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What is the definition
of a shock absorber?
A careless electrician.
Recall Basics of Electricity
2. Amperage (Current)
What is "voltage"?
Voltage is a measure of the electrical force that
seems to push the current along.
The symbol for voltage is "V".
What is "voltage"?
Think of voltage as a lot of water
stored in a high water tank.
Because the water tank is high,
the water will have more force
behind it as it flows down the
This is why they put water tanks
up high! If the same tank was
placed at ground level, the water
pressure would not be as great.
What is “Amperage"?
Amperage is the unit used to measure the amount of
Amperage is often referred to as "current" by
electrical workers and engineers.
The symbol for amperage is "I".
Let's go back to the water tank.
If diameter of the pipe coming from
the water tank is large, a lot of
water (amperage) will flow through
If the pipe's diameter is small, a
smaller amount will of water flow.
If you need a lot of current to
operate the equipment, you'll need
large wires to run the current.
What is "amperage"?
What is “Resistance"?
Resistance is the unit (ohms)
used to measure the opposition to
the flow of electrical current.
It's that simple. In an electrical
circuit, components are usually
sources of resistance.
Any component that heats up due
to electrical current is a source of
The symbol for resistance is "R".
What is a "circuit"?
A circuit is the complete
path for the flow of
Electrical current may
flow through a circuit in a
series or parallel path.
What's a "series" circuit?
For example, water from high in the mountains may flow down
one stream (series) into a river that flows into the ocean.
What is a Parallel Circuit ?
Ex: The water flowing from a water falls on a hill will flow through
many different water branches (parallel) before it reaches the ocean.
What kills – Voltage or Current ?
A common phrase heard in reference to electrical safety
goes something like this:
"It's not Voltage that kills, it’s Current!"
While there is an element of truth to this, there's more to
understand about shock hazard than this simple adage.
If voltage presented no danger, no one would ever print
and display signs saying:
“ DANGER - HIGH VOLTAGE”
How a Electrical shock occur ?
The principle that "current kills" is essentially correct. It is
electric current that burns tissue, freezes muscles, and
However, electric current doesn't just occur on its own; there
must be voltage available to motivate electrons to flow through
A person's body also provide resistance to current, which must
be taken into account.
Obviously, the more voltage available to cause electrons to
flow, the easier they will flow through any given amount of
resistance. Hence, the danger of high voltage.
Effects of Electricity on the
The four major types of electrical injuries are:
Electrocution Vs Electrical Shock
‘Electrical Shock’ aren’t
‘Electrocuted’ can only be
used when an electrical
shock results in death.
If death does not occur,
the term ‘shocked’ should
The electric shock is caused by a current passing
through the body.
The lethality of an electric shock is dependent on:
Current (the higher the current, the more likely it is lethal);
Duration (the longer the duration, the more likely it is lethal);
Voltage (the higher the voltage, the more likely it is lethal);
Pathway (if current flows through the heart muscle it is
more likely to be lethal).
Severity of Electrical Shock
The severity of injury
from electrical shock
depends on the amount
of electrical current and
the length of time the
current passes through
Touching a live wire
and an electrical
ground will cause a
Touching two live wires
of different voltages
will cause electrical
Electric shock is the passing of electric current through the
The electrical current may
Prevent you from releasing your grip from a live
Throw you into contact with a higher voltage conductor.
Cause you to lose your balance and fall.
Cause severe internal and external burns.
The most common shock-related, nonfatal
injury is a burn.
Burns caused by electricity may be of three types:
Arc burns, and
Thermal contact burns.
An electrical burn is a burn
that results from electricity
passing through the body
causing rapid injury.
For a burn to be classified as
electrical, electricity must be
the direct cause.
An arc flash is a release of energy
caused by an electric arc. The flash
causes an explosive expansion of
air and metal.
The blast produces
A dangerous pressure wave
A dangerous sound wave
Extreme heat & Extreme light.
Temperatures as high as
35,000 F have been reached
These dangers can result in
blast injuries, lung injuries,
ruptured eardrums, shrapnel
wounds, severe burns, and
blindness and can also result
Thermal Contact Burns
Thermal contact burns can
occur when electricity ignites
Thermal contact burns occur
when skin comes in contact
with overheated electric
equipment, or when clothing is
ignited in an electrical incident.
What route avoids your heart?
Right hand to left hand
Right hand to right foot
Right hand to left foot
Left hand to right foot
Left hand to left foot
Always use your right hand when working with live
power- and keep your left hand in your pocket!
What is Electrical Hazard?
An electrical hazard can be defined as:
A dangerous condition where a worker could make
electrical contact with energized equipment or a
conductor, and from which the person may sustain an
injury from shock; and/or,
There is potential for the worker to receive an arc flash
burn, thermal burn, or blast injury due to the electrical
Protection Against Electrical Hazards
Most electrical accidents result from one or more of the
following three factors:
Unsafe equipment or installation,
Unsafe work practices.
