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Topic 7 : Electrical hazard
Topic Learning outcome :
1) Describe the definition of Electrical hazard
2) Explain the possible source of electrical hazard.
3) Describe the identifying and assessing technique of
4) Describe the electrical hazard control and prevention
• A dangerous condition such that contact or equipment failure can
result in electric shock, arc-flash burn, thermal burn, or blast.
• How much Electricity is Dangerous?
Electricity – related hazards;
1) Electric shock
• Direct contact with energized electrical conductors 50V or more
can lead to injury.
• 3 factors involved in electric shock:
a) Resistance – the lower resistance of human body, the greater
potential of electrical shock occur.
b) Voltage – the higher voltage, the greater potential of electrical
shock occur. Voltage exceed 50V is dangerous.
c) Current – the higher current, the greater potential of electrical
shock. Current exceed 5mA is dangerous.
Electricity – related hazards;
2) Arc-flash burn
• Contact with live conductor.
• At entry and exit points of electrical current flowing through the
• Electrical current with arc example flash, spark.
3) Thermal Burn
• Electricity is a common cause of many fires.
• The cause of the electrical ignition covers :
a) spark between a conductor
b) Arc- discharge from greater electric power
c) Short circuit
Electricity – related hazards;
• Caused by short circuit or spark from electrical connection
• Example : Short circuit during maintenance job.
5) Electrostatic/ Static electricity
• Effect generates by electrical charge that trapped in the insulation.
• Source of electrostatic discharge include following;
a) Moving large sheets of plastic which may discharge sparks.
b) Vehicle tires rolling across a road surface.
c) Friction between a flowing liquid and a solid surface
The major causes of electrical hazard, e.g. electrical shock :
• Contact with a bare wire carrying current. The bare wire
may have deteriorated insulation or be normally bare.
• Working with electrical equipment that lacks the UL label
for safety inspections.
• Electrical equipment that has not properly grounded.
• Working with electrical equipment on damps floors or other
sources of wetness.
• Static electricity discharge
• Using metal ladder to work on electrical equipment. These
ladders can provide a direct line from the power source to the
ground, again causing a shock
• Working on electrical equipment without ensuring that the
power has been shut off
• Lightning strikes.
Performing the Electrical Hazards Analysis is vital to the safety of
personnel who are or may be exposed to live parts operating at 50
volts or more that are not placed in an electrically safe work
Shock Hazard Analysis
Shock hazard analysis determines the system voltage to which
personnel can be exposed, the protection boundary
requirements and identifies PPE required to minimize shock
In order to appropriately assess the electrical shock hazard
associated with any type of maintenance or repair work it is
necessary to evaluate the procedures or work practices that
will be involved. These practices should be evaluated against
both regulatory and consensus standards requirements as well as
recognized good practice within the industry.
FLASH Hazard Analysis
The Flash Hazard Analysis is performed in order to protect
personnel from the possibility of being injured by an arc-flash.
The analysis also determines the Flash Protection Boundary and
the personal protective equipment that personnel working within
this boundary must use.
The analysis required the available fault current to calculated and
documented at every point in the electrical system
Table A provides a basic formula for calculating the flash
There are various ways of protecting people from the hazards caused
by electricity. These include: insulation, guarding, grounding,
electrical protective devices, and safe work practices.
• One way to safeguard individuals from electrically energized wires
and parts is through insulation. An insulator is any material with
high resistance to electric current.
• Insulators-such as glass, mica, rubber, and plastic-are put on
conductors to prevent shock, fires, and short circuits. Before
employees prepare to work with electric equipment, it is always a
good idea for them to check the insulation before making a
connection to a power source to be sure there are no exposed
Live parts of electric equipment operating at 50 volts or more must
be guarded against accidental contact. Guarding of live parts may
be accomplished by:
• location in a room, vault, or similar enclosure accessible only to
• use of permanent, substantial partitions or screens to exclude
Indoor electric wiring more than 600 volts and that is open to
unqualified persons must be made with metal-enclosed equipment
or enclosed in a vault or area controlled by a lock. In addition,
equipment must be marked with appropriate caution signs.
• Grounding is another method of protecting employees from
electric shock; however, it is normally a secondary protective
• The "ground" refers to a conductive body, usually the earth, and
means a conductive connection, whether intentional or accidental,
by which an electric circuit or equipment is connected to earth or
the ground plane.
• By "grounding" a tool or electrical system, a low-resistance path to
the earth is intentionally created. When properly done, this path
offers sufficiently low resistance and has sufficient current
carrying capacity to prevent the buildup of voltages that may result
in a personnel hazard.
Circuit Protection Devices
• Circuit protection devices are designed to automatically limit or
shut off the flow of electricity in the event of a ground-fault,
overload, or short circuit in the wiring system. Fuses, circuit
breakers, and ground-fault circuit interrupters are three well-
known examples of such devices.
Safe work practice
• These include: de energizing electric equipment before inspecting
or making repairs, using electric tools that are in good repair,
using good judgment when working near energized lines, and
using appropriate protective equipment.
• To ensure that they use safe work practices, employees must be
aware of the electrical hazards to which they will be exposed.
Employees must be trained in safety-related work practices as well
as any other procedures necessary for safety from electrical