Domestric Installations

7/21/2019 Domestric Installations

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TUDAWE ENGINEERING SERVICES BIT

CHAPTER 01

INTRODUCTION ON TRAINING ORGANIZATION

About Tudawe Brothers Liited

I was selected for my industrial trainin Tudawe !rot"ers #td at $%$&' El(itiala)awat"a*

Colom!o $* w"ic" is one of t"e leadin contractors in ci(il enineerin as well as electrical and

mec"anical in Sri #an+a, Amon t"ose fields -ast acti(ities of construction fieid says Tudawe

Bros #td is s-ecialist in construction !ecause t"ey "a(e !uilt multi story !uildin more t"an ten

stories wit" (ery finis"in in resent -ast,

Today Tudawe Bros #td administrated !y a c"aiman wit" a !oard of directors !ut it was

esta!lis"ed in ./0' as a !uildin construction field, E(ery acti(ities of construction* electrical

and mec"anical are done accordin to IS1 stranded today, Tudawe Bros "as o!tained IS1 /%%'certificated in .//2 for construction wor+s first time in Sri #an+a,

Histor! o" #o$a%!

Tudawe Bros #td was founded at ./0' as a com-any* w"ic" is underta+en !uildin wor+s in

concentratin mainly on construction "ouses durin its initial ste-, W"en it rowin u- t"eir

attention oes to under ta+en lare construction wor+s of multistoried !uildin as well and

su!se3uently focused mainly on multistoried !uildin, Durin a last few years Tudawe Bros #td

"as focused t"eir attention towards road construction and ot"er ci(il enineerin acti(ities suc"

as road construction* !ride construction* ele(ated water tower construction* water su--ly anddrainae etc, and also Tudawe "a(e forced t"eir attention towards electrical enineerin and

mec"anical enineerin fields durin last twenty years as well,

W"en e4-ansion t"e com-any* in(ested for -lant and mac"ines to wor+ wit" modern tec"noloy

and to satisfactory wit" t"e needs of industry as a result t"ey "a(e t"eir own !atc"in -lant and

!ar !endin yard today and lot of modern e3ui-ment w"ic" can !e used to wor+ con(eniently

and low time consumin, Also its -roduction rane followed !y t"e ready mi4ed concrete since

.//5, Today* Tudawe Bros #td t"at is leadin construction com-any in Sri #an+a t"ou"

esta!lis"ed in ./0',

&isio% 'tatee%t

6To !ecome a self su--ortin -rofessional constructor offerin 3uality -roducts 7 ser(ices to

de(elo- Sri #an+a * t"rou" (ertical interation wit" di(ersified !usiness units ser(in our needs

and t"at of t"e industry8

(issio% 'tatee%t

6 1ur )ission is t"e timely deli(ery of 3uality construction at com-etiti(e cost * t"rou"

moti(ated staff* su-erior tec"noloy 7 efficient system8

1

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Co$a%! 'tru#ture

2

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(ai% )i%e o" busi%ess

3

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Pro*e#t C)ie%t Date o" #o$)etio%

Rehabi)itatio% o" road i% Co)obo

#ite a%d suburbs

Road de(elo-ment aut"ority 5.&.%&/9

Na+i%%a,(iriha%a road a%d

Dehiwa)a,(ahara-aa road

Road de(elo-ment aut"ority %0&.%&/2

Co%stru#tio% o" brid-e .Ethua)e,

/aatuwa Road

Road de(elo-ment aut"ority 5.&%9&%.

Re#o%stru#tio% o" brid-e

.2a)awe))awa,Be))a$iti!a

Road de(elo-ment aut"ority .0&..&%.

Rehabi)itatio% o" road i% (atara

distri#t

Sout"ern -ro(incial road

de(elo-ment aut"ority

5.&%5&%'

'outher% $ro+i%#ia) road

i$ro+ee%t $ro*e#t

Sout"ern -ro(incial road

de(elo-ment aut"ority

%'&%$&%5

Co$)eted $ro*e#ts

T"e com-leted -ro:ect of t"is com-any can !e cateori;ed into two -arts as a-artments and

ot"er construction wor+s wit" in last ten years as follows,

3i%%i%- Awards

4

NDES : EP/10/7946

Busi%ess Coe%#ee%t

Bui)di%- #o%stru#tio% Since ./0'

'tru#tura) stee) Since ./0$

E)e#tri#a) e%-i%eeri%- Since ./2%

E)e+ated water tower Since ./29

3ater su$$)! a%d drai%a-e Since ./29

'ewa-e Since ./29

(4E ser+i#e Since ./29

5ire "i-hti%-4 $rote#tio% Since ./2/

Air #o%ditio% Since ./2/

Earth wor Since ./2/

Raw water 6 e"")ue%t water treate%t s!ste Since .//.

Road #o%stru#tio% Since .//5

A)ui%u wors Since .//$

Brid-e #o%stru#tio% Since .///


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Wit"in last few years Tudawe Brot"ers #td "as win a few awards for t"e construction wor+ in

!uildin side,

Construction e4cellence for -remier -acific a-artment com-le4 in '%%. s court a-artment in .//?


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is* 6International 1rani;ation for Standard8, In earlier time is s-reads o(er only few field li+e

communication* manufacturin* etc, after t"at it was -o-ular o(er t"e world, T"erefore in ./29

aain a committee .9? -eo-le ot toet"er to reesta!lis" t"e orani;ation, T"ey called it was

6IS1 SSTE)8, After t"is it s-read o(er many countries,

If any institute or firm wants to et IS1 facility t"ey s"ould re3uest if from t"at orani;ation,

After e(aluate institute or firm* if t"e t"ins are to t"eir satisfaction* t"ey are awardin t"e

facility, Also t"ey are comin -eriodically to ins-ect t"at institute or firm, So t"e institute of firm

s"ould -erfectly maintain t"e system,

TudaweBrit"ers #td


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DE'CRIPTION O5 THE PRO8ECT

PRO8ECT NA(E 9 Refur!is"ment of Fotel Serendi!

PRO8ECT LOCATION 9 Bentota

CLIENT 9 Ceylon etroleum Cor-oration

CON'ULTANT 9 Central Enineerin consultant Bureau

0.$* !audd"alo+a )w*

Colom!o %.,

CONTRACTOR 9 Tudawe Enineerin Ser(ices


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CHAPTER 0:

BA'IC DO(E'TRIC IN'TALLATION'

LIGHTING

T"e rane of modern li"tin fittins and lam-s is so lare* t"at only t"e !asic ty-es were

considered !elow, Before we continue* "owe(er* it is -er"a-s wise to list t"e (arious units and

3uantities associated wit" t"is su!:ect,

Luminous intensity :- symbol - I , unit - candela (cd)

T"is is a measure of t"e -ower of a li"t source and is sometimes referred to as !ri"tness,

Luminous flux : - symbol F, unit - lumen (lm)

T"is is a measure of t"e flow or amount of li"t emitted from a source,

I))ui%a%#e 9, s!bo) ; E< u%it , )u= .)= or )6:

T"is is a measure of t"e amount of li"t fallin on a surface, It is also referred to as illumination,

Luminous efficacy :- symbol K, unit - lumen per watt (lm/)

T"is is t"e ratio of luminous flu4 to electrical -ower in-ut, It could !e t"ou"t of as t"e efficiency > of

t"e li"t source,

!aintenance factor (!F) :- no unit

In order to allow for t"e collection of dirt on a lam- and also aein* !ot" of w"ic" cause loss of li"t* a

maintenance factor is used,

As an e4am-le* consider a new 2% W fluorescent lam- wit" a lumen out-ut of$9%% lm,

After a!out 5 or 0 mont"s t"is out-ut would "a(e fallen and settled at around $'%% lm,

Fence t"e li"t out-ut "as decreased !y*

$'%%&$9%% H %,/

T"is (alue* %,/* is t"e maintenance factor and s"ould not fall !elow %,2, T"is is ensured

!y reular cleanin of t"e lam-s,

"oefficient of utili#ation ("$) :- no unit

T"e amount of useful li"t reac"in a wor+in -lane will de-end on t"e lam- out-ut* t"e reflectors and&or

diffusers used* -osition of lam-* colour of walls and ceilins* etc, T"e li"tin desiner will com!ine all

of t"ese considerations and determine a fiure to use in "is or "er li"tin calculations,

Tu%-ste%,"i)ae%t )a$

Fi%ure&'&s"ows t"e !asic com-onents of a tunstenfilament lam-,T"e tunsten filament is eit"er

sinle or dou!le coiled


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Fi%ure '& on%ston Filament Lamp

Fi%ure '&' (a) *in%le coil,

(b) coiled coil Filament arran%ements

T"e efficacy of asfilled lam-s is increased !y usin a coiledcoil filament* as t"is ty-e "as in

effect a t"ic+er filament w"ic" reduces t"e "eat loss due to con(ection currents in t"e as,

ilament lam-s are of two main ty-es* (acuum and as filled,

&a#uu t!$e

T"e filament o-erates in a (acuum in t"e lass !ul!, It "as a -oor efficacy as it can o-erate only

u- to around '%%%JC,

Gas,"i))ed t!$e

In t"is case t"e !ul! is filled wit" an inert as suc" as nitroen or aron, T"is ena!les t"e

o-eratin tem-erature to reac" '$%%JC, T"e efficacy increases and t"e !ul! is usually so !ri"t

t"at it is i(en an o-a3ue coatin internally, T"is ty-e of lam- is usually called a -earl> lam-,

T"e followin code refers to lam- ca-s*

BC ; Ba!o%et

'BC ; 'a)) ba!o%et

'CC ; 'a)) #e%tre #o%ta#t

E' ; Ediso% s#rew

'E' ; 'a)) Ediso% s#rew

(E' ; (i%iature Ediso% s#rew

GE' ; Go)iath Editio% s#rew

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T"e efficacy of a tunsten lam- will de-end on se(eral factors* includin t"e ae of t"e lam- and

its si;e* !ut tends to !e around .' lm&W for a .%% W lam-, T"e colour of its li"t tends to !e

mostly red and yellow and in its !asic form t"is ty-e of lam- is used only in situations t"at do

not re3uire a "i" le(el of illumination, 1t"er lam-s of t"e filament ty-e include tu!ular stri-

li"ts* o(en lam-s* infrared "eatin lam-s* s-ot and floodli"ts* and tunstenK"aloen lam-s,

Dis#har-e )i-hti%-

T"is ty-e of li"tin relies on t"e ioni;ation of a as to -roduce li"t, As "i" (oltaes are

-resent in suc" li"tin circuits* s-ecial -recautions* outlined in t"e IEE Reulations* must !e

ta+en, Ty-ical disc"are lam-s include decorati(e neon sins* fluorescent li"tin* and mercury

and sodium(a-our lam-s used for street li"tin,

Neo% tube

In t"e same way t"at t"e trade name Foo(er > is collo3uially used to indicate any ma+e of

(acuum cleaner* so neon > tends to !e used to descri!e any sort of asfilled tu!e, T"ere are in

fact se(eral different ases used to i(e different colours* includin "elium* nitroen and car!on

dio4ide,

'odiu,+a$our )a$

T"ere are two ty-es of sodium(a-our lam- a(aila!le* wor+in at "i" and low -ressure*

res-ecti(ely,

T"e low-ressure ty-e consists of a Us"a-ed dou!let"ic+ness lass tu!e* t"e inner wall ofw"ic" is of lowsilica lass w"ic" can wit"stand attac+ !y "ot sodium, Inside t"e tu!e is a

