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(1)

Basic Electrical

Basic Electrical

and

and

Safety Precautions

Safety Precautions

Prepared by: Prepared by: Engr.

(2)
(3)

Objectives

Objectives

Be familiar it! t!e fundamentalBe familiar it! t!e fundamental

concepts of electricity. concepts of electricity.

Be familiar it! t!e effects ofBe familiar it! t!e effects of

electricity on t!e !uman body. electricity on t!e !uman body.

Be able to recogni"e commonBe able to recogni"e common

electrical !a"ards electrical !a"ards..

Be familiar it! electrical protectiveBe familiar it! electrical protective

devices. devices.

(4)

#$%&OD'(%#O$

#$%&OD'(%#O$

Electrical %e

Electrical %ermrminologyinology

            (urrent )

(urrent ) t!e movt!e movement of ement of electrical c!argeelectrical c!arge &esistance ) opposition to current flo

&esistance ) opposition to current flo *o

*oltage ) a measure of ltage ) a measure of electrical forceelectrical force (onductors )

(onductors ) substances+ suc! as metals+ t!atsubstances+ suc! as metals+ t!at !av

!ave little resie little resistance to electricitystance to electricity

#nsulators ) substances+ suc! as ood+ rubber+ #nsulators ) substances+ suc! as ood+ rubber+ glass+ and ba,elite+ t!at !ave !ig! resistance glass+ and ba,elite+ t!at !ave !ig! resistance to electricity

to electricity

Grounding ) a conductive connection to t!e Grounding ) a conductive connection to t!e eart! 

(5)
(6)

(oncept of Electricity

Voltage

- electrical pressure (water pressure) Amperage

- electrical flow rate (gallons/min)

Impedance

- restriction to electrical flow (pipe friction)

(7)

(oncept of Electricity

%o flo electricity must !ave a complete

pat!.

Electricity flos t!roug! conductors 

• ater+ metal+ t!e !uman body

#nsulators are non-conductors

(8)

E = Voltage (volts)

 R = Resistance (ohms)

E

I R

O!ms /a

I = Current (amperes)

(9)

Electricity isnt live until current flos

Electrical current ont flo until t!ere is

a complete loop+ out from and bac, to t!e poer source.

(10)

0o electricity or,s

 (urrent flos from a generating

source t!roug! conductors+ to a load

 (omplete

circuits are needed

(11)

0o electricity or,s

 $ormal route is t!roug!

conductors

 S!oc, occurs

!en t!e body becomes a

part of t!e electrical circuit

(12)
(13)
(14)
(15)

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.

(16)
(17)
(18)

/ocation of Disconnecting

Means

(19)

Electrical Protective Devices

%!ese devices s!ut off electricity flo

in t!e event of an overload or ground-fault 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

(20)

(ircuit protective

devices

 (ircuit protective devices include:

• fuses and circuit brea,ers

-protect conductors and e2uipment

• G6(#s - limit or s!ut off current

(21)

• Provided to protect E7'#PME$% not people

• Do not reset brea,ers it! a line

voltage !ig!er t!an 89* and only reset if you ,no !y it tripped

(22)

/ocation of (ircuit

Brea,ers

(23)
(24)

Ground fault circuit

interrupters

 ; 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 <m; above is

detected t!e G6(# can s!ut off

electricity flo in as little as 8=> of a second+ protecting you from a

(25)
(26)

Permissible 'ses of 6le5ible

(ords

E5amples

Pendant, or  Fixture Wiring Portable lamp, tool or applian!e Stationar" e#uipment$ to %a!ilitate inter!hange

(27)

'se of 6le5ible (ords

   • • • • • 

More *ulnerable t!an fi5ed iring

Do not use if a proper iring met!od can be used instead

6le5ible cords can be damaged by:

;ging

Edges of doors+ indos+ e2uipment frames

Staples or fastenings

;brasion from nearby materials 3roc,s+ t!e ground+ ot!er mac!inery4

;ctivities in t!e area

(28)

ro

e

ses

o

e5

e

(ords

E5amples

Subtitute %or %ixed &iring

Run through &all, !eiling, %loor,

door, or &indo&

'on!ealed behind or atta!hed to

(29)

(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

(30)
(31)

%amper ) &esistant &eceptacles

#nsertion of n object in ny one side does not open t!e s!utter 3left4+ but

to-bl ded plug or grounding plug compresses t!e Spring nd simult neously opens bot! s!utters 3rig!t4

(32)

Grounding

1!y Electrical Grounding and Bonding?

 %!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.

(33)

Grounding

 Protects you from electrical s!oc,

Safeguards

against fire

 Protects electrical e2uipment

(34)

Grounding

Grounding

 %o %o types of types of grogrounding inclunding include:ude:

• Service or systemService or system ground

ground

(35)

Grounded conductor ) a system or circuitGrounded conductor ) a system or circuit

conductor t!at is intentionally grounded. conductor t!at is intentionally grounded.

