i) Core or conductor:
* It function is carry current.
* Cable may have single or more than single core conductor.
* Conductor are made up of copper or aluminium material
* Cross section of conductor is directly proportional to current. (Cross section of
conductor depends upon current carrying capacity)
* Conductor used is -
* Each core of conductor is provided with suitable thickness of insulation to avoid
short circuit between two conductors.
* The thickness of insulation layer depends on magnitude of voltage for which it
* Commonly used materials for insulation are e.g.:-
◘PVC (Polyvinyl Chloride)
◘XLPE (Cross- linked polyethylene)
iii) Lead (Metallic) Sheath:
* It is provided over insulation.
* To provide the protection of core from entry of moisture, gases or other
damaging liquids (acids & alkaline) in the soil & atmospheric.
* The metallic sheath is made up of lead or lead alloys recently aluminum is also
being used as a metallic sheath.
* Over the metallic sheath there is layer of bedding.
* The function of bedding is protecting the metallic sheath against corrosion & from the mechanical injury due to armouring.
* It is made from fibrous material such as jute, hessian tape
* This layer is over a bedding only for underground cable and not for over head
* Its function is to protect the cable from mechanical injury.
* It covers the bedding, which consists of 1 or 2 layers of galvanized steel wire or
* This layer is last layer which comes over armouring.
* Its function is to protect armouring against rusting and it also helps for easy
handling of cables.
* It is similar to bedding & consists of fiborous material such as jute.