What is a power cable ? Types of cables

What is a power cable

A cable is an insulated conductor which could carry and transmit electric power, data, signals from one place to another. It is an assembly of two or more conductors usually held together with an overall sheath. Power cables can be installed as permanent wiring within a building, buried in the ground, run overhead


What are the required properties of power cables

  • High resistivity
  • High dielectric strength
  • Low thermal-coefficient
  • Low water absorption
  • Non-inflammable
  • High mechanical and tensile strength

Types of Electric cables

Cables are classified according to the voltage level for it is manufactured and the material which is used for the insulation. Classification of cables according to the voltage level is low tension cables, medium, and tension voltage cables

Belted cables

These cables are used for the voltage level up to 11KV in this the core is not in a circular shape and it is insulated from each other by using impregnated paper. The belt is covered with lead sheath and the gaps are filled with fibrous material like jute.


Screened type cables

They are used at the voltage range of 22-33KV there are two types of screened cables they are

  • H-type cables
  • S.L type cables

H-type cables – in this type of cables no paper belt is used and each conductor is insulated with paper, covered with a metallic screen


S.L cables – These are separate lead screened cables and each lead is insulated with an impregnated paper



  • Core to core fault is minimized because of individual lead sheath
  • Electrical stresses are radial in nature
  • Bending of cable is easy

Super tension cables

These cables are used at the range of 132 – 275KV voltage level. Some methods are used to avoid void formation they are

  • It doesn’t use solid type insulation instead of that it uses low viscosity oils under pressure is used for impregnation
  • It uses inert gas at high pressure in between the lead sheath and dielectric

Oil-filled cables

In this type of cable, the ducts are provided within or adjacent to the core through which oil under pressure is circulated. It consists of the concentric standard conductor but it is built around a hollow cylindrical steel spiral core, which is the channel for oil


  • Insulation thickness is less
  • Thermal resistance is less
  • Void possibility is eliminated
  • Temperature range is high
  • Perfect Impregnation


  • Initial cost is high
  • Long length is not possible
  • Oil leakage


Gas pressure cables

Nitrogen gas is introduced at high pressure to lead sheath and dielectric. Pressure range is about 12-15 atmosphere and the working power factor is high


  • It can carry 1.5 times the normal load current
  • Less maintenance
  • No need for tanks and reservoirs
  • Power factor is improved
  • Possibility of ionization and void is eliminated