103574321 copper for busbars

8/13/2019 103574321 Copper for Busbars

1/104

+Copper for Busbars

Prefaces

1. Design Considerations

2. Copper for Busbar Purposes

3. Current-carrying Capacity of Busbars

4. Alternating Current Effects in Busbars

. Effect of Busbar Arrange!ents on "ating

#. $%ort-Circuit Effects

&. 'ointing of Copper Busbars

(. )ec%anical $trengt% "e*uire!ents

. Busbar ,!pedance

1. Appendices

Bibliograp%y

COPPER DEVELOPMENT ASSOCATION

Publication 22, June 1996

Re!inte" Janua!# 2$$1 %it& 'o(e a(en"(ent'
http://www.cda.org.uk/megab2/elecapps/pub22/prefaces.htmhttp://www.cda.org.uk/megab2/elecapps/pub22/sec1.htm#1.%20Design%20Considerationshttp://www.cda.org.uk/megab2/elecapps/pub22/sec2.htm#2.%20Copper%20for%20Busbar%20Purposeshttp://www.cda.org.uk/megab2/elecapps/pub22/sec3.htm#3.%20Current-carrying%20Capacity%20of%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec4.htm#4.%20Alternating%20Current%20Effects%20in%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#5.%20Effect%20of%20Busbar%20Arrangements%20on%20Ratinghttp://www.cda.org.uk/megab2/elecapps/pub22/sec6.htm#6.%20Short-Circuit%20Effectshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#7.%20Jointing%20of%20Copper%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#8.%20Mechanical%20Strength%20Requirementshttp://www.cda.org.uk/megab2/elecapps/pub22/sec9.htm#9.%20Busbar%20Impedancehttp://www.cda.org.uk/megab2/elecapps/pub22/sec10.htm#10.%20Appendiceshttp://www.cda.org.uk/megab2/elecapps/pub22/sec11.htm#Bibliographyhttp://www.cda.org.uk/megab2/elecapps/pub22/prefaces.htmhttp://www.cda.org.uk/megab2/elecapps/pub22/sec1.htm#1.%20Design%20Considerationshttp://www.cda.org.uk/megab2/elecapps/pub22/sec2.htm#2.%20Copper%20for%20Busbar%20Purposeshttp://www.cda.org.uk/megab2/elecapps/pub22/sec3.htm#3.%20Current-carrying%20Capacity%20of%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec4.htm#4.%20Alternating%20Current%20Effects%20in%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#5.%20Effect%20of%20Busbar%20Arrangements%20on%20Ratinghttp://www.cda.org.uk/megab2/elecapps/pub22/sec6.htm#6.%20Short-Circuit%20Effectshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#7.%20Jointing%20of%20Copper%20Busbarshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#8.%20Mechanical%20Strength%20Requirementshttp://www.cda.org.uk/megab2/elecapps/pub22/sec9.htm#9.%20Busbar%20Impedancehttp://www.cda.org.uk/megab2/elecapps/pub22/sec10.htm#10.%20Appendiceshttp://www.cda.org.uk/megab2/elecapps/pub22/sec11.htm#Bibliography


2/104

Prefaces

Preface to 1(4 Edition

T&i' C)D)A) ublication &a' lon* been accete" a' t&e 'tan"a!" !e+e!ence %o! on bu'ba! "e'i*n)T&i' !e-i'e" an" u"ate" e"ition inco!o!ate' !ecent !o*!e'' in t&e tec&nolo*# o+ bu'ba! "e'i*na' !e+lecte" in ne% 'tan"a!"' an" en*inee!in* !actice')

All "ata an" +o!(ulae &a-e been (et!icate" an" t&e (et&o" o+ !e'entation +acilitate' t&e u'e o+calculato!' o! co(ute!') T&e (an# -a!iable' to be con'i"e!e" a!e clea!l# e.laine" an" 'ecialattention &a' been *i-en to "ete!(inin* t&e (o't econo(ic loa"in*' in o!"e! to (a.i(i'e cu!!entca!!#in* caacit# +o! (ini(u( in'tallation co't' an" !unnin* lo''e') T&e!e i', t&e!e+o!e, a u'e+ulco(a!i'on o+ t&e elect!ical an" (ec&anical !oe!tie' o+ &i*& con"ucti-it# coe! an" alu(iniu()E.t!a attention &a' been *i-en to !eco((en"e" /ointin* tec&ni0ue', bot& b# boltin* an" %el"in*)

I(!o-e(ent' &a-e al'o been (a"e to t&e 'ection "ealin* %it& 'in e++ect') T&e in+o!(ation oni(e"ance &a' been e.an"e" 'o t&at o%e! +acto! -a!iation' can no% be +u!t&e! !e"icte") T&etable' o+ !atin*' an" !oe!tie' &a-e been e.an"e" a' &a-e t&e e.a(le' o+ t#ical calculation')

T&e !e+e!ence' &a-e been u"ate" to inclu"e !ecent ublication')

CDA %i'&e' to acno%le"*e t&e con'i"e!able &el *i-en in t&e !e-i'ion o+ t&i' te.t b# M! Moot&(an, C&ie+ En*inee!, u'ba! 3nit, al+ou! eatt# Po%e! Con't!uction Lt" an" b# M! 4Je++e!ie', C&ie+ Metallu!*i't, T&o(a' olton 5 Son' Lt") al'o +o! (an# &el+ul co((ent' (a"e ont&e te.t b# M! Ca!# 7Si(le. 8 )E) Lt", M! A Jac'on 7AMICA, M! J C Po%e!7!iti'& Elect!ic Reai!' Lt", M! E 4!i*&t 7Otte!(ill S%itc&*ea! Lt" an" (e(be!' o+ t&e !iti'&Non8:e!!ou' Metal' :e"e!ation ;i*& Con"ucti-it# Coe! !ou)

Preface to 1# Edition

1. Design Considerations


3/104

,ntroduction

ypes of Busbar

C%oice of Busbar )aterial

,ntroduction

T&e %o!" bu'ba!, "e!i-e" +!o( t&e Latin %o!" o(nibu' 7


4/104

bAi! in'ulate" %it& 'e*!e*atin* ba!!ie!' bet%een con"ucto!' o+ "i++e!ent &a'e')cTotall# enclo'e" but &a-in* t&e con't!uction a' t&o'e +o! 7a an" 7b"Ai! in'ulate" %&e!e eac& &a'e i' +ull# i'olate" +!o( it' a"/acent &a'e7' b# an ea!t&e"enclo'u!e) T&e'e a!e u'uall# calle"


5/104

12 Co't Lo% %&en co(a!e" %it& a''ociate" lant) Ma/o! con'i"e!ation in (an# ca'e')Pa!ticula!l# %&enoti(i'ationcaitali'ation i' u'e")

1@ E++ect' o+ +ailu!e Ve!# 'e!iou') ;i*& ene!*ie' "i''iate" into+ault)

Li(ite" b# lo% -olta*e an" bu'ba!'ie)

1? Coe! t#e ;i*& con"ucti-it#) ;i*& con"ucti-it#)

1>Coe! '&ae3'uall# !ectan*ula!) Tubula! u'e" +o! &i*& cu!!ent +o!ce8coole")3'uall# la!*e c!o'' 'ection !ectan*ula!) Tubula!u'e" +o! 'o(e lo% cu!!ent &i*& -olta*e alication' an" &i*& cu!!ent +o!ce8coole")

C%oice of Busbar )aterial

At t&e !e'ent ti(e t&e onl# t%o co((e!ciall# a-ailable (ate!ial' 'uitable +o! con"ucto! u!o'e'a!e coe! an" alu(iniu() T&e table belo% *i-e' a co(a!i'on o+ 'o(e o+ t&ei! !oe!tie') It can

be 'een t&at +o! con"ucti-it# an" 't!en*t&, &i*& con"ucti-it# coe! i' 'ue!io! to alu(iniu() T&eonl# "i'a"-anta*e o+ coe! i' it' "en'it#= +o! a *i-en cu!!ent an" te(e!atu!e !i'e, an alu(iniu(con"ucto! %oul" be li*&te!, e-en t&ou*& it' c!o''8'ection %oul" be la!*e!) In enclo'e" '#'te('&o%e-e!, 'ace con'i"e!ation' a!e o+ *!eate! i(o!tance t&an %ei*&t) E-en in oen8ai! '#'te('t&e %ei*&t o+ t&e bu'ba!', %&ic& a!e 'uo!te" at inte!-al', i' not nece''a!il# t&e "eci'i-e +acto!)

able 2 ypical relatie properties of copper and alu!iniu!

CopperC4A5 Alu!iniu! 135 6nitsElect!ical con"ucti-it#7anneale"

1$1 61 G IACS

Elect!ical !e'i'ti-it# 7anneale" 1)2 2)F@ c(

Te(e!atu!e coe++icient o+!e'i'tance7anneale"

$)$$@9 $)$$? H C

T&e!(al con"ucti-it# at 2$HC @9 2@$ 4(

Coe++icient o+ e.an'ion 1 . 1$6 2@ . 1$6 H C

Ten'ile 't!en*t& 7anneale" 2$$ 2>$ >$ 6$ N((2

Ten'ile 't!en*t& 7&al+&a!" 26$ @$$ F> 1$$ N((2

$)2G !oo+ 't!e'' 7anneale" >$ >> 2$ @$ N((2

$)2G !oo+ 't!e'' 7&al+&a!" 1$ 2$$ 6$ 6> N((2

Ela'tic (o"ulu' 116 1@$ $ N((2

Seci+ic &eat @F> 9$$ J*

Den'it# F)91 2)$ *c(@

Meltin* oint 1$F@ 66$ HC

T&e elect!o(a*netic 't!e''e' 'et u in t&e ba! a!e u'uall# (o!e 'e-e!e t&an t&e 't!e'' int!o"uce"b# it' %ei*&t) In a!ticula!, &ea-# cu!!ent8ca!!#in* e0ui(ent nece''itate' t&e u'e o+ la!*e 'iecon"ucto!', an" 'ace con'i"e!ation' (a# be i(o!tant) It '&oul" be !eali'e" t&at t&e u'e o+


6/104

coe! at &i*&e! oe!atin* te(e!atu!e' t&an %oul" be e!(i''ible +o! alu(iniu( allo%' '(alle!an" li*&te! coe! 'ection' to be u'e" t&an %oul" be !e0ui!e" at lo%e! te(e!atu!e')

T&e abilit# o+ coe! to ab'o!b t&e &ea-# elect!o(a*netic an" t&e!(al 't!e''e' *ene!ate" b#o-e!loa" con"ition' al'o *i-e' a con'i"e!able +acto! o+ 'a+et#) Ot&e! +acto!', 'uc& a' t&e co't o++!e0uent 'uo!t' +o! t&e !elati-el# li( alu(iniu(, an" t&e *!eate! co't o+ in'ulation o+ t&e la!*e!

