1- Conductor or core
: This section consists of single conductor or more than one
conductors. The conductors are also called cores. A cable with three
conductors is called three core cable. The conductors used are aluminium
or annealed copper. The conductors are stranded conductors in order to
provide flexibility to the cable.
2- Insulation
: Each conductors or core is covered by insulation of proper thickness.
The commonly used insulating materials are varnished cambric,
vulcanized bitumen and impregnated paper.
3- Metallic sheath :
The insulated conductors are covered by lead sheath or aluminium
sheath. This provides the mechanical protection but mainly restricts
moisture and other gases to reach to the insulation.
4- Bedding
: The metallic sheath is covered by by another layer called bedding.
The bedding consists of paper tape compounded with a fibrous material
like jute strands or hessian tape. The purpose of bedding is to protect
the metallic sheath from corrosion and from mechanical injury resulting
due to aemouring.
5- Armouring : This layer consists of the layer of galvanized steel wires which provide protection to the cable from the mechanical injury.
6- Serving
: The last layer above the armouring is serving. It is a layer of
fibrous material like jute cloth which protects the armouring from the
atmospheric conditions.
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| Fig. 1 General construction of a cable |
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