Tuesday, 2 July 2019

General Construction of Underground Cable

General Construction of Underground Cable

The Engineering Street 

The general construction of underground cable. The under ground cable consists of core, paper insulation, lead sheath, bedding, armouring and serving.

Conductor or Core : The conductor is placed at the centre and it is made up of tinned copper or aluminum. The conductor is stranded to get better flexibility. The cable may have one or more (multi ) cores or conductors depends upon service requirements. Figure shows single core cable.

Paper Insulation : Each core or conductor is coated with insulation of impregnated paper, varnished cambre or rubber mineral compound. The thickness of the insulation depends upon voltage rating.

Lead sheath or metallic sheath : A metallic sheath of lead or aluminum is provided over the paper insulation. This sheath protect the cable from moisture, gasses or other damaging liquids like acids or alkalies.

Bedding : Bedding is the layer provided over a lead sheath. It consists of fibrous material like jute or Hessian tape. The bedding is provided in a cable to protect lead sheath against corrosion and mechanical injury.

Armouring : Armouring is a layer of galvanised steel wire or tape, which protects cable from mechanical injury during laying and handling.

Serving : Serving is a layer of fibrous material like jute, similar to that of bedding provided over the armouring, Serving protects armouring from atmospheric conditions.