Cables

Control Cables

The main advantages of PVC Cables can thus be summarized as under:
  • The insulation resistance and breakdown strength are practically unaffected by moisture. These cables are thus suitable for laying even under water.
  • Cables can be overloaded for short periods without any appreciable effect on cable life.
  • The cables can be laid vertically and on steep slopes as there is no impregnating compound involved.
  • The cables are flame retardant since PVC ignites with great difficulty and is self extinguishing.
  • These cables are immune to chemicals normally encountered in practice.
  • Due to their lightweight, PVC Cables are easy to install and handle. Small bending rapider permit the termination of these cables in limited space.
  • Low tension PVC Cables do not normally require sealing ends, when terminated indoor. The terminations can therefore be effected quickly and economically.
  • PVC Cables have tough but smooth outer covering and are thus abrasion proof.
  • PVC cables are not affected by vibration.
  • PVC Cables have high short circuit capacity since they can withstand a high transient temperature without any deformation of insulation or displacement of conductor.
  • PVC Cables have a long service life.

General Construction of PVC Cables

Conductor
The conductor shall be composed of plain copper or aluminum wires complying with IS: 8130-1984. Mining Cables to be used in gassy mines shall be of copper conductor only.

Insulation
The conductors are insulated with suitably compounded PVC, which is applied to the conductor by extrusion process.

Core Identification & Colour Scheme
Cores are identified by colour scheme of PVC insulation.

The following colour scheme is adopted.

One core Red, Black, Yellow or Blue
Two Core Red and Black
Three Core Red, Yellow and Blue
Four Core Red, Yellow, Blue and Black (reduced neutral core is also Black)
Five core Red, Yellow, Blue, Black and Light Grey
For cables having more than 5 cores Two adjacent cores (counting and directional) in each layer are coloured Blue & Yellow respectively and the remaining cores are Light Grey.

Inner Sheath
For all cables having two or more cores, a common covering (inner sheath) is provided over the laid up cores either by extrusion or by wrapping of plastic or proofed tapes. Single core cables do not require inner sheath.

Armouring
Depending upon the application, the cables can be armoured. The armouring can be Round Steel Wire or Steel Strips. In case of cables where diameter over the inner sheath does not exceed 13 mm, the armour consists of Galvanished Round Steel Wires; above this size, the armour can be Galvanished Flat Steel Strips or Galvanished Round Steel Wires as per customers' requirement. In case of single core cables intended for use of an A.C. Systems, the armouring shall be of Aluminium Wires/Stripes or any other non-magnetic material.

Armouring of PVC Mining Cables consist of Galvanised Round Steel Wires/Strips, but wherever necessary, a few Tinned Copper Wires/Strips are also included to meet the resistance requirements of armouring for Mining Cables.

Outer Sheath
Over the armouring, or in case of unarmoured mechanical control cables, over the inner sheath (for single core cables over the insulation), a tough outer sheath of PVC is applied by extrusion. This is normally Black in colour. This provides a tough but smooth outer covering to PVC Cables.

Type Designation
The following code is used for designating the type of cable.

Constituents Code
Aluminium conductor A
PVC insulation Y
Steel round wire armour W
Steel strip armour F
Steel double round wire armour WW
Steel double strip armour FF
PVC outer sheath Y

Testing of PVC Cables
Testing is a vital part of cable manufacturing and all raw materials and finished cables are thoroughly tested to ensure quality control. These are classified in three different groups:
  • Routine Tests
  • Type Tests
  • Acceptance Test

Routine Tests
The following tests constitute Routine Tests, which are carried out on each and every length of cable before it leaves the factory :
Conductor Resistance Test
This test ensures that conductor resistance is with the specified limits, thereby ensuring that the continuity of conductor is maintained throughout the cable length and that the conductor has the required cross section area. The DC resistance is measured at room temprature and is then corrected to standard reference temperature at 20°C.
High Voltage Tests
This test ensures that the insulation will safely withstand the rated voltage within permissible normal operation.
Type Tests
These tests are carried out on samples taken from each production lot. They are carried out to prove conformity as regards the general qualities and design to the specification of particular type of cable. These tests are enumerated in the relevant Indian Standards.
Acceptance Tests
The customers can request the various acceptance tests as provided in the relevant Indian Standard to be carried out before accepting the cables.