Some ways to prevent these accidents are through the
use of insulation, guarding, grounding, electrical
protective devices, and safe work practices.
The Electrical Safety Model
What Must Be Done to Be Safe?
To make sure all employees are safe before, during
and after electrical work is performed, electrical
workers should follow the three-step process.
Electrical Safety Model:
1. Recognize hazards
2. Evaluate risk
3. Control hazards
How do your recognize hazards?
The first step toward protecting yourself is recognizing the many
hazards you face on the job. To do this, you must know which
situations can place you in danger. Some examples to recognize
Exposed electrical parts.
Overhead power lines.
Electrical systems and tools
that are not grounded or
Damaged power tools and
Using the wrong PPE & Wrong
Wires with bad .
Evaluating the Risks
After you recognize a hazard, your next step is to evaluate your
risk from the hazard. The closer you work to the "danger zone,"
the more likely you'll be exposed to the electrical hazard.
Wet conditions combined with other hazards also increase your
risk. You will need to make decisions about the nature of
hazards in order to evaluate your risk and do the right thing to
Another factor increasing your risk of injury is working around
combinations of hazards.
Evaluating the Risks (Contd..)
There may be important clues that electrical
For example, if a GFCI keeps tripping while you are using a power
tool, that's a clue that there is a problem. A GFCI that trips indicates
there is current leakage from the circuit.
Don't keep resetting the GFCI and continue to work. You must
evaluate the "clue" and decide what action should be taken to control
A cable, fuse box, or junction box that feels warm may indicate too
much current in the circuits.
Evaluating the Risks (Contd..)
Some examples of evaluating the Risks.
Tripped circuit breakers.
An electrical tool, wire, or connection that feels warm.
A burning odor of electrical tools, cables, switches etc;
Worn, frayed, or damaged insulation.
Any of these conditions, or "clues," tells you something
important: There is a risk of fire and electrical shock. The
equipment or tools involved must be avoided or rectified.
Control the Hazards
How Do You Control Hazards?
In order to control hazards, you must first create a safe
work environment, then work in a safe manner.
Generally, it is best to remove the hazards altogether
and create an environment that is truly safe.
Use as many safeguards as possible. If one fails,
another may protect you from injury or death.
Earthing & Grounding
Earth is used for the safety of the human body in
fault conditions while Grounding (As neutral earth) is
used for the protection of equipment.
Earthing is a preventive measure while Grounding is
just a return path.
Earthing is accomplished through bonding of a metallic
system to earth. It is normally achieved by inserting
ground rods or other electrodes deep inside earth.
Grounding means connecting the live part to the
earth (for example neutral of power transformer).
Installation of Circuit
Breakers & GFCI:
Circuit Breaker is
provided to protect
equipment, where as
GFCI (Ground Fault
Circuit Interrupter) is
provided to protect the
Provide Double Earthing
Provide double Earthing is
required for welding
machine & electrical tools:
Double earthing gives low
resistance and also if any one
earth is out of order, second
will do the required work of
earthing the equipment.
Treat all conductors as if they are energized until they are
locked out and tagged.
Always test a circuit to make sure it is de-energised
before working on it.
(Lock-Out / Tag-Out) LOTO
Lockout/Tag-out is an essential
safety procedure that protects
workers from injury while
working on or near electrical
circuits and equipment.
Lock-out involves applying a
physical lock to the power
source(s) of circuits and
equipment after they have been
shut off and de-energized.
Provide proper enclosures
Prevent exposure to live electrical parts by isolating them.
Use correct size of cables
Prevent overloaded wiring by using the right size and type of wire.
Use Proper testing appliances
Use approved portable meters and leads, not
improvised test lamps.
Close unused openings
in panels, cabinets,
boxes and fittings
must be effectively
Take proper precautions while working near
overhead power lines.
Best Safety Practice:
Survey the site for overhead
Never get closer than 10 feet
to an overhead power line!
If work beneath live OH power
lines cannot be avoided,
barriers, and warning notices
should be provided.
Safety precautions during Welding
Connect electrical equipment
and work piece correctly.
Use the correct cable size.
Make sure all electrical
connections are tight, clean,
Insulate yourself from work
piece and ground.
Remove metal jewelry.
Use proper PPE.
Other General Factors
Ensure that the locations of all buried electrical cables are
marked before work begins on any excavation.
You can prevent electrical shocks in two ways; de-
energizing the circuit prior to work or using safety
equipment on the energized circuit.
Ensure all rotating machinery components are protected
with proper guards. (Like chains, belts, wheels, fans etc).
Do not work in wet conditions.
Do not attempt to carry out repair works by yourself even if
it is of minor nature.
Electrical accidents don't happen without cause.
Sometimes it's equipment failure; Other times, it's operator
Electrical accidents are often fatal. No device that will
provide 100% protection.
Regardless, properly using required safety equipment
might reduce the seriousness of electrical shocks.
Take the necessary time to properly plan a job, it may help
avoid later delays caused by an accident.
Working with electricity can be dangerous. However,
electricity can be safe if properly respected.