'u!+ace a!ea, (u't be con'i"e!e" %&en e-aluatin* t&e (ate!ial')

:!o( ubli'&e" c!ee "ata, it can be 'een t&at &i*& con"ucti-it# alu(iniu( e.&ibit' e-i"ence o+'i*ni+icant c!ee at a(bient te(e!atu!e i+ &ea-il# 't!e''e") At t&e 'a(e 't!e'', a 'i(ila! !ate o+c!ee i' onl# '&o%n b# &i*& con"ucti-it# coe! at a te(e!atu!e o+ 1>$HC, %&ic& i' abo-e t&eu'ual oe!atin* te(e!atu!e o+ bu'ba!')

able 3 Co!parison of creep and fatigue properties of %ig% conductiity copper andalu!iniu!

a5 Creep properties

)aterial esting e!p. 7C )in. Creep "ate 8 per 1%

$tress 9:!!2

Al 71$F$ anneale" 2$ $)$22 26

;C Cu anneale" 1>$ $)$22 26

Cu8$)$F6G A* >$G c)%) 1@$ $)$$? 1@F

Cu8$)$F6G A* >$G c)%) 22> $)$29 96)

>

Inte!olate" +!o( +i*)@

b5 0atigue properties

)aterial 0atigue strengt% 9:!!2 9o. of cycles ; 1#;C Al anneale" 2$ >$

&al+8&a!" 7;F ?> >$;C Coe! anneale" 62 @$$

&al+8&a!" 11> @$$I+ (uc& &i*&e! 't!e''e' o! te(e!atu!e' a!e to be allo%e" +o!, coe! containin* '(all a(ount'7about $)1G o+ 'il-e! can be u'e" 'ucce''+ull#) T&e c!ee !e'i'tance an" 'o+tenin* !e'i'tance o+coe!8'il-e! allo#' inc!ea'e %it& inc!ea'in* 'il-e! content)

In t&e con"ition' in %&ic& &i*& con"ucti-it# alu(iniu( an" coe! a!e u'e", eit&e! anneale" 7o!a'8%el"e" o! &al+8&a!", t&e +ati*ue 't!en*t& o+ coe! i' a!o.i(atel# "ouble t&at o+ alu(iniu()T&i' *i-e' a u'e+ul !e'e!-e o+ 't!en*t& a*ain't +ailu!e initiate" b# (ec&anical o! t&e!(al c#clin*)

T&e *!eate! &a!"ne'' o+ coe! co(a!e" %it& alu(iniu( *i-e' it bette! !e'i'tance to (ec&anical"a(a*e bot& "u!in* e!ection an" in 'e!-ice) It i' al'o le'' liel# to "e-elo !oble(' in cla(e"/oint' "ue to col" (etal +lo% un"e! t&e !olon*e" alication o+ a &i*& contact !e''u!e) It' &i*&e!


7/104

(o"ulu' o+ ela'ticit# *i-e' it *!eate! bea( 'ti++ne'' co(a!e" %it& an alu(iniu( con"ucto! o+ t&e'a(e "i(en'ion') T&e te(e!atu!e -a!iation' encounte!e" un"e! 'e!-ice con"ition' !e0ui!e ace!tain a(ount o+ +le.ibilit# to be allo%e" +o! in t&e "e'i*n) T&e lo%e! coe++icient o+ linea!e.an'ion o+ coe! !e"uce' t&e "e*!ee o+ +le.ibilit# !e0ui!e")

ecau'e coe! i' le'' !one to t&e +o!(ation o+ &i*& !e'i'tance 'u!+ace o.i"e +il(' t&an

alu(iniu(, *oo" 0ualit# (ec&anical /oint' a!e ea'ie! to !o"uce in coe! con"ucto!') 4el"e"/oint' a!e al'o !ea"il# (a"e) S%itc& contact' an" 'i(ila! a!t' a!e nea!l# al%a#' !o"uce" +!o(coe! o! a coe! allo#) T&e u'e o+ coe! +o! t&e bu'ba!' to %&ic& t&e'e a!t' a!e connecte"t&e!e+o!e a-oi"' contact' bet%een "i''i(ila! (etal' an" t&e in&e!ent /ointin* an" co!!o'ion!oble(' a''ociate" %it& t&e()

T&e &i*&e! (eltin* oint an" t&e!(al con"ucti-it# o+ coe! !e"uce t&e o''ibilit# o+ "a(a*e!e'ultin* +!o( &ot 'ot' o! acci"ental +la'&o-e!' in 'e!-ice) I+ a!cin* occu!', coe! bu'ba!' a!ele'' liel# to 'uo!t t&e a!c t&an alu(iniu() Table ? '&o%' t&at coe! can 'el+8e.tin*ui'& a!c'ac!o'' '(alle! 'ea!ation', an" at &i*&e! bu'ba! cu!!ent') T&i' 'el+8e.tin*ui'&in* be&a-iou! i'!elate" to t&e (uc& la!*e! &eat inut !e0ui!e" to -ao!i'e coe! t&an alu(iniu()

able 4 $elf-e;tinguis%ing arcs in copper and alu!iniu! busbars

Copper Alu!iniu!Mini(u( bu'ba! 'acin*, (( >$ 1$$

Ma.i(u( cu!!ent e! bu'ba!, A ?>$$ @22$

Coe! libe!ate' con'i"e!abl# le'' &eat "u!in* o.i"ation t&an alu(iniu( an" i' t&e!e+o!e (uc&

le'' liel# to 'u'tain co(bu'tion in t&e ca'e o+ acci"ental i*nition b# an a!c) T&e la!*e a(ount' o+&eat libe!ate" b# t&e o.i"ation o+ alu(iniu( in t&i' e-ent a!e 'u++icient to -ao!i'e (o!e (etalt&an %a' o!i*inall# o.i"i'e") T&i' -ao!i'e" alu(iniu( can it'el+ !ai"l# o.i"i'e, t&u' 'u'tainin*t&e !eaction) T&e e.ce'' &eat *ene!ate" in t&i' %a# &eat' nea!b# (ate!ial', inclu"in* t&e bu'ba!it'el+, t&e ai! an" an# 'uo!tin* +i.tu!e') A' t&e bu'ba! an" ai! te(e!atu!e' !i'e, t&e !ate' o+ t&e-ao!i'ation an" o.i"ation inc!ea'e, 'o accele!atin* t&e %&ole !oce'') A' t&e ai! te(e!atu!e i'inc!ea'e", t&e ai! e.an"' an" !oel' &ot o.i"e a!ticle') T&e bu'ba! (a# !eac& it' (eltin*oint, +u!t&e! inc!ea'in* t&e !ate o+ o.i"ation an" !o-i"in* &ot li0ui" to be !oelle", %&ile ot&e!(ate!ial' 'uc& a' %oo" anel' (a# be !ai'e" to t&ei! i*nition te(e!atu!e') T&e'e "an*e!' a!eob-iate" b# t&e u'e o+ coe! bu'ba!')

:inall#, coe! i' an econo(ical con"ucto! (ate!ial) It *i-e' lon* an" !eliable 'e!-ice at (ini(u((aintenance co't', an" %&en an in'tallation i' e-entuall# !elace" t&e coe! %ill &a-e a &i*&

!eco-e!# -alue) ecau'e o+ it' (an# a"-anta*e', coe! i' 'till u'e" %o!l"%i"e a' an elect!icalcon"ucto! (ate!ial "e'ite atte(t' at 'ub'titution)

2.Copper for Busbar Purposes

ypes of


8/104


9/104

Coe! to be u'e" +o! elect!ical u!o'e' i' o+ &i*& u!it# becau'e i(u!itie' in coe!, to*et&e!%it& t&e c&an*e' in (ic!o8't!uctu!e !o"uce" b# %o!in*, (ate!iall# a++ect t&e (ec&anical an"elect!ical !oe!tie') T&e "e*!ee to %&ic& t&e elect!ical con"ucti-it# i' a++ecte" b# an i(u!it#"een"' la!*el# on t&e ele(ent !e'ent) :o! e.a(le, t&e !e'ence o+ onl# $)$?G &o'&o!u'!e"uce' t&e con"ucti-it# o+ &i*& con"ucti-it# coe! to a!oun" F$G IACS) 7T&e a!o.i(ate e++ecton con"ucti-it# o+ -a!iou' i(u!it# ele(ent' i' '&o%n in :i*u!e 1) T&e le-el o+ total i(u!itie',

inclu"in* o.#*en, '&oul" t&e!e+o!e be le'' t&an $)1G an" coe! o+ t&i' t#e i' no%n a' &i*&con"ucti-it# 7;C coe!)

Mic!o'coic an" anal#tical cont!ol' a!e alie" to en'u!e a con'i'tent !o"uct an" in t&eanneale" con"ition con"ucti-itie' o-e! 1$$G IACS a!e u'ual) T&i' +i*u!e co!!e'on"' to t&e

'tan"a!" !e'i'ti-it# o+ $)$12?1 ( 'et 'o(e #ea!' a*o b# t&e Inte!national Elect!otec&nicalCo((i''ion)

0igure 1 - Appro;i!ate effect of i!purity ele!ents on t%e electrical resistiity of copper

ypes of


10/104

"!o*en an" i' no%n a' ;ygen-free %ig%-conductiity copper= C(A C135

In -ie% o+ t&e abo-e !e(a!', i+ %el"in* an" b!ain* oe!ation' un"e! !e"ucin* con"ition' a!e

una-oi"able, it i' nece''a!# to u'e a "i++e!ent 7an" (o!e e.en'i-e *!a"e o+ &i*& con"ucti-it#coe! %&ic& i' 'eciall# !o"uce" +o! t&i' u!o'e) T&i' t#e o+ coe!, no%n a'


11/104

9, A(e!ican Stan"a!" ANSI C@)2$, etc) T&e'e 'tan"a!"' *i-e (a.i(u(te(e!atu!e !i'e' a' %ell a' (a.i(u( a(bient te(e!atu!e')

S 1>9 'tiulate' a (a.i(u( te(e!atu!e !i'e o+ >$HC abo-e a 2? &ou! (ean a(bientte(e!atu!e o+ u to @>HC, an" a ea a(bient te(e!atu!e o+ ?$HC)

ANSI C@)2$ alte!nati-el# e!(it' a te(e!atu!e !i'e o+ 6>HC abo-e a (a.i(u( a(bient o+ ?$HC,

!o-i"e" t&at 'il-e!8late" 7o! accetable alte!nati-e bolte" te!(ination' a!e u'e") I+ not, ate(e!atu!e !i'e o+ @$HC i' allo%e")

T&e'e ue! te(e!atu!e li(it' &a-e been c&o'en becau'e at &i*&e! (a.i(u( oe!atin*te(e!atu!e' t&e !ate o+ 'u!+ace o.i"ation in ai! o+ con"ucto! (ate!ial' inc!ea'e' !ai"l# an" (a#*i-e !i'e in t&e lon* te!( to e.ce''i-e local &eatin* at /oint' an" contact') T&i' te(e!atu!e li(iti' (uc& (o!e i(o!tant +o! alu(iniu( t&an coe! becau'e it o.i"i'e' -e!# (uc& (o!e !ea"il#t&an coe!) In !acti'e t&e'e li(itation' on te(e!atu!e !i'e (a# be !ela.e" +o! coe! bu'ba!' i+'uitable in'ulation (ate!ial' a!e u'e") A no(inal !i'e o+ 6$HC o! (o!e abo-e an a(bient o+ ?$HCi' allo%e" b# S EN 6$?@981199? !o-i"e" t&at 'uitable !ecaution' a!e taen) S EN 6$?@981199? 7e0ui-alent to IEC ?@9 'tate' t&at t&e te(e!atu!e !i'e o+ bu'ba!' an" con"ucto!' i'li(ite" b# t&e (ec&anical 't!en*t& o+ t&e bu'ba! (ate!ial, t&e e++ect on a"/acent e0ui(ent, t&ee!(i''ible te(e!atu!e !i'e o+ in'ulatin* (ate!ial' in contact %it& t&e ba!', an" t&e e++ect on

aa!atu' connecte" to t&e bu'ba!')

