Diploma i boee u 5 electrical wiring & safety and protection
1. Electrical wiring and safety and protection
Subject: Basics of Electrical Engineering
2. Connectors and switches
• An electrical connector is an electro-
mechanical device for joining electrical circuits as
an interface using a mechanical assembly.
Connectors consist of plugs (male-ended) and jacks
(female-ended). The connection may be temporary,
as for portable equipment, require a tool for assembly
and removal, or serve as a permanent electrical joint
between two wires or devices. An adapter can be
used to effectively bring together dissimilar
3. Factors affecting electrical wiring
1.Durability:-Type of wiring selected for particular
application must be sufficiently durable .It should fulfill
the requirement of the consumer. It should be according to
2.Safety:-As there is danger of loosing life in case of electric
shocks, safety must be observed strictly.
3.Accessibility:-There should be certain prevision for future
4.Cost:-There must be proper balance between convenience
and look of the wiring from installation cost point of view.
5. Types of Wiring
2)CTS wiring or "FRS wiring or batten wiring
3)Metal sheathed wiring or lead sheathed wiring
4)Casing and capping
• The types of wiring to be adopted is dependent on
various factors, viz, durability, safety, appearance,
cost, consumer's budget etc.
• Cleat Wiring
• This System uses insulated Cables sub protected in
• Cleat wiring is recommended only for temporary
installations. The cleats are made in pairs having
bottom and top halves. The bottom half is
grooved to receive the wire and the top half is
for cable grip. Initially the bottom and top cleats
are fixed on the wall loosely according to the
layout. Then the cable is drawn, tensioned and
the cleats are tightened by the screw. Cleats are
of three types, having one, two or three grooves,
so as to receive one, two or three wires. Two
types of cleats.
• Cleat wiring is one of the cheapest wiring
considering the initial cost and labor, and is
most suitable for temporary n :ring. This
wiring can be quickly installed, easily
inspected and altered. When not required,
this wiring could be dismantled without
damage to the cables, cleats and
9. • Care should also be taken ensure that
grooves f porcelain cleats are essential and
the difference in size shall be reasonable.
Care should also be taken ensure that
grooves of porcelain cleats do not
compress the insulation nor be too wide for
a loose fit. Under no circumstances two
wires shall be placed in one groove of the
• Batten Wiring
10. • Advantages:
I) Easy installation.
Materials can be retrieved for reuse.
Flexibility provided for inspection, modifications and
Skilled manpower not required.
Appearance is not good.
Open system of wiring requiring regular cleaning.
Higher risk of mechanical injury.
11. • In this wiring symant. wires •harathed In tough nahlter are
are quite nesIble. They are c. on wooden I eeeee ns with
Oink or Jolts° and nays. on to Me walls or re iiiii us by nat
• IS/T RS WIRING
• h cables are moisture and chemical proof. 'I hey Sr.,
• damp ell 00000 but not •ullable for outdoor use In sunlight.lkS
wiring Is mailable for lighting In low voltage Installations.
• Metal Sheathed or Lead Sheathed wiring: The wiring
is similar to that of CTS but the conductors (two or
three) are individually insulated and covered with a
common outer lead-aluminum alloy sheath. The
sheath protects the cable against dampness.
atmospheric extremities and mechanical damages.
The sheath is earthed at every junction to provide a
path to ground for the leakage current. They are fixed
by means of metal clips on wooden battens. The
wiring system is very expensive. It is suitable for low
13. • Lead-sheathed electrical wiring in Pilot
• Precautions to be taken during installation: The
clips used to fix the cables on battens should
not react with the sheath.
• Lead sheath should be properly earthed to
prevent shocks due to leakage currents.
• Cables should not be run in damp places and in
areas where chemicals (may react with the
lead) are used.
14. • Advantages: Easy installation and is aesthetic in
• Highly durable.
• Suitable in adverse climatic conditions provided the
joints arc not exposed.
• Requires skilled labor-
• 'Very expensive.
• Unsuitable for- eilcolicfli industries.
15. • Casing and Capping:
• It consists of insulated conductors laid inside rectangular,
teakwood or PVC boxes having grooves inside it. A
rectangular strip of wood called capping having same
width as that of casing is fixed over it. Both the casing and
the capping are screwed together at every 15 crns- Casing
is attached to the wall. Two or more wires of same polarity
are drawn through different grooves- The system is
suitable for indoor and domestic installations.
• Cheaper than lead sheathed and conduit wiring.
• Provides good isolation as the conductors are placed apart
reducing the risk of short circuit.
• Easily accessible for inspection and repairs.
• Since the wires are not exposed to atmosphere, insulation
is less affected by dust, dirt and climatic variations.
16. Domestic wiring system
• Accessories required for domestic wiring:-
a)Wire and cable
c)Switch:-They are classified in two types:-
II) Flush switches
According to operation required they are classified as
One way switch
Two way switch
Centre off switch
Double pole switch
push button switch
Table lamp switch
The main advantage of electrical energy is that it can
be transported over large distances to our homes.
Wires carry electricity from power stations to our
18. Electric Shocks
Electricity is dangerous and can kill!!
An electric shock can:
You can get an electric shock from anything which
is plugged in or connected to the mains supply.
• Affect your muscles.
• Affect your nerves.
• Paralyse you.
• Stop your heart beating.
19. Electrical Safety
The wires which carry electricity consist of two parts:
• The metal wires.
• The plastic coating round the metal wires.
20. Electrical Safety
The metal wires act as a conductor of electricity.
The plastic coating acts as an insulator which prevents
people from being electrocuted.
Conductors are materials which allow electricity to
pass through them easily.
Insulators are materials which do not allow electricity
to pass through them easily.
22. The Plug
Most electric cables normally contain three wires:
Each of these three wire have different colours of
• The live wire.
• The neutral wire.
• The earth wire.
23. The Plug
You have to remember the names and colours of each
of these three wires. You also have to remember the
position of each of these three wires in a standard
LIVE BRown BR – bottom right
NEUTRAL BLue BL – bottom left
EARTH Green/Yellow Centre
24. Electrical Safety
Appliances have three safety devices:
• The fuse.
• The earth wire.
• The switch.
These devices are designed to stop you from being
electrocuted and to prevent the appliance from being
25. The Fuse
A fuse is a thin piece of wire which will melt when too
much current passes through it.
A 3A fuse will melt when the current is greater than 3A.
When a fuse has blown, the wire inside it has melted.
Current is a flow of electricity and is measured in amps
26. The Fuse
When the wire melts, all current is stopped from
reaching the appliance and switches it off.
The fuse stops a large current from flowing through the
appliance which could cause wires to overheat, melt or
27. The Switch
Together, the fuse and switch control the amount of
electricity that enters an appliance.
The fuse and the switch are connected to the live wire.
Electricity comes in through the live wire.
If the fuse is blown, or the switch is off, then the
electricity cannot reach the appliance.
28. What can go wrong!
The most dangerous thing that can happen is that the
live wire can become loose inside an appliance and
touches the casing.
This makes the casing LIVE!
If you touch the LIVE casing, you could be electrocuted
as you are providing a path for the electricity to flow.
To prevent electrocution, the earth wire is connected to
the casing of the appliance.
If the live wire touches the
casing, the earth wire
provides a path for the
electricity to flow.
This blows the fuse and switches the appliance off,
leaving you safe.
30. Fault Spotting
Fault What could happen!
bare wires showing Danger of electrocution.
live and neutral wires
The appliance will still
work but when it is
switched off it can still
wrong fuse used The fuse will not blow
when it should and there is
a danger of overheating