Power Cables

CONSTRUCTION OF CABLES

Conductor:

The conductors made from E.C. grade aluminium wires are stranded together and compacted. All sizes of conductors of single or three core cables for HT cable are circular compacted.
Conductor construction and testing comply to IS 8130-1984 as amended up to date & IEC: 60228.
Cables with copper conductor are also manufactured by GEMSCAB.

Conductor Screening:

Conductor screening is provided for all cables above 3.3 KV grade in the form of an extruded layer of semi conducting extrusion over the conductor.

XLPE Insulation:

High quality XLPE unfilled insulating compound of natural colour is used for insulation. Insulation is applied by extrusion process and is as per IS:7098 / (Part-2) & IEC: 60502.

Insulation Screening:

The cables rated above 3.3 KV are provided with insulation shielding over the insulation. The screening is provided with an extruded layer of semi conducting compound. Over the semi conducting covering, a metallic screen in the form of copper tape is provided.

Core Shielding:

XLPE insulation and insulation shielding are all extruded in one operation by a special process called Triple Extrusion i.e. all three layers in one operation. This process ensures perfect bonding of inner and outer shielding. The bond prevents the formation of cavities at the surface of the conductor when the cable is subjected to bends. The void formation, at the interface of the semiconducting layer and insulation, too is eliminated even during heating and cooling cycles in the operation.

Core Identification:

The Core identification complies with the requirements of
IS-7098 (Part II) as shown below:
By numerals (1, 2, 3) printed on cores.

OR

By colored strips applied on the cores.
Inner Sheath (Common Covering)
In case of multi core cables, cores are laid up together with suitable non-hygroscopic fillers in the interstices and provided with common covering of plastic tapes wrapping. As an alternative to wrapped inner sheath, extruded PVC inner sheath is also provided.

Armouring:

Armouring is applied over the inner sheath and normally comprise of galvanized Steel Wire or galvanized Steel Strips for multi core Cables. For Mining use and other special applications, double Wire/Strip armoured cables with Tinned Copper wires can also be offered. Single core armoured cables are provided with non-magnetic armour consisting of hard drawn flat or round aluminum wires to avoid magnetic hysteresis losses on A.C. System.

Outer Sheath:

A tough Outer Sheath of Heat Resisting PVC compound
(Type ST2) as per IS : 5831 is extruded over the armouring in case of armoured cables or over non-magnetic metallic tape covering the insulation or over the non-magnetic metallic part of insulation screening in case of unarmoured single core cables. This is always black in color for best resistance to outdoor exposure.

Marking on Outer Sheath

The outer sheath is embossed with GEMSCAB voltage grade, cable size, and year of manufacturing as desired. Cables are also sequentially marked for length at every meter.

Testing and quality control:

XLPE Cables are manufactured under advanced manufacturing and testing facilities. The cables are type tested and routine tested in accordance with IS : 7098 (Part 2) 1985.
The following tests are carried out as routine tests on every length of cables manufactured:
Conductor resistance test
Partial discharge test
High voltage test

Test Voltages:
The following test voltage is applied between conductor and screen / armour.


In order to achieve consistency in quality, in addition to above tests, rigorous quality control measures are taken at every stage of production. Accordingly every batch of raw materials and process cables are tested to check for their physical and electrical properties.

Main Features

HT-XLPE Cables have longer life as compared to conventional PVC Cables
HT-XLPE Cables have a higher conductor temperature rating i.e. 900C
HT-XLPE Cables have a higher emergency overload capacity 1300C
Max. temperature limit under short circuit conditions for HT-XLPE Cables is 2500C. Hence XLPE Cables have higher short circuit rating
Insulation resistance of HT-XLPE Cable is excellent & superior to Identical PVC / PILC Cables
HT-XLPE Cables have high corrosion resistance in polluted atmosphere
HT-XLPE Cables have better properties of resistance to chemical and corrosive gases
HT-XLPE Cables have low installation cost because of light weight, dimensions and are far more flexible
HT-XLPE Cables have better properties to withstand vibrations, hot impacts
Jointing of HT-XLPE Cables is easier and quicker





Features : HT-XLPE Cables have longer life as compared to conventional PVC Cables
HT-XLPE Cables have a higher conductor temperature rating i.e. 900C
HT-XLPE Cables have a higher emergency overload capacity 1300C
Max. temperature limit under short circuit conditions for HT-XLPE Cables is 2500C. Hence XLPE Cables have higher short circuit rating
Insulation resistance of HT-XLPE Cable is excellent & superior to Identical PVC / PILC Cables
HT-XLPE Cables have high corrosion resistance in polluted atmosphere
HT-XLPE Cables have better properties of resistance to chemical and corrosive gases
HT-XLPE Cables have low installation cost because of light weight, dimensions and are far more flexible
HT-XLPE Cables have better properties to withstand vibrations, hot impacts
Jointing of HT-XLPE Cables is easier and quicker