T&e !atin* o+ a bu'ba! (u't al'o tae account o+ t&e (ec&anical 't!e''e' 'et u "ue toe.an'ion, '&o!t8ci!cuit cu!!ent' an" a''ociate" inte!8&a'e +o!ce') In 'o(e bu'ba! '#'te('con'i"e!ation (u't al'o be *i-en to t&e caitali'e" co't o+ t&e &eat *ene!ate" b# t&e e++ecti-eo&(ic !e'i'tance an" cu!!ent 7I2R %&ic& lea"' to an oti(i'e" "e'i*n u'in* el-in


12/104


13/104

It can be 'een %&en "ia*!a(' 7a an" 7b a!e co(a!e" an" a''u(in* a 'i(ila! c!o''8'ectionala!ea t&e &eat lo'' +!o( a!!an*e(ent 7b i' (uc& la!*e!, !o-i"e" t&e *a bet%een t&e la(ination'i' not le'' t&an t&e t&icne'' o+ eac& ba!)

Conection %eat loss forced air cooling

I+ t&e ai! -elocit# o-e! t&e bu'ba! 'u!+ace i' le'' t&an $)> (' t&e abo-e +o!(ulae +o! 4-, 4 &an"4cal#) :o! &i*&e! ai! -elocitie' t&e +ollo%in* (a# be u'e"

%&e!e4aK &eat lo't e! unit len*t& +!o( ba!, 4(- K ai! -elocit#, ('

A K 'u!+acea!ea e! unit len*t& o+ ba!, (2(

"adiation

T&e !ate at %&ic& &eat i' !a"iate" +!o( a bo"# i' !oo!tional to t&e "i++e!ence bet%een t&e +ou!t&o%e! o+ t&e te(e!atu!e' o+ t&e bo"# an" it' 'u!!oun"in*', an" i' !oo!tional to t&e !elati-e

e(i''i-it# bet%een t&e bo"# an" it' 'u!!oun"in*')


14/104

T&e +ollo%in* table li't' t#ical ab'olute e(i''i-itie' +o! coe! bu'ba!' in -a!iou' con"ition')C&an*e' in e(i''i-it# *i-e !i'e to c&an*e' in cu!!ent !atin*', a' '&o%n in Table )

!i*&t (etal$)1Pa!tiall# o.i"i'e" $)@$

;ea-il# o.i"i'e"$)$Dull non8(etallic aint$)9able & Percentage increase in current rating /%en is increased fro! .1 to . - t%ree-p%ase arrange!ent

P%ase centres= !!

9o. of bars in parallel 1 2 2

1 2@ 2@ 2>

2 1> 16 1F

@ 1$ 11 1?

? 9 9 12

> 6 9

T&e +i*u!e' *i-en in Table a!e a!o.i(ate -alue' alicable to F$ to 16$ (( %i"e bu'ba!' +o!a 1$>HC oe!atin* te(e!atu!e an" ?$HC a(bient) T&e !elati-e e(i''i-it# i' calculate" a' +ollo%'


15/104

%&e!e e K !elati-e e(i''i-it#

1K ab'olute e(i''i-it# o+ bo"# 1

2K ab'olute e(i''i-it# o+ bo"# 2

T&e !ate o+ &eat lo'' b# !a"iation +!o( a bo"# 74(2 i' *i-en b#

%&e!ee K !elati-e e(i''i-it#

T1K ab'olute te(e!atu!e o+ bo"# 1,

T2K ab'olute te(e!atu!e o+ bo"# 2, 7i)e), a(bient te(e!atu!e o+ t&e 'u!!oun"in*'

Ra"iation i' con'i"e!e" to t!a-el in 't!ai*&t line' an" lea-e t&e bo"# at !i*&t an*le' to it' 'u!+ace)T&e "ia*!a(' abo-e "e+ine t&e e++ecti-e 'u!+ace a!ea' +o! !a"iation +!o( con"ucto!' o+ co((on'&ae')


16/104

%&e!eR+K e++ecti-e a)c) !e'i'tance o+ con"ucto!, 7'ee abo-eAppro;i!ate dc Current "atings for 0lat and "ound bars

T&e +ollo%in* e0uation' can be u'e" to obtain t&e a!o.i(ate ")c) cu!!ent !atin* +o! 'in*le +latan" !oun" coe! bu'ba!' ca!!#in* a "i!ect cu!!ent) T&e e0uation' a''u(e a natu!all# b!i*&tcoe! +ini'& %&e!e e(i''i-it# i' $)1 an" %&e!e !atin*' can be i(!o-e" 'ub'tantiall# b# coatin*%it& a (att blac o! 'i(ila! 'u!+ace) T&e e0uation' a!e al'o a!o.i(atel# t!ue +o! a)c) cu!!ent!o-i"e" t&at t&e 'in e++ect an" !o.i(it# !atio' 'ta# clo'e to 1)$, a' i' t!ue +o! (an# lo% cu!!entalication') Met&o"' o+ calculation +o! ot&e! con+i*u!ation' an" con"ition' can be +oun" in'ub'e0uent 'ection')

7a :lat ba!' on e"*e

71

%&e!eI K cu!!ent, AA K c!o''8'ectional a!ea, ((2

K e!i(ete! o+ con"ucto!, ((

K te(e!atu!e "i++e!ence bet%een con"ucto! an" t&e a(bient ai!, HC

K !e'i'tance te(e!atu!e coe++icient o+ coe! at t&e a(bient te(e!atu!e, e! HC

K !e'i'ti-it# o+ coe! at t&e a(bient te(e!atu!e, c(

7b ;ollo% !oun" ba!'

72

7c Soli" !oun" ba!'

7@

I+ t&e te(e!atu!e !i'e o+ t&e con"ucto! i' >$HC abo-e an a(bient o+ ?$HC an" t&e !e'i'ti-it# o+

t&e coe! at 2$HC i' 1)2? c(, t&en t&e abo-e +o!(ulae beco(e

7i :lat ba!'


17/104


18/104

a!inated bars

4&en a nu(be! o+ con"ucto!' a!e u'e" in a!allel, t&e total cu!!ent caacit# i' le'' t&an t&e !atin*+o! a 'in*le ba! ti(e' t&e nu(be! o+ ba!' u'e") T&i' i' "ue to t&e ob't!uction to con-ection an"!a"iation lo''e' +!o( t&e inne! con"ucto!') To +acilitate t&e (ain* o+ inte!lea-e" /oint', t&e'acin* bet%een la(inate" ba!' i' o+ten (a"e e0ual to t&e ba! t&icne'') :o! 6)@ (( t&ic ba!'u to 1>$ (( %i"e, (ounte" on e"*e %it& 6)@ (( 'acin*' bet%een la(ination', t&e i'olate"ba! ")c) !atin* (a# be (ultilie" b# t&e +ollo%in* +acto!' to obtain t&e total !atin*)

9o. of la!inations)ultiplying factor9o. ofla!inations

)ultiplyingfactor

2 1)F

@ 2)>

? @)2

> @)9

6 ?)?

F >)>

1$ 6)>


19/104


20/104

%&e!eS K Sin e++ect !atio

" K "ia(ete! o+ !o", ((

+ K +!e0uenc#, ;

K !e'i'ti-it#, c(

K e!(eabilit# o+ coe! 7K1

:o! ;C coe! at 2$HC, K 1)2? c(, &ence

%&e!eA K c!o''8'ectional a!ea o+ t&e con"ucto!, ((20igure 4 $@in effect in


21/104

Copper tubes

Sin e++ect in tubula! coe! con"ucto!' i' a +unction o+ t&e t&icne'' o+ t&e %all o+ t&e tube an"t&e !atio o+ t&at t&icne'' to t&e tube "ia(ete!, an" +o! a *i-en c!o'' 'ectional a!ea it can be!e"uce" b# inc!ea'in* t&e tube "ia(ete! an" !e"ucin* t&e %all t&icne'')

:i*u!e >, :i*u!e 6, an" :i*u!e , %&ic& &a-e been "!a%n +!o( +o!(ulae "e!i-e" b# D%i*&t 71922an" A!nol" 719@6, can be u'e" to +in" t&e -alue o+ 'in e++ect +o! -a!iou' con"ucto! 'ection') Int&e ca'e o+ tube' 7:i*u!e >, it can be 'een t&at to obtain lo% 'in e++ect !atio -alue' it i' "e'i!able

to en'u!e, %&e!e o''ible, lo% -alue' o+ t" an" 7+!) :o! a *i-en c!o''8'ectional a!ea t&e 'ine++ect !atio +o! a t&in coe! tube i' a!eciabl# lo%e! t&an t&at +o! an# ot&e! +o!( o+ con"ucto!)Coe! tube', t&e!e+o!e, &a-e a (a.i(u( e++icienc# a' con"ucto!' o+ alte!natin* cu!!ent',a!ticula!l# t&o'e o+ &i*& (a*nitu"e o! &i*& +!e0uenc#)

T&e e++ect o+ %all t&icne'' on 'in e++ect +o! a 1$$ (( "ia(ete! tube ca!!#in* a >$; alte!natin*

cu!!ent i' clea!l# '&o%n in :i*u!e >)


22/104

0igure "esistance of


23/104

0lat copper bars

T&e 'in e++ect in +lat coe! ba!' i' a +unction o+ it' t&icne'' an" %i"t&) 4it& t&e la!*e! 'ie' o+con"ucto!, +o! a *i-en c!o''8'ectional a!ea o+ coe!, t&e 'in e++ect in a t&in ba! o! 't!i i' u'uall#le'' t&an in a ci!cula! coe! !o" but *!eate! t&an in a t&in tube) It i' "een"ent on t&e !atio o+ t&e%i"t& to t&e t&icne'' o+ t&e ba! an" inc!ea'e' a' t&e t&icne'' o+ t&e ba! inc!ea'e') A t&incoe! 't!i, t&e!e+o!e, i' (o!e e++icient t&an a t&ic one a' an alte!natin* cu!!ent con"ucto!):i*u!e can be u'e" to +in" t&e 'in e++ect -alue +o! +lat ba!')

0igure & $@in effect for rectangular conductors


24/104

$*uare copper tubes

T&e 'in e++ect !atio +o! '0ua!e coe! tube' can be obtaine" +!o( :i*u!e F)

0igure ( $@in effect ratio for %ollo/ s*uare conductors


25/104

Pro;i!ity Effect

n t&e +o!e*oin* con'i"e!ation o+ 'in e++ect it &a' been a''u(e" t&at t&e con"ucto! i' i'olate" an"at 'uc& a "i'tance +!o( t&e !etu!n con"ucto! t&at t&e e++ect o+ t&e cu!!ent in it can be ne*lecte")4&en con"ucto!' a!e clo'e to*et&e!, a!ticula!l# in lo% -olta*e e0ui(ent, a +u!t&e! "i'to!tion o+cu!!ent "en'it# !e'ult' +!o( t&e inte!action o+ t&e (a*netic +iel"' o+ ot&e! con"ucto!')

