3.Electrical Safety

7/25/2019 3.Electrical Safety

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INTRODUCTION

Three Important Commodities Air ,

Water and Electricity

!e"tri"it# C!ean and $$i"ient $orm o$ner%#

Respe"t !e"tri"it# it respe"ts #o&

Dire"t Wor'in% n%ineers, Te"hni"iansand (ro$essiona!s

Indire"t Wor'in% )er# Indi)id&a!


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!e"tri"it#+

orm o$ ner%# i-e- po.er to do or mo)ethin%s

enerated in po.er p!ants

ro&%ht to &sers termed !oads thro&%htransmission !ines distri3&tion !ines

When a de)i"e is p!&%%ed in "ir"&it is "omp!eted

!e"tri"it# tra)e!s thro&%h "ond&"tors A! / C&

4&man 3od# a %ood "ond&"tor most!# .ater

!e"tri"it# propa%ates at 5(D o$ i%ht *00m/&s


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!e"tri"it# + Contd8

Ins&!ators Con$ine !e"tri"it# !ass

(!asti" Cerami" R&33er

I$ Ins&!ation 9 dama%ed or 3ro'en !e"tri"it# !ea's "a&ses sho"'

I$ an o&t!et o)er!oaded Ins&!ation

o)erheats and me!ts

:; ire or 5ho"'


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Therma! Radiation

1- de%ree o$ in?&r# depends on 5'in Co!or, area o$"onta"t and t#pe o$ "!othin%

2- Einimi>ed 3# (roper C!othin%, maintainin% .or'in%distan"es and o)er9"&rrent prote"tion

(ress&re Wa)e eneration

1- 4i%h ner%# Ar"in% a&!ts !ead to 4i%h (ress&re

2- T#pi"a!!# 2F a.a# $rom 2< 'A press&re eGperien"ed 70

po&nds*- eads to serio&s ear dama%e memor# !oss d&e to

mi!d "on"&ssions


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Ar" !ast 4a>ards Contd8

(ro?e"ti!es

1- (ress&re .a)es prope! !ar%e o3?e"ts o)er "onsidera3!e

distan"es

2- no&%h to me!t "opper and a!&min&m "omponents

*- &rns more intense than in?&r# $rom pro?e"ti!es

Gp!osions

1- o""&r d&e to i%nition o$ eGp!osi)e miGt&res in the

atmosphere or en)ironment2- !amma3!e )apors %enerated 3# so&r"e and pro"ess

*- I%nition d&e to o)erheated "ond&"tors or e&ipment or

norma! ar"in% at s.it"h "onta"ts

E-5&dha'aran


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!e"tri"a! ires

!e"tri"it# is most "ommon "a&se o$ ire 3othat home and in o$$i"e

Eain "a&se is &se o$ de$e"ti)e e!e"tri"a!

e&ipment and mis&se o$ e!e"tri"a! apparat&s 4i%h resistan"e "onne"tions 3ein% primar#

so&r"e o$ i%nition

4i%h resistan"e "onne"tions o""&r either d&e to

improper sp!i"in% o$ .ires or improper"onne"tion o$ re"epta"!es/ s.it"hes spe"ia!!#.hen emp!o#in% a!&min&m "ond&"tors


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$$e"t o$ 5ho"' on 4&man od#

a"tors responsi3!e

1- C&rrent

2- o!ta%e

*- Resistan"e

7- (ath Thro&%h the 3od#


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Electric

Current(1

second

contact)

Physiological Effect

1 mA Threshold of feeling, tingling sensation.

5 mA Accepted as maximum harmless current

1!"

mA

#eginning of sustained muscular contraction ($Can%t let go$

current.)

1!&

mA

'entricular firillation, fatal if continued. espiratory function

continues.

* A

+ustained entricular contraction follo-ed y normal heart rhythm.

(efirillation). Temporary respiratory paralysis and possily

urns.


