This document provides information about cables used in civil engineering. It discusses the structure and composition of cables, including the conductor, insulation, lead sheath, bedding, and armouring. It describes the manufacturing process of cables and the types of cables, including power cables classified by voltage, core, and armouring. It also discusses networking cables, underground cables, common cable brands in Pakistan, color coding of wires, and factors in determining cable suitability.
3. “Topics”
Intoduction to Cables
Structure / Compostion of Cables
Manufacturing process of Cables
Types of Cables
Brands of Cables in Pakistan
Colour Coding System of Wires
Suitability of Cables
4. Introduction to Cables
The generation, transmission, and distribution of power involve electrical
facilities, apparatus, and components, to carry the electrical energy from its
generating site to where it is utilized. An important part of this power system
is the cable system that is used exclusively to carry power from the main
substations to secondary substations at load centers.
“A cable is an assemblage of two or more wires running side by side and
bonded, twisted or braided together to form a single assembly.
The assembly is used for transmission of electrical power.
5. Structure/Compostion of Cables:
Structure of Cables consist of following parts.
1) Conductor
2) Insulation
3) Lead Sheath
4) Bedding
5) Armouring
6. Structure/Compostion of Cables:
Conductor:
A conductor is the material which allows the flow of current.
An electrical cable consists of a conductor which is usually a copper wire.
The reason of using copper wire is that after silver, copper has excellent
conducting properties and offers less resistance to the flow of current as
compared to other metals. We cannot use silver as it is very expensive so in
order to achieve economy copper is used for the long distance transmission of
electrical power with minimum losses.
Moreover high quality aluminum can also be used depending upon the cable
type.
7. Structure/Compostion of Cables:
Insulation:
Insulation is a protective covering around the cable which prevents it from damage
caused due to water, oil and other chemicals. Moreover it prevents the leakage of
current and damages due to bending. Folllowing are the two types of materials used
in insulation:
1) Polyvinyl chloride:
PVC is widely used in electrical cable construction for insulation, bedding and
sheathing.
This material has good dielectric strength, high insulation resistance and high
melting temperatures.
It is suitable for operating temperature of
70°C degrees celcius.
8. Structure/Compostion of Cables:
2) XLPE ( cross-linked polyethene):
Cross-linked polyethylene is widely used as electrical insulation in power
cables of all voltage ranges
This material has temperature range beyond 250 – 300 C
This material gives good insulating properties
It is light in weight, small overall dimensions, low dielectric constant and high
mechanical strength, low water absorption.
Difference b/w PVC & XLPE :
XLPE Cables have higher current rating and longer service life compared to
PVC Cables.
Under short circuit condition,this cable can withstand up to 250ºC
temperature compared to 160ºC for PVC cables.
XLPE has also higher overloading capacity under emergency conditions.
Hence we can conclude that XLPE is better than PVC.
9. Structure/Compostion of Cables:
Lead Sheath:
It is a metallic sheath of lead or aluminium.
It is usually coated over the insulation.
It is used to protect the cable from moisture,gases or other damaging liquid in
the soil or atmosphere
10. Structure/Compostion of Cables:
Bedding:
Bedding is provided to protect the metallic sheath from corrosion and from
mechanical damage during handling.
It is a fibrous material like jute or hessian tape.
11. Structure/Compostion of Cables:
Armouring:
It consist of two or more layers of galvanized steel wire or steel tape.
It is applied over bedding.
It’s purpose is to protect the cable from mechanical injury while laying or
handling it.
12. Structure/Compostion of Cables:
Serving:
It is a layer of fibrous material which is provided over the armouring.
To protect armouring from atmospheric damages
14. Manufacturing Process of Cable:
Manufacturing process of cable consist of following parts.
1.Conductor
a) Wire Drawing
b) Annealing
c) Wiring /Stranding
2. Insulation
3. Phase Wiring
4. Additional Covering
5. Outer Sheath
15. Manufacturing Process of Cable:
Conductor:
1.1 Wire Drawing:
The first step in manufacturing process consists of reducing the diameter of
the copper wire gradually to its final diameter.
The copper arrives in large coils.
This copper, 8 mm in diameter, is technically known as “wire rod”. The
diameter of the wire rod is reduced to 2 mm during this process.
This 2 mm wire is then drawn further to reduce the diameter of the wire to
the size needed for each kind of conductor
16. Manufacturing Process of Cable:
1.2 Annealing:
After the wire-drawing, all the wires undergo a heat treatment called “annealing”
to increase the ductility and conductivity of the copper.
1.3 Wiring/ Stranding:
In this Step copper wires are grouped together to make conductors with different
cross-sections, e.g. 0.5 mm2 to 240 mm2, 400 mm2 or even higher for larger
current capacities.
