Construction of Under Ground Cable

Construction of Under Ground Cable:

The general construction of under ground cable is shown in below. The various parts of the cable are,

Cores or Conductors: 

• A cable may have one or more than one core (conductor) depending upon the type of service for which it is intended. The conductors are made of tinned copper or aluminum and are usually stranded in order to provide flexibility to the underground cable.

 Insulation:

•  Each core or conductor is provided with a suitable thickness of insulation, the thickness of layer depending upon the voltage to be withstood by the cable. The commonly used materials for insulation are impregnated paper, varnished cambric or rubber mineral compound.

Metallic sheath :  

• In order to protect the underground cables from moisture, gases or other damaging liquids (acids or alkalis) in the soil and atmosphere, a metallic sheath of lead or aluminum is provided over the insulation 

Bedding: 

• Over the metallic sheath is applied a layer of bedding which consists of a fibrous material like jute or hessian tape. It protects the lead sheath against the corrosion and mechanical injury from armouring.

Armouring:

•  Over the bedding, armouring is provided which consists of one or two layers of galvanised steel wire or steel tape. Its purpose is to protect the cable from mechanical injury while laying it and during the course of handling. Armouring may not be done in the case of some underground cables.

Serving:

•  In order to protect armouring from atmospheric conditions, a layer of fibrous material (like jute) similar to bedding is provided over the armouring. This is known as serving.

• Single Core Under Ground cable
• Belted cables
• Construction of Screened cables
• Under Ground Pressure cables