3uantity of solid sodium and a small amount of neon as


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Fi%ure '& "ontrol "ircuit for t.e *odium apour Lamp

T"e out-ut from t"e autotransformer is in t"e reion of 02% V

and t"e -ower factor


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Hi-h,$ressure er#ur!,+a$our )a$

T"is ty-e consists of a 3uart; tu!e containin mercury at "i" -ressure and a little aron as toassist startin, T"ere are t"ree electrodes* two main and one au4iliary* t"e latter is used for

startin t"e disc"are Fi%ure '&0,

Fi%ure '&0 1i%. 2ressure !ercury apour Lamp

Fi%ure '&3 s"ows t"e control circuit for a "i"-ressure mercury(a-our lam-, T"e initial

disc"are ta+es -lace in t"e aron as !etween t"e au4iliary electrode and t"e main electrodeclose to it, T"is causes t"e main electrode to "eat u- and t"e main disc"are !etween t"e two

main electrodes ta+es -lace,

Fi%ure '&3 "ontrol "ircuit of !ercury apour Lamp

Se(eral ty-es of mercury(a-our lam- are a(aila!le* includin t"e followin two -o-ular ty-es*

!4 typeK Standard mercury(a-our lam-@ ES or GES ca-@ any mountin -osition* efficacy

around 0% lm&W, #arely su-erseded !y t"e )B ty-e,

Fi%ure '& arious 5esi%ns of 6L* Lamp


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!4F typeK Standard* !ut wit" fluorescent -"os-"or coatin on t"e inside of t"e "ard lass

!ul!@ ES or GES ca-* efficacy around $% lm&W, Used for industrial and street li"tin*

commercial and dis-lay li"tin* any mountin -osition,

T"e colour i(en !y "i"-ressure mercury(a-our lam-s tends to !e !luereen,

Low,$ressure er#ur!,+a$our )a$

A low-ressure mercury(a-our lam-* more -o-ularly +nown as a fluorescent lam- * consists of

a lass tu!e* t"e interior of w"ic" is coated in fluorescent -"os-"or, T"e tu!e is filled wit"

mercury (a-our at low -ressure and a little aron to assist startin, At eac" end of t"e tu!e is

situated an o4idecoated filament, Disc"are ta+es -lace w"en a "i" (oltae is a--lied across

t"e ends of t"e tu!e, Fi%ure '&7s"ows t"e circuit diaram for a sinle fluorescent tu!e, T"e lam-

construction is s"own in Fi%ure '&8

Fi%ure '&7 "ircuit 5ia%ram for *in%le Fluorescent ube


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Fi%ure '&8 - Fluorescent Lamp "onstruction

E%er-!,e""i#ie%t )a$s

C#s are miniature or com-act fluorescent lam-s desined to re-lace ordinary G#S lam-s, T"ey

are a(aila!le in a (ariety of s"a-es and si;es so t"at t"ey can !e fitted into e4istin li"t fittins,

Fi%ure '&9s"ows t"ree ty-ical s"a-es, T"e stic+> ty-e i(es most of t"eir li"t out-ut radially

w"ile t"e flat dou!le D> ty-e i(e most of t"eir li"t out-ut a!o(e and !elow,

Fi%ure '&9 ner%y fficient Lamps

Eneryefficient lam-s use electricity muc" more efficiently t"an an e3ui(alent G#S lam-, or

e4am-le* a '% watt enery efficient lam- will i(e t"e same li"t out-ut as a .%% watt G#Slam-, An .. watt enery efficient lam- is e3ui(alent to a ?% watt G#S lam-, Eneryefficient

lam-s also "a(e a lifes-an of a!out ei"t times loner t"an a G#S lam- and so* t"ey do use

enery (ery efficiently,

Fowe(er* eneryefficient lam-s are e4-ensi(e to -urc"ase and t"ey do ta+e a few minutes to

attain full !rilliance after switc"in on, T"ey cannot always !e controlled !y a dimmer switc"

and are unsuita!le for incor-oratin in an automatic -resence detector !ecause t"ey are usually

not switc"ed on lon enou" to !e wort"w"ile* !ut enery efficient lam-s are e4cellent for

outside security li"tin w"ic" is left on for se(eral "ours eac" ni"t,


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T"e electrical contractor* in discussion wit" a customer* must !alance t"e ad(antaes and

disad(antaes of eneryefficient lam-s com-ared to ot"er sources of illumination for eac"

indi(idual installation,

Pra#ti#a) o$eratio%

W"en t"e su--ly is switc"ed on* t"e circuit is com-leted (ia t"e c"o+e* first lam- element*

starter switc"* second lam- element and t"e neutral, T"e elements* w"ic" are coated in o4ide*

!ecome warm and t"e o4ide coatin emits some electrons and t"e as ioni;es at t"e ends of t"e

tu!e


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Fi%ure '&

.ermal *tarter

T"e low starter is t"e most -o-ular of all t"e means of startin t"e disc"are, It com-rises a

-air of o-en contacts

close* and t"is eneri;es t"e tu!e filaments, As t"e contacts "a(e closed* t"e disc"are in t"e

"elium ceases* t"e contacts cool and -art* o-encircuitin t"e c"o+e across t"e tu!e and

disc"are ta+es -lace,


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Fi%ure '&'

6low *tarter

In t"e case of t"e 3uic+ start or instant starter* startin is ac"ie(ed !y t"e use of an auto

transformer and an eart"ed metal stri- in close -ro4imity to t"e tu!e < Fi%ure '&+=,,

Fi%ure '&+ =uic< *tarter


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W"en t"e su--ly is switc"ed on* mains (oltae a--ears across t"e ends of t"e tu!e* and t"e small

-art of t"e windin at eac" end of t"e transformer eneri;es t"e filaments t"at "eat u-, T"e

difference in -otential !etween t"e electrodes and t"e eart"ed stri- causes ioni;ation t"at s-reads

alon t"e tu!e,

5)uores#e%t tube )i-ht out$ut

T"ere is a wide rane of fluorescent tu!es for different a--lications as able '&indicates, T"e

w"ite tu!e "as t"e "i"est efficacy* w"ic" for a '0%% mm* .'$ W tu!e is around 9% lm&W,

able '& ube "olour and Its >pplications

'trobos#o$i# e""e#t

W"ile a fluorescent lam- is in o-eration t"e li"t may flic+er, Under some circumstances t"is

may ma+e it a--ear t"at rotatin mac"inery "as slowed down or e(en sto--ed, T"is is called t"e

stro!osco-ic effect, T"is is an undesira!le state of affairs w"ic" is usually remedied !y one of

t"e two followin met"ods*

4alancin% t.e li%.tin% load (t.ree p.ase)

If a lare li"tin load is installed in a t"ree-"ase installation w"ere t"ere is some rotatin

mac"inery* t"e stro!osco-ic effect may !e o(ercome !y connectin alternate rou-s of lam-s to

a different -"ase, T"is also "as t"e ad(antae of !alancin t"e li"tin load < Fi%ure '&=,


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Fi%ure

'& Li%.tin% Load

.e leadla% circuit

In t"is met"od a ca-acitor is wired in series wit" e(ery alternate lam- in a rou-, T"e (alue of

t"e ca-acitor is suc" t"at t"e lam- unit is fitted to "a(e an o(erall leadin , T"is means t"at

any -air of lam-s "a(e a lain and a leadin , T"is "as t"e effect of cancellin out t"e

resultant flic+er* in t"e same way as two e3ual !ut o--osin forces cancel eac" ot"er out


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)ost of t"e domestic installations in Sri #an+a are of sinle -"ase


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IEE reulation "as 1n Site Guide deals wit" t"e assumed current demand of -oints* and states

t"at for li"tin outlets, We s"ould assume a current e3ui(alent to a minimum of .%%W -er lam-

"older, T"is means t"at for a domestic li"tin circuit rated at $ A* a ma4imum of .. li"tin

outlets could !e connected to eac" circuit, In -ractice* it is usual to di(ide t"e fi4ed li"tin

outlets into a con(enient num!er of circuits of se(en or ei"t outlets eac", In t"is way t"e w"ole

installation is not -luned into dar+ness if one li"tin circuit fuses


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Fi%ure '&3 ?ne ay Li%.tin% irin% 5ia%ram

W"en we are doin any wirin for t"e domestic -ur-oses* we can follow !elow instructions*

., T"e ends of !lac+* !lue or rey switc" wires "a(e !rown slee(in to denote line

conductor,


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t"e a--liance to t"e source of su--ly, Soc+et outlets t"erefore -ro(ide an easy and con(enient

met"od of connectin -orta!le electrical a--liances to a source of su--ly,

Soc+et outlets can !e o!tained in .$* .5* $ and ' A ratins* !ut t"e .5 A flat -in ty-e com-lyin

wit" BS .5?5 is t"e most -o-ular for domestic installations in t"e United indom, Eac" .5 A

-lu to- contains a cartride fuse to i(e ma4imum -otential -rotection to t"e fle4i!le cord and

t"e a--liances w"ic" it ser(es,

Soc+et outlets may !e wired on a rin or radial circuit and in order t"at e(ery a--liance can !e

fed from an ad:acent and con(eniently accessi!le soc+et outlet* t"e num!er of soc+ets is

unlimited -ro(ided t"at t"e floor area co(ered !y t"e circuit does not e4ceed accordin to t"e

IEE Reulations,

Radia) Cir#uits

In a radial circuit eac" soc+et outlet is fed from t"e -re(ious one, #i(e is connected to li(e*

neutral to neutral and eart" to eart" at eac" soc+et outlet, T"e fuse and ca!le si;es are i(en in

t"e IEE Reulations !ut circuits may also !e e4-ressed wit" a !loc+ diaram* as s"own in

Fi%ure '&'9, T"e num!er of -ermitted soc+et outlets is unlimited !ut eac" radial circuit must

not e4ceed t"e floor area stated and t"e +nown or estimated load,

W"ere two or more circuits are installed in t"e same -remises* t"e soc+et outlets and

-ermanently connected e3ui-ment s"ould !e reasona!ly s"ared out amon t"e circuits* so t"at

t"e total load is !alanced,

Fi%ure '&'9 @adial "ircuit


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W"en desinin rin or radial circuits s-ecial consideration s"ould !e i(en to t"e loadin in

+itc"ens w"ic" may re3uire se-arate circuits, T"is is !ecause t"e ma4imum demand of current

usin e3ui-ment in +itc"ens may e4ceed t"e ratin of t"e circuit ca!le and -rotection de(ices,

Rin and radial circuits may !e used for domestic or ot"er -remises w"ere t"e ma4imum

demand of t"e current usin e3ui-ment is estimated not to e4ceed t"e ratin of t"e -rotecti(e

de(ices for t"e c"osen circuit,

Ri%- Cir#uits

Rin circuits are (ery similar to radial circuits in t"at eac" soc+et outlet is fed from t"e -re(ious

one* !ut in rin circuits t"e last soc+et is wired !ac+ to t"e source of su--ly, Eac" rin final

circuit conductor must !e loo-ed into e(ery soc+et outlet or :oint !o4 w"ic" forms t"e rin and

must !e electrically continuous t"rou"out its lent", T"e num!er of -ermitted soc+et outlets is

unlimited !ut eac" rin circuit must not co(er more t"an .%% m'

of floor area,

T"e circuit details are i(en in t"e IEE Reulations !ut may also !e e4-ressed !y t"e !loc+

diaram i(en in Fi%ure '&' &

Additional -rotection !y 5% mA residual current de(ice


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able '&' : "onductors 5iameters and its maximum >mpere rates used in circuit preparation

and distribution

)etric Value Diameter Am-ere Im-erial

.&.,.5 . .' .&%00

.&.,52 .,$ .0 5&%'/

9&%,$% .,$ .0 5&%5?

