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 ofelectrical hazard.

4) Describe the electrical hazard control and preventionstrategies.

Electrical Hazard definition :

• 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?

Electrical Hazard definition :

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.

Electrical Hazard definition :

Electricity – related hazards;

2) Arc-flash burn

• Contact with live conductor.

• At entry and exit points of electrical current flowing through the

body.

• 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

Electrical Hazard definition :

Electricity – related hazards;

4) Blast

• 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 wiremay have deteriorated insulation or be normally bare.

• Working with electrical equipment that lacks the UL labelfor safety inspections.

• Electrical equipment that has not properly grounded.

• Working with electrical equipment on damps floors or othersources of wetness.

• Static electricity discharge

• Using metal ladder to work on electrical equipment. Theseladders can provide a direct line from the power source to theground, again causing a shock

• Working on electrical equipment without ensuring that thepower has been shut off

• Lightning strikes.

Source of Electrical Hazard :

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

condition.

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

hazard.

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.

Identifying and assessing electrical hazard:

Identifying and assessing electrical hazard:

Shock Protection Boundary

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

protection boundary.

Identifying and assessing electrical hazard:

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.

Insulation

• 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

wires.

Electrical hazard Control & Prevention Strategies

Guarding

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

qualified persons;

• use of permanent, substantial partitions or screens to exclude

unqualified persons;

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.

Electrical hazard Control & Prevention Strategies

Grounding

• Grounding is another method of protecting employees from

electric shock; however, it is normally a secondary protective

measure.

• 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.

Electrical hazard Control & Prevention Strategies

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.

Electrical hazard Control & Prevention Strategies

Training

• 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

hazards.

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Electrical hazard Control & Prevention Strategies