ELECTRICAL SAFETY

Secondary Title in 16pt Calibri

 ELECTRICAL INSTRUCTORS
WELCOME TO THE MAJNOON TRAINING CENTRE

Electrical Instructors at the Majnoon Training Centre are:

•John Blades
•Danny Bobis

Between us we have nearly fifty years of experience in the

electrical field in various industries.
OVERVIEW OF MAJNOON TRAINING CENTRE
SMOKING

No Smoking In
Classrooms Or
Buildings. You
Must Use
Designated
Smoking Areas
MOBILE PHONES

Please switch off your

mobile phone or put it
silent while the course is
ongoing.
 TRAINING OBJECTIVES
After completing this unit, you will:
• Be familiar with the basic concepts of electrical
• Safety.
• Understand the potential effects of electric.
• shock on the human body.
• Be able to recognise common hazards
associated
• with electrical work.
• Be familiar with protective devices.
• Be knowledgeable of safe work practices.
 TAKE ELECTRICITY SERIOUSLY
• Electricity is the second leading cause
of death in Industry.
• Electrocutions make up 12% of
construction fatalities annually.
• Over 30,000 non-fatal shocks occur
each year.
• Over 600 deaths occur annually due
to electrocution.

S
 ELECTRICAL ACCIDENTS
• Leading Causes of Electrical Accidents:
– Drilling and cutting through cables
– Using defective tools, cables and equipment
– Failure to maintain clearance distance of 10 feet
– Failure to de-energise circuits and follow Lockout/Tagout
procedures
– Failure to guard live parts from accidental worker contact
– Unqualified employees working with electricity
– Improper installation/use of temporary electrical systems and
equipment
– By-passing electrical protective devices
– Not using RCD or GFCI (ground fault circuit interrupters)
devices
– No earth or ground connection
 HAZARDS OF ELECTRICITY
• Shock – Most common and can cause electrocution or
muscle contraction leading to secondary injury which
includes falls
• Fires – Enough heat or sparks can ignite combustible
materials
• Explosions – Electrical spark can ignite vapors in the air
• Arc Flash - can cause burns ranging from 14,000 degrees
f. to 35,000 degrees f
• Arc Blast – In a short circuit event copper can expand
67,000 times. The expansion causes a pressure wave. Air
also expands adding to the pressure wave
 FUNDAMENTALS OF ELECTRICITY

Like Water In A Garden

Hose

Resistance = Diameter of Hose ater

Flow of W
Example – Larger hose (less resistance),
more water flows

Current = Flow Rate

Voltage = Water Pressure Example – 15 gallons per minute
Example – 45 PSI
 FUNDAMENTALS OF ELECTRICITY
 Electrical current is the flow of electrons
through a conductor.
 A conductor is a material that allows
electrons to flow through it.
 An insulator resists the flow of
electrons.
 Resistance opposes electron flow.
 CURRENT FLOWS IN A CIRCUIT
• Circuits are AC
(alternating current) or
DC (direct current).
• Current is usually AC.
• AC current has five parts:
o Electrical supply.
o Live conductor or wire
(hot).
o Tools itself
o Neutral conductor or wire
(returns current from tool)
o Earth or ground
 EARTH FAULT LOOP

The distribution system is connected to earth at the secondary winding

of the supply transformer. The neutral or star point, of the secondary
output winding is connected to an Earth Electrode in the earth.

The complete circuit taken by the fault current to earth is called the
Earth Fault Loop. The path of the Earth Fault Current is shown in
above.
 HOW SHOCKS OCCUR
• Current travels in closed circuits through
conductors (water, metal, the human body).
• Shock occurs when the body becomes a part
of the circuit.
• Current enters at one point & leaves at
another.
 SHOCKS OCCUR IN THREE WAYS
• Contact with both
conductors
• Contact with one
conductor and ground
• With a tool: contact
with “hot” metal part
and ground (1), (2) &
(3)
 SEVERITY OF THE SHOCK
Severity of the Shock depends on:
Amount of current
• Determined by voltage and resistance to flow
Path through the body
Duration of flow through the body
Other factors such as general health and
individual differences.
 EFFECTS OF CURRENT FLOW
• More than 3 milliamps (ma): painful shock
• More than 10 ma: muscle contraction
• More than 20 ma: considered severe shock
• More than 30 ma: lung paralysis - usually
temporary
• More than 50 ma: possible ventricular fibrillation
(usually fatal)
• 100 ma to 4 amps: certain ventricular fibrillation
(fatal)
• Over 4 amps: heart paralysis; severe burns
EFFECTS OF CURRENT FLOW
Using a 120 volt circuit and resistance for
wet & dry skin:

