Gas-Filled Cable

a high-voltage (35-275 kilovolts) electrical cable in which the cavities within the insulating layer (paper tape or synthetic film) are filled with gas (usually nitrogen) under pressure. There are low-pressure (0.07-0.15, meganewtons per sq m [MN/m²]), medium-pressure (0.3-0.5 MN/m²), and high-pressure (1.5-3 MN/m²) types.

Gas-filled cables ordinarily have a common metal sheath containing solid or packed segmented cores covered with several layers of insulating material. They are made in single-core and triple-core types with a lead or aluminum sheath and in triple-core types with a steel conduit. The advantages of gas-filled cables are the ease of supplying a cable line with additional gas and the convenience of producing a cable of great length with preimpregnated insulation, which is especially important in laying underwater cables. However, their insulation has a relatively low dielectric strength, which is dependent to a considerable extent on variations in temperature and gas pressure.