Table of Contents

  1. What are Cable Components & Constructional details?
  2. What are the type designations/ nomenclature of cable?
  3. What are different cable types and categories?
  4. Comparison of XLPE cables with PVC cables
  5. What is FRLS H cable?
  6. What are the general Packing practices followed?

What are Cable Components and Constructional details?

* Conductor 

Conductor is a current carrying element made up of Aluminium or Copper with a specific cross section for the assigned rating, having resistance / km within certain specified limits. 

* Electrical Insulation (dielectric) 

Insulation is provided over the conductors to electrically isolate them from one another. Various types of insulating materials used are : PVC, XLPE (Cross Linked Polyethylene), Rubber, Impregnated Paper, etc. 

An insulated conductor is termed as Core. A cable may have one or more cores. In a multiple core cable , the cores are helically stranded together.

In twin, three & multi-core cables, the cores are laid up together with a suitable lay; the outer most layer has right-hand lay and the successive layers are laid with opposite lay direction. 

* Inner sheath (bedding)   

Cables with stranded cores are provided with Inner Sheath applied either by extrusion or by wrapping. It is ensured that the shape is as circular as possible. Inner Sheath is so applied that it fits closely on the laid up cores & it should be possible to remove it without damage to the insulation. Thickness of Inner Sheath is specified in relevant standard and is based on calculated diameter over laid-up cores.   

* Armour  A wire, strip or a tape applied helically over the cable, to protect the cable from penetration by sharp objects, crushing forces, and damage from rodents or boring insects, is termed as Armour.

Armour is applied over the insulation in case of single core cables & over inner sheath in case of twin, three & multi core cables.   

* Outer Sheath   

Outer sheath /Jacket is usually an extruded plastic cover over the laid-up or armoured core. PVC is a common sheathing material. Outer sheath provides mechanical, thermal, chemical and environmental protection. No electrical function is assigned to Outer sheath. The colour of outer sheath is normally black.

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What are the type designations/nomenclature of cable?

TYPE DESIGNATION FOR PVC & XLPE HEAVY DUTY CABLES:  

a)  Letters used in Type Designations:

A = Appearing as a first letter denotes Aluminium Conductor.  

Y = PVC Insulation or PVC Sheath depending on the position in which it appears.

2X = Cross-linked Polyethylene Insulation 

W = Round Steel Wire Armouring  

WW = Double Round Steel Wire Armouring

F = Formed Steel Wire (Strip) Armouring

FF = Double Formed Steel Wire (Strip) Armouring

C = Metallic Screening (Usually of Copper)  

CE = Metallic Screening (Usually of Copper) over each individual core.

Gb = Holding Helix Tape (of Steel)  

Wa = Aluminium Round Wire & Aluminium Formed Wire (Strip) Fa Armouring.

b)  Type Designations:  

AYY- Aluminium Conductor, PVC Insulated, PVC Outer Sheathed Heavy Duty Cables.

AYWY- Aluminium Conductor, PVC Insulated, Galvanised Round Steel Wire Armoured and PVC Outer Sheathed Heavy Duty Cables.  

AYFY-   Aluminium Conductor, PVC Insulated, Galvanised Flat Steel Wire (Strip) Armoured and PVC Outer Sheathed Heavy Duty Cables.  

AYCYAluminium Conductor, PVC Insulated, Metallic Screened and PVC Outer Sheathed Heavy Duty Cable.  

A2XCYAluminium Conductor, XLPE Insulated, Metallic Screened and PVC Outer Sheathed Heavy Duty Cables.  

AYCEFYAluminium Conductor, PVC Insulted, Individual Core Metallic Screened, Flat Steel Wire (Strip) Armoured and PVC Outer Sheathed Heavy Duty Cables.

A2XCEFYAluminium Conductor, XLPE Insulated, Individual Cores Metallic Screened, Flat Steel Wire (Strip) Armoured and PVC Outer Sheathed Heavy Duty Cables.

NOTE: If the first letter A is dropped in the above designations (i.e. YY, YWY, YFY, etc.), they will denote corresponding types with Copper Conductors. YWWGby - ... (Mining) Copper Conductor, PVC Insulated, double round wire armoured and PVC Outer Sheathed Heavy Duty Mining Cables.                        

YFFGby- ... (Mining) Copper Conductor, PVC Insulted double flat wire (strip) armoured and PVC Outer Sheathed Heavy Duty Mining Cables.

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What are different cable types and categories?

Cables can be divided into large number of types based on a combination of classifications as follows:  

* Based on the voltage ratings as low voltage, high voltage, extra high voltage cables, etc. 

* Based on the conductor material, Copper conductor or Aluminium conductor. 

* Based on the insulating material as Paper Insulated, PVC insulated, Rubber insulated, XLPE insulated, etc. 

* Armoured or Unarmoured cables. 

* Based on the sheathing material, as PVC Sheathed, Rubber Sheathed, Lead Sheathed, Aluminium Sheathed, etc. 

* Based on the number of cores as single core, two core, three core, three-and-a-half core, four core, multicore, etc. 

* Based on the cross-section of the conductor. 

* Based on the type of conductor, solid, stranded, sector shaped, etc.   

From above it is evident that the types of cables will differ widely depending upon various factors involved. To facilitate identification and description of the type of cable it is general practice to adopt some form of type designations. With these designations it becomes easier to convey in a few words the right type of cable.

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Comparision of XLPE cables with PVC cables

The important difference is the extra toughness of insulation and, in particular, the ability to withstand much high temperature without deformation due to mechanical pressure. The better physical properties of XLPE enable the insulation thickness to be reduced and hence overall size of the cable. The continuous temperature rating is increased from 70C to 90C and the temperature for short circuit ratings for the cable from 160C to 250C.   

In general, XLPE insulated cables are competitive alternative to PVC cables for industrial use and Paper insulated cables for power supply systems.

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What is FRLS H Cable?

Flame Retardant Low Smoke and Low Halogen cables have improved flame resistant characteristics and emit lower smoke and toxic gases. 

Special features 

  • Reduced flame propagation

  • Low smoke emission

  • Low acid gas generation

Formulation for the FRLS compounds, which are mainly for the sheathing materials, require special ingredients. These cables may have insulation of PVC or XLPE, but sheath is PVC based, suitably compounded to meet FRLS H requirements.

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What are the general Packing practices followed?

Cables are generally received on wooden/steel drum. There is an arrow painted on the flanges of the drum which indicate the direction in which the drum should be rolled. The cable will unwind and become loose if the drum is rolled in the opposite direction. All drums should be stored in such a manner as to leave sufficient space between them for air circulation. In no case should the drums be stored ' on the flat' i.e. with flange horizontal.

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