In t&e 'a(e %a# a' an e)()+) (a# be in"uce" in a con"ucto! b# it' o%n (a*netic +lu., 'o (a# t&e(a*netic +lu. o+ one con"ucto! !o"uce an e)()+) in an# ot&e! con"ucto! 'u++icientl# nea! +o! t&ee++ect to be 'i*ni+icant)

I+ t%o 'uc& con"ucto!' ca!!# cu!!ent' in oo'ite "i!ection', t&ei! elect!o8(a*netic +iel"' a!eoo'e" to one anot&e! an" ten" to +o!ce one anot&e! aa!t) T&i' !e'ult' in a "ec!ea'e o+ +lu.


26/104

lina*e' a!oun" t&e a"/acent a!t' o+ t&e con"ucto!' an" an inc!ea'e in t&e (o!e !e(ote a!t',%&ic& lea"' to a concent!ation o+ cu!!ent in t&e a"/acent a!t' %&e!e t&e oo'in* e)()+) i' a(ini(u() I+ t&e cu!!ent' in t&e con"ucto!' a!e in t&e 'a(e "i!ection t&e action i' !e-e!'e" an"t&e# ten" to c!o%" into t&e (o!e !e(ote a!t' o+ t&e con"ucto!')

T&i' e++ect, no%n a' t&e


27/104

%&e!e" K "et& o+ enet!ation, ((K !e'i'ti-it# o+ coe!, c(

+ K +!e0uenc#, ;

. Effect of Busbar Arrange!ents on "ating

a!inated copper bars C%annel and angle bars
http://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#Laminated%20copper%20barshttp://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#Channel%20and%20angle%20barshttp://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#Laminated%20copper%20barshttp://www.cda.org.uk/megab2/elecapps/pub22/sec5.htm#Channel%20and%20angle%20bars


28/104

,nter-leaing of conductors

ransposition of conductors


29/104

a!inated copper bars

To obtain t&e be't an" (o't e++icient !atin* +o! !ectan*ula! 't!i coe! con"ucto!' t&e# '&oul" be(ounte" %&ene-e! o''ible %it& t&ei! (a/o! c!o''8'ectional a.e' -e!tical 'o *i-in* (a.i(u(coolin* 'u!+ace')

La(ination' o+ 6 o! 6)@ (( t&icne'', o+ -a!#in* %i"t&' an" %it& 6 o! 6)@ (( 'acin*' a!e!obabl# t&e (o't co((on an" a!e 'ati'+acto!# in (o't a)c) lo% cu!!ent ca'e' an" +o! all ")c)'#'te(')

It i' not o''ible to *i-e an# *ene!all# alicable +acto!' +o! calculatin* t&e ")c) !atin* o+ la(inate"ba!', 'ince t&i' "een"' uon t&e 'ie an" !oo!tion' o+ t&e la(ination' an" on t&ei!

a!!an*e(ent) A *ui"e to t&e e.ecte" !elati-e !atin*' a!e *i-en in Table F belo% +o! a >$ ;'#'te() T&e !atin*' +o! 'in*le ba!' can be e'ti(ate" u'in* t&e (et&o"' *i-en in Section @ an"Section ?)

able ( )ultiplying factors for la!inated bars

Table 1@ 7Aen"i. 2 *i-e' a)c) !atin*' +o! -a!iou' con+i*u!ation' o+ la(inate" ba!' ba'e" on te't(ea'u!e(ent')


30/104


31/104

T&e unbalance" cu!!ent "i't!ibution in a la(inate" ba! ca!!#in* a)c) cu!!ent "ue to 'in an"!o.i(it# e++ect' (a# be counte!acte" b# t!an'o'in* la(ination' o! *!ou' o+ la(ination' atinte!-al') Tain*' an" ot&e! connection' (ae t!an'o'ition "i++icult, but it can be %o!t&%&ile%&e!e lon* 'ection' o+ ba!' a!e +!ee +!o( tain*') T&e a!!an*e(ent i' a' '&o%n in :i*u!e 9e)


32/104


33/104

Enclosed copper conductors

In (an# ca'e' bu'ba!' a!e 'u!!oun"e" b# enclo'u!e', no!(all# (etallic, %&ic& !e"uce t&e bu'ba!&eat "i''iation "ue to !e"uction in coolin* ai! +lo% an" !a"iation lo''e' an" t&e!e+o!e *i-e cu!!ent!atin*' %&ic& (a# be con'i"e!abl# le'' t&an t&o'e +o! +!ee ai! e.o'u!e) Ventilate" enclo'u!e',&o%e-e!, !o-i"e (ec&anical !otection an" 'o(e coolin* ai! +lo% %it& t&e lea't !e"uction incu!!ent !atin*)

T&e !e"uction in !atin* +o! a *i-en te(e!atu!e !i'e %ill -a!# con'i"e!abl# %it& t&e t#e an" 'ie o+

ba! an" enclo'u!e) T&e *!eate't "ec!ea'e in cu!!ent !atin* occu!' %it& ba!' %&ic& "een" (ainl#on +!ee ai! ci!culation an" le'' on uni+o!( cu!!ent "i't!ibution 'uc& a' t&e (o"i+ie" &ollo% '0ua!ea!!an*e(ent 7:i*u!e 9") In t&e'e ca'e' t&e !atin* (a# be !e"uce" to bet%een 6$ an" 6>G %&ent&e con"ucto!' a!e enclo'e" in non8(a*netic (etal enclo'u!e') In t&e ca'e o+ tubula! con"ucto!'o! t&o'e o+ clo'el# *!oue" +lat la(ination', %&ic& a!e no!(all# not 'o %ell coole" b# ai!ci!culation, t&e !atin*' (a# be !e"uce" to about >G o+ +!ee ai! !atin*' +o! no!(al te(e!atu!e!i'e')

4&e!e t&e bu'ba! '#'te( i' enclo'e" in t&ic (a*netic enclo'u!e', 'uc& a' in (etal8cla"'%itc&*ea!, t&e !e"uction i' a!o.i(atel# a +u!t&e! 1>G) T&e e++ect o+ t&in '&eet8'teel enclo'u!e'i' 'o(e%&at le'') T&e'e a""itional !e"uction' a!e "ue to t&e &eat *ene!ate" b# t&e alte!natin*(a*netic +iel"' t&!ou*& 'te!e'i' an" e""# cu!!ent lo''e') e'i"e' t&e "e!atin* cau'e" b#enclo'u!e con"ition', ot&e! li(itation' on (a.i(u( %o!in* te(e!atu!e a!e o+ten !e'ent, 'uc&

a' %&en t&e out'i"e o+ enclo'u!e' '&oul" not e.cee" a *i-en 'a+et# -alue) T&e'e "e!atin*' a!ea++ecte" b# t&e elect!ical clea!ance' in-ol-e" an" t&e "e*!ee o+ -entilation in t&e enclo'u!e) T&eabo-e +i*u!e' an" t&e cu!-e' '&o%n in :i*u!e 12 '&oul" onl# be taen a' a !ou*& *ui"e to t&e!e0ui!e" "e!atin*= an accu!ate +i*u!e can onl# be obtaine" b# te'tin*)

All a!t' 'uc& a' con"ucto! an" '%itc& +ittin*', enclo'u!e' an" inte!&a'e ba!!ie!' (a# be 'ub/ectto a!eciable te(e!atu!e !i'e "ue to ci!culatin* an" e""# cu!!ent lo''e' %&en clo'e to t&e&ea-# cu!!ent ba!' an" connection') T&e'e lo''e' can be !e"uce" to a (ini(u( b# (ain* t&e'ea!t' +!o( &i*& con"ucti-it# non8(a*netic (ate!ial 'uc& a' coe! o! coe! allo#)

0igure 12 Co!parison of appro;i!ate current ratings for busbars in different enclosures


34/104

Co!pound insulated conductors

T&e cu!!ent !atin* o+ coe! i((e!'e" in oil o! co(oun" "een" uon a nu(be! o+ +acto!' %&ic&(a# -a!# %i"el# %it& "e'i*n, an" can no!(all# onl# be con+i!(e" b# ca!!#in* out te(e!atu!e !i'ete't' on t&e co(lete a''e(bl#)

T&e !atin*' o+ enclo'e" ba!' a!e nea!l# al%a#' (uc& lo%e! t&an t&e +!ee ai! !atin*') T&ete(e!atu!e !i'e i' "een"ent on t&e !ate at %&ic& &eat i' con"ucte" t&!ou*& t&e in'ulatin* (e"iaan" "i''iate" +!o( t&e out'i"e ca'in* b# !a"iation an" con-ection) T&e!e i' nea!l# al%a#' aclo'e! &a'e 'acin* bet%een con"ucto!' *i-in* &i*& !o.i(it# e++ect' an" &i*&e! &eat lo''e' in

t&e (a*netic oute! ca'in*' an" 'o *i-in* !i'e to &i*&e! te(e!atu!e !i'e')

P!o.i(it# e++ect i' o+ten (o!e i(o!tant +o! in'ulate" ba!' t&an t&o'e in ai!) La(inate" ba!' &a-e+e%e! a"-anta*e' %&en i((e!'e" in oil o! co(oun" an" ci!cula! coe! con"ucto!' eit&e! 'oli"o! &ollo% t&ou*& a!e o+ten !e+e!!e" a!ticula!l# +o! &i*&8-olta*e *ea! an" &i*& cu!!ent *ene!ato!',t!an'+o!(e!', etc), %&e!e (o!e e++ecti-e coolin* 'uc& a' %ate! coolin* can be e(lo#e" toi(!o-e con"ucto! (ate!ial utili'ation an" &ence !e"uce t&e o-e!all 'ie o+ lant)

Plastic insulated conductors

T&e!e i' a %i"enin* u'e o+ la'tic continuou' in'ulation a' t&e !i(a!# in'ulation +o! lo% cu!!entan" -olta*e bu'ba!') T&i' in'ulation i' u'uall# o+ t&e '&!in8on P)V)C) t#e t&ou*& %!a8on tae i'

'o(eti(e' u'e") T&i' (et&o" i' u'e" +o! -olta*e' u to about 1> V, t&ou*& (uc& &i*&e! le-el'can be attaine" %&en 'eciali'e" in'ulation '#'te(' 'uc& a' eo.# !e'in o! 'i(ila! ba'e" tae'an" o%"e!' a!e e(lo#e") T&e'e '#'te(' a!e a!ticula!l# u'e+ul %&e!e &i*& ato(ic !a"iation


35/104

le-el', o! &i*& te(e!atu!e' 7u to 1@$HC a!e encounte!e", alt&ou*& account (u't be taen o+t&e o''ibilit# o+ &alo*en *a''in* +!o( P)V)C) in'ulation' at te(e!atu!e' a!oun" 1$$HC) Mo"i+ie"P)V)C) (ate!ial' %it& i(!o-e" &i*&8te(e!atu!e e!+o!(ance a!e a-ailable)

