Gas-Insulated Cables

Compressed-gas insulated transmission lines or cables have been in service since 1968, with over 13 km (circuit length) in operation worldwide at voltages from 145 to 550 kV. The design philosophy and development are reviewed for the "rigid", flexible, and semi-flexible isolated phase lines, the three-conductor lines and the prototype dc gas-insulated cable system. The various designs of insulators, conductors, enclosures, particle traps, and terminations are described, together with the techniques for grounding and corrosion protection, factory and site testing, fault diagnostics, and calculation of current ratings.