Wire and cable
The use of Conductors and their insulation is regulated by Indian Electricity (IE) regulation and Indian Standard (IS) Code of Practice. Wires and cables are the most common forms of conductors.
They carry electric current through all types of circuits and systems. A conductor is a wire or cable or any other form of mental, suitable for carrying current from generating station the point where it is used.
Difference Between Wire and Cable
According to Bureau of Indian Standards (BIS), wire and cable can be defined as follows:
Bare Conductors: They have no covering. The best example is overhead transmission and distribution lines.
Wire: If bare conductors are provided with Insulation, then it is known as a wire. The insulation separates the conductor electrically from other conductors.
Cable: It consists of two or more conductors covered with suitable insulation and surrounded by a protecting cover. The necessary requirements of a cable are that it should conduct electricity efficiently, cheaply, and safely. This should neither be so small that it has a large internal voltage drop nor be too large
so that it costs too much. Its insulation should be such that it prevents leakage of current in unwanted direction to minimize risk of fire and shock.
The cable essentially consists of three parts
(i) Conductor or core- the metal wire, or strand of wires, carrying the current
(II) insulation of dielectric- a covering of insulating material to avoid leakage of current from the conductor and
(iii) protective covering for protection of insulation from mechanical damage
Basically, there is no difference between a cable and a wire. It is a relative term. The term cable is used for all heavy section insulated conductors, whereas a wire means a thin (i.e., smaller) section insulated conductor used for carrying current from one point to another point.
Classifications of Wire / Cables
The wires/ cables used for domestic or industrial wiring are classified into different groups as follows :
(i) According to the conductor material used
(a) Copper conductor cables
(b) Aluminum conductor cable
(ii) According to number of cores
(a) Singles core cable (SCC)
(b) Double core or twin core cables (DCC)
(c) Three core cables
(d) four core cables
(e) Two core with earth continuity conductor cables
(iii) According to type of insulation
(a) Vulcanized Indian rubber (VIR) insulated wires/cables
(b) Tough rubber sheathed (TRS) or cable tyre sheathed (CTS) cables
(c) Polyvinyl chloride (PVC) cables
(b) Lead sheathed cables
(e) Weather proof cables
(f) Flexible cords and cables
(g) XLPE cables
(IV) According to the voltage at which they are manufactured
(a) Low tension (LT) cables – up to 1000V
(b) High tension (HT) cables – up to 11kV
(c) Super tension (ST) cables – from 22-33kV
(d) Extra high tension (EHT) cables – from 33-66kV
(e) Extra super voltage cables – beyond 132 kV
Specifications of Cables
Cables are specified by providing
(i) Size of the cable in metric system (e.g., 19/2.24, 7/1.70, 7/2.24, 7/2.50 etc) giving the Number of strands used and diameter of each strand, or giving the area of cross- section of conductor used.
(ii) Type of conductor used in cables (copper or aluminium)
(iii) Number of cores that cable consists of e.g. single core, twin core, three core, four core etc.
(iv) Voltage grade (240/415V or 650/1100V grade)
(v) Type of cable with clear description regarding insulation, shielding, armouring, bedding etc.
A few specifications of a cable are given below
(i) 7/20, VIR, aluminum conductor, twin core,650/1100 grade. in this case, the numerator 7 indicates the number of stands in cable and denominator 20 represents the gauge number of each strand. The cable has two cores made with Aluminum, With VIR insulation and is used for 650/1100 voltage
(ii) 19/1.12, aluminium conductor,3 ½ core, 1100V, PVC cable, PVC sheathed. in this case, the cable consists of 19 strands, each strand has a diameter of 1.12mm. The conductor is made with aluminium, insulation is made with PVC, is covered with PVC sheathing, and is used for 1100Vsupply system.
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