,solated p%ase busbars

'olate" &a'e bu'ba!' con'i't o+ a (etallic enclo'e" con"ucto! %&e!e eac& in"i-i"ual &a'e o!ole i' 'u!!oun"e" b# a 'ea!atel# ea!t&e" '&eat& %&ic& i' connecte" at it' en"' b# a +ull '&o!t8ci!cuit cu!!ent !ate" ba!) T&e '&eat& i' inten"e" !i(a!il# to !e-ent inte!&a'e '&o!t8ci!cuitcu!!ent' "e-eloin*) T&e# &a-e t&e +u!t&e! a"-anta*e t&at t&e &i*& (a*netic +iel"' c!eate" b# t&econ"ucto! cu!!ent a!e al(o't co(letel# cancelle" b# an e0ual an" oo'ite cu!!ent in"uce" int&e enclo'u!e o! '&eat& %it& !e"uction' o+ 9>G o! bette! in t&e e.te!nal (a*netic +iel" bein*o''ible) An i(o!tant !e'ult i' t&at t&e lieli&oo" o+ 'teel%o! o-e!&eatin* %&en a"/acent to t&ebu'ba! '#'te( i' con'i"e!abl# !e"uce" e.cet %&e!e t&e '&eat& '&o!t8ci!cuit ba!' a!e locate")T&i' cu!!ent +lo%in* in t&e enclo'u!e (ae' t&e (et&o" o+ e'ti(atin* t&e e!+o!(ance o+ t&ebu'ba! '#'te( (uc& (o!e co(licate" an" can onl# be !e'ol-e" b# obtainin* a &eat balancebet%een con"ucto! an" enclo'u!e u'in* an inte!acti-e calculation (et&o")

T&e'e bu'ba!' a!e u'e" no!(all# +o! oe!atin* -olta*e' o+ bet%een 11 V an" @6 V t&ou*&e0ui(ent u'in* (uc& lo%e! -olta*e' an" &i*&e! -olta*e' a!e inc!ea'in*l# c&an*in* to t&i''#'te() E.a(le' o+ 'uc& e0ui(ent a!e e.cite! connection', '%itc&*ea! inte!connection',*ene!ato! to t!an'+o!(e! connection', &i*& -olta*e '%itc&*ea! u'in* S:67'ul&u! &e.a+luo!i"e*a' in'ulation 7t&i' *a' &a-in* an in'ulation le-el (an# ti(e' bette! t&an ai!) T&e cu!!ent +lo%in*in t&e con"ucto! !an*e' +!o( a' little a' 1$$$ A to in e.ce'' o+ ?$ A) To obtain t&e &i*&e!cu!!ent' +o!ce" coolin* i' u'e", t&e (o't co((onl# u'e" coolin* (e"ia bein* ai! an" %ate!t&ou*& ot&e! coolin* *a'e' o! li0ui"' can be u'e") T&e u'e o+ t&e'e coolin* '#'te(' u'uall#c!eate' (uc& inc!ea'e" &eat lo''e' an" 'o t&ei! u'e (u't be /u'ti+ie" b# bene+it' in ot&e! a!ea',e)*), !e"uce" ci-il co't', !e"uce" 'ical 'ie %&e!e 'ace i' at a !e(iu( o! !e"uction in 'ie toenable no!(al (anu+actu!in* (et&o"' be u'e" bot& +o! t&e ba'ic bu'ba! (ate!ial an" al'o t&eco(lete bu'ba! '#'te()

Anot&e! +acto! %&ic& in+luence' t&e (et&o" c&o'en +o! +o!ce" coolin* i' t&e natu!all# coole" !atin*o+ t&e bu'ba! '#'te( an" al'o it' abilit# to 'u'tain o-e!loa" con"ition') T&e bu'ba!' a!e u'uall#(anu+actu!e" in 'in*le8&a'e unit' o+ t!an'o!table len*t& an" con'i't o+ a cent!al con"ucto!u'uall# tubula! o+ !oun", '0ua!e o! c&annel c!o''8'ection, 'uo!te" b# o!celain o! eo.# !e'inin'ulato!') T&e in'ulato!' a!e locate" b# t&e e.te!nal (etallic '&eat& t&!ou*& %&ic& t&e# a!eno!(all# !e(o-e" +o! 'e!-icin*)


36/104

#. $%ort-Circuit Effects

$%ort-Circuit


37/104

T&e -alue o+ t obtaine" +!o( t&e abo-e e0uation '&oul" al%a#' be *!eate! t&an t&e !e0ui!e" '&o!tci!cuit %it&'tan" ti(e %&ic& i' u'uall# 1 to ? 'econ"')

T&e te(e!atu!e !i'e e! 'econ" "ue to a cu!!ent I i' *i-en b# t&e +ollo%in* a!o.i(ate +o!(ula

7IA '&oul" be le'' t&an $)2> +o! !ea'onable accu!ac#)

T&e (a.i(u( '&o!t8ci!cuit te(e!atu!e i' -e!# o+ten c&o'en to be @$$HC +o! ea!t& ba! '#'te('but t&e ue! li(it +o! t&e &a'e' i' no!(all# lo%e! an" i' "een"ent on t&e (ec&anical !oe!tie'!e0ui!e" an" 'u!+ace +ini'& o+ t&e coe! (ate!ial)


38/104

( K (a'', *

c K 'eci+ic &eat, J*

T&e ti(e con'tant *i-e' t&e ti(e taen to !eac& $)6@6 o+ t&e (a.i(u( te(e!atu!e !i'e, (a.)

Electro!agnetic $tresses

4&en a con"ucto! ca!!ie' a cu!!ent it c!eate' a (a*netic +iel" %&ic& inte!act' %it& an# ot&e!(a*netic +iel" !e'ent to !o"uce a +o!ce) 4&en t&e cu!!ent' +lo%in* in t%o a"/acent con"ucto!'a!e in t&e 'a(e "i!ection t&e +o!ce i' one o+ att!action, an" %&en t&e cu!!ent' a!e in oo'ite"i!ection' a !eul'i-e +o!ce i' !o"uce")

In (o't bu'ba! '#'te(' t&e cu!!ent8ca!!#in* con"ucto!' a!e u'uall# 't!ai*&t an" a!allel to oneanot&e!) T&e +o!ce !o"uce" b# t&e t%o con"ucto!' i' !oo!tional to t&e !o"uct' o+ t&ei!cu!!ent') No!(all# in (o't bu'ba! '#'te(' t&e +o!ce' a!e -e!# '(all an" can be ne*lecte", butun"e! '&o!t8ci!cuit con"ition', t&e# beco(e la!*e an" (u't be taen into account to*et&e! %it&t&e con"ucto! (ate!ial +ib!e 't!e''e' %&en "e'i*nin* t&e con"ucto! in'ulato! an" it' a''ociate"

'uo!t' to en'u!e a"e0uate 'a+et# +acto!')

T&e +acto!' to be taen into account (a# be 'u((a!i'e" a' +ollo%'

a't!e''e' "ue to "i!ect late!al att!acti-e an" !eul'i-e +o!ce')bVib!ational 't!e''e')cLon*itu"inal 't!e''e' !e'ultin* +!o( late!al "e+lection)"T%i'tin* (o(ent' "ue to late!al "e+lection)In (o't ca'e' t&e +o!ce' "ue to '&o!t8ci!cuit' a!e alie" -e!# 'u""enl#) Di!ect cu!!ent' *i-e !i'eto uni"i!ectional +o!ce' %&ile alte!natin* cu!!ent' !o"uce -ib!ational +o!ce')

)a;i!u! stresses

4&en a bu'ba! '#'te( i' !unnin* no!(all# t&e inte!&a'e +o!ce' a!e no!(all# -e!# '(all %it& t&e'tatic %ei*&t o+ t&e bu'ba!' bein* t&e "o(inant co(onent) 3n"e! '&o!t8ci!cuit con"ition' t&i' i'-e!# o+ten not t&e ca'e a' t&e cu!!ent !i'e' to a ea o+ 'o(e t&i!t# ti(e' it' no!(al -alue, +allin*a+te! a +e% c#cle' to ten ti(e' it' initial -alue) T&e'e &i*& t!an'ito!# cu!!ent' c!eate la!*e(ec&anical +o!ce' not onl# in t&e bu'ba!' t&e('el-e' but al'o in t&ei! 'uo!tin* '#'te() T&i'(ean' t&at t&e 'uo!t in'ulato!' an" t&ei! a''ociate" 'teel%o! (u't be "e'i*ne" to %it&'tan"t&e'e &i*& loa"' a' %ell a' t&ei! no!(al 't!uctu!al !e0ui!e(ent' 'uc& a' %in", ice, 'ei'(ic an"

'tatic loa"')

T&e ea o! +ull# a'#((et!ical '&o!t ci!cuit cu!!ent i' "een"ent on t&e o%e! +acto! 7co' o+t&e bu'ba! '#'te( an" it' a''ociate" connecte" elect!ical lant) T&e -alue i' obtaine" b#(ultil#in* t&e !)()') '#((et!ical cu!!ent b# t&e a!o!iate +acto! *i-en in alance" t&!ee8&a'e'&o!t8ci!cuit 't!e''e')

I+ t&e o%e! +acto! o+ t&e '#'te( i' not no%n t&en a +acto! o+ 2)>> %ill no!(all# be clo'e to t&eactual '#'te( -alue e'eciall# %&e!e *ene!ation i' conce!ne") Note t&at t&e t&eo!etical (a.i(u(

+o! t&i' +acto! i' 22 o! 2)F2F %&e!e co' K $) T&e'e ea -alue' !e"uce e.onentiall# an" a+te!a!o.i(atel# 1$ c#cle' t&e +acto! +all' to 1)$, i)e), t&e '#((et!ical !)()') '&o!t ci!cuit cu!!ent) T&eea +o!ce' t&e!e+o!e no!(all# occu! in t&e +i!'t t%o c#cle' 7$)$? ' a' '&o%n in :i*u!e 1@)


39/104

In t&e ca'e o+ a co(letel# a'#((et!ical cu!!ent %a-e, t&e +o!ce' %ill be alie" %it& a +!e0uenc#e0ual to t&at o+ t&e 'ul# +!e0uenc# an" %it& a "ouble +!e0uenc# a' t&e %a-e beco(e''#((et!ical) T&e!e+o!e in t&e ca'e o+ a >$ ; 'ul# t&e'e +o!ce' &a-e +!e0uencie' o+ >$ o! 1$$;)

T&e (a.i(u( 't!e''e' to %&ic& a bu' 't!uctu!e i' liel# to be 'ub/ecte" %oul" occu! "u!in* a

'&o!t8ci!cuit on a 'in*le8&a'e bu'ba! '#'te( in %&ic& t&e line '&o!t8ci!cuit cu!!ent' a!e "i'lace"b# 1F$H)

In a t&!ee8&a'e '#'te( a '&o!t8ci!cuit bet%een t%o &a'e' i' al(o't i"entical to t&e 'in*le8&a'eca'e an" alt&ou*& t&e &a'e cu!!ent' a!e no!(all# "i'lace" b# 12$H, un"e! '&o!t8ci!cuitcon"ition' t&e &a'e cu!!ent' o+ t&e t%o &a'e' a!e al(o't 1F$H out o+ &a'e) T&e e++ect o+ t&et&i!" &a'e can be ne*lecte")

In a balance" t&!ee8&a'e '&o!t8ci!cuit, t&e !e'ultant +o!ce' on an# one o+ t&e t&!ee &a'e' i' le''t&an in t&e 'in*le8&a'e ca'e an" i' "een"ent on t&e !elati-e 'ical o'ition' o+ t&e t&!ee&a'e')

In t&e ca'e o+ a 'in*le8&a'e '&o!t8ci!cuit, t&e +o!ce' !o"uce" a!e uni"i!ectional an" a!et&e!e+o!e (o!e 'e-e!e t&an t&o'e "ue to a t&!ee8&a'e '&o!t8ci!cuit, %&ic& alte!nate in "i!ection)

T&e '&o!t8ci!cuit +o!ce' &a-e to be ab'o!be" +i!'t b# t&e con"ucto!) T&e con"ucto! t&e!e+o!e (u't&a-e an a"e0uate !oo+ 't!en*t& to ca!!# t&e'e +o!ce' %it&out e!(anent "i'to!tion) Coe!'ati'+ie' t&i' !e0ui!e(ent a' it &a' &i*& 't!en*t& co(a!e" %it& ot&e! con"ucto! (ate!ial' 7Table2) ecau'e o+ t&e &i*& 't!en*t& o+ coe!, t&e in'ulato!' can be (o!e %i"el# 'ace" t&an i'o''ible %it& lo%e!8't!en*t& (ate!ial')

0igure 13 $%ort-circuit current /aefor!

