Basic definitions of wires and cables, with little details of their uses.

1. Structure ofan electricwire
BUILDING SERVICES

2. Wires and Cables
Wires and cablesarepurpose built conductors.
Thesize andtype of Wire/Cable must suit the power rating required for
their use. Thehigher the powerthe thicker the Wire/Cable.
WIRES
Domesticandsmall industrywiring
In appliances
CABLES
Smallandbig industries
Distributionlines
Transmissionlines

3. INTRODUCTIONTO WIRES
There are mainly 6 types of wires. They are:
Vulcanised indianrubber wire (V.I.R)
Tough rubber sheathed wire (T.R.S)
Poly vinyl chloride wire (P.V.C.)
Lead alloy sheathedwire
Weather proof wires
Flexible wire

5. A VIR wire mainly consists of a tinned conductorhaving rubber coating.
Tinning of conductor prevents the sticking of rubber to the conductor.
Thickness of rubber mainly depends onthe operating voltage to which wire is
designed.
A cotton bradding is done over the rubber insulations to protect the conductor
against the moisture.
Finally the wire is finished with wax for cleanliness.
Nowadays these wires are not used since a better quality wires areavailable at a
cheaperrate.
V.I.R(Vulcanised Indian Rubber) wires.

7. This type of wire is a modification of V.I.R. wire. It consist of the
ordinary rubber coated conductors with an additional sheath of tough
rubber.
This layer provides better protection againstmoisture and wear and
tear. Also it provides an extra insulation.
These wires are generally availablein single conductor, two
conductors or three conductors.
T.R.S.(Tough Rubber Sheathed) wires.

9. The ordinary wires can be used only at dry places but for damp places
these wires are covered with continuous lead sheaths.
The layer of lead covering is very thin like 0.12 cm thick.
These wires provides little mechanical protections to the wires.
Leadalloysheathedwires.

10. These types of wires are used outdoor i.e. providing a service
connection from overhead line to building etc.
In this type of wire the conductor is not tinned and the conductor is
covered with three braids of fibrous yarn and saturated with water proof
compound.
Weatherproof wires.

11. These wires consists of number of strands instead of a single
conductor. (Strand is a very thin conductor).
The conductor is insulated with P.V.C. material.
These wires are very useful for household portable applianceswhere
flexibility of wire is more important.
Typical specifications
55/.01mm(55 strands of 0.1mm diameter), maximum current 6A,used
for household purposes.
Flexiblewires.

12. A power cable is an assembly of two or more electrical conductors,
usuallyheld together with an overall sheath. The assembly is used for
transmission of electrical power. Power cables may be installed as
permanent wiring within buildings, buried in the ground, run overhead, or
exposed.
Flexible power cables are used for portable devices, mobile tools and
machinery.
INRODUCTION TO CABLES.

13. GENERAL CONSTRUCTION
1. Conductor or Core.
2. Insulation.
3. Metallic Sheath.
4. Bedding.
5. Armouring.
6. Serving.

14. TYPESOF CABLES.
Thetypes of cables basically
decided based on the voltage
level for which it is manufactured
and material used for the insulation
such as paper, cotton, rubber etc. the
classification of cables according to
the voltage levels is,
 Low Tension Cables (L.T. Cables).
Medium and High tension Cables
(H.T.Cables).

15. BELTED CABLES These cables are used for the
voltage level up to 11 kV. The
construction of belted cable is
is shown in fig.
 The cores are not in circular
shape.
 The cores are insulated from
each other by use of impregnated
paper.
 The gaps are filled with fibrous
material like jute.
 The belt is covered with lead
sheath.

16. SUPER TENSION (S.T.)CABLES
The S.T.cables are intended for
132 kV to 25 kV voltage levels.
In such cables, the following
methods are specially used to
eliminate the possibility of
void formation:
Instead of solid type insulation,
low viscosity oils under pressure
is used for impregnation.
Using inert gas at high pressure in
b/w the lead sheath & dielectric.

17. OIL FILLEDCABLES
In case of oil filled cables, the
channels or ducts are provided
within or adjacent to the cores,
through which oil under pressure
is circulated.
It consists of concentric standard
conductor but built around a hallow
cylindrical steel spiral core, which
acts as a channel for oil.

18. CableStructure

19. GASPRESSURE CABLES
An inert gas like Nat high pressure
is introduced lead sheath and
dielectric.
Gas like SF6 is also used in
cables.
Pressure is about 12-15
atmosphere.
Working power factors is
also high.

20. Chandan 1OX13AT016
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