Download Electrical Installation - I

Eng. Rose Hasan
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describe the workplace electrical hazards and the importance of safe
work practices.
define Personal Protective Equipment and the importance of wearing
safety clothes.
define safe procedures for using ladders, scaffolds and tools during
Electrical Installation.
identify the different safety signs, and explain their meaning.
identify the different safety signs, and explain their meaning;
5. define the fundamental concepts of electricity such as current,
voltage, resistance, circuit, power, conductors, insulators, AC and
DC;
6. define the concept of ‘circuit’ and differentiate between series and
parallel circuits.
7. troubleshoot faults in simple virtual circuits using the virtual
multimeter and taking into account the safety precautions.
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So lets find the hidden dangers !!!!
 http://www.clp.com/electricsafetyworld/index.html
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Why electricity is dangerous?
 Electrical Shock
 Burns
 Explosion
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How the electrical shock happens ?
› Electrical passing through human body
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What does the severity of a shock
depends on:
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Current (10 mA)
Voltage
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A man receives a shock in two cases:
Current flows between parts of the
body
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Current flows through body to
ground
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The severity of a shock depends on:
› Amount of current.
› The current’s path.
› The length of time.
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Online Activity
› http://kerala.skoool.in/content/KS3%20LOs/s
cience/electricity_rules/index.html
Homework
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In order to work safely you have to do
the following:
› Wear safety clothes
› Use ladders and scaffolds correctly
› Operate tools safely
› Practice safe work habits
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What is PPE ?
What are the
basic pieces of
PPE ?
Gloves
Glasses
Shoes
Flame-resistant
clothing
› Hard hat
› Earplugs
› Face shield
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To access a working area you may need
a ladder or a scaffold.
But you can’t use them without supervision
or training !!!!!!!
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Tips to follow
when you use a
ladder:
› Made of wood
or fiberglass (But
Why ???)
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Should be set at a safe angle (Why???)
Avoid slipping or falling
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How to position the
ladder (safe angle)?
› Use a simple
calculation
› W= ¼*h
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Find the horizontal
distance (w) when
the ladder touches
the wall at a height
(h=20m) ???
› W= ____________ m
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h
W
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The ladder must have a firm support.
Use a ladder leveler
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Tips to follow when
you use a scaffold:
› Wooden
› Wheels must be
locked to prevent
movement
› A ladder must be
used to get onto it.
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Tips to be used before
using electricity:
› Switch OFF the power
before plugging the power
socket.
› Change damaged cord
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Use Insulated tools when required to
work when the power is ON
Insulator
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Wear safety clothes (PPE).
 Turn the power off, and never work on
energized equipment unless it is absolutely
necessary.
 Use proper equipments and tools.
 Maintain good housekeeping (Why ?)
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› Do not leave tools lying around the benches or
workshop:
 to avoid tripping hazards, and lost tools and
materials.
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Take precautions to avoid fire (As what ?).
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Find the 7 deliberate mistakes
(Fill in your Table) !
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Colored Signs & Logos
Displayed at the workplace
Provide safety awareness
They must be obeyed strictly
Different types of safety signs:
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Warning Signs
Advisory/Safe Condition Signs
Mandatory Signs
Prohibitive Signs
Signs for Fire Safety
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Warn of any type
of hazards
 Triangular yellow
with a black
border.
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Provide information
about safe
conditions.
 They are square /
rectangular green
signs with a white
symbol
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Indicate that a
specific course of
action must be
taken
 Circular blue signs
with a white
symbol
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Indicate that a
certain behavior is
not allowed
 circular red signs
with a black symbol
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Shows the location
of fire fighting
equipment.
 They are either
square or oblong
with a red
background.
 Examples include:
fire alarm control,
fire alarm do not
switch off!
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Identify the following safety signs and
indicate the type to which they belong.
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Current:
 Current is the flow of electrons.
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› With no voltage applied, there is no current
flow.
› With more voltage applied, a larger amount
of electrons will flow, which means a higher
current.
› Unit: ampere (A)
› Measured instrument: Ammeter.
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Current flow in a circuit
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Voltage:
 The driving force that causes electrons to
move through a conductor.
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› Called also: electromotive force (emf)
unit: of volt (V)
 Measured Instrument: A voltmeter
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The opposition to the flow of current
through the conductor
 Unit: ohms (Ω).
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› Like other forms of friction, resistance is
responsible for creating heat and loss of
power.
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Measured Instrument: Ohmmeter.
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There are two types of
electric current,
depending on the
direction of the current:
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Direct Current (DC):
current flows in one
direction only.
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Direct Current is provided
by batteries and is used in
battery operated devices
such as flashlights,
automobiles,…
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Alternating Current (AC):
it continually reverses the
direction of flow.
 This change in direction is
represented by the sine
wave.
 voltage supplied to
houses and businesses in
the UAE is 230V.
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AC Circuit
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Converts AC voltage from the power
lines to a constant DC voltage regulated
at various voltage levels.
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Power: The electrical power determines
how fast a certain amount of energy is
consumed by a load.
 Unit: Watts, kilowatts (1,000 watts) and
megawatts (1,000,000 watts).
 Power is calculated using the formula,
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› P = VI = I2R = V2/R.
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Electrical energy is measured in powertime units
 called watt-hours or kilowatt-hours (kWh).
1kWh = 1000 watts power being used for
one hour.
 i.e: The energy consumed by a 100W
lamp that is turned on 5 hours is W = P X t
= 100 X 5 = 500 watt-hours.
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Conductors : a material that allows
current to flow through it easily
 Insulators: a material in which current
movement is difficult
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A multimeter is used to measure current,
voltage and resistance in an electrical
circuit.
 A Digital multimeter (DMM) provides a
digital readout of the measurement
quantity.
 Some digital multimeters also offer the
ability to test some electronic
components.
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To measure current
using a DMM through
the resistor circuit
must first be broken.
The DMM must be set
as an ammeter (the
round function switch
should be in the DC A
position), and it must
be connected in
series with the circuit
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Voltage is always
measured relative to
some other point in a
circuit.
To measure voltage
across the resistor, the
DMM must be set as a
voltmeter (the round
function switch points to
the DC V position), and
must be connected
across / in parallel with
the component
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In a water system, the pathway is the piping,
which moves the water from storage to where
it is used.
In electrical systems, the wires form the
pathway for current to flow.
A simple electric circuit consists of the following
elements:
› Power Source: For a residence, the electrical
generating stations could be considered the power
source. However, batteries could be considered as
primary power sources.
› Conductors: Wires provide a path for the current to
travel.
› Loads: These are devices through which the
electricity produces work. Examples: Lamp and
Motor.
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These devices include switches, fuses
and circuit breakers.
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A load is any device that uses an electric
current and converts the energy to another
form. Loads include the following:
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Series Circuit: In a series circuit, only one
path is provided for the current to flow.
The electricity flows through every
device in the circuit, and if one device
burns out, the circuit will not function.
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Parallel Circuit: The parallel circuit has more than one
path available for the current to flow. Each path
goes to a load that can operate independently of
the other branches and loads in the circuit. If one
load, such as a lamp, burns out, the other branches
would continue to operate.
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Loads such as lamps, heater, or motors
may not operate properly in a series
circuit, and are therefore usually
connected in parallel. Only switches,
fuses, and circuit breakers are generally
connected in series.
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Simutech TEC software/ Edison
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