$ingle p%ase s%ort circuit stresses


40/104

T&e elect!o(a*netic +o!ce "e-eloe" bet%een t%o 't!ai*&t a!allel con"ucto!' o+ ci!cula! c!o''8'ection eac& ca!!#in* t&e 'a(e cu!!ent i' calculate" +!o( t&e +ollo%in* +o!(ula

%&e!e:(a.K +o!ce on con"ucto!, N(I K cu!!ent in bot& &a'e', A

' K &a'e 'acin*, ((

T&e -alue o+ I i' no!(all# taen in t&e +ull# a'#((et!ical con"ition a' 2)>> ti(e' t&e !)()')'#((et!ical -alue o! 1)F ti(e' t&e ea !)()') -alue o+ t&e '&o!t8ci!cuit cu!!ent a' "i'cu''e"abo-e) It i' o''ible, in ce!tain ci!cu('tance', +o! t&e +o!ce' to be *!eate! t&an t&i' "ue to t&ee++ect o+ an i(ul'e in t&e ca'e o+ a -e!# !i*i" con"ucto!, o! "ue to !e'onance in t&e ca'e o+ ba!'

liable to (ec&anical -ib!ation) It i' t&e!e+o!e u'ual to allo% a 'a+et# +acto! o+ 2)> in 'uc& ca'e')

Balanced t%ree-p%ase s%ort-circuit stresses

A t&!ee8&a'e '#'te( &a' it' no!(al cu!!ent' "i'lace" b# 12$H an" %&en a balance" t&!ee8&a'e '&o!t8ci!cuit occu!' t&e "i'lace(ent i' (aintaine") A' %it& all balance" t&!ee8&a'ecu!!ent', t&e in'tantaneou' cu!!ent in one &a'e i' balance" b# t&e cu!!ent' in t&e ot&e! t%o&a'e') T&e "i!ection' o+ t&e cu!!ent' a!e con'tantl# c&an*in* an" 'o t&e!e+o!e a!e t&e +o!ce')T&e (a.i(u( +o!ce' a!e "een"ent on t&e oint in t&e c#cle at %&ic& t&e +ault o! '&o!t8ci!cuitoccu!')

T&e (a.i(u( +o!ce aea!in* on an# &a'e !e'ultin* +!o( a +ull# o++'et a'#((et!ical ea

cu!!ent i' *i-en b#

79

T&e con"ition %&en t&e (a.i(u( +o!ce aea!' on t&e out'i"e &a'e' 7Re" o! lue i' *i-en b#

71$

T&e con"ition %&en t&e (a.i(u( +o!ce i' on t&e cent!e &a'e 7ello% i' *i-en b#


41/104


42/104

T&e +o!(ula %ill t&en be o+ t&e +o!(

712

I+

i' -e!# la!*e t&en

i' al(o't e0ual to

an" t&e!e+o!e t&e (o"i+ie" +o!(ula beco(e' al(o't i"entical %it& t&e 'tan"a!" +o!(ula) In (an#ca'e', t&e +ollo%in* +o!(ula i' 'u++icientl# accu!ate

71@

%&e!e :toti' a*ain t&e total +o!ce alon* t&e con"ucto! in Ne%ton')

:o!(ulae 9 to 11 (a# be u'e" %&e!e

i' *!eate! t&an 2$) :o! -alue' bet%een 2$ an" ?, i' *!eate! t&an 2$) :o! -alue' bet%een 2$ an" ?,

e0uation 1@ abo-e '&oul" be u'e") :o! -alue' le'' t&an ?, e0uation 12 '&oul" be u'e")


43/104

Pro;i!ity factor

0igure 14 - Pro;i!ity factor for rectangular copper conductor

T&e +o!(ulae in t&e !e-iou' 'ection u'e" +o! calculatin* '&o!t8ci!cuit +o!ce' "o not tae intoaccount t&e e++ect o+ con"ucto!' %&ic& a!e not !oun" a' t&e# 't!ictl# onl# al# to !oun"con"ucto!') To o-e!co(e t&i' %&en con'i"e!in* !ectan*ula! con"ucto!', a !o.i(it# +acto! i'int!o"uce" into t&e o!"ina!# +o!ce +o!(ulae, it' -alue bein* +oun" u'in* t&e cu!-e' in :i*u!e 1?)

E.cet in ca'e' %&e!e t&e con"ucto!' a!e -e!# '(all o! a!e 'ace" a con'i"e!able "i'tance aa!tt&e co!!ecte" *ene!al +o!(ula +o! +o!ce e! unit len*t& beco(e'


44/104

T&e -alue o+

i' +i!'t calculate" t&en i' !ea" +!o( t&e cu!-e +o! t&e a!o!iate

!atio)

:!o( t&e cu!-e' it can be 'een t&at t&e e++ect o+ con"ucto! '&ae "ec!ea'e' !ai"l# %it&inc!ea'in* 'acin* an" i' a (a.i(u( +o! 't!i con"ucto!' o+ '(all t&icne'') It i' al(o't unit# +o!'0ua!e con"ucto!' an" i' unit# +o! a ci!cula! con"ucto!)

Alte!nati-el#, t&e !o.i(it# +acto! can be calculate" u'in* t&e +ollo%in* +o!(ula, +!o( %&ic& t&ecu!-e' in :i*u!e 1? %e!e "!a%n 7D%i*&t 191) 7See :i*u!e 1? +o! e.lanation o+ '#(bol')

T&i' +o!(ula *i-e' t&e inte!(e"iate cu!-e' o+ :i*u!e 1?, +o! 'a, b$, a$

Fibrational stresses


45/104

St!e''e' %ill be in"uce" in a con"ucto! b# natu!al o! +o!ce" -ib!ation' t&e a(litu"e o+ %&ic&"ete!(ine' t&e -alue o+ t&e 't!e'', %&ic& can be calculate" +!o( t&e +o!(ulae *i-en in Section F)

T&e con"ucto! '&oul" be "e'i*ne" to &a-e a natu!al +!e0uenc# %&ic& i' not %it&in @$G o+ t&e-ib!ation' in"uce" b# t&e (a*netic +iel"' !e'ultin* +!o( t&e cu!!ent' +lo%in* in a"/acentcon"ucto!') T&i' t#e o+ -ib!ation no!(all# occu!' "u!in* continuou' !unnin* an" "oe' not occu!

%&en '&o!t8ci!cuit cu!!ent' a!e +lo%in*)

T&e 't!e''e' !e'ultin* +!o( t&e '&o!t8ci!cuit +o!ce' a!e calculate" u'in* t&e bea( t&eo!# +o!(ulae+o! 'i(l# 'uo!te" bea(' +o! a 'in*le cantile-e! to (ulti'an a!!an*e(ent', t&e alie" +o!ce'bein* "e!i-e" +!o( t&e !e-iou' 'ection') T&e !e'ultin* "e+lection' enable t&e con"ucto! 't!e'' tobe calculate" an" 'o "ete!(ine i+ it i' liel# to e!(anentl# "a(a*e t&e con"ucto! becau'e it &a'e.cee"e" t&e !oo+ 't!e'' o+ t&e con"ucto! (ate!ial)

)et%ods of reducing conductor stresses

In ca'e' %&e!e t&e!e i' a lieli&oo" o+ -ib!ation at no!(al cu!!ent' o! %&en 'ub/ecte" to '&o!t8ci!cuit +o!ce' cau'in* "a(a*e to t&e con"ucto!, t&e +ollo%in* can &e u'e" to !e"uce o! eli(inate

t&e e++ect

a Re"uce t&e 'an bet%een in'ulato! 'uo!t')

T&i' (et&o" can be u'e" to !e"uce t&e e++ect' o+ bot& continuou' -ib!ation an" t&at "ue to '&o!t8ci!cuit +o!ce')

b Inc!ea'e t&e 'an bet%een in'ulato! 'uo!t')

T&i' (et&o" can onl# be u'e" to !e"uce t&e e++ect' o+ -ib!ation !e'ultin* +!o( a continuou'cu!!ent) It %ill inc!ea'e t&e 't!e''e' "ue to a '&o!t8ci!cuit cu!!ent)

c Inc!ea'e o! "ec!ea'e t&e +le.ibilit# o+ t&e con"ucto! 'uo!t')

T&i' (et&o" %ill !e"uce t&e e++ect' o+ -ib!ation "ue to continuou' cu!!ent but &a' -e!# little e++ecton t&at "ue to '&o!t8ci!cuit +o!ce')

" Inc!ea'e t&e con"ucto! +le.ibilit#)

T&i' can onl# be u'e" to !e"uce t&e e++ect' o+ -ib!ation "ue to a continuou' cu!!ent) T&e '&o!t8ci!cuit e++ect i' inc!ea'e")

e Dec!ea'e t&e con"ucto! +le.ibilit#)

T&i' (et&o" %ill !e"uce t&e e++ect' o+ -ib!ation "ue to eit&e! a continuou' cu!!ent o! a '&o!t8ci!cuit)

It %ill be note" t&at in ca!!#in* out t&e -a!iou' 'u**e'tion' abo-e, c&an*e' can onl# be (a"e%it&in t&e o-e!all "e'i*n !e0ui!e(ent' o+ t&e bu'ba! '#'te()

Corona Disc%arge

4it& -e!# &i*& -olta*e ai!8in'ulate" bu'ba!', a!ticula!l# o+ t&e t#e u'uall# in'talle" out o+ "oo!',it i' nece''a!# to en'u!e t&at %it& t&e 'acin* a"ote" bet%een con"ucto!' o+ "i++e!ent &a'e', o!bet%een con"ucto!' an" ea!t&, t&e elect!o(a*netic 't!e'' in t&e ai! 'u!!oun"in* t&e con"ucto!' i'lo% enou*& not to cau'e a co!ona "i'c&a!*e) Co!ona "i'c&a!*e i' to be a-oi"e" %&e!e o''ible

a' it c!eate' ioni'e" *a' %&ic& can lea" to a la!*e !e"uction in t&e ai! in'ulation 'u!!oun"in* t&econ"ucto! an" 'o can cau'e +la'&8o-e!) S&oul" +la'&8o-e! occu!, t&i' %ill in (an# ca'e' lea" to a


46/104

'&o!t8ci!cuit bet%een eit&e! a"/acent &a'e' o! ole' o! t&e nea!e't ea!t& oint o! lane) T&i' %illcau'e con'i"e!able bu!nin* o+ t&e con"ucto!' an" a''ociate" e0ui(ent to*et&e! %it&(ec&anical "a(a*e) Co!ona "i'c&a!*e can al'o cau'e !a"io inte!+e!ence %&ic& (a# beunaccetable)

To a-oi" t&e'e con"ition' t&e bu'ba! '#'te( '&oul" be +!ee +!o( '&a! e"*e' o! '(all !a"ii on

t&e con"ucto! '#'te() I+ t&i' i' not o''ible t&en a""itional e0ui(ent %ill &a-e to be inco!o!ate"in t&e "e'i*n 'uc& a' co!ona !in*' an" 't!e'' !elie-in* cone' (ounte" in t&e a!ea' o+ &i*&elect!ic 't!e'') T&e '(alle't !a"ii !e0ui!e" +o! !e-ention o+ co!ona can be calculate" +!o( t&e+o!(ula

%&e!eE K !)()') -olta*e to neut!al, V! K con"ucto! !a"iu', ((

" K "i'tance bet%een con"ucto! cent!e', ((

K ai! "en'it# +acto!