 Grounding (onductor ) a conductor used Grounding (onductor ) a conductor used

to connect e2uipment or t!e grounded to connect e2uipment or t!e grounded circuit of

circuit of a iring system to a groundinga iring system to a grounding electrode

electrode conductor.conductor.

!

! t t is is t!e t!e difdifferference betence beteeneen groun

groun ded ded conductor conductor nd nd grougrou ndingnding conductor?

(36)

Definition of Grounded (onductor 

(37)

Definition of Grounded (onductor 

(38)

Definition of Grounding

Definition of Grounding

(onductor 

(39)

Grounded (onductor 

(40)

#dentifying Grounded $eutral

(41)

Proper iring St rts it! t!e &ig!t (olor 'sed in (ond uctor 1iring

(42)
(43)

Grounding Electrode for

0ig! *oltage

(44)
(45)
(46)

Electrical

Grounding

(47)
(48)
(49)
(50)
(51)

6our Main %ypes of

Electrical #njuries

• Electrocution 3deat! due to electrical s!oc,4

Electrical s!oc,Burns

(52)
(53)

od! Area

"#$%

&r! %'in

*

+et %'in

,*

Internal "rgans -

Ear to Ear

,

0uman &esistance

(54)

. Volts

,* "#$ = . amps (. mA)

. Volts

 , "#$ = . amps (. mA)

(55)

,-0 mA = shoc'* not painful 0-,. mA = 1ain

,.-2 mA = $uscle contraction

2-, mA = %evere pain 3 paral!sis of 4reathing muscles

,-, mA = Ventricular fi4rillation (5suall! cause death)  6 ,* mA = #eart stops

(56)

Electricitys

P!ysiological Effect

 .8 amps  .8< amps  .9 amps  .8  8.9  8<.  Barely felt

“let go” thresholdMuscular paralysisVentricular fibrillation100 Watt light bulb

(57)

Dangers of Electrical

S!oc,

(urrents greater t!an @<

m;A can cause ventricular fibrillation 3rapid+

ineffective !eartbeat4

1ill cause deat! in a fe

minutes unless a

defibrillator is used

@< m; is not muc! current

 ) a small poer drill uses  times as muc!

- m. / milliampere / 101,+++ o% an ampere

(58)

Electrical Burns

 Most common s!oc,-related+ nonfatal injury  Occurs !en you touc!

electrical iring or e2uipment t!at is improperly used or maintained

%ypically occurs on t!e !ands

 *ery serious injury t!at needs immediate

(59)

6alls

 Electric s!oc, can also cause indirect or secondary injuries  1or,ers in elevated locations !o

(60)

0o is an electrical s!oc,

received?

1!en to ires !ave different potential

differences 3voltages4+ current ill flo if t!ey are connected toget!er 

• #n most !ouse!old iring+ t!e blac, ires are at 88 volts relative to

ground

%!e !ite ires are at "ero volts

because t!ey are connected to ground

#f you come into contact it! an

energi"ed 3live4 blac, ire+ and you are also in contact it! t!e !ite grounded ire+ current ill pass t!roug! your body and CO' 1#// &E(E#*E ; S0O(

(61)

0o is an electrical s!oc,

received?

3contd4

 #f you are in contact it! an energi"ed ire or any energi"ed electrical

component+ and also it! any grounded object+ CO' 1#// &E(E#*E ; S0O(

Cou can even receive a s!oc, !en you are not in contact it! a ground

#f you contact bot! ires of a 9>-volt

cable+ CO' 1#// &E(E#*E ; S0O( and possibly be electrocuted

(62)

Overload 0a"ards

#f too many devices are plugged into a circuit+ t!e current ill !eat t!e ires to a very !ig! temperature+

!ic! may cause a fire  #f t!e ire insulation

melts+ arcing may

occur and cause a fire in t!e area !ere t!e overload e5ists+ even inside a all

(63)

Over!ead Poerline

0a"ards

 Most people dont reali"e t!at over!ead poerlines are usually not insulated  Poerline or,ers need

special training and personal protective

e2uipment 3PPE4 to or, safely

 Do not use metal ladders ) instead+ use fiberglass

ladders

Beare of poerlines !en you or, it!

(64)

Grounding Pat!