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Power Cables


General Construction of Power Cables


Conductor 
The conductor shall be composed of plain copper or aluminum wires complying with IS: 8130-1984. Mining Cables to be used in gassy mines shall be of copper conductor only.
Insulation
The conductors are insulated with suitably compounded PVC, which is applied to the conductor by extrusion process.
Core Identification & Colour Scheme
Cores are identified by colour scheme of PVC insulation.
The following colour scheme is adopted.
One core - Red, Black, Yellow or Blue 
Two Core - Red and Black 
Three Core - Red, Yellow and Blue 
Four Core - Red, Yellow, Blue and Black (reduced neutral core is also Black) 

Inner Sheath
For all cables having two or more cores, a common covering (inner sheath) is provided over the laid up cores either by extrusion or by wrapping of plastic or proofed tapes. Single core cables do not require inner sheath.
Armouring
Depending upon the application, the cables can be armoured. The armouring can be Round Steel Wire or Steel Strips. In case of cables where diameter over the inner sheath does not exceed 13 mm, the armour consists of Galvanished Round Steel Wires; above this size, the armour can be Galvanished Flat Steel Strips or Galvanished Round Steel Wires as per customers' requirement. In case of single core cables intended for use of an A.C. Systems, the armouring shall be of Aluminium Wires/Stripes or any other non-magnetic material.
Armouring of PVC Mining Cables consist of Galvanised Round Steel Wires/Strips, but wherever necessary, a few Tinned Copper Wires/Strips are also included to meet the resistance requirements of armouring for Mining Cables.

Outer Sheath
Over the armouring, or in case of unarmoured mechanical control cables, over the inner sheath (for single core cables over the insulation), a tough outer sheath of PVC is applied by extrusion. This is normally Black in colour. This provides a tough but smooth outer covering to PVC Cables.

Type Designation
The following code is used for designating the type of cable.

Constituents Code
Aluminium conductor A
PVC insulation Y
Steel round wire armour W
Steel strip armour F
Steel double round wire armour WW
Steel double strip armour FF
PVC outer sheath Y

Testing of PVC Cables
Testing is a vital part of cable manufacturing and all raw materials and finished cables are thoroughly tested to ensure quality control.
  • Routine Tests
  • Type Tests
  • Acceptance Test

Routine Tests
The following tests constitute Routine Tests, which are carried out on each and every length of cable before it leaves the factory :

Conductor Resistance Test
This test ensures that conductor resistance is with the specified limits, thereby ensuring that the continuity of conductor is maintained throughout the cable length and that the conductor has the required cross section area. The DC resistance is measured at room temprature and is then corrected to standard reference temperature at 20°C.
High Voltage Tests
This test ensures that the insulation will safely withstand the rated voltage within permissible normal operation.
Type Tests
These tests are carried out on samples taken from each production lot. They are carried out to prove conformity as regards the general qualities and design to the specification of particular type of cable. These tests are enumerated in the relevant Indian Standards.
Acceptance Tests
The customers can request the various acceptance tests as provided in the relevant Indian Standard to be carried out before accepting the cables

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XLPE Cables

Conductor
Conductors are made from electrolytic grade aluminium/copper conforming to IS:8130, and are compact circular or compact shaped.
Insulation
HMT XLPE insulated cables are specially made high grade cross-linked polyethylene for insulation by extrusion process.

Core Identification
Different colours identify the cores

Single core Black
Two Core Red & Black
Three Core Red, Yellow & Blue
Four Core Red, Yellow, Blue & Black
Three and half Core Red, Yellow, Blue and reduced neutral core in Black

Laying up
In multi-core cables, cores are laid up as per the above colour scheme, interstices are filled wherever necessary to make the laid up cores circular.

Inner Sheath
Laid up cores are bedded over with thermoplastic material for protection against mechanical and electrical damage.

Armouring
Armouring is provided over the inner sheath to guard against mechanical damage. Armouring is generally of galvanized steel wires or strips (In single core cables used in AC system armouring is by non-magnetic hard aluminum wires/strips). Round steel wires are used where the diameter over the inner sheath does not exceed 13mm. Above 13mm, flat steel strip armour is used. Round wire of different sizes can be provided against specific request.