2. Insulation:
The next process in the manufacture of electrical cables is the insulation. It
involves the placement of an insulating cover over the conductor to prevent
current leakages.
The insulating material is added by a process of extrusion at high temperature.
Several insulating materials may be used: PVC, EPR, XLPE, etc.
The material’s insulation capacity and its thickness determine the cable’s
maximum service voltage.
17. Manufacturing Process of Cable:
3.Phase Wiring:
Phase wiring is the grouping of different insulated conductors to make a multicore
cable.
The phases can be identified by color or by numbering them.
A voltage test is also carried out on the whole length of the manufactured cable
during this process.
4. Additional Covering:
In some cases, the cable may require additional elements in order to improve its
protection or operation.
Mechanical coverings, also called “armour”, protect the cable from external
damage.
The armour is made from steel or aluminum and can come in the form of metal
strips, wires or braids.
Electrical coverings, also called “screens”, insulate the signals that circulate in
the cable from possible external interference
18. Manufacturing Process of Cable:
5. Outer Sheath:
Cables usually have an outer polymer covering for protection.This is called
the “outer-sheath”.
This sheath protects the conductors and their insulation from external
elements including mechanical aggression, which may occur during the
installation of the cable.
The outer-sheath is applied like the insulation via a process of extrusion at
high temperature.
The sheath may be made from different materials depending on the required
protection level, the final flexibility of the cable, the work environment, etc.
20. Classification of Cables:
Cables can be Classified in the Following catagroies:
1) Power Cables,
2) Networking Cables,
3) Underground Cables,
Power Cables:
A power cable is an assembly of two or more electrical conductors, usually
held 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.
21. Power cables
Classification of Power Cables:
The classification of these cable can be done on the basis of several criteria.
1. On basis of Voltage
2. On basis of Core
3. On basis of Armouring
22. Types of power cable on Basis of Voltages:
1-Low tension cables:
Cable Which Transmit voltage up to 1000 V (1 kV)
2-High tension cables:
These Cable Transmit voltage up to 11 kV.
3-Super tension cables:
These Cable Transmit Voltage from 22kv to 33 kV.
4-Extra high tension cables:
These Cable Which Transmit voltage 33kv to 66 kV.
5-Extra super voltage cables:
These are used for applications with voltage requirement above 132 kV.
23. Types of power cables on Basis of No: of Cores
Single Core Cable:
Single core cables are made up of a single conductor covered by a PVC
insulation.
Conductor Made of mostly Copper or Aluminimum.
These are widely used for domestic purpose.
2 Core Cable:
In Two Core Cable Two Conductor are Covered by PVC Insulation.
The cable only has two cores being live and neutral.
This type of cable is used to connect small appliances
which are double insulated and need no earth.
24. Types of power cable on Basis of Core:
3 Core Cable:
The cable has three cores, a live core, a neutral core and the earth core.
The live and neutral cores are insulated and carry the current to and from the outlet
socket.
The earth is not insulated, except for outer Sheath
and provides a path for the current to flow to ground.
4 Core Cable:
These Cable has 4 core, with 3 live and 1 neutral.
Each of the cores is covered in a colour coded PVC insulation and then grouped
together and covered in a layer known as the sheath (inner sheath) this is then
surrounded by a layer of twisted galvanised steel wire which providing armoured
protection
The armoured layer is then covered in an additional
layer of PVC insulation which protects the armour from rust.
25. Types of power cable on Basis of aurmouring
Armoured Cable:
These are hard wearing power cable designd for
the supply of main Electricity.
These are also called steel wire armoured cable
abbreviated as “SWA”.
It Consist of one or two layers of galvanized steel wire.
The SWA Cable is designed to have mechanical protection, That is why these
cable is often used for external use.
These cable widely use as Main Cable, Power Cable.
These are also used for underground cabling.
These exist from 2 core SWA Cable to 7 Core SWA.
26. Types of power cable on Basis of Armouring:
Unamoured Cable:
Those Cable which have not provided armouring.
Construction of Armoured cable and unamoured
Cable is same except of armouring.
These Cable have not protection against mechanical damage.
These are less expensive then armoured cable.
These cable are installed in protected location, where they can not exposed
to mechanical damage i.e inside wall,
these cable mainly used for control system.
27. Networking Cable:
Cable is the medium through which information usually moves from one
network device to another.
Networking cables are networking hardware used to connect one network
device to other network devices or to connect two or more computers to
share printers,scanners etc.
Different types of network cables,such as coaxial cable,optical fibre cable are
used depending on the network’s.
Types of Networking Cable:
1) Coaxial Cable
2) Optical Fiber Cable
28. Types of Networking Cable
Coaxial Cable:
Coaxial cabling has a single copper conductor at its center.
A plastic layer provides insulation between the center
conductor and a braided metal shield.
