Electrical Safety

Basic Electrical and Safety Precautions

Prepared by:

Objectives Be familiar it! t!e fundamental concepts of electricity.  Be familiar it! t!e effects of electricity on t!e !uman body.  Be able to recogni"e r ecogni"e common electrical !a"ards. !a"ards.  Be familiar it! electrical protective devices. 

#$%&OD'(%#O$ Electrical %erm %erminology inology    

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(oncept of Electricity

(oncept of Electricity Voltage - electrical pressure (water pressure) Amperage - electrical flow rate (gallons/min) Impedance - restriction to electrical flow (pipe friction)

(oncept of Electricity 

%o flo electricity must !ave a complete pat!.

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Electricity flos t!roug! conductors  • ater+ metal+ t!e !uman body

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#nsulators are non-conductors

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%!e !uman body is a conductor.

O!ms /a

E I R I = Current (amperes) E = Voltage (volts)  R = Resistance (ohms)

asic Rules of Electrical Action

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Electricity isnt live until current flos

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Electrical current ont flo until t!ere is a complete loop+ out from and bac, to t!e poer source.

0o electricity or,s 

(urrent flos from a generating source t!roug! conductors+ to a load

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(omplete circuits are needed

0o electricity or,s 

$ormal route is t!roug! conductors

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S!oc, occurs !en t!e body becomes a part of t!e electrical circuit

Proper 1iring #nstallation

Service Entrance

Service

Service E2uipment 

%!e necessary e2uipment+ usually consisting of a circuit brea,er3s4 or sitc!3es4 and fuse3s4 and t!eir accessories+ connected to t!e load end of t!e of service conductors to a building or ot!er structure+ or an ot!erise designated area+ and intended to constitute t!e main control and cutoff of t!e supply.

Service E2uipment

E5isting Practice

/ocation of Disconnecting Means “Shall not”

Electrical Protective Devices 

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%!ese devices s!ut off electricity flo in t!e event of an overload or groundfault in t!e circuit #nclude fuses+ circuit brea,ers+ and ground-fault circuit-interrupters 3G6(#s4 6uses and circuit brea,ers are overcurrent devices • 1!en t!ere is too muc! current:  – 6uses melt  – (ircuit brea,ers trip open

(ircuit protective devices 

(ircuit protective devices include: • •

fuses and circuit brea,ers protect conductors and e2uipment G6(#s - limit or s!ut off current flo

(ircuit Brea,ers •

Provided to protect E7'#PME$% not people

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Do not reset brea,ers it! a line voltage !ig!er t!an 89* and only reset if you ,no !y it tripped

/ocation of (ircuit Brea,ers

&eadily ;ccessible

Ground fault circuit interrupters 

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; fast-acting circuit brea,er t!at senses small imbalances in t!e circuit caused by current lea,age to ground #f a ground fault rated  of a second+ protecting you from a dangerous s!oc,

Ground-6ault (ircuit #nterrupter 

Permissible 'ses of 6le5ible (ords E5amples

Pendant, or  Fixture Wiring

Portable lamp, tool or applian!e

Stationar" e#uipment$ to %a!ilitate inter!hange

'se of 6le5ible (ords  

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• • •

• • 

ro (ords

e

ses o

e5

e

E5amples

Subtitute %or %ixed &iring

Run through &all, !eiling, %loor, door, or &indo&

'on!ealed behind or atta!hed to building ur%a!e

(lues t!at Electrical 0a"ards E5ist %ripped circuit brea,ers or blon fuses  1arm tools+ ires+ cords+ connections+ or junction bo5es  G6(# t!at s!uts off a circuit  1orn or frayed insulation around ire or connection 

&eceptacles

%amper ) &esistant &eceptacles

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Grounding 

1!y Electrical Grounding and Bonding?

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 %!e most controversial and misunderstood concepts in t!e (ode.  %!e most neglected subject by electrical practitioners.  1!en improperly installed+ it may results to p!ysical injuries+ costly damage to electrical facilities or even deat! to individual.  Eac! utility 3poer+ telep!one+ cable %*4 !as its on grounding electrodes.  Electrical Grounding and Bonding circuit follos t!e basic las of electricity.

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Grounding 

Protects you from electrical s!oc,

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Safeguards against fire

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Protects electrical e2uipment from damage

Grounding 

%o types of grounding grounding include: include: • •

Service or system ground E2uipment ground

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Grounded conductor ) a system or circuit conductor t!at is intentionally grounded.

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 Grounding (onductor ) a conductor used to connect e2uipment or t!e grounded circuit of a iring system to a grounding electrode conductor.

Definition of Grounded (onductor 

Definition of Grounded (onductor 

Definition of Grounding (onductor 

Grounded (onductor 

)ot a “neutral” be!aue it i not a * +r ( &ire "tem

#dentifying Grounded $eutral (onductors of Different System

Grounding Electrode

Grounding Electrode for 0ig! *oltage

Proper Grounding

Grounded Properly

Electrical Grounding

Electric S!oc,

6our Main %ypes of Electrical #njuries • • • •

Electrocution 3deat! due to electrical s!oc,4 Electrical s!oc, Burns 6alls

Effects of ;( Electric S!oc,

0uman &esistance od! Area

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