( K con"ucto! 'u!+ace con"ition +acto!

T&e -alue' +o! t&e +acto!' ( an" " a!e a' +ollo%'

( K 1 +o! a oli'&e" con"ucto! 'u!+ace, $)9F to $)9@ +o! !ou*&ene" o! %eat&e!e" 'u!+ace', an"

$)F to $)F$ +o! 't!an"e" con"ucto!')

" K 1 at 1 ba! ba!o(et!ic !e''u!e an" 2>HC) At ot&e! !e''u!e' an" te(e!atu!e' t&e -alue i'+oun" a' +ollo%'

%&e!eb K ba!o(et!ic !e''u!e, ba!T K te(e!atu!e, HC

At location' abo-e 'ea le-el t&e no!(al !e''u!e i' !e"uce" b# a!o.i(atel# $)12 ba! e! 1$$$( o+ altitu"e)

T&e -olta*e E- at %&ic& t&e co!ona "i'c&a!*e no!(all# beco(e' -i'ible i' 'o(e%&at &i*&e! t&an*i-en b# t&e abo-e +o!(ula an" can be "ete!(ine" a' +ollo%'


47/104

In ba" %eat&e! con"ition' t&e "i'c&a!*e (a# aea! at a -olta*e lo%e! t&an t&at in"icate" b# t&e+o!(ulae an" it i' t&e!e+o!e a"-i'able to (ae an allo%ance o+ about 2$G a' a 'a+et# +acto!)


48/104

&. 'ointing of Copper Busbars

Busbar 'ointing )et%ods

'oint "esistance

Bolting Arrange!ents

Cla!ps

elded 'oints

Busbar 'ointing )et%ods

It i' nece''a!# t&at a con"ucto! /oint '&all be (ec&anicall# 't!on* an" &a-e a !elati-el# lo%

!e'i'tance %&ic& (u't !e(ain 'ub'tantiall# con'tant t&!ou*&out t&e li+e o+ t&e /oint)

E++icient /oint' in coe! bu'ba! con"ucto!' can be (a"e -e!# 'i(l# b# boltin*, cla(in*,!i-etin*, 'ol"e!in* o! %el"in*, t&e +i!'t t%o bein* u'e" e.ten'i-el#, t&ou*& coe! %el"in* i' no%(o!e *ene!all# a-ailable t&!ou*& i(!o-e(ent' in %el"in* tec&nolo*#)

elded Gointsin coe! bu'ba!' &a-e t&e a"-anta*e t&at t&e cu!!ent ca!!#in* caacit# i'uni(ai!e", a' t&e /oint i' e++ecti-el# a continuou' coe! con"ucto!)

Bolted Gointsa!e co(act, !eliable an" -e!'atile but &a-e t&e "i'a"-anta*e t&at t&e# nece''itatet&e "!illin* o! unc&in* o+ &ole' t&!ou*& t&e con"ucto!' %it& t&e bolt &ole' cau'in* 'o(e"i'to!tion o+ t&e line' o+ cu!!ent +lo%) T&i' /oint t#e al'o &a' a 'o(e%&at (o!e une-en contact

!e''u!e t&an one u'in* cla( late')

Cla!ped Gointsa!e ea'# to (ae %it& t&e +ull c!o''8'ection bein* uni(ai!e") T&e e.t!a (a'' att&e /oint an" &ence coolin* a!ea &el' to *i-e a coole! !unnin* /oint an" %it& a %ell8"e'i*ne"cla(, *i-e' a -e!# e-en contact !e''u!e) T&e +u!t&e! a""e" a"-anta*e i' t&at o+ ea'# e!ection"u!in* in'tallation) A "i'a"-anta*e i' t&e (uc& &i*&e! co't' o+ t&e cla(' an" a''ociate" +i.in*')

"ieted Gointsa!e e++icient i+ %ell (a"e, but &a-e t&e "i'a"-anta*e t&at t&e# cannot ea'il# beun"one o! ti*&tene" in 'e!-ice an" t&at t&e# a!e not 'o con-enient to (ae +!o( an in'tallationoint o+ -ie%)

$oldered or braed Gointsa!e !a!el# u'e" +o! bu'ba!' unle'' t&e# a!e !ein+o!ce" %it& bolt' o!

cla(' 'ince &eatin* un"e! '&o!t8ci!cuit con"ition' can (ae t&e( bot& (ec&anicall# an"elect!icall# un'oun")

'oint "esistance

T&e !e'i'tance o+ a /oint i' a++ecte" (ainl# b# t%o +acto!'

aSt!ea(line e++ect o! '!ea"in* !e'i'tance R', t&e "i-e!'ion o+ t&e cu!!ent +lo% t&!ou*& a /oint)bT&e contact !e'i'tance o! inte!+ace !e'i'tance o+ t&e /oint R/)T&e total /oint !e'i'tance R/K R' Ri)
http://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Busbar%20Jointing%20Methodshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Joint%20Resistancehttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Bolting%20Arrangementshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Clampshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Welded%20Jointshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Busbar%20Jointing%20Methodshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Joint%20Resistancehttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Bolting%20Arrangementshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Clampshttp://www.cda.org.uk/megab2/elecapps/pub22/sec7.htm#Welded%20Joints


49/104

T&e abo-e i' 'eci+icall# +o! a ")c) cu!!ent) 4&e!e a)c) cu!!ent' a!e +lo%in*, t&e c&an*e' in!e'i'tance "ue to 'in an" !o.i(it# e++ect' in t&e /oint one (u't al'o be taen into account)

e+o!e con'i"e!in* t&e e++ect o+ t&e abo-e +acto!' on t&e e++icienc# o+ a /oint, it i' i(o!tant to!eali'e t&e natu!e o+ t&e t%o contact 'u!+ace') No (atte! &o% %ell a contact 'u!+ace i' oli'&e",t&e 'u!+ace i' !eall# (a"e u o+ a la!*e nu(be! o+ ea' an" t!ou*&' %&ic& a!e !ea"il# -i'ible

un"e! a (ic!o'coe) 4&en t%o 'u!+ace' a!e b!ou*&t to*et&e! contact i' onl# (a"e at t&e ea',%&ic& a!e 'ub/ecte" to (uc& &i*&e! contact !e''u!e' t&an t&e a-e!a*e /oint contact !e''u!e,an" &ence "e+o!( "u!in* t&e /ointin* !oce'') T&e actual contact a!ea in t&e co(lete" /oint i'(uc& '(alle! t&an t&e total 'u!+ace a!ea o+ t&e /oint) It &a' been '&o%n t&at in a t#ical bu'ba!/oint 'u!+ace t&e e++ecti-e contact a!ea i' con+ine" to t&e !e*ion in %&ic& t&e !e''u!e i' alie",i)e), nea! t&e bolt' in t&e ca'e o+ a lae" /oint)

$trea!line effect

T&e "i'to!tion o+ t&e line' o+ cu!!ent +lo% at an o-e!lain* /oint bet%een t%o con"ucto!' a++ect't&e !e'i'tance o+ t&e /oint) T&i' e++ect (u't al'o occu! %&en t&e cu!!ent +lo%' +!o( ea to ea+!o( 'u!+ace to 'u!+ace t&ou*& t&e o-e!all e++ect i' t&at t&!ou*& t&e /oint)

In t&e ca'e o+ an o-e!lain* /oint bet%een t%o +lat coe! ba!', t&e 't!ea(line e++ect i'"een"ent onl# on t&e !atio o+ t&e len*t& o+ t&e o-e!la to t&e t&icne'' o+ t&e ba!' an" not on t&e%i"t&, !o-i"e" t&at t&i' "i(en'ion i' t&e 'a(e +o! bot& ba!') It &a' been '&o%n bot&(at&e(aticall# an" e.e!i(entall# t&at e-en in a e!+ectl# (a"e o-e!lain* /oint bet%een t%o!elati-el# t&in +lat con"ucto!' &a-in* a uni+o!( contact !e'i'tance, t&e "i't!ibution o+ cu!!ent o-e!t&e contact a!ea i' not uni+o!() P!acticall# all o+ t&e cu!!ent +lo%in* ac!o'' t&e contact 'u!+ace' i'concent!ate" to%a!"' t&e e.t!e(itie' o+ t&e /oint an" t&e cu!!ent "en'it# at t&e en"' o+ t&eo-e!lain* con"ucto!' (a# be (an# ti(e' t&at at t&e cent!e o+ t&e /oint)

It i' e-i"ent +!o( t&e abo-e t&at t&e e++icienc# o+ an o-e!lain* /oint "oe' not inc!ea'e a' t&elen*t& o+ t&e o-e!la inc!ea'e' an" t&at +!o( a u!el# elect!ical oint o+ -ie% no a"-anta*e i' tobe *aine" b# e(lo#in* an un"ul# lon* o-e!la)

T&e !elation bet%een t&e !e'i'tance "ue to 't!ea(line e++ect o+ an o-e!lain* /oint bet%een t%o+lat coe! con"ucto!' an" t&e !atio o+ t&e len*t& o+ t&e o-e!la to t&e t&icne'' i' '&o%n in :i*u!e1>) It &a' al'o been +oun" t&at t&e "i'to!tion e++ect in a T8/oint i' about t&e 'a(e a' a 't!ai*&t/oint)

T&e !e'i'tance !atio e in :i*u!e 1> i' t&e !atio o+ t&e !e'i'tance o+ a /oint "ue to 't!ea(line e++ectRS, to t&e !e'i'tance o+ an e0ual len*t& o+ 'in*le con"ucto! Rb, i)e)

%&e!ea K b!ea"t& o+ ba!, ((b K t&icne'' o+ ba!, ((

l K len*t& o+ o-e!la, ((

K !e'i'ti-it# o+ t&e con"ucto!, ((

:!o( t&e *!a& it can be 'een t&en t&at t&e e++ect +all' -e!# !ai"l# +o! !atio' u to t%o an" t&en

-e!# (uc& (o!e 'lo%l# +o! -alue' u to 'e-en) T&i' (ean' t&at in (o't ca'e' t&e 't!ea(linee++ect &a' -e!# little e++ect a' t&e o-e!la i' o+ nece''it# (uc& *!eate! t&an 'e-en)