9&%,?9 ',$ .9 9&%'/

9&%,2$ 0 '/ 9&%5?

9&.,%0 ? 59 9&%00

9&.,5$ .% $. 9&%$'

9&.,9% .? ?? 9&%?0

9&',.0 '$ 29 ./&%00

./&.,5$ '$ 29 ./&%$'

./&.,$5 5$ .%? ./&%?0

./&.,92 $% .'$ ./&%95

./&',.0 9% .?% ./&%25

59&.,92 /$ ./$ 59&%9'

59&',%5 .'% ''% 59&%25

59&','$ .$% '?% 59&%/5

59&',$' .2$ '/$ 59&.%5

?.&','$ '0% 5?% ?.&%/5

?.&',$' 5%% 0.% ?.&.%5

?.&',2$ 0%% 0$9

?.&5,'% $%% $'% /.&.%5

CHAPTER 0@


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IN'TALLATION (ATERIAL' 4 TOOL'

@>1 IN'ULATION

P)asti#s

T"e uses of -lastic materials


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A conduit is a tu!e or -i-e in w"ic" conductors are run, In effect* t"e conduit re-laces t"e VC

s"eat"in of a ca!le* -ro(idin mec"anical -rotection for t"e insulated conductors, T"ere are

t"ree ty-es of conduits metal* fle4i!le , Fea(y aue is made from a sinle s"eet of steel and welded alon t"e seam*

w"ile soliddrawn is -roduced in tu!ular form and is t"erefore seamless, T"is ty-e of conduit is

used only for flame-roof installations


29/141

Fi%ure +&' "onduit 4ends

T"ere are se(eral ways of :oinin and terminatin conduit as s"own in Fi%ure +&+, Fi%ure +&+ "

s"ows a runnin cou-ler >, T"e conduits to !e :oined are t"readed to a distance reater t"an t"e

lent" of t"e cou-ler, T"e cou-ler is t"en screwed ri"t on to one t"read* t"e ot"er conduit is

!utted to t"e first conduit and t"e cou-ler is screwed !ac+ o(er t"e second t"read, T"is met"od

ena!les two conduits to !e :oined wit"out actually turnin t"e conduits t"emsel(es, T"e loc+nuts

are -ro(ided to -re(ent t"e cou-ler from mo(in,

Fi%ure +&+ "onduit erminations and Aoints

5i=i%- #o%duit


30/141

Fi%ure +&s"ows t"e common met"ods used for securin or fi4in conduit, Cram-ets are used

for securin conduit in -lace -rior to co(erin wit" -laster, S-acer!ar ty-es are often used to

s-ace t"e conduit out from a wall in order to a(oid t"e need for sets>,

Fi%ure +& "onduit *upports

Distance saddles s-ace t"e conduit far enou" from t"e fi4in surface to -re(ent dust from

collectin !etween t"e conduit and t"e surface, T"ey were in t"e -ast often used in "os-itals

w"en t"ey were +nown as "os-ital saddles,

1t"er accessories for use wit" conduit include el!ows ccessories

5)e=ib)e #o%duit


31/141

le4i!le conduit is of reat use w"en a riid conduit system is su--lyin mac"inery, T"e use of a

s"ort connectin lent" of fle4i!le conduit ensures t"at t"e (i!ration of t"e motor does not affect

t"e riid conduit and ena!les t"e motor easily to !e alined* or remo(ed for re-air @ TRUN2ING

Trun+in may !e t"ou"t of sim-ly as a larer and more accessi!le conduit system, It is

a(aila!le in two ranes ordinary wirin trun+in and !us!ar trun+in, T"e ordinary system is

furt"er a(aila!le in eit"er metal or VC,

P&C tru%i%-

T"e main areas in w"ic" VC trun+in is used are domestic and office -remises, It is -er"a-s

!etter descri!ed as c"annellin > rat"er t"an trun+in > , All necessary fittins are a(aila!le to

com-lete any s"a-e of run wit" little difficulty, oins in VC trun+in are usually made wit"

ad"esi(e,

(eta) tru%i%-

)etal trun+in is used e4tensi(ely in enineerin -remises, It allows a lare num!er of ca!les to

!e drawn into one system wit" relati(e ease and !ecause of its accessi!ility ena!les c"anes or


32/141

additions to circuits to !e made wit" t"e minimum of effort, As wit" conduit* it is a(aila!le

eit"er -ainted or al(ani;ed, A w"ole rane of fittins are a(aila!le* ena!lin t"e most difficult

runs to !e constructed, It is a(aila!le in many different si;es and desins, or e4am-le*

com-artment trun+in allows t"e sereation of certain circuits and su--ort of ca!les in (ertical

runs, Fi%ure +&3s"ows se(eral different ty-es of trun+in,

Fi%ure +&3

"ondiut run


33/141

Fi%ure +&7 1ole"uttin%

'u$$orts "or tru%i%-

Trun+in may !e secured direct to a surface or sus-ended !y means of !rac+ets, As trun+in

material is t"in* t"ere is no room for countersun+ "oles, Round"ead screws are suested* unless

of course t"e fi4in surface re3uires !olts, T"ere are occasions w"en t"e trun+in "as to !e

sus-ended !y means of !rac+ets, Fi%ure +&8s"ows ty-ical !rac+et,

Fi%ure +&8 *crew Fixin% >nd run


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Fi%ure +&9 ?Ber.ead 4usbar run


35/141

Fi%ure +&' "able ray

@> 5IING AND TOOL'

An im-ortant as-ect of installation wor+ is t"e fi4in of accessories to (arious surfaces, Fi%ure

+&+ s"ows se(eral different met"ods of fi4in,

T"e main disad(antae of ra(ity and s-rin toles is t"at it is not -ossi!le to remo(e t"e !olt

wit"out losin t"e tole,

Too)s

T"e followin is a list of tools used !y t"e electrician* a com-lete !asic tool +it will "a(e all

t"ese items, T"ese tools are used for c"asin walls* liftin floor!oards*

a= "lub .ammer T"is is for use wit" cold c"isels and !olsters, Ensure t"at t"e "andle

is in ood condition, Do not use t"e "ammer if t"e "ead is loose,

!= 4olster (lar%e and small) T"is tool is used for c"asin walls and !ric+wor+ and

for ma+in "oles for metal !o4es, Ensure no mus"roomin ,

c= Floorboard c.isel T"is is similar to a !olster !ut wit" a loner "andle, T"e same

-recautions s"ould !e ta+en as for !olsters,

d= *cutc. .ammer and combs T"ese tools are used for c"asin !ric+wor+,

e= "old c.isels (a selection of Barious si#es) T"ese are for use on !ric+wor+ and

concrete, T"e same -recautions s"ould !e ta+en as for !olsters,

f= enon saw and pad saw or cuttin floor!oards* etc,


36/141

Fi%ure +&+ !et.ods of Fixin%

T"ese tools are used for fittin accessories suc" as soc+ets and so on*

a= Lar%e cabinet-ma selection of files iles are used for remo(in s"ar- edes and !urrs, Always use a

"andle on a file,

"= @eamin% tool or remo(in !urrs from t"e inside ede of t"e conduit,


37/141

i= *toc< and dies T"ese tools are used for cuttin t"reads, A recommended lu!ricant suc"

as tallow s"ould !e used, Dies must !e +e-t clean@ do not allow a !uildu- of tallow and

metal,

:= >dAustable pipe wrenc. and *tillson Used for ti"tenin and unti"tenin conduit,

+= 4us. spanner T"is tool is for use on inaccessi!le !us" nuts,

l= 5raw tape Used for -ullin ca!les t"rou" conduit,

m= !easurin% tape Steel ta-es must not !e used near li(e e3ui-ment,n= *et of twist drills or use wit" a "and or electric drill, Cuttin edes s"ould !e +e-t

s"ar-, A "ot drill must ne(er !e 3uenc"ed in water,

o= *election of spanners or eneral use,

-= *et-s;uare or use in mar+in out trun+in,

3= *criber Used for mar+in metal, T"e -oints s"ould !e +e-t s"ar-,

r= "entre punc. or mar+in metal -rior to drillin,

s= 1ole saw T"is ty-e of saw is used for cuttin "oles in trun+in, It s"ould !e used only

wit" a "and drill or a lows-eed electric drill,

t= 2utty


38/141

3or harde%i%-

E4cessi(e "ammerin* rollin or !endin* etc,* of a metal causes it to "arden and !ecome !rittle,

It may !e returned to its oriinal condition !y annealin,

CHAPTER 0

5U'E'

I%trodu#tio%


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A fuse is a s"ort -iece of metal* inserted in t"e circuit* w"ic" melts w"en e4cessi(e current flows

t"rou" it and t"us !rea+s t"e circuit

T"e fuse element is enerally made of materials "a(in low meltin -oint* "i" conducti(ity and

least deterioration due to o4idation* E, , Sil(er* Co--er etc* It is inserted in series wit" t"e

circuit to !e -rotected, Under normal o-eratin o-enin conditions* t"e fuse element is at a

tem-erature !elow its meltin -oint, T"erefore* it carries t"e normal current wit"out

o(er"eatin, Fowe(er* w"en a s"ort K circuit or o(erload occurs* t"e current t"rou" t"e fuse

increases !eyond its rated (alue, T"is raises t"e tem-erature and fuse element melts


40/141

T"e a!o(e discussion re(eals t"at no material -rossesses all t"e c"aracteristics, or instance*

lead "as low meltin -oint !ut it "as "i" s-ecific resistance and is lia!le to o4idation, Similarly*

co--er "as "i" conducti(ity and low cost !ut o4idises ra-idly, T"erefore* a com-romise is

made in t"e selection of material for a fuse,

5use E)ee%t (ateria)s

T"e most commonly used materials for fuse element are lead* tin* co--er* ;inc and sil(er, or

small currents u-to .%A* tin or an alloy of lead and tin


41/141

',= 5usi%- Curre%tK It is t"e minimum current at w"ic" t"e fuse element melts and t"us

disconnects t"e circuit -rotected !y it, 1!(iously* its (alue will !e more t"an t"e current

ratin of t"e fuse element,

or a round wire* t"e a--ro4imate relations"i- !etween fusin current I and

diameter d of t"e wire is I d@6: * W"ere + is a constant* called t"e fuse

constant,Its (alue de-ends u-on t"e metal of w"ic" t"e fuse element is made, Sir W,F,

reece found t"e (alue of + for different material as i(en in t"e able +&*

able &: K alue for different materials

.e fusin% current depends upon t.e Barious factors suc. as*

)aterial of fuse element

#ent" K t"e smaller t"e lent"* t"e reater t"e current !ecause a s"ort

fuse can easily conduct away all t"e "eat,

Diameter

Si;e and location of terminals

re(ious "istory

Ty-e of enclosure used

5,= 5usi%- "a#torK it is t"e ratio of minimum fusin current to t"e current ratin of t"e fuse

element,

Fusin% factor !inimum fusin% current

"urrent ratin% of fuse

Its (alue is always more t"an one, T"e smaller t"e fusin factor* t"e reater is t"e

difficulty in a(oidin deterioration due to o(er"eatin and o4idation at rated carryincurrent, or a semi K enclosed or rewira!le fuse w"ic" em-loys co--er wire as t"e fuse

element* t"e fusin factor is usually ', #ower (alues of fusin factor can !e em-loyed for

enclosed ty-e cartride fuses usin sil(er or !imetallic elements,

0,= Pros$e#ti+e Curre%tKollowin Fi%ure +&s"ows "ow A, C, current is cut off !y a

fuse, T"e fault current would normally "a(e a (ery lare first loo* !ut it actually

enerates sufficient enery to melt t"e fusea!le element well !efore t"e -ea+ of t"is first

loo- is reac"ed, T"e r, m, s, (alue of t"e first loo- of fault current is +nown as

-ros-ecti(e current* T"erefore* -ros-ecti(e current can !e defined as under*

S, No )aterial Value of +

d in cm d in mm

. Co--er '$5% 2%

' Alluminium .295 $/

5 Tin 0%$,$ .',2

0 #ead 50%,? .%,2


42/141

Fi%ure

+&-

1ow >& "&

current is cut off

Gote on fi%ure:It is the r.m.s value o the irst loop o the ault current obtained i the

use is replaced b! an ordinar! conductor o negligible resistance.

