Electrical Safety
1
Electricity is the flow of
energy from one place to
another.
Requires a source of power:
usually a generating station
A flow of electrons (current)
travels through a conductor.
Travels in a closed circuit.
2
Circuit -- complete path of the current. Includes
electricity source, a conductor, and the output
device or load (such as a lamp, tool, or heater).
Current -- electrical movement (measured in
amps).
Resistance -- restriction to electrical flow .
Conductors – substances, like metals, with little
resistance to electricity that allow electricity to flow .
Grounding – a conductive connection to the earth
which acts as a protective measure.
Insulators -- substances with high resistance to
electricity like glass, porcelain, plastic, and dry wood
that prevent electricity from getting to unwanted
areas.
3
You will get an electrical shock if a part of
your body completes an electrical circuit by.
Touching a live wire and an electrical
ground
Touching a live wire and another wire at a
different voltage.
4
Severity of the shock
depends on:
Path of current
through the body.
Amount of current
flowing through the
body (amps).
Duration of the
shocking current
through the body.
5
Currents above 10 mA*
can paralyze or “freeze”
muscles.
Currents more than 75
mA can cause a rapid,
ineffective heartbeat --
death will occur in a few
minutes unless a
defibrillator is used . Defibrillator in use
6
Most common shock-
related injury.
Occurs when you touch
electrical wiring or
equipment that is
improperly used or
maintained.
Typically occurs on hands.
Very serious injury that
needs immediate
attention.
7
Electric shock can
also cause indirect
injuries.
Workers in elevated
locations who
experience a shock
may fall, resulting in
serious injury or
death.
8
Electrical accidents are
caused by a combination
of three factors:
Unsafe equipment or
installation.
Workplaces made unsafe by
the environment.
Unsafe work practices.
9
Cover removed from wiring or breaker box
10
Use guards or
barriers
Replace covers
Guard live parts of electric equipment
operating at 50 volts or more against
accidental contact.
11
Conductors going into them must be protected,
and unused openings must be closed
12
Junction boxes, pull boxes and
fittings must have approved
covers.
Unused openings in cabinets,
boxes and fittings must be
closed (no missing knockouts).
Photo shows violations
of these two requirements
13
Hazard - wire too small for the
current .
Example - portable tool with an
extension cord that has a wire too
small for the tool.
The tool will draw more current Wire Gauge
than the cord can handle, causing
overheating and a possible fire WIRE
without tripping the circuit breaker Wire gauge measures wires
The circuit breaker could be the ranging in size from number
right size for the circuit but not for 36 to 0 American wire gauge
the smaller-wire extension cord. (AWG)
14
Wire used depends on operation, building
materials, electrical load, and environmental
factors.
Use fixed cords rather than flexible cords.
Use the correct extension cord.
15
Plastic or rubber
covering is missing .
Damaged extension
cords & tools .
16
Insulate live wires.
Use only cords that are 3-
wire type
Use only cords marked for
hard or extra-hard usage.
Use only cords, connection
devices, and fittings
equipped with strain relief.
Remove cords by pulling on
the plugs, not the cords.
17
Grounding creates a low-
resistance path from a tool
to the earth to disperse
unwanted current.
When a short or lightning
occurs, energy flows to the
ground, protecting you
from electrical shock,
injury and death.
18
Protects you from shock.
If ground fault detected,
GFCI shuts off electricity in
1/40th of a second.
Use GFCI’s on all 120-volt,
single-phase, 15- and 20-
ampere receptacles, or
have an assured equipment
grounding conductor
program.
19
Hazards may result from:
Too many devices plugged
into a circuit, causing
heated wires and possibly
a fire.
Damaged tools
overheating.
Lack of over current
protection.
Wire insulation melting,
which may cause arcing
and a fire in the area
where the overload exists,
even inside a wall.
20
Automatically opens circuit
if excess current from
overload or ground-fault is
detected shutting off
electricity.
Includes GFCI’s, fuses, and
circuit breakers.
Fuses and circuit breakers
are over current devices.
When too much current:
Fuses melt.
Circuit breakers trip
open.
21
Apply locks to power source
after de-energizing.
Tag deactivated controls.
Tag de-energized equipment
and circuits at all points where
they can be energized.
Tags must identify equipment
or circuits being worked on.
22
Use barriers and guards to prevent
passage through areas of exposed
energized equipment.
Pre-plan work, post hazard warnings and
use protective measures.
Keep working spaces and walkways clear
of cords.
Use special insulated tools when working
on fuses with energized terminals .
Don’t use worn or frayed cords and
cables.
Don’t fasten extension cords with
staples, hang from nails, or suspend by
wire.
23
Plan your work with
others
Plan to avoid falls
Plan to lock-out and tag-
out equipment
Remove jewelry
Avoid wet conditions and
overhead power lines
24
If you touch a live wire or other
electrical component while standing
in even a small puddle of water
you’ll get a shock.
Damaged insulation, equipment, or
tools can expose you to live
electrical parts.
Improperly grounded metal switch
plates & ceiling lights are especially
hazardous in wet conditions.
Wet clothing, high humidity, and
perspiration increase your chances
of being electrocuted.
25
Proper foot protection
(not tennis shoes)
Rubber insulating
gloves, hoods, sleeves,
matting, and blankets .
Hard hat (insulated -
nonconductive).
26
Electrical equipment must be:
Listed and labeled
Free from hazards
Used in the proper manner
If you use electrical tools you must be:
Protected from electrical shock
Provided necessary safety
equipment
27
28