E=IR: Voltage=Current x Resistance

(Volts) (Amps) (Ohms)

So: I=E/R

Dry Skin =120/100,000=.0012 amps

=1.2ma flowing through
body to ground

Wet skin =120/1000=.120 amps

=120ma flowing through
body to ground

Remember: 1 Amp = 1000 milliamps

 POTENTIAL FAULT CURRENT
Example: a 240 V circuit is protected by a 15
A semi-enclosed fuse and has an earth-fault
loop impedance of 1.6 Ohms

Uo 240
If    150 A
Zs 1. 6
EFFECTS OF CURRENT FLOW
 CONTROLLING ELECTRICAL HAZARDS
• Employers must follow Electrical Standards &
regulations.
• Electrical installation to be tested & inspected.
• Methods of controlling hazard:
– Electrical Isolation
– Equipment Grounding
– Circuit Interruption
– Safe Work Practices
 ELECTRICAL ISOLATION
We can be safe by keeping electricity away
from us:
•Carry effective isolation before working on equipment, Lock
out tag out. Control work on equipment.
•Insulate the conductors.(Example: The insulation on
extension cords)
•Place out of reach the conductors. (Example: Overhead
power line)
•Barrier the conductors by enclosing them (Example:
Receptacle covers, boxes, & conduit)
 INSULATING THE CONDUCTORS
• The to safeguard workers from
electrically energised wires is through
insulation.
• Rubber and plastic is put on wires to
prevent shock, fires, short circuits and
for strain relief.
• It is always necessary to check the
insulation on equipment and cords
before plugging them in.
• Remember, even the smallest defect will
allow leakage!
DEFECTIVE EXTENSION CORDS

Photos depict hazardous condition

 DEFECTIVE CORD INCIDENT
• Worker attempted to
climb scaffold with electric
drill.
• Drill’s cord was damaged
with bare wires showing.
• The bare wire contacted
the scaffolding.
• The worker died!

Depicts hazardous condition

 PLACING OUT OF REACH
• Another way to safeguard workers from
electrically energised wires is by placing them
out of reach.
• Wires are often elevated by the power
company.
• It is always necessary to check the location of
overhead lines before you begin work.
• Remember, never allow yourself, your tools,
or the materials you are working with to be
within 10 feet of energized lines!

Photo depicts hazardous condition

 WORKING NEAR OVERHEAD LINES
Clearance of worker and any equipment, tools,
materials, or scaffold near un-insulated lines is 10
feet!

Photo depicts hazardous condition

 OVERHEAD LINE INCIDENT
• A worker was
attempting to
move mobile
scaffold.
• Scaffold made
contact with 7200
volt line.
• The worker died.

Photo depicts hazardous condition

 BARRIERS
Another way to safeguard workers from
electrically energised wires or equipment is
by using barriers.

Covers, boxes, and enclosures are often put

around conductors to prevent worker contact.

It is always necessary to check that electrical

boxes and panels are covered and free from
missing “knock-outs”.

Also metal enclosures need to be connected to

earth

Photo depicts hazardous condition

BAD BARRIER EXAMPLES

Photos depict hazardous condition

 BARRIERS

Photos depict hazardous condition

 EQUIPMENT EARTHING OR
GROUNDING
• We can be safe by providing a
separate, low resistance pathway
for electricity when it does not follow
normal flow (earth wire).

• Earthing or Grounding gives the

stray current somewhere to go and
keeps you from becoming part of
the circuit.

Electricity always takes the path of

least resistance!
 CAN YOU RELY ON EARTHING OR
GROUNDING?
• Earthing or grounding will not work if the
electricity can flow through you more
easily than the earth conductor. This can
happen when:
– You don’t have an earth connection.
– Your earth conductor has high impedance.
– Your earthing connection is broken.
 WHAT MUST BE EARTHED OR
GROUNDED?
• All circuits and extension
cords.
• All noncurrent carrying
metal parts.
• Portable & semi-portable
tools and equipment
unless double insulated.
 DO NOT ELIMINATE THE EARTH
OR GROUND!

You become the next-best path for current!

Photos depict hazardous condition
 EARTH LEAKAGE
We can be safer by automatically shutting off the
flow of electricity in the event of current leakage,
overload, or short circuit.
• Ground Fault Circuit Interrupters (GFCI)
• Residual current devices (RCD)
• Residual current circuit breaker overload
(RCBO)
• Circuit breakers & fuses
These items protect you the worker and the
equipment .
 CIRCUIT PROTECTIVE DEVICES
• Circuit Breakers and Fuses
– Only protect the building, equipment, and
tools from heat build-up!
– Never depend on circuit breakers or fuses
to prevent shocks!
• RCD, RCBO, GFCI
– Are the only devices which will protect the
worker from shock and electrocution!
GFCI PROTECTION
 HOW A GFCI WORKS
The GFCI detects
‘leakage’ of 4-6
milliamps & opens
the circuit in 1/40th
of a second.