$,= Cut ,O"" Curre%tK it is t"e ma4imum (alue of fault current actually reac"ed !efore t"e

fuse melts,1n t"e occurrence of a fault* t"e fault current "as a (ery lare first loo- due to

a fair deree of asymmetry, T"e "eat enerated is sufficient to melt t"e fuse element well

!efore t"e -ea+ of first loo- is reac"ed, T"e current corres-ondin to -oint a> is t"e cut

off current, T"e cut off (alue de-ends u-on*

a= Current ratin of fuse!= Value of -ros-ecti(e current

c= Asymmetry of s"ort K circuit current

It may !e mentioned "ere t"at outstandin feature of fuse action is t"e !rea+in of circuit

!efore t"e fault current reac"es its first -ea+, T"is i(es t"e fuse a reat ad(antae o(er a

circuit !rea+er since t"e most ser(e t"ermal and electro K manetic effects of s"ort K

circuit currents


43/141

?,= Pre ,Ar#i%- tieK It is t"e time !etween t"e commencement of fault and t"e instant

w"en cut off occurs,

W"en a fault occurs* t"e fault current rises ra-idly and enerates "eat in t"e fuse element,

As t"e fault current reac"es t"e cut off (alue* t"e fuse element melts and an arc in

initiated, T"e time from t"e start of t"e fault to t"e instant t"e arc is initiated is +nown

-re arcin time, T"e -re arcin time is enerally small* a ty-ical (alue !ein %,%%.

second,

9,= Ar#i%- tieK T"is is t"e time !etween t"e end of -re K arcin time and t"e instant w"en

t"e arc is e4tinuis"ed,

2,= Tota) o$erati%- tieK It is t"e sum of -re K arcin and arcin times,

It may !e noted t"at o-eratin time of a fuse is enerally 3uite low 6 F$**

#ow (oltae fuses can !e su!di(ided into two classes (i;,*


44/141

Rewirea!le fuse


45/141

of t"e fuse is decreased* i, e,* t"e fuse o-erates at a lower current t"an oriinally

rated,

0,= T"e -rotecti(e ca-acity of suc" a fuse is uncertain as it affected !y t"e am!ient

conditions,

$,= Accurate cali!ration of t"e fuse wire is not -ossi!le !ecause fusin current (ery

muc" de-ends u-on t"e lent" of t"e fuse element,

Semi K enclosed rewirea!le fuses are made u-to $%%A rated current* !ut t"eir !rea+in ca-acity

is low*E. g. on "##V service, the brea$ing capacit! is about "###%, T"erefore* t"e use of t"is

ty-e of fuses is limited to domestic and li"tin loads,

:> Hi-h ; Ru$turi%- Ca$a#it! .H> R> C> Cartrid-e 5use

T"e -rimary o!:ection of low and uncertain !rea+in ca-acity of semi K enclosed rewirea!le

fuses is o(ercome in F, R, C, cartride fuse, It consists of a "eat resistin ceramic !ody "a(inmetal end K ca-s to w"ic" is welded sil(er current K carryin element, T"e s-ace wit"in t"e !ody

surroundin t"e element is com-letely -ac+ed wit" a fillin -owder, T"e fillin material may !e

c"al+* -laster of -aris* 3uart; or mar!le dust and acts as an arc 3uenc"in and coolin medium, s solder is used in con:unction wit" a flu4, T"e flu4 +ee-s

t"e wor+ clean and -re(ents it from !ein o4idi;ed durin solderin, or smaller :o!s on fine

ca!le* a solder wit" a flu4 incor-orated in it is used,

Teri%atio% i%to a$$)ia%#es

T"e met"ods used to terminate conductors "a(e already !een discussed, Fowe(er* an im-ortant

as-ect of termination of ca!le into a--liances* es-ecially t"e -orta!le ty-e* is t"e securin of t"e

ca!le at or near t"e -oint of entry < Fi%ure 3&+=, A ood e4am-le of t"is is t"e ca!le clam- in a

-lu to-,

Fi%ure 3&+ "able "ord 6rip

It is im-ortant to note t"at in any termination and any run of conductor or ca!le* measures must

!e ta+en to a(oid any undue strain on t"at conductor or ca!le,


65/141

CHAPTER 0

PROTECTION

T"e meanin of t"e word 6-rotection8 as used in t"e electrical industry is no difficult to t"at in

e(eryday use, eo-le -rotect t"emsel(es aainst -ersonal or financial loss !y means of insurance

and from in in:ury or discomfort !y t"e use of t"e correct -rotecti(e clot"in, T"ey furt"er

-rotect t"eir -ro-erty !y t"e insulation of security measures suc" as loc+s and alarm systems, In

t"e same way* electrical systems need*

., To !e -rotect aainst mec"anical damae* t"e effects of t"e en(ironment and electrical

o(er currents,

', To !e installed in suc" a fas"ion t"at -ersons and or li(estoc+ are -rotected from t"e

daners t"at suc" an electrical installation may create,

#et us now loo+ at t"ese -rotecti(e measures in more detail,

Cab)e Co%stru#tio%

A ca!le com-rises one or more conductors* eac" co(ered wit" an insulatin material, T"is

insulation -ro(ides -rotection from s"oc+ !y direct contact and -re(ents t"e -assae of lea+ae

currents !etween conductors clearly* insulation in (ery im-ortant and itself* s"ould !e -rotected

from damae, T"is may !e arc"ie(ed !y co(erin t"e insulated conductors wit" a -rotecti(e

s"eat"in durin manufacture or !y enclosin t"em in conduit or trun+in at t"e insulation stae,

T"e ty-e of s"eat"in c"osen and t"e insulation met"od will de-end on t"e en(ironment in

w"ic" t"e ca!le is to !e installed* for e4am-le* in an en(ironment su!:ect to mec"anical damae*metal conduit wit" VC sinles or mineral K insulated ca!le would !e used in -reference to

VC K s"eat"ed ca!le cli--ed direct* in an industrial en(ironment, Fi%ure 7&s"ows t"e effect

of -"ysical im-act on ),I, ca!le,

Fi%ure 7& - ffected !ineral "able

Prote#tio% A-ai%st Corrosio%


66/141

)ec"anical damae to ca!le s"eat"s and t"e metalwor+ of wirin systems can occur t"rou"

corrosion* and so care must !e ta+en to c"oose corrosion K resistance materials and to a(oid

contact !etween dissimilar metals in dam- situations,

Prote#tio% A-ai%st Thera) E""e#ts

T"e IEE reulations !asically re3uire commonsense decisions reardin t"e -lacin of fi4ede3ui-ment* so t"at surroundin materials are not at ris+ from damae !y "eat, Added to t"ese

re3uirements* is t"e need to -rotect -ersons and li(estoc+ from !urns !y uardin -arts of

e3ui-ment lia!le to e4cessi(e tem-erature,

De-radatio%

All VC -olymers are deraded or reduced in 3uality !y "eat and li"t, S-ecial sta!ili;er added

durin manufacture "el- to retard t"is deradation at "i" tem-eratures, Fowe(er* it is

recommended in t"e IEE reulations t"at VC Ks"eat"ed ca!les or t"ermo K -lastic fittins for

luminaires


67/141

., irst Numerical Is for (e#ha%i#a) Prote#tio%,

', Second Numerical is for Liuid Prote#tio%,

First Gumerical

0 ; No -rotection of -ersons aainst contact wit" li(e or mo(in -arts inside t"e enclosure,

No -rotection of e3ui-ment aainst inress of solid forein !odies,

1 ; rotection aainst accidental or inad(ertent contact wit" li(e or mo(in -arts inside t"e

enclosure !y a lare surface of t"e "uman !ody, E, , a "and* !ut not -rotection aainst

inress of lare solid forein !odies,

: , rotection of -ersons aainst contact wit" li(e or mo(in -arts inside t"e enclosure !y

finers, rotection aainst inress of medium si;e solid* forein !odies,


68/141

; rotection aainst water :ets, Water -ro:ected !y a no;;le from any direction under

stated conditions s"all "a(e no "armful effect,

? ; rotection aainst condition on s"i-s* dec+s s reac"@ for e4am-le* t"e "i" le(el of t"e !are conductors of

tra(ellin cranes,

$, By usin a residual current de(ice


69/141

1ften referred to as dou!leinsulated e3ui-ment* t"is is ty-ical of modern a--liances w"ere

t"ere is no -ro(ision for t"e connection of a circuit -rotecti(e conductor


70/141

Fi%ure 7&' lectrical *eparation

Prote#tio% b! autoati# dis#o%%e#tio% o" su$$)!

