General Construction - HT Cables upto 66 KV (Earthed System)
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 3.3KV grade in the form of an extruded layer of semi conducting extrusion or semi conducting tape 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 or wire is provided. |
Core Shielding :
XLPE insulation, conductor screening and insulation screening 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 with insulation. The formation of voids/protrusions at the interface of the semiconducting layer and insulation, too is eliminated in the triple extrusion process. |
Core Identification :
The Core identification complies with the requirements of IS-7098 (Part II) as shown below :
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Armouring :
Armouring is applied over the inner sheath and normally comprises of Galvanized Steel Strips for multi core cables and galvanized steel wire can be offered as per customer requirements. 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 aluminium 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 screening in case of unarmoured single core cables. This is always black in color for best resistance to outdoor exposure. Outer sheath can be FR / FRLS depend upon customer requirement |
Marking on Outer Shealth :
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. |
- HT-XLPE Cables have longer life as compared to conventional PVC Cables.
- HT-XLPE Cables have a higher conductor temperature rating i.e. 90°C.
- HT-XLPE Cables have a higher emergency overload capacity 130°C.
- Max. temperature limit under short circuit conditions for HT-XLPE Cables is 250°C and 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.
HT 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 Relevant Standard. The following tests are carried out as routine tests on every length of cables manufactured.
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| FLOW CHART FOR MANUFACTURING PROCESS AND QUALITY CONTROL CHECKS FOR XLPE CABLES CONFORMING TO IS:7098(PART-2) 1985 |
HT XLPE-Catalogue