Outer Sheath
Specially formulated heat resistant black PVC compound confirming to the requirement of Type ST-2 of IS:5831-1984, extruded to form the outer sheath. .


Product Code

Constituents Code
Aluminum conductor A
HMT XLPE insulation 2X
Steel round wire armour W
Steel strip armour F
Steel double round wire armour WW
Steel Double strip armour FF
Non-magnetic (A1) round wire armour Wa
Non-magnetic (A1) strip armour Fa
PVC outer sheath Y


Cable Type Manufacturing Range Relevant Specification
XLPE Power Cables with Aluminum Conductor 1.1KV S/core upto 1000 mm²; Multi-core upto 400 mm² IS 7098/Part-1/1988
Control Cables with copper conductor Upto 61 core IS 7098/Part-1/1988

Know the Superior Product - The LT-XLPE Cables
  • LT-XLPE Cables have longer life as compared to conventional PVC Cables.
  • LT-XLPE Cables have higher conductor temperature rating i.e, 90°C as against 70°C of PVC and hence higher current rating.
  • LT-XLPE Cables have higher emergency overload capacity than PVC Cables (upto 60%).
  • Max. temperature limit under short circuit conditions for LT-XLPE Cables is 250°C as against 160°C for PVC Cables. Hence XLPE cables have higher short circuit rating.
  • The moisture resistance of LT-XLPE Cables is nearly 100 times that of PVC.
  • Insulation resistance of LT-XLPE Cables is very high as compared to PVC Cables.
  • LT-XLPE Cables have high corrosion resistance in polluted atmosphere as compared to PVC Cables.
  • LT-XLPE Cables have better properties of resistance to chemical and corrosive gases.
  • LT-XLPE Cables have low installation cost because of light weight, dimensions and are far more flexible.
  • LT-XLPE Cables have better properties to withstand vibrations, hot impacts.
  • Jointing of LT-XLPE Cables is easier and quicker.
  • LT-XLPE Cables are ideal for transmission and distribution of power.

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FRLS Cables

The specific properties, which are checked for various Flame Retardant Smoke characteristics are evaluated as per norms of prevalent international specifications. Every customer decides its own set of requirements and HMT are in a position to offer a wide range of PVC power cables & electrical power cables to suit these requirements and cover the needs of particular application economically. These tests are to be carried out apart from those physical & electrical tests to evaluate the cable parameters specified in the standards to which it is manufactured.

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Aerial Bunched Cables

Applications
Aerial bunched cables can be conveniently used :

  • In theft prone areas.
  • As replacement of bare lines in Rural areas, in woods and in other localities & narrow streets where the space is limited.
  • As replacement of bare lines where reliability of supply is of prime importance.
  • As replacement of bare lines where high degree of stability of supply voltage is of importance.
  • In hilly terrains where cost of erection of overhead lines or under ground cable becomes very high.
  • As reinforcement of existing system without increasing voltage.
  • For temporary supplies.
Advantages
In comparison of bare overhead distribution lines, ABC has very high reliability in maintaining services because power and neutral conductors are insulated with the best dielectric, resulting in the following advantages : 

1) Less fault rate on account of good protection against line and ground fault by high winds or falling trees or birds especially in hilly areas & forests as encountered in Rural distribution networks.
2) High Insulation resistance to earth in all seasons and polluted atmospheres. Negligible leakage currents and low losses.
3) Multiple circuits of Power and Telephone Cables could be strung in the same set of poles or any ther supports like walls etc.
4) Better adaptability to run concurrently with existing over-head bare conductor system without any interference.
5) High capacitance and low inductance leading to low impedance of lines.
6) Lower voltage drop, higher current carrying capacities, vis-a-vis better Voltage Regulation.
7) Longer spans and longer distance lines are possible with better system stability.
8) Power distribution cables are much safer than bare Conductors.
9) It can be over hung in dense vegetation and forests.
10) Additional connections can be easily and quickly made with hot-line connectors.
11) Total lines costs are reduced. 
12) Maintenance is very easy.
13) Very difficult to tap the AB cables, thus reducing theft which leads to lower distribution loses
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