T"is measure is a com!ination of !asic and fault -rotection,

'e$arated e=tra )ow +o)ta-e

T"is is sim-ly e4tra low (oltae


71/141

Fi%ure 7&+ @educed Low olta%e *ystem

Prote#tio% A-ai%st O+er #urre%t

An o(er current is a current reater t"an t"e rated current of a circuit, It may occur in two ways*

., As An o(erload current

', As a fault current

i, An s"ort K circuit current

ii, An eart" fault current

T"ese conditions need to !e -rotected aainst in order to a(oid damae to circuit conductors and

e3ui-ment, In -ractice* fuses and circuit !rea+ers will fulfill !ot" of t"ese needs,

O+er)oad

1(erload are o(ercurrents occurrin in "ealt"y circuits, T"ey may !e caused* for e4am-le* !y

faulty a--liances or !y sures due to motors startin or !y -luin in too many a--liances* in a

soc+et outlet circuit,

'hort #ir#uits a%d Earth 5au)ts

A S"ort circuit current is t"e current t"at will flow w"en a 6dead s"ort8 occurs !etween li(e

conductors,


72/141

E)e#tri#a) testi%-

T"e electrical contractor is c"ared wit" a res-onsi!ility to carry out a num!er of tests on an

electrical installation and electrical e3ui-ment,

T"e reasons for testin t"e installation are*

., To ensure t"at t"e installation com-lies wit" t"e Reulations,

', To ensure t"at t"e installation meets t"e s-ecification,

5, To ensure t"at t"e installation is safe to use,

T"ose w"o are to carry out t"e electrical tests must first consider t"e followin safety factors*

., An assessment of safe wor+in -ractice must !e made !efore testin !eins,

', All safety -recautions must !e -ut in -lace !efore testin !eins,

5, E(eryone must !e notified t"at t"e test -rocess is a!out to ta+e-lace* for e4am-le t"e

client and ot"er wor+ers w"o may !e affected !y t"e tests,

0, ermitstoWor+ > must !e o!tained w"ere rele(ant,

$, All sources of information rele(ant to t"e tests "a(e !een o!tained,

?, T"e rele(ant circuits and e3ui-ment "a(e !een identified,

9, Safe isolation -rocedures "a(e !een carried out K care must !e e4ercised "ere* in

occu-ied -remises* not to switc" off com-uter systems wit"out first o!tainin

-ermission,

2, T"ose w"o are to carry out t"e tests are com-etent to do so,

T"e electrical contractor is c"ared !y t"e IEE Reulations for Electrical Installations to test all

new installations and ma:or e4tensions durin erection and u-on com-letion !efore !ein -ut

into ser(ice, T"e contractor may also !e called u-on to test installations and e3ui-ment in order

to identify and remo(e faults, T"ese re3uirements im-ly t"e use of a--ro-riate test instruments*

and in order to ta+e accurate readins consideration s"ould !e i(en to t"e followin -oints*

., Is t"e instrument suita!le for t"is test

', Fa(e t"e correct scales !een selected

5, Is t"e test instrument correctly connected to t"e circuit

)any commercial instruments are ca-a!le of ma+in more t"an one test or "a(e a rane of

scales to c"oose from, A rane selector switc" is usually used to c"oose t"e a--ro-riate scale, A

scale rane s"ould !e c"osen w"ic" suits t"e rane of t"e current* (oltae or resistance !ein

measured, or e4am-le* w"en ta+in a readin in t"e 2 or / V rane t"e o!(ious scale c"oice

would !e one i(in .% V full scale deflection, To ma+e t"is readin on an instrument wit" .%%

V full scale deflection would lead to errors* !ecause t"e deflection is too small,

Ammeters must !e connected in series wit" t"e load* and (oltmeters in -arallel across t"e load

as s"own in Fi%ure 8&, T"e -ower in a resisti(e load may !e calculated from t"e readins of

(oltae and current since H VI , T"is will i(e accurate calculations on !ot" a,c, and d,c,su--lies* !ut w"en measurin t"e -ower of an a,c, circuit w"ic" contains inductance or

ca-acitance a wattmeter must !e used !ecause t"e (oltae and current will !e out of -"ase,


73/141

Fi%ure 8&

attmeter, >mmeter, oltmeter, correctly connectin% to load&

(easuree%t o" $ower i% a three,$hase #ir#uit

., O%e,3atteter (ethod

W"en t"ree-"ase loads are !alanced* for e4am-le in motor circuits* one wattmeter may !e

connected into any -"ase* as s"own in Fi%ure 8&', T"is wattmeter will indicate t"e -ower in

t"at -"ase and since t"e load is !alanced t"e total -ower in t"e t"ree-"ase circuit will !e i(en

!y*

otal power + H attmeter readin%

:> Two,3atteter (ethod

T"is is t"e most commonly used met"od for measurin -ower in a t"ree-"ase* t"reewire system

since it can !e used for !ot" !alanced and un!alanced loads connected in eit"er star or delta, T"e

current coils are connected to any two of t"e lines* and t"e (oltae coils are connected to t"e

ot"er line* t"e one wit"out a current coil connection* as s"own in Fi%ure 8&+, T"en*

otal power '

T"is e3uation is true for any t"ree-"ase load* !alanced or un!alanced* star or delta connection*

-ro(ided t"ere is no fourt" wire in t"e system,


74/141

Fi%ure8&' ?ne

attmeter

measurement of

power&

Fi%ure 8&+ wo attmeter measurement power

@> Three,3atteter (ethod

If t"e installation is fourwire* and t"e load on eac" -"ase is un!alanced* t"en t"reewattmeter

readins are necessary* connected as s"own in Fi%ure 8&&Eac" wattmeter measures t"e -ower

in one -"ase and t"e total -ower will !e i(en !y*

otal power ' +


75/141

Fi%ure 8&

.ree attmeter measurement power

>1 TE'TER'

To%- tester

T"e ton tester or cli-on ammeter wor+s on t"e same -rinci-le as t"e transformer, T"e

laminated core of t"e transformer can !e o-ened and -assed o(er t"e !us!ar or sinlecore ca!le,

In t"is way a measurement of t"e current !ein carried can !e made wit"out disconnection of t"e

su--ly, T"e construction is s"own in Fi%ure 8&,

Fi%ure 8& on% tester or "lip on >mmeter

Phase seue%#e testers


76/141

"ase se3uence is t"e order in w"ic" eac" -"ase of a t"ree-"ase su--ly reac"es its ma4imum

(alue, T"e normal -"ase se3uence for a t"ree-"ase su--ly is !rownK!lac+Krey* w"ic" means

t"at first !rown* t"en !lac+ and finally t"e rey -"ase reac"es its ma4imum (alue,

"ase se3uence "as an im-ortant a--lication in t"e connection of t"ree-"ase transformers, T"e

secondary terminals of a t"ree-"ase transformer must not !e connected in -arallel until t"e

-"ase se3uence is t"e same,

A -"ase se3uence tester can !e an indicator w"ic" is* in effect* a miniature induction motor* wit"

t"ree clearly colourcoded connection leads, A rotatin disc wit" a -ointed arrow s"ows t"e

normal rotation for -"ase se3uence !rownK!lac+Krey, If t"e se3uence is re(ersed t"e disc

rotates in t"e o--osite direction to t"e arrow, Fowe(er* an onsite -"ase se3uence tester can !e

made !y connectin four '5% V !y .%% W lam-s and a -,f, correction ca-acitor from a

fluorescent luminaire as s"own in Fi%ure& 8&0,

T"e ca-acitor ta+es a leadin current w"ic" results in a -"ase dis-lacement in t"e ot"er two

-"ases, T"e -"asor addition of t"e (oltae in t"e circuit results in one -air of lam-s illuminatin

!ri"tly w"ile t"e ot"er -airs are illuminated dimly, Two lam-s must !e connected in series as

s"own in Fi%ure 8&0!ecause most of t"e line (oltae will !e across t"em durin t"e test,

Fi%ure 8&0 2.ase se;uence test by Li%.t 4ri%.t , Li%.t 5im met.od,

Test eui$e%t used b! e)e#tri#ia%s

T"e Fealt" and Safety E4ecuti(e


77/141

., T"e -ro!es must "a(e finer !arriers or !e s"a-ed so t"at t"e "and or finers cannot ma+e

contact wit" t"e li(e conductors under test,

', T"e -ro!e ti- must not -rotrude more t"an ' mm* and -refera!ly only . mm* !e s-rin

loaded and screened,

5, T"e lead must !e ade3uately insulated and coloured so t"at one lead is readily

distinuis"ed from t"e ot"er,

0, T"e lead must !e fle4i!le and sufficiently ro!ust,

$, T"e lead must !e lon enou" to ser(e its -ur-ose !ut not too lon,

?, T"e lead must not "a(e accessi!le e4-osed conductors e(en if it !ecomes detac"ed from

t"e -ro!e or from t"e instrument,

9, W"ere t"e leads are to !e used in con:unction wit" a (oltae detector t"ey must !e

-rotected !y a fuse,

A suita!le -ro!e and lead is s"own in Fi%ure 8&3,

Fi%ure 8&3 est 2robes >nd Leads&

GS 52 also tells us t"at w"ere t"e test is !ein made sim-ly to esta!lis" t"e -resence or a!sence

of a (oltae* t"e -referred met"od is to use a -ro-rietary test lam- or (oltae indicator w"ic" is

suita!le for t"e wor+in (oltae* rat"er t"an a multimeter, Accident "istory "as s"own t"at

incorrectly set multimeters or ma+es"ift de(ices for (oltae detection "a(e fre3uently caused

accidents,

i, /,2 s"ows a suita!le (oltae indicator, Test lam-s and (oltae indicators are not failsafe*

and t"erefore GS 52 recommends t"at t"ey s"ould !e reularly -ro(ed* -refera!ly !efore and

after use* as descri!ed in t"e flowc"art for a safe isolation -rocedure s"own in Fi%ure 8&7&


78/141

Fi%ure 8&7 olta%e Indicator&

Test $ro#edures

., T"e circuits must !e isolated usin a safe isolation -rocedure > * suc" as t"at descri!ed

!elow* !efore !einnin to test,

', All test e3ui-ment must !e a--ro(ed > and connected to t"e test circuits !y recommendedtest -ro!es as descri!ed !y t"e FSE Guidance Notes GS 52, T"e test e3ui-ment used must

also !e -ro(ed > on a +nown su--ly or !y means of a -ro(in unit,

5, Isolation de(ices must !e secured > in t"e off > -osition,

0, Warnin notices must !e -osted,

$, All rele(ant safety and functional tests must !e com-leted !efore restorin t"e su--ly,

Li+e testi%-

T"e Electricity at Wor+ Act tells us t"at it is -refera!le > t"at su--lies !e made dead !eforewor+ commences to carry out t"e acti(ity@

only use a--ro(ed test e3ui-ment@

set u- !arriers and warnin notices so t"at t"e wor+ acti(ity does not create a situation

danerous to ot"ers,


79/141


80/141

Fi%ure 8&8 Flow ".art for *ecure Installations


81/141

&isua) I%s$e#tio%

T"e installation must !e (isually ins-ected !efore testin !eins, T"e aim of t"e (isualins-ection is to confirm t"at all e3ui-ment and accessories are undamaed and com-ly wit" t"e

rele(ant Britis" and Euro-ean Standards* and also t"at t"e installation "as !een securely and

correctly erected, Reulation ?..,5 i(es a c"ec+list for t"e initial (isual ins-ection of an

installation* includin,

Connection of conductors@

Identification of conductors@

Routin of ca!les in safe ;ones@

Selection of conductors for current carryin ca-acity and (olt dro-@

Connection of sinle-ole de(ices for -rotection or switc"in in -"ase conductorsonly@

Correct connection of soc+et outlets* lam-"olders* accessories and e3ui-ment@

resence of fi re !arriers* suita!le seals and -rotection aainst t"ermal effects@

)et"ods of Basic -rotection > aainst electric s"oc+* includin t"e insulation of

li(e -arts and -lacement of li(e -arts out of reac" !y ittin a--ro-riate !arriers and

enclosures@

)et"ods of ault rotection > aainst electric s"oc+ includin t"e -resence of

eart"in conductors for !ot" -rotecti(e !ondin and su--lementary !ondin,

re(ention of detrimental influences


82/141

T"is is re-eated for eac" a--ro-riate item on t"e c"ec+list,

T"ose tests w"ic" are rele(ant to t"e installation must t"en !e carried out in t"e se3uence i(en

in Reulation ?.',. for reasons of safety and accuracy, T"ese tests are as follows*

eore the suppl! is connected

., Test for continuity of -rotecti(e conductors* includin -rotecti(e e3ui-otential and

su--lementary !ondin,

', Test t"e continuity of all rin final circuit conductors,

5, Test for insulation resistance,

0, Test for -olarity usin t"e continuity met"od,

$, Test t"e eart" electrode resistance,

/ith the suppl! connected

?, Rec"ec+ -olarity usin a (oltmeter or a--ro(ed test lam-,

9, Test t"e eart" fault loo- im-edance,

2, Carry out additional -rotection testin


83/141

)odern diital test instruments are reasona!ly ro!ust* !ut to maintain t"em in ood wor+in

order t"ey must !e treated wit" care, An a--ro(ed test instrument costs e3ually as muc" as a

ood3uality camera@ it s"ould* t"erefore* recei(e t"e same care and consideration,