 %!e pat! to ground from circuits+

e2uipment+ and

enclosures must be permanent and

continuous

*iolation s!on !ere is an e5tension cord it! a missing

(65)

Guarding of /ive Parts

 Must guard live parts of

electric e2uipment operating at < volts or more against accidental contact by:

;pproved

cabinets=enclosures+ or 

• /ocation or permanent partitions ma,ing t!em

accessible only to 2ualified persons+ or 

• Elevation of  ft. or more above t!e floor or or,ing surface

(66)

Guarding of /ive Parts

Must enclose or guard electric e2uipment in locations !ere it

ould be e5posed to p!ysical damage

*iolation s!on !ere is p!ysical damage to

(67)

(abinets+ Bo5es+ and

6ittings

Function bo5es+ pull

bo5es and fittings must !ave approved covers

 'nused openings in

cabinets+ bo5es and

fittings must be closed 3no missing ,noc,outs4

P!oto s!os violations

of t!ese to re2uirements

(68)

 %!e ;EG( program is an

inspection program covering:

• all cord sets

• receptacles t!at are not part of a

permanent iring structure

• e2uipment connected by cord and

plug

;ssured E2uipment

Grounding (onductor

program

(69)

 E2uipment must be visually

inspected for damage=defects before eac! days use

;ssured E2uipment

Grounding (onductor

program

(70)

 %ests must be performed:

• before t!e first use of ne

e2uipment

• after suspected damage to

e2uipment

• at t!ree mont! intervals

 – continuity test

 – grounding conductor test

;ssured E2uipment

Grounding (onductor

program

(71)

/oc,out=%agout

 Electrical e2uipment

deactivated for repair must be loc,ed out and tagged at t!e

point !ere it can be energi"ed

 Protects maintenance or,ers

 1arns ot!ers t!at or, is being

(72)

/oc,out=%agout

 Only t!e person !o

loc,ed=tagged t!e e2uipment can turn it bac, on

 Before e2uipment is energi"ed+ a 2ualified person must conduct tests and visual inspections

(73)

/oc,out=%agout

 Eac! loc,=tag must be removed

(74)

/oc,out=%agout

 #f t!e employee is absent+ t!e loc,=tag can be removed by a 2ualified person if:

• t!e employee !o applied t!e loc,

!as left t!e premises

• it is visually determined t!at all employees are clear of t!e

(75)

Guarding re2uirements

 ;ny live parts of electrical

e2uipment operating at < volts or more must be guarded to

(76)

Guarding re2uirements

 Entrances to areas it! live

electrical parts must be mar,ed it! arning signs

 Signs s!ould

forbid entrance e5cept by

(77)

#nsulation

 (!ec, e2uipment daily for

insulation brea,don  (!ec, for:

• e5posed ires

• bro,en ires

• scuffed insulation on e5tension

(78)

Dos and

Donts

Dos and

Donts

 lug poer e2uipment into all

receptacles it! poer sitc!es in t!e Off position.

unplug electrical e2uipment by

grasping t!e plug and pulling. Do not pull or jer, t!e cord to unplug t!e

e2uipment.

 Do not drape poer cords over !ot

(79)

Dos and

Donts

Dos and

Donts

 Do c!ec, t!e receptacle for

missing or damaged parts.

 Do not plug e2uipment into

defective receptacles.

Do c!ec, for frayed+ crac,ed+ or e5posed iring on e2uipment

(80)

 c!ec, for defective cords clamps

at locations !ere t!e poer cord enters t!e e2uipment or t!e

attac!ment plug.

E5tension cords s!ould not be used

in office areas. Generally+ e5tension cords s!ould be limited to use by

maintenance personnel

Dos and

Donts

Dos and

Donts

(81)

Dos and

Donts

Dos and

Donts

 H(!eater plugsI+ e5tension

cords it! junction bo5

receptacle ends or ot!er injury-rigged e2uipment s!ould not be used.

(82)

Dos and

Donts

Dos and

Donts

 (onsumer electrical e2uipment

or appliances s!ould not be

used if not properly grounded. 3/oo, for t!e '/ /abel4

(83)

 Employees s!ould ,no t!e location of electrical circuit brea,er panels t!at control

e2uipment and lig!ting in t!eir respective areas. (ircuits and

e2uipment disconnects must be identified

Dos and

Donts

Dos and

Donts

(84)

Dos and

Donts

Dos and

Donts

 %emporary or permanent storage of

any materials must not be alloed it!in  feet of any electrical panel or electrical e2uipment.

;ny electrical e2uipment causing

s!oc,s or it! !ig! lea,age

potential must be tagged it! a Danger tag or e2uivalent.

(85)

Myt!s and

Misconceptions Myt!s and

Misconceptions

Electricity ta,es t!e pat! of least

resistance.

Electricity ants to go to ground.

 #f an electric tools falls into a sin, or

(86)

Myt!s and

Misconceptions

Myt!s and

Misconceptions

 ;( reverse polarity is not !a"ardous.

 #t ta,es !ig! voltage to ,illJ 89 volts is not dangerous.

 Double insulated poer tools

are doubly safe and can be used in et and damp locations.

(87)

#nsulation

 'se non-conducting mats+

s!ields+ or barriers !en necessary

 'se

non-conducting coatings on !and tools

(88)

Personal protective

e2uipment

 Employers must provide

electrical protective e2uipment to employees

!o or, near electrical

(89)

Personal protective

e2uipment

 'se appropriate e2uipment for

t!e !a"ards+ including:

• !elmets

• eye and face

protection

• gloves and

sleeves

• aprons

(90)

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