Flexible gas insulated cable for high power transmission

The dielectric losses which increase as the square of voltage and limit power transmission capacity of paper/oil impregnated isolated cables were studied. This limitation disappears by using gas insulation. Tube transmission lines isolated with SF6 gas were developed. Their conception was paired with a lot of inconveniences: short length, numerous connections, special curved sections and necessity of dilation joints. A test cable was fabricated from Al wire conductors, epoxy resin spacer insulators, and an external sheath of 3 mm thick Al-Mn alloy strip. A special high tension testing device was also constructed. The development of such a cable for 220 kV and of its components involved electric field computations, electrical, mechanical, and thermal measurements, elaboration of test and calculation methods, manufacture and testing of cable samples. Tests show that the transmission capacity of the cable in air surpasses 1000 MVA. Due to the limits set by the sheath diameter and the gas pressure, the 380 kV level cannot be attained with the design.