#et us now loo+ at t"e re3uirements of four often used test meters,

Co%ti%uit! tester

To measure accurately t"e resistance of t"e conductors in an electrical installation we must use

an instrument w"ic" is ca-a!le of -roducin an o-en circuit (oltae of !etween 0 and '0 V a,c,

or d,c,* and deli(er a s"ortcircuit current of not less t"an '%% mA s law calculation and

dis-lays t"e test result as a resistance readin,

RCD tester

W"ere circuits are -rotected !y an RCD we must carry out a test to ensure t"at t"e de(ice will

o-erate (ery 3uic+ly under fault conditions and wit"in t"e time limits set !y t"e IEEReulations, T"e instrument must* t"erefore* simulate a fault and measure t"e time ta+en for t"e

RCD to o-erate, T"e instrument is* t"erefore* cali!rated to i(e a readin measured in

milliseconds to an inser(ice accuracy of .%O,

If you -urc"ase ood3uality a--ro(ed > test instruments and leads from s-ecialist

manufacturers t"ey will meet all t"e Reulations and Standards and t"erefore i(e (alid test

results, Fowe(er* to carry out all t"e tests re3uired !y t"e IEE Reulations will re3uire a num!er

of test instruments,

#et us now consider t"e indi(idual tests,


84/141

1> Testi%- "or Co%ti%uit! o" Prote#ti+e Co%du#tors .?1:>:>1

T"e o!:ect of t"e test is to ensure t"at t"e circuit -rotecti(e conductor s main -rotecti(e eart"in terminal to (erify t"at it is electrically

sound and correctly connected* includin t"e -rotecti(e e3ui-otential and su--lementary

!ondin conductors,

A d,c, test usin an o"mmeter continuity tester is suita!le w"ere t"e -rotecti(e conductors are of

co--er or aluminium u- to 5$ mm' , T"e test is made wit" t"e su--ly disconnected* measurin

from t"e consumer>s main -rotecti(e eart"in terminal to t"e far end of eac" CC* as s"own in

Fi%ure 8&9 , T"e resistance of t"e lon test lead is su!tracted from t"ese readins to i(e t"e

resistance (alue of t"e CC,

Fi%ure 8&9 estin% "ontinuity

W"ere steel conduit or trun+in forms t"e -rotecti(e conductor* t"e standard test descri!ed

a!o(e may !e used* !ut additionally t"e enclosure must !e (isually c"ec+ed alon its lent" to

(erify t"e interity of all t"e :oints, If t"e ins-ectin enineer "as rounds to 3uestion t"e

soundness and 3uality of t"ese :oints t"en t"e -"ase eart" loo- im-edance test descri!ed later in

t"is c"a-ter s"ould !e carried out,

If* after carryin out t"is furt"er test* t"e ins-ectin enineer still 3uestions t"e 3uality and

soundness of t"e -rotecti(e conductor formed !y t"e metallic conduit or trun+in t"en a furt"ertest can !e done usin an a,c, (oltae not reater t"an $% V at t"e fre3uency of t"e installation

and a current a--roac"in .,$ times t"e desin current of t"e circuit* !ut not reater t"an '$ A,


85/141

T"is test can !e done usin a low(oltae transformer and suita!ly connected ammeters and

(oltmeters* !ut a num!er of commercial instruments are a(aila!le suc" as t"e Clare tester* w"ic"

i(e a direct readin in o"ms,

Because fault currents will flow around t"e eart" fault loo- -at"* t"e measured resistance (alues

must !e low enou" to allow t"e o(ercurrent -rotecti(e de(ice to o-erate 3uic+ly, or a

satisfactory test result* t"e resistance of t"e -rotecti(e conductor s"ould !e consistent wit" t"ose

(alues calculated for a line conductor of similar lent" and crosssectional area,

: >Testi%- "or Co%ti%uit! o" Ri%- 5i%a) Cir#uit Co%du#tors .?1:>:>:

T"e o!:ect of t"e test is to ensure t"at all rin circuit ca!les are continuous around t"e rin* t"at

is* t"at t"ere are no !rea+s and no interconnections in t"e rin* and t"at all connections are

electrically and mec"anically sound, T"is test also (erifies t"e -olarity of eac" soc+et outlet,

T"e test is made wit" t"e su--ly disconnected* usin an o"mmeter !y disconnect and se-arate

t"e conductors of !ot" les of t"e rin at t"e main fuse,

T"ere are t"ree ste-s to t"is test,

'TEP 1

)easure t"e resistance of t"e line conductors


86/141

Fi%ure 8& !easurin% t.e

@esistance of 2.ase, Geutral

>nd 2rotectiBe "onductors

'TEP :

T"e li(e and neutral conductors s"ould now !e tem-orarily :oined toet"er as s"own in Fi%ure

8&', An o"mmeter readin s"ould t"en !e ta+en !etween li(e and neutral at e(ery soc+et outlet

on t"e rin circuit, T"e readins o!tained s"ould !e su!stantially t"e same* -ro(ided t"at t"ere

are no !rea+s or multi-le loo-s in t"e rin, Eac" readin s"ould "a(e a (alue of a--ro4imately

"alf t"e li(e and neutral o"mmeter readins measured in Ste- . of t"is test, Soc+ets connected as

a s-ur will "a(e a sli"tly "i"er (alue of resistance !ecause t"ey are fed !y only one ca!le*

w"ile eac" soc+et on t"e rin is fed !y two ca!les, Record t"e results on a ta!le suc" as t"at

s"own in able 8&,

'TEP @

W"ere t"e CC is wired as a rin* for e4am-le w"ere twin and eart" ca!les or -lastic conduit is

used to wire t"e rin* tem-orarily :oin t"e li(e and CCs toet"er as s"own in Fi%ure 8&+ , An

o"mmeter readin s"ould t"en !e ta+en !etween li(e and eart" at e(ery soc+et outlet on t"e rin,

T"e readins o!tained s"ould !e su!stantially t"e same -ro(ided t"at t"ere are no !rea+s or

multi-le loo-s in t"e rin, T"is (alue is e3ual to R. R' for t"e circuit, Record t"e results on an

installation sc"edule suc" as t"at i(en in t"e IEE Reulations or a ta!le suc" as t"at s"own in


87/141

able 8&, T"e Ste- 5 (alue of R. R' s"ould !e e3ual to < r. r' =&0* w"ere r. and r' are t"e

o"mmeter readins from Ste- . of t"is test 1=,

Fi%ure 8&' "onnection of main "onductors and est "onditions

Fi%ure 8&+ - "onnection of main "onductors and est "onditions

@> Testi%- I%su)atio% Resista%#e .?1:>@


88/141

T"e o!:ect of t"e test is to (erify t"at t"e 3uality of t"e insulation is satisfactory and "as not

deteriorated or s"ortcircuited, T"e test s"ould !e made at t"e consumer>s unit wit" t"e mains

switc" off* all fuses in -lace and all switc"es closed, Neon lam-s* ca-acitors and electronic

circuits s"ould !e disconnected* since t"ey will res-ecti(ely low* c"are u- or !e damaed !y

t"e test,

T"ere are two tests to !e carried out usin an insulation resistance tester w"ic" must "a(e a test

(oltae of $%% V d,c, for '5% V and 0%% V installations, T"ese are line and neutral conductors to

eart" and !etween line conductors, T"e -rocedures are*

Li%e a%d %eutra) #o%du#tors to earth

., Remo(e all lam-s,

', Close all switc"es and circuit !rea+ers,

5, Disconnect a--liances,0, Test se-arately !etween t"e line conductor and eart"* and !etween t"e neutral conductor and

eart"* for e(ery distri!ution circuit at t"e consumer>s unit as s"own in Fi%ure 8& &Record

t"e results on a sc"edule of test results suc" as t"at i(en in A--endi4 ? of t"e IEE

Reulations,

Fi%ure 8& Insulation resistance est

4etween line conductors

., Remo(e all lam-s,


89/141


90/141

Fi%ure 8& 2olarity est&

or a satisfactory test result t"e o"mmeter or continuity meter s"ould read (ery close to ;ero for

eac" test,

Remo(e t"e test lin+ and record t"e results on a sc"edule of test results suc" as t"at i(en in

A--endi4 ? of t"e IEE Reulations,

> Testi%- Earth E)e#trode Resista%#e .?1:>F

W"en an eart" electrode "as !een sun+ into t"e eneral mass of eart"* it is necessary to (erify

t"e resistance of t"e electrode, T"e eneral mass of eart" can !e considered as a lare conductor

w"ic" is at ;ero -otential, Connection to t"is mass t"rou" eart" electrodes -ro(ides a reference

-oint from w"ic" all ot"er (oltae le(els can !e measured, T"is is a tec"ni3ue w"ic" "as !een

used for a lon time in -ower distri!ution systems,

T"e resistance to eart" of an electrode will de-end u-on its s"a-e* si;e and t"e resistance of t"esoil, Eart" rods form t"e most efficient electrodes, A rod of a!out . m will "a(e an eart"

electrode resistance of !etween .% and '%% , E(en in !ad eart"in conditions a rod of a!out '

m will normally "a(e an eart" electrode resistance w"ic" is less t"an $%% , In countries w"ic"

e4-erience lon dry -eriods of weat"er t"e eart" electrode resistance may !e t"ousands of o"ms,

T"e IEE Reulation $0',',. reconi;es t"e use of t"e followin ty-es of eart" electrodes

Eart" rods or -i-es

Eart" ta-es or wires

Eart" -lates Eart" electrodes em!edded in foundations

Welded metallic reinforcement of concrete structures


91/141

1t"er suita!le underround metalwor+

#ead s"eat"s or ot"er metallic co(erins of ca!les,

T"e eart" electrode is sun+ into t"e round* !ut t"e -oint of connection s"ould remain accessi!le

s unit to isolate t"e installation,

5, Usin a line eart" loo- im-edance tester* test !etween t"e incomin line conductor and

t"e eart" electrode,

0, Reconnect t"e -rotecti(e !ondin conductors w"en t"e test is com-leted,


92/141

Record t"e result on a sc"edule of test results suc" as t"at i(en in A--endi4 ? of t"e IEE

Reulations, T"e IEE Guidance Note 5 tells us t"at an acce-ta!le (alue for t"e measurement of

t"e eart" electrode resistance would !e less t"an '%% ,

ro(idin t"e first fi(e tests were satisfactory* t"e su--ly may now !e switc"ed on and t"e finaltests com-leted wit" t"e su--ly connected,