It will work without

the ground plug
but not fast
enough if you are
the ground .
TYPES OF GFCI PROTECTION
 TYPES OF GFCI PROTECTION

A GFCI breaker must be installed to protect

workers using 220V masonry saws.
GFCI TESTERS
 RCD (RESIDUAL CURRENT DEVICE)
Residual Current
Circuit-Breakers
give protection
not only against
fire risk but also
give adequate
protection against
shock risk.
HOW AN RCD WORKS
The current taken by the load is fed through
two equal opposing coils wound on to a
common transformer core. When the
phase and neutral currents are balanced,
(as they should be on a healthy circuit) they
produce equal and opposing fluxes in the
transformer core resulting in no voltage in
the trip coil. If more current flows in the
phase side than in the neutral side, an out
of balance flux will be produced which will
be detected by the fault detector coil. The
fault detector coil opens the DP switch by
energising the trip coil.

Test switch

The test switch is a requirement of BS 842.

The test switch tests only that the circuit-
breaker is functioning correctly and is
operating in the correct order of sensitivity,
as specified by BS 4293.
RCD TYPES
 RESIDUAL CURRENT CIRCUIT
BREAKER OVERLOAD (RCBO)
• RCBO is a residual current
breaker that has an
overload protection. It has
combined functions of the
MCB and RCD in one unit.
It combines the functions
of leakage detection and
over current protection. It
is used to protect the
particular circuit and
mostly to separate RCD
and MCBs.
 CHECKING EARTHING OR
GROUNDING CONTINUITY

What else we should we notice here?

Photo depicts hazardous condition
 PERMANENT EQUIPMENT IN
TEMPORARY USE

What is wrong with using this as a ‘splitter’?

Photo depicts hazardous condition
 EXTENSION CORDS AND CABLES
• Must be in good shape without splices.
• Cannot be secured with staples, nails or bare
wire.
• Must be protected from damage.
• Must have a Earth or ground pin.
• Should be inspected regularly and pulled from
service if defective.
• Cannot be repaired with electrical or duct tape.
Must repair with heat-shrink sleeve or
bonding/vulcanizing tape to retain original
insulation properties.

Photos depict hazardous condition

 SAFE WORK PRACTICES
• Before work begins, the employer must
determine where electrical hazards are
located.(risk assessment)
• Once found, controls put in place.
• Workers need to know the location,
hazards, and protective measures.
 SAFE WORK PRACTICES
• Competent Person determines if
performance of work could bring
contact with energy.
– Distance of the worker to the energy
source should be considered first.
– Tools, materials, and processes should
also be considered to see if they could
potentially shorten the safe separation
distance.
• Examples: Metal Ladders, Re-bar,
Forklift, Scaffold Frames, etc.
 SAFE WORK PRACTICES
• Must not permit work near electric circuits
unless the worker is protected by:
– De-energizing the circuit and grounding it.
– Guarding it effectively by insulation.
– Other means (maintaining safe separation)
• De-energized circuits and equipment must
be locked/tagged out.
 SAFE WORK PRACTICES
• No metal ladders for or near electrical
work.
• No wet hands when plugging or
unplugging cords/equipment.
• No raising or lowering tools by the cord.
• Unless equipment is designed for it,
cannot be used in damp and wet
locations.

Photo depicts hazardous condition

 REVIEW QUESTIONS
True or False?

1.Shocks and Electrocutions are the most common

type of electrical accident and are the fourth leading
cause of worker deaths.

2.The human body will not conduct electricity.

3.It takes at least 1 amp going through a worker to

kill them.

4.Insulation on extension cords & elevating power

lines are examples of protection through isolation.
 REVIEW QUESTIONS
True or False?

5.All portable and semi-portable tools and equipment

must be grounded unless double insulated.

6.You, your tools, and the materials you are working

with, must never be closer than 3 feet of energised
power lines!

7.Electric equipment operating at 50 volts or more

must be guarded!

8.All circuits and extension cords must be grounded.

 REVIEW QUESTIONS
True or False?

9.Circuit breakers and fuses are designed to

protect the worker from electrocution.

10.GFCI protection or Assured Ground Continuity is

required on all temporary circuits.

11. Extension cords are not required to have a

ground prong when they are GFCI-protected.

12.It is OK to work on a circuit which has not been

de-energized.
THE END