For example, the outside diameter of the 362kV rated GIL design is only 15 inches (381mm) per phase. With a phase spacing of 22 inches (599mm) center to center, a typical 362kV GIL bus circuit requires a trench of only 6 feet (1.85m) in width.
This compact right of way requirement is less than 10% of what would be required by conventional transmission lines, yet the GIL system can transmit in excess of 3000MVA. GIL’s compact design is also more adaptable to tight space limitations than typical high voltage cable systems because GIL lines can turn corners at extremely sharp angles, unlike the large radius bends required by cable systems. Also, the large current carrying capacity allows the combination of outputs from multiple generator step-up transformers into feeder circuits, resulting in more compact transmission line and GIS arrangements than would be required with cable.