?> Testi%- Po)arit! ; 'u$$)! Co%%e#ted

Usin an a--ro(ed (oltae indicator suc" as t"at s"own at Fi%ure 8&7or test lam- and -ro!es

w"ic" com-ly wit" t"e FSE Guidance Note GS 52* aain carry out a -olarity test to (erify t"at

all fuses* circuit !rea+ers and switc"es are connected in t"e li(e conductor,

Test from t"e common terminal of switc"es to eart"* t"e li(e -in of eac" soc+et outlet to eart"and t"e centre -in of any Edison screw lam- "olders to eart", In eac" case t"e (oltmeter or test

lam- s"ould indicate t"e su--ly (oltae for a satisfactory result,

F> Testi%- Earth 5au)t Loo$ I$eda%#e , .'UPPL/ CONNECTED .?1:>

T"e o!:ect of t"is test is to (erify t"at t"e im-edance of t"e w"ole eart" fault current loo- line to

eart" is low enou" to allow t"e o(er current -rotecti(e de(ice to o-erate wit"in t"e

disconnection time re3uirements of Reulations 0..,5,',' and 0..,0,? and 0..,0,9* s"ould a

fault occur,

T"e w"ole eart" fault current loo- e4amined !y t"is test is com-rised of all t"e installation

-rotecti(e conductors* t"e main -rotecti(e eart"in terminal and -rotecti(e eart" conductors* t"e

eart"ed neutral -oint and t"e secondary windin of t"e su--ly transformer and t"e line

conductor from t"e transformer to t"e -oint of t"e fault in t"e installation,

T"e test will* in most cases* !e done wit" a -ur-osemade line eart" loo- im-edance tester

w"ic" circulates a current in e4cess of .% A around t"e loo- for a (ery s"ort time* so reducin

t"e daner of a faulty circuit, T"e test is made wit" t"e su--ly switc"ed on* and carried out from

t"e furt"est -oint of e(ery final circuit* includin li"tin* soc+et outlets and any fi4ed

a--liances, Record t"e results on a sc"edule of test results,

ur-ose!uilt testers i(e a readout in o"ms and a satisfactory result is o!tained w"en t"e loo-

im-edance does not e4ceed t"e a--ro-riate (alues i(en in Ta!les 0.,' and 0.,5 of t"e IEE

Reulations,


93/141

> Additio%a) Prote#tio%9 Testi%- o" RCD ; 'u$$)! Co%%e#ted .?1:>1@

T"e o!:ect of t"e test is to (erify t"e effecti(eness of t"e RCD* t"at it is o-eratin wit" t"e

correct sensiti(ity and -ro(in t"e interity of t"e electrical and mec"anical elements, T"e test

must simulate an a--ro-riate fault condition and !e inde-endent of any test facility incor-orated

in t"e de(ice,

W"en carryin out t"e test* all loads normally su--lied t"rou" t"e de(ice are disconnected,

T"e testin of a rin circuit -rotected !y a eneral-ur-ose RCD to BS EN ?.%%2 in a s-lit

!oard consumer unit is carried out as follows*

., Usin t"e standard lead su--lied wit" t"e test instrument* disconnect all ot"er loads and -lu

in t"e test lead to t"e soc+et at t"e centre of t"e rin


94/141

In !ot" cases t"e certificate must include t"e test (alues w"ic" (erify t"at t"e installation

com-lies wit" t"e IEE Reulations at t"e time of testin,

Suested fre3uency of -eriodic ins-ection inter(als are i(en !elow*

Domestic installations K .% years

Commercial installations K $ years Industrial installations K 5 years

Aricultural installations K 5 years

Cara(an site installations K . year

Cara(ans K 5 years

Tem-orary installations on construction sites K 5 mont"s,

'a"e wori%- $ro#edures whe% testi%-

W"et"er you are carryin out t"e test -rocedure -osition,

ut u- warnin notices so t"at ot"er wor+ers will +now w"at is "a--enin,

Notify e(eryone in t"e !uildin t"at testin is a!out to start and for a--ro4imately "ow

lon it will continue,

1!tain a -ermittowor+ > if t"is is rele(ant,

1!tain a--ro(al to "a(e systems s"ut down w"ic" mi"t !e damaed !y your testin

acti(ities, or e4am-le* com-uter systems may cras" > w"en su--lies are switc"ed off,

Ventilation and fume e4traction systems will sto- wor+in w"en you disconnect t"esu--lies,

For the saet! o other people,

i4 warnin notices around your wor+ area,

Use cones and "i"ly (isi!le warnin ta-e to screen off your wor+ area,

)a+e an effort to let e(eryone in t"e !uildin +now t"at testin is a!out to !ein, ou

mi"t !e a!le to do t"is w"ile you carry out t"e initial ins-ection of t"e installation,

1!tain (er!al or written aut"ori;ation to s"ut down information tec"noloy* emerency

o-eration or stand!y circuits,


95/141

o saeguard other s!stems,

Com-uter systems can !e se(erely damaed !y a loss of su--ly or t"e in:ection of a "i"

test (oltae from* for e4am-le* an insulation resistance test, Com-uter systems would

normally !e disconnected durin t"e test -eriod !ut t"is will enerally re3uire some

orani;ation !efore t"e testin !eins, Commercial orani;ations may !e una!le to

continue to wor+ wit"out t"eir com-uter systems and* in t"ese circumstances it may !e

necessary to test outside t"e normal wor+in day,

Any resistance measurements made on electronic e3ui-ment or electronic circuits must

!e ac"ie(ed wit" a !attery o-erated o"mmeter in order to a(oid damain t"e electronic

circuits,

arm animals are creatures of "a!it and may !ecome (ery rum-y to find you testin

t"eir mil+in -arlour e3ui-ment at mil+in time,

Fos-itals and factories may "a(e emerency stand!y enerators w"ic" reeneri;e

essential circuits in t"e e(ent of a mains failure, our isolation of t"e circuit for testin

may cause t"e emerency systems to o-erate, Discuss any s-ecial systems wit" t"e-erson aut"ori;in t"e wor+ !efore testin !eins,

Coissio%i%-

W"en t"e fault "as !een identified and re-aired* t"e circuit* system or e3ui-ment must !e

ins-ected* tested and functional c"ec+s carried out as re3uired !y IEE Reulations C"a-ter ?.,

T"e -ur-ose of ins-ectin and testin t"e re-aired circuit* system or e3ui-ment is to confirm t"e

electrical interity of t"e system !efore it is reeneri;ed,

he tests recommended b! Part 0 o the IEE Regulations are,

., Test t"e continuity of t"e -rotecti(e conductors includin t"e -rotecti(e e3ui-otential and

su--lementary !ondin conductors,

', Test t"e continuity of all rin final circuit conductors,

5, Test t"e insulation resistance !etween li(e conductors and eart",

0, Test t"e -olarity to (erify t"at sinle -ole control and -rotecti(e de(ices are connected in

t"e line conductor only,

$, Test t"e eart" electrode resistance w"ere t"e installation incor-orates an eart" electrode

as a -art of t"e eart"in system,

he suppl! ma! no' be connected and the ollo'ing tests carried out.

?, Test t"e -olarity usin an a--ro(ed test lam- or (oltae indicator,

9, Test t"e eart" fault loo- im-edance w"ere t"e -rotecti(e measures used re3uire a

+nowlede of eart" fault loo- im-edance,


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T"ese tests w"ere rele(ant must !e carried out in t"e order i(en a!o(e to com-ly wit" IEE

Reulation ?.',., If any test indicates a failure* t"at test and any -recedin test must !e re-eated

after t"e fault "as !een rectified, T"is is !ecause t"e earlier tests may "a(e !een influenced !y

t"e fault,

As t"e client&customer is to recei(e t"e oriinals of any certification* it is im-ortant t"at all

rele(ant details are com-leted correctly, T"is ensures t"at future ins-ectors are aware of t"e

installation details and test results t"at may indicate a slow -roressi(e deterioration in some or

all of t"e installations,

Ha%d O+er to the C)ie%t

Fandin o(er t"e re-aired circuit* system or e3ui-ment is an im-ortant -art of t"e fault

dianosis and re-air -rocess, ou are effecti(ely sayin to t"e client "ere is your circuit*

system or e3ui-ment* it is now safe to use and it wor+s as it s"ould wor+ > ,

T"e client will -ro!a!ly !e interested in t"e followin*

W"at "as !een done to identify and re-air t"e fault

T"e -ossi!le reasons w"y t"e fault occurred and recommendations w"ic" will -re(ent a

reoccurrence of t"e -ro!lem,

A demonstration of t"e o-eration of t"e circuit* system or e3ui-ment to s"ow t"at t"e

fault "as !een fully rectified,

inally* t"e "andin o(er of certificates of test results and manufacturer>s instructions* ifnew e3ui-ment "as !een installed,

>:CIRCUIT BREA2ER'

Durin t"e o-eration of -ower system* it is often desira!le and necessary to switc" on or off t"e

(arious circuits


97/141

disad(antaes, irstly* w"en a fuse !lows out* it ta+es 3uite sometime to re-lace it and restore

su--ly to t"e customers, Secondly* a fuse cannot successfully interru-t "ea(y fault currents t"at

result from faults on modern "i"(oltae and lare ca-acity circuits, Due to t"ese

disad(antaes* t"e use of switc"es and fuses is limited to low(oltae and small ca-acity

circuits w"ere fre3uent o-erations are not e4-ected, E,, for switc"in and -rotection of

distri!ution transformers* li"tin circuits* !ranc" circuits of distri!ution lines etc,

Wit" t"e ad(ancement of -ower system* t"e lines and ot"er e3ui-ment o-erate at (ery "i"

(oltaes and carry lare currents, T"e arranement of switc"es alon wit" fuses cannot ser(e t"e

desired function of switc"ear in suc" "i" ca-acity circuits, T"is necessitates to em-loy a more

de-enda!le means of control suc" as is o!tained !y t"e use of circuit !rea+ers, A circuit !rea+er

can ma+e or !rea+ a circuit eit"er manually or automatically under all conditions (i;,* noload*

fullload and s"ortcircuit conditions, T"is c"aracteristic of t"e circuit !rea+er "as made it a (ery

useful e3ui-ment for switc"in and -rotection of (arious -arts of t"e -ower system,

Cir#uit Breaer

A circuit !rea+er is a -iece of e3ui-ment w"ic" can*

.,= )a+e or !rea+ a circuit eit"er manually or !y remote control under normal

conditions

',= Brea+ a circuit automatically under fault conditions

5,= )a+e a circuit eit"er manually or !y t"e remote control under fault conditions,

T"us a circuit !rea+er incor-orates manual


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T"ere are se(eral ways of classifyin t"e circuit !rea+ers, Fowe(er* t"e most eneral way of

classification is on t"e !asis of medium used for arc e4tinction is usually oil*air* sul-"ur

"e4afluoride


99/141

W"ic" use a lare 3uantity of oil, T"e oil "as to ser(e two -ur-oses, irstly* It e4tinuis"es t"e

arc durin o-enin of contacts and Secondly* it insulates t"e current conducin -arts from one

anot"er and from t"e eart"ed tan+, Suc" circuit !rea+ers may !e classified into*

.,= lain Brea+ 1il Circuit Brea+ers

',= Arc Control 1il Circuit !rea+ers

In t"e former ty-e* no s-ecial means is a(aila!le for controllin t"e arc and t"e contacts are

directly e4-osed to t"e w"ole of t"e oil in t"e tan+, Fowe(er* in t"e latter ty-e* s-ecial arc

control de(ices are em-loyed to et t"e !eneficial action of t"e arc as efficiently as -ossi!le,

', Low Oi) Cir#uit Breaers

W"ic" use minimum amount of oil* In suc" circuit !rea+ers* oil is used only for arc e4tinction*

t"e current conducin -arts are insulated !y air or -orcelain or oranic insulatin material,

