Gas filled cables are used in many applications. In these cables, the insulation is filled with gas, usually nitrogen. The inert gas fills up the voids which may form in the insulation. There are low pressure and high pressure variants in this type of cable.
The gas is filled in the insulation and is enclosed by means of a sheath. Since Nitrogen is easily available, any losses can be easily replaced during installation.
However, the gas has a low dielectric strength. It cannot be used at very high voltages. Gas filled cables can be used up to 275 kV.
Oil Filled cables have almost replaced Gas filled cables in recent times. However, there are situations where oil filled cables cannot be used such as undersea applications and in hilly terrain.