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HT CABLES

COMPONENTS OF HV CABLES
Element
Construction /Purpose
Material
Standards
Conductor
Stranded compacted circular conductors to carry continous
load and short circuit current.
Compacted stranded –
Class 2, Annealed / Plain
Copper/Aluminium
IS:8130 / IEC: 60228
/ BS EN 60228
Conductor
Screen /
Shield
Conductors for cables rated above 3.3 kV are screened with an extruded layer of semiconducting compound. This eliminates the chance of electrical discharge at the interface between conductor and insulation.
Extruded Semiconducting
Compound
IS:7098-Part 2 / IEC:
60502- Part 2 /
BS:6622 / BS:7835
Insulation
The insulation is of natural. Cross Linked Polyethylene with high di-electric strength is extruded over semiconducting conductor screening. Thickness of insulation is as per the relevant tables.
XLPE
IS:7098-Part 2 /
IEC: 60502- Part 2 /
BS:6622 / BS:7835
Non-metallic Insulation screen
Cables rated above 3.3 kV will have a screening consisting of non metallic part, in combination with a metallic part over the insulation. The non-metallic part of the screening consists of either a semiconducting tape applied helically or a layer of extruded semi-conducting compound or both. The conductor screening, XLPE insulation and the non-metallic part of insulation screening are all extruded in one operation by TRIPLE EXTRUSION which eliminates the formation of micro voids during the extrusion and curing resulting in longer life of cables.
Extruded Semiconducting Compound
IS:7098-Part 2 /
IEC: 60502- Part 2 /BS:6622 / BS:7835
Metallic Insulation screen
Bare annealed copper tape / copper wire are applied over insulation screen to carry fault current.
Copper Tape / Wire
IS:7098-Part 2 /
IEC: 60502- Part 2 /BS:6622 / BS:7835
Laying up
Insulated cores are laid up together, interstices filled up with non hygroscopic fillers to make the cable circular. The phase identifi cation of three core cable is done either by coloured strips / numbered applied on the cores.
Non Hygroscopic PVC / Polypropylene
Fiber
Inner Sheath
The cable cores are provided with a common covering of extruded PVC/PE sheath or wrapped plastic tapes as per the requirement of the customer.
PVC / Polyethylene / Halogen Free
IS:7098-Part 2 /
IEC: 60502- Part 2 /BS:6622 / BS:7835
Armour
GI Round wire / Flat wire (Strip) / Double steel tape armouring is applied over the inner sheath in case of three core cables. The direction of lay of armouring is left hand side of final layer.
For single core cables non magnetic armouring is applied over the inner sheath.
GI / Aluminium – Round wire / Flat strip / Double steel tape / Double Aluminium tape
IS:7098-Part 2 /
IS:3975
IEC: 60502- Part 2 /BS:6622 / BS:7835
Outer sheath
The cables are provided with an extruded PVC / PE / LSZH / FR / FRLS outer sheath over the armour. For Single core unarmoured cables the outer sheath is extruded over the non magnetic metallic part of insulation screening. Outer sheath is generally of Black colour, but any other colour as per customer requirement can be provided.
PVC / FR PVC / FRLS PVC / Polyethylene / Halogen Free
IS:7098-Part 2 /
IEC: 60502- Part 2 /BS:6622 / BS:7835
TYPICAL CROSS SECTIONAL VIEW OF SINGLE CORE & THREE CORE CABLES

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