@> P)ai% Brea Oi) Cir#uit Breaers

A lain !rea+ oil circuit !rea+er in(ol(es t"e sim-le -rocess of se-aratin t"e contacts under t"e

w"ole of t"e oil in t"e tan+, T"ere is no s-ecial system for arc control ot"er t"an t"e increase in

lent" caused !y t"e se-aration of contacts, T"e arc e4tinction occurs w"en a certain critical a-

!etween t"e contacts is reac"ed,

T"e -lain !rea+ oil circuit !rea+er is t"e earliest ty-e from w"ic" all ot"er circuit !rea+ers "a(e

de(elo-ed, It "as a (ery sim-le construction, It consists of fi4ed and mo(in contacts enclosed

in a stron weat"erti"t eart"ed tan+ containin oil u-to a certain le(el and an air cus"ion a!o(e

t"e oil le(el, T"e air cus"ion -ro(ides sufficient room to allow for t"e rece-tion of t"e arc ases

wit"out t"e eneration of unsafe -ressure in t"e dome of t"e !rea+er, It also a!sor!s t"e

mec"anical s"oc+ of t"e u-ward oil mo(ement, It is called a dou!le !rea+ !ecause it -ro(ides

two !rea+s in series,

Under normal o-eratin conditions* t"e fi4ed and mo(in contacts remain closed and t"e

!rea+er carries t"e normal circuit current, W"en a fault occurs* t"e mo(in contacts are -ulled

down !y t"e -rotecti(e system and an arc is stuc+ w"ic" (a-ourises t"e oil mainly into "ydroenas, T"e arc e4tinction is facilitated !y t"e followin -rocesses,

i, T"e "ydroen as !u!!le enerated around t"e arc cools t"e arc column and aids

t"e deionisation of t"e medium !etween t"e contacts,

ii, T"e as sets u- tur!ulence in t"e oil and "el-s in eliminatin t"e arcin -roducts

from t"e arc -at",

iii, As t"e arc lent"ens due to t"e se-aratin contacts* t"e dielectric strent" of t"e

medium is increased,

T"e result of t"ese actions is t"at at some critical a- lent"* t"e arc is e4tinuis"ed and t"e

circuit is interru-ted,

3isadvantages


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.,= T"ere is no s-ecial control o(er t"e arc ot"er t"an t"e increase in lent" !y

se-aratin t"e mo(in contacts* T"erefore* for successful interru-tion* lon arc

lent" is necessary,

',= T"ese !rea+ers "a(e lon and inconsistent arcin times,

5,= T"ese !rea+ers do not -ermit "i" s-eed interru-tion,

Due to t"ese disad(antaes* -lain !rea+ oil circuit !rea+ers are used only for low(oltaea--lications w"ere "i" !rea+in ca-acities are not im-ortant, It is a usual -ractice to use suc"

!rea+ers for low ca-acity installations for (oltaes not e4ceedin .. +V,

> Ar# Co%tro) Oi) Cir#uit Breaers

In case of -lain !rea+er discussed a!o(e* t"ere is (ery little artificial control o(er t"e arc,

T"erefore* com-arati(ely lon arc lent" is essential in order t"at tur!ulence In t"e oil caused !y

t"e as may assist in 3uenc"in it, Fowe(er* it is necessary and desira!le t"at final arc e4tinctions"ould occur w"ile t"e contacts a- is still s"ort, or t"is -ur-ose* some arc control is

incor-orated and t"e !rea+ers are t"en called arc control circuit !rea+ers, T"ere are two ty-es of

suc" !rea+ers* namely*

.,= Self K !last 1il Circuit Brea+ers K in w"ic" arc control is -ro(ided !y internal means

i,e, t"e arc itself is em-loyed for its own e4tinction efficiently,

',= orced K Blast oil Circuit Brea+ers K in w"ic" arc control is -ro(ided !y mec"anical

means e4ternal to t"e circuit !rea+er,

> 'e)" ; B)ast Oi) Cir#uit Breaers

In t"is ty-e of circuit !rea+er* t"e ases -roduced durin arcin are confined to a small (olume

!y t"e use of an insulatin riid -ressure c"am!er* a (ery "i" -ressure de(elo-ed to force t"e

oil and as t"rou" or around t"e arc to e4tinuis" it, T"e manitude of -ressure is enerated !y

t"e arc itself* t"erefore* suc" !rea+ers are sometimes called self enerated -ressure oil circuit

!rea+ers,

T"e -ressure c"am!er is relati(ely c"ea- to ma+e and i(es reduced final arc e4tinction a-

lent" and arcin time as aainst t"e -lain K!rea+ oil circuit !rea+er,

?> 5or#ed ; B)ast Oi) Cir#uit Breaers

In t"e self !last oil circuit !rea+ers discussed a!o(e* t"e arc itself enerates t"e necessary

-ressure to force t"e oil across t"e arc -at", T"e ma:or limitation of suc" !rea+ers is t"at arcin

times tend to !e lon and inconsistent w"en o-eratin aainst currents considera!ly less t"an t"e

rated currents, It is !ecause t"e as enerated is muc" reduced at low (alues of fault currents,T"is difficulty is o(ercome in forced!last oil circuit !rea+ers in w"ic" t"e necessary -ressure is

enerated !y e4ternal mec"anical means inde-endent of t"e fault currents to !e !ro+en,


101/141

In a forced K !last oil circuit !rea+er* oil -ressure is created !y t"e -iston K cylinder

arranement, T"e mo(ement of t"e -iston is mec"anically cou-led to t"e mo(in contact, W"en

a fault occurs* t"e contacts et se-arated !y t"e -rotecti(e system and an arc is stuc+ !etween

t"e contacts, T"e -iston forces a :et of oil towards t"e contact a- to e4tinuis" t"e arc, It may

!e noted t"at necessary oil -ressure -roduced does not in any way de-end u-on t"e fault current

to !e !ro+en,

%dvantages

.,= Since oil -ressure de(elo-ed is inde-endent of t"e fault current to !e interru-ted* t"e

-erformance at low currents is more consistent t"an wit" self K !last oil circuit

!rea+ers,

',= T"e 3uantity of oil re3uired is reduced considera!ly,

F> Low Oi) Cir#uit Breaers

In t"e !ul+ circuit !rea+ers discussed so far* t"e oil "as to -erform two functions, irstly* it acts

as an arc 3uenc"in medium and Secondly* it insulates t"e li(e -arts from eart", It "as !een

found t"at only a small -ercentae of oil is actually used for arc e4tinction w"ile t"e ma:or -art

is utili;ed for insulation -ur-oses, or t"is reason* t"e 3uantity of oil in !ul+ oil circuit !rea+ers

reac"es a (ery "i" fiure as t"e system (oltae increases, T"is not only increases t"e e4-enses*

tan+ si;e and wei"t of t"e !rea+er !ut it also increases t"e fire ris+ and maintenance -ro!lems,

T"e fact t"at only a small -ercentae of oil


102/141

., Su--ortin c"am!er K It is a -orcelain c"am!er mounted on a metal c"am!er, It is

filled wit" oil w"ic" is -"ysically se-arated from t"e oil in t"e circuit !rea+in

com-artment, T"e oil inside t"e su--ortin c"am!er and t"e annular s-ace formed

!etween t"e -orcelain insulation and !a+e lised -a-er is em-loyed for insulation

-ur-oses only,

', Circuit Brea+in c"am!er K It is a -orcelain enclosure mounted on t"e to- of t"e

su--ortin com-artment, It is filled wit" oil and "as followin -arts*

i, U--er and lower fi4ed contacts

ii, )o(in contact

iii, Tur!ulator

T"e mo(in contact is "ollow and includes a cylinder w"ic" mo(es down o(er a

fi4ed -iston, T"e tur!ulator is an arc control de(ice and "as !ot" a4ial and

radial (ents, T"e a4ial (entin ensures t"e interru-tion of low currents w"ere as

radial (entin "el-s in t"e interru-tion of "ea(y currents,

5,= To- c"am!er K It is a metal c"am!er and is mounted on t"e circuit !rea+in c"am!er,

It -ro(ides e4-ansion s-ace for t"e oil in t"e circuit !rea+in com-artment, T"e to-

c"am!er is also -ro(ided wit" a se-arator w"ic" -re(ents any loss of oil !y

centrifual action caused !y circuit !rea+er o-eration durin fault conditions,

O$eratio% o" Low Oi) Cir#uit Breaers

Under normal o-eratin condition* t"e mo(in contact remains enaed wit" t"e u--er fi4ed

contact, W"en a fault occurs* t"e mo(in contact is -ulled down !y t"e tri--in s-rins and an

arc is stuc+, T"e arc enery (a-ori;es t"e oil and -roduces ases under "i" -ressure, T"e action

constrains t"e oil to -ass t"rou" a central "ole in t"e mo(in contact and results in forcin

series of oil t"rou" t"e res-ecti(e -assaes of t"e tur!ulator, T"e -rocess of tur!ulation is

orderly mo(in across eac" section of t"e arc are successi(ely 3uenc"ed !y t"e effect of se-arate

streams of oil mo(in across eac" section in turn and !earin away its ases,

%dvantages

A low oil circuit !rea+er "as t"e followin ad(antaes o(er a !ul+ oil circuit !rea+er,

., It re3uires lesser 3uantity of oil

', It re3uires smaller s-ace

5, T"ere is reduced ris+ of fire

0, )aintenance -ro!lems are reduced

3isadvantages


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A low oil circuit !rea+er "as t"e followin disad(antaes as com-ared to a !ul+ oil circuit

!rea+er,

., Due to smaller 3uantity of oil* t"e deree of car!oni;ation is increased,

', T"ere is a difficulty of remo(in t"e ases from t"e contact s-ace in time,

5, T"e dielectric strent" of t"e oil deteriorates ra-idly due to "i" deree of

car!oni;ation,

(ai%te%a%#e o" Oi) Cir#uit Breaers

T"e maintenance of oil circuit !rea+er is enerally concerned wit" t"e c"ec+in of contacts and

dielectric strent" of oil, After a circuit !rea+er "as interru-ted fault currents a few times or load

currents se(eral times* its contacts may et !urnt !y arcin and t"e oil may lose some of its

dielectric strent" due to car!oni;ation, T"is results in t"e reduced ru-turin ca-acity of t"e

!rea+er, T"erefore* it is a ood -ractice to ins-ect t"e circuit !rea+er at reular inter(als of 5 or ?mont"s, Durin ins-ection of t"e !rea+er* t"e followin -oints s"ould !e +e-t in (iew,

., C"ec+ t"e current carryin -arts and arcin contacts, If t"e !urnin is se(ere* t"e

contacts s"ould !e re-laced,

', C"ec+ t"e dielectric strent" of t"e oil, If t"e oil is "ardly discoloured* it s"ould !e

c"aned or reconditioned, T"e oil in ood condition s"ould wit"stand 5% +V for

one minute in a standard oil testin cu- wit" 0 mm a- !etween electrodes,

5, C"ec+ t"e insulation for -ossi!le damae, Clean t"e surface and remo(e car!on

de-osits wit" a stron and dry fa!ric,

0, C"ec+ t"e oil le(el,

$, C"ec+ closin and tri--in mec"anism,

> Air B)ast Cir#uit Breaers

T"ese !rea+ers em-loy a "i" -ressure air !last as an arc 3uenc"in medium, T"e contacts are

o-ened in a flow of air!last esta!lis"ed !y t"e o-enin of !last (al(e, T"e air K !last cools t"e

arc and swee-s away t"e arcin -roducts to t"e atmos-"ere, T"is ra-idly i

Documents

Domestric Installations