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Electric Current

(1 second contact)

Voltage required to producethe current with assumedbody resistance:

1 mA 1 ' 1 '

5 mA 5 ' 5 '

1!" mA 1 ' 1 '

1!& mA 1 ' 1 '

* A * ' * '

1, ohms 1, ohms


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5ho"' (arameters

C&rrent = )o!ta%e

1- Tho&%h at 4i%h o!ta%es massi)e

destr&"tion at the point o$ "onta"t

2- C&rrent "a&ses detrimenta! e$$e"t o$ !e"tri"sho"',

*- Tho&%h I : )/r ho!ds %ood, "onta"t resistan"e

)aries dependin% on !o"a! "onditions7- A!! domesti" app!ian"es "an %i)e $ata! "&rrents


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ina!!# !eads to death

entri"&!ar $i3ri!!ation is a se)ere!#a3norma! heart rh#thm arrh#thmia that "an

3e !i$e9threatenin%-
http://www.ncbi.nlm.nih.gov/pubmedhealth/n/pmh_adam/A001101/http://www.ncbi.nlm.nih.gov/pubmedhealth/n/pmh_adam/A001101/


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Resistan"e

aries .ith

1- Eoist&re Content

2- (ress&re at the Conta"t (oint

*- Area o$ Conta"t

pidermis presents )er# hi%h resistan"e &nder dr#"onditions, 3e"omes !o.er .hen .et, or d&e to "&ts or3rea' in s'in

5ho"' se)erit# hi%her

1- With in"rease in "onta"t press&re

2- With in"rease in "onta"t area Resistan"e de"reases .ith )o!ta%e D&e to ro'en s'in at hi%her )o!ta%es


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C&rrent (aths

(ath A$$e"ts the de%ree o$ in?&r#

5ma!! "&rrent $rom one eGtremit#, thro&%hheart, to the other eGtremit# "a&ses

se)ere in?&r# or e!e"tro"&tion When "&rrent $!o.s thro&%h a portion o$

!im3 .itho&t passin% thro&%h tr&n' ma#

"a&se on!# 3&rnin% o$ !im3s O$ten path in)o!)es arms to !e%s thro&%h

heart and !&n%s !eadin% to $ata! sho"'


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5ho"' D&ration

Net e$$e"t depends on d&ration

5hort d&ration ma# %i)e pain$&! eGperien"e

L100 mA e)en $e. s o$ sho"' "an 3e $ata!

Remem3er !i%ht d&t# porta3!e dri!! dra.s

a3o&t * A i-e- *0 times $ata! "&rrent

4i%h C&rrents $or e)en appre"ia3!e d&ration

!ead to ine)ita3!e death


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5&mmar# o$ $$e"ts

C&rrent ; J!et %oK thresho!d !ead to "o!!apse or

&n"ons"io&s or death

D&ration %reater than


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5&mmar# o$ $$e"ts "ontd--

Eost dan%ero&s e$$e"t e)en $air!# sma!! "&rrent$!o.s thro&%h heart re%ion

Ca&ses )entri"&!ar $i3ri!!ation res&!tin% in death.ith in min&tes

As#n"hrono&s mo)ement "a&sin% heart 3eat tostop

I$ !ar%e "&rrents $!o. thro&%h heart hearta"ti)it# stops immediate!#

5e"ondar# e$$e"t "o&!d 3e tiss&e dama%e anddama%e to interna! or%ans .hen "&rrent $!o.sthro&%h ma?or portions o$ the 3od#


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Ca&ses o$ !e"tri"a! a""idents

Inade&ate .irin%

Gposed parts

Conta"t .ith o)erhead po.er !ines

De$e"ti)e or Inade&ate ins&!ation Improper %ro&ndin% o$ e&ipment

O)er!oaded "ir"&its

Dama%ed (o.er too!s or e&ipment 5tati" !e"tri$i"ation

Inade&ate (rote"tion to i%htnin%


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Ca&ses o$ !e"tri"a! a""idents

"ontd--

A%%ra)ated 3#

1- Inade&ate trainin%

2- Unsa$e .or' en)ironment

9 .et .or' s&r$a"es

9 in"!ement .eather

9 toGi" "hemi"a!s

9 eG"essi)e noise

9 $!amma3!es


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A""ident (re)ention

Eost !e"tri"a! A""idents are pre)enta3!e

Desira3!e pre)ention te"hni&e is to

e!iminate or red&"e 4a>ard at so&r"e

De9ener%i>e and !o"' o&t e&ipment prior

to repair or inspe"tion


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3.Electrical Safety

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