Explain Construction of cable with suitable diagram.

(1) Conductors

• Conductors used for cables are generally made up of tinned copper or aluminium.
• To provide the sufficient flexibility conductors are used in stranded form.
• Cable may consists of one, two, three of four conductors depending upon the service required.

(2) Insulation

• The type and thickness of insulation depends upon the voltage level.
• Insulating materials should provide the following properties: High insulation resistance, High mechanical strength, Non-porous, Chemically inert, High die-electric strength, Non-inflammable etc.
• Following are the different materials used for cable insulation: Rubber, Vulcanized India Rubber, Impregnated paper, PVC etc.

(3) Metallic Sheath

• As the cable is placed under ground, soil may present, moisture, gases and some other liquids.
• Therefore to protect the cable metallic sheath made up of lead or aluminium is provided over the insulation.

(4) Bedding

• To protect the metallic sheath from corrosion and some mechanical injury, bedding is provided.
• It is made up of some fibrous material such as jute.

(5) Armouring

• Armouring is used to protect the cable from mechanical injury while handling.
• It consists of one or two layers of galvanised steel wire or steel tape.

(6) Serving

• Serving is provided to protect the armouring from atmospheric conditions.
• It is made up of some fibrous material like jute.