It is used to transmit radio frequency signals. It has lower emission losses and
provides protection from electromagnetic interference, allowing signals with
lower power to transmit over long distances.
Uses:
It is used to carry television signals and connect video equipment together.
It carries radio signal and connects the receiver, transmitter and antenna
together.
It is used for connecting computers in local area networks is widely used in
cable broadband.
29. Types of Networking Cable
Optical Fiber cables:
Optical Fibre cables are cables that contains
Several thousands of optical fibres in a protective,
insulatated jacket.
The optical fibres are very thin strands of pure glass, which transmit
information in the form of light.
Modern fiber cables can contain up to a thousand fibers in a single cable.
Uses:
Fibre opticl cables transmits large amount of data at very high speeds.This
technology is therefore widely used in internet cables.
Other uses in Telephone, computer networking, Lighting and decorations.
30. Underground Cables
Underground cable is a cable that is buried below the ground
Undergrounding is the replacement of overhead cables providing electrical
power or telecommunications, with underground cables.
This is typically performed for aesthetic purposes, but also serves the
additional significant purpose of making the power lines less susceptible to
outages during high wind thunderstorms or heavy snow or ice storms.
Uses:
They are used in places where laying overhead cables becomes impossible.
31. Advantages & Disadvantages of Underground Cables
Advantages:
Less subject to damage from severe weather conditions.
Transmission loss is negligible.
More secured compared to overhead cables.
Underground cables have much less danger of conductor theft, illegal
connections.
Disadvantages:
Laying of cables requires excavation which might be difficult in congested
areas.
Undergrounding is more expensive, since the cost of burying cables at
transmission voltages is several times greater than overhead power lines.
Susceptible to damage due to underground water and moisture in the soil.
32. Brands of Cable in Pakistan:
1) Pakistan Cable:
Pakistan Cables is the premier cable manufacturer and market
leader in Pakistan. Since its inception in 1953.
Pakistan cable uses 99.9 percent pure Copper in the manufacturing of wires
and cables.
2) Fast Cable:
Fast Cable is leading and most trusted electrical cable
manufacturer in pakistan. Since its inception in 1985,
Fast Cables one of the most reliable brands in the Cable Industry of Pakistan.
3) Newage Cable:
4) A.G.C Cable:
5) Allied Cables:
33. Colour Coding System of Wires:
The Wire are Cloured Coded to Identify their function.
Black Wires: Hot
The term "hot" is used for source wires that carry power from the electric
service panel to a destination, such as a light or an outlet.
do not use a black wire as a neutral or ground wire, or for any purpose other
than for carrying live electrical loads.
Red Wires: Hot
Red wires are used to designate hot wires.
Red wires are sometimes used as the second hot wire in 240-volt installations.
White or Gray Wires: Neutral
White or gray indicates a neutral wire. It provides a return path to the
current.
34. Colour Coding System of Wires:
White Wires With Black or Red Tape: Hot
When a white wire is augmented with a red or black color marking, this often
indicates that it is being used as a hot wire rather than a neutral wire.
Typically, this is indicated with a band of black or red electrical tape (but
other colors may be used) wrapped around the wire's insulation.
Blue and Yellow Wires: Sometime Hot
Blue and yellow wires are sometimes used as hot wires inside electrical
conduit.
Rarely are blue and yellow wires found in NM cable.
Green Wires: Ground
Green insulated wires are sometimes used for grounding.
Bare Copper Wires: Ground
Bare copper wires are the most common type of wire used for grounding.
36. Suitability of Cables
To determine the suitability of cables we have gauge system :
The term gauge refers to of the diameter (thickness)of the wire so that we
can determine the electrical resistance and the amount of current that can
be safely carried by the wire
There are two internally accepted measures of wire gauge which are the
metric wire gauge(MWG) and the American wire gauge(AWG) standards.
MWG:
This standard provides wire gauge diameter in millimeters for example, a
40 gauge wire would be 4 mm in diameter. As the diameter Increases, the
gauge in metric standard also increases .
37. Suitability of Cables
AWG:
This standardized gauge system provides a common means of producing and
using common dimensions for the diameter of solid, round, non-ferrous wire
in construction.it is opposite to metric system as in this standard as the gauge
number increases the diameter of the wire decreases.
Significance:
By providing wires of appropriate gauge, the structure will experience a
steadier power source and minimum light flicker. Thick wire offers less
resistance so by using thick wires (small gauge value in case of AWG) less
power loss in the form of heat is experienced. Hence, as we can see from the
table that for heavy appliances small gauge wires will be used whereas for
light circuits requiring small amount of current will require large gauge wires.
Otherwise if large gauge wires are used in circuits with large amount of
current so the heating effect due to resistance will cause the wires to melt
and fire hazards may occur.