50/104

0igure 1 $trea!line effect in oerlapping Goints

Contact resistance

T&e contact inte!+ace bet%een t&e t%o +ace' o+ a bu'ba! /oint con'i't' o+ a la!*e nu(be! o+'ea!ate oint contact', t&e a!ea o+ %&ic& inc!ea'e' a' (o!e !e''u!e i' alie" an" t&e ea'a!e c!u'&e")

T&e!e a!e t%o (ain +acto!' %&ic& t&e!e+o!e a++ect t&e actual inte!+ace !e'i'tance o+ t&e 'u!+ace')

aT&e con"ition o+ t&e 'u!+ace')bT&e total alie" !e''u!e)T&e t#e o+ coatin* alie" to t&e contact 'u!+ace' to !e-ent o! "ela# t&e on'et o+ o.i"ation %&enoe!atin* at ele-ate" te(e!atu!e' o! in a &o'tile en-i!on(ent i' al'o i(o!tant, a!ticula!l# in t&elon* te!()

Condition of contact surfaces

T&e con"ition o+ t&e contact 'u!+ace' o+ a /oint &a' an i(o!tant bea!in* on it' e++icienc#) T&e'u!+ace' o+ t&e coe! '&oul" be +lat an" clean but nee" not be oli'&e") Mac&inin* i' not u'uall#!e0ui!e") Pe!+ectl# +lat /oint +ace' a!e not nece''a!# 'ince -e!# *oo" !e'ult' can in (o't ca'e' be


51/104

obtaine" (e!el# b# en'u!in* t&at t&e /oint i' ti*&t an" clean) T&i' i' a!ticula!l# t&e ca'e %&e!ee.t!u"e" coe! ba!' a!e u'e") 4&e!e ca't coe! ba!' a!e u'e", &o%e-e!, (ac&inin* (a# benece''a!# i+ t&e /oint' a!e to obtain a 'u++icientl# +lat contact 'u!+ace)

O.i"e', 'ul&i"e' an" ot&e! 'u!+ace conta(inant' &a-e, o+ cou!'e, a &i*&e! !e'i'tance t&an t&eba'e (etal) Coe!, lie all ot&e! co((on (etal', !ea"il# "e-elo' a -e!# t&in 'u!+ace o.i"e +il(

e-en at o!"ina!# te(e!atu!e' %&en +!eel# e.o'e" to ai!, alt&ou*& alu(iniu( o.i"i'e' (uc&(o!e !ai"l#, an" it' o.i"e &a' a (uc& &i*&e! !e'i'ti-it#)

T&e ne*ati-e te(e!atu!e coe++icient o+ !e'i'tance o+ coe! o.i"e (ean' t&at t&e /ointcon"ucti-it# ten"' to inc!ea'e %it& te(e!atu!e) T&i' "oe' not, o+ cou!'e, (ean t&at a /oint can be(a"e %it&out cleanin* /u't !io! to /ointin* to en'u!e t&at t&e o.i"e la#e! i' t&in enou*& to beea'il# b!oen a' t&e contact 'u!+ace ea' "e+o!( %&en t&e contact !e''u!e i' alie")

Preparation of surfaces

Contact 'u!+ace' '&oul" be +lattene" b# (ac&inin* i+ nece''a!# an" t&o!ou*&l# cleane") A *!oun"o! 'an"8!ou*&ene" 'u!+ace i' !e+e!able to a '(oot& one)

It i' i(o!tant to !e-ent t&e !e8o.i"ation o+ t&e /oint in 'e!-ice an" it i' t&e!e+o!e !eco((en"e"t&at t&e contact +ace' '&oul" be co-e!e" %it& a t&in la#e! o+ et!oleu( /ell# i((e"iatel# a+te!cleanin* t&e contact 'u!+ace') T&e /oint 'u!+ace' '&oul" t&en be bolte" to*et&e!, t&e e.ce''et!oleu( /ell# bein* !e''e" out a' t&e contact !e''u!e i' alie") T&e !e(ainin* /ell# %ill &elto !otect t&e /oint +!o( "ete!io!ation)

It '&oul" be note" t&at in ca'e' %&e!e /oint' &a-e to e!+o!( !eliabl# in &i*&e! t&an no!(ala(bient te(e!atu!e con"ition', it (a# be a"-i'able to u'e a &i*& (eltin* oint /ell# to !e-ent it+!o( +lo%in* out o+ t&e /oint, lea-in* it liable to attac b# o.i"ation an" t&e en-i!on(ent)

T&e +ollo%in* 'ection' "e'c!ibe t&e u'e o+ coatin*' on con"ucto! contact 'u!+ace') It '&oul" benote" t&at !ecent te't' ca!!ie" out to in-e'ti*ate t&e e!+o!(ance o+ bolte" /oint' un"e! c#clic&eatin* %it& %i"e te(e!atu!e -a!iation' in"icate t&at /oint' %it&out coatin*' *i-e t&e (o't !eliablelon*8te!( e!+o!(ance 7Jac'on 19F2) T&e !ea'on +o! t&i' i' t&at (o't coatin*' a!e o+ 'o+t(ate!ial' %&ic& %&en 'ub/ecte" to continuou' !e''u!e' an" !ai'e" te(e!atu!e' ten" to +lo%)T&i' &a' t&e e++ect o+ !e"ucin* t&e nu(be! o+ &i*& !e''u!e contact oint' +o!(e" %&en t&e /ointi' ne%l# bolte" to*et&e!)

inning.T&e tinnin* o+ t&e contact 'u!+ace' o+ a bolte" o! cla(e" /oint %it& u!e tin o! a lea"8tinallo# i' no!(all# unnece''a!#, alt&ou*& a"-anta*e' can be *aine" in ce!tain ci!cu('tance')

I+ t&e /oint +ace' a!e -e!# !ou*&, tinnin* (a# !e'ult in 'o(e i(!o-e(ent in e++icienc#) In (o'tca'e', &o%e-e!, it' c&ie+ -i!tue lie' in t&e +act t&at it ten"' to !e-ent o.i"ation an" &ence'ub'e0uent /oint "ete!io!ation) It (a# t&e!e+o!e be !eco((en"e" in ca'e' %&e!e t&e /oint'

oe!ate at unu'uall# &i*& te(e!atu!e' o! cu!!ent "en'itie' o! %&en 'ub/ecte" to co!!o'i-eat(o'&e!e')

:o! t&e be't !e'ult' t&e 'u!+ace' '&oul" be tinne" o! !e8tinne" i((e"iatel# !io! to t&e +inal /ointcla(in*) It '&oul" be note" t&at bot& t&e elect!ical con"ucti-it# an" t&e o.i"ation !otecti-eaction "ec!ea'e a' t&e lea" content o+ t&e 'ol"e! inc!ea'e') Lea" al'o &a' t&e e++ect o+ !e"ucin*t&e 'u!+ace &a!"ne'' o+ t&e coatin* an" a &i*& lea" content in t&e tinnin* (ate!ial '&oul" bea-oi"e" a' t&i' can cau'e t&e latin* to c!ee once t&e /oint i' bolte" to*et&e! !e'ultin* in!e(atu!e +ailu!e "ue to o-e!&eatin*)

$iler or nic@el plating.T&i' t#e o+ latin* i' bein* u'e" inc!ea'in*l#, a!ticula!l# %&e!ee0ui(ent i' (anu+actu!e" to A(e!ican 'tan"a!"' %&ic& !e0ui!e late" /oint' +o! &i*&te(e!atu!e oe!ation) Nicel8latin* !o-i"e' a &a!"e! 'u!+ace t&an 'il-e! an" (a# t&e!e+o!e be!e+e!able) T&e'e latin*' a!e e.en'i-e to al# an" (u't be !otecte" !io! to t&e +inal /ointin*!oce'' a' t&e# a!e al%a#' -e!# t&in coatin*' an" can t&e!e+o!e be ea'il# "a(a*e") T&e!e i' al'o


52/104

'o(e "oubt a' to t&e 'tabilit# o+ t&e'e /oint' un"e! !olon*e" &i*& te(e!atu!e c#clin*) Ve!# &i*&contact !e'i'tance' can be "e-eloe" 'o(e ti(e a+te! /ointin*) It i' t&e!e+o!e 'u**e'te" t&atnatu!al (etal /oint' a!e in (o't ca'e' !e+e!able)

Effect of pressure on contact resistance

It &a' been '&o%n abo-e t&at t&e contact !e'i'tance i' "een"ent (o!e on t&e total alie"!e''u!e t&an on t&e a!ea o+ contact) I+ t&e total alie" !e''u!e !e(ain' con'tant an" t&econtact a!ea i' -a!ie", a' i' t&e ca'e in a '%itc& bla"e (o-in* bet%een '!in* loa"e" contact',t&e total contact !e'i'tance !e(ain' !acticall# con'tant) T&i' can be e.!e''e" b# an e0uation o+t&e +o!(

%&e!eR

i

K !e'i'tance o+ t&e contact

K total contact !e''u!e

n K e.onent bet%een $)? an" 1

C K a con'tant

T&e *!eate! t&e alie" total !e''u!e t&e lo%e! %ill be t&e /oint !e'i'tance an" t&e!e+o!e +o! &i*&e++icienc# /oint' &i*& !e''u!e i' u'uall# nece''a!#) T&i' &a' t&e a"-anta*e t&at t&e &i*& !e''u!e&el' to !e-ent "ete!io!ation o+ t&e /oint) :i*u!e 16 '&o%' t&e e++ect o+ !e''u!e on /oint!e'i'tance)

0igure 1# %e effect of pressure on t%e contact resistance of a Goint bet/een t/o copperconductors

Joint !e'i'tance +all' !ai"l# %it& inc!ea'in* !e''u!e, but abo-e a !e''u!e o+ about 1> N((2t&e!e i' little +u!t&e! i(!o-e(ent) Ce!tain !ecaution' (u't be ob'e!-e" to en'u!e t&at t&e

contact !e''u!e i' not un"ul# &i*&, 'ince it i' i(o!tant t&at t&e !oo+ 't!e'' o+ t&e con"ucto!(ate!ial o! it' bolt' an" cla(' i' not e.cee"e")


53/104

A' a ba! &eat' u un"e! loa" t&e contact !e''u!e in a /oint (a"e %it& 'teel bolt' ten"' toinc!ea'e becau'e o+ t&e "i++e!ence in e.an'ion coe++icient' bet%een coe! an" t&e 'teel) It i't&e!e+o!e e''ential t&at t&e initial contact !e''u!e i' et to a 'uc& a le-el t&at t&e contact!e''u!e i' not e.ce''i-e %&en at oe!atin* te(e!atu!e) I+ t&e ela'tic li(it o+ t&e ba! i' e.cee"e"t&e /oint %ill &a-e a !e"uce" contact !e''u!e %&en it !etu!n' to it' col" 'tate "ue to t&e /oint(ate!ial' &a-in* "e+o!(e" o! 't!etc&e")

To a-oi" t&i', it i' &el+ul to u'e "i'c '!in* %a'&e!' %&o'e '!in* !atin* i' c&o'en to (aintain a'ub'tantiall# con'tant contact !e''u!e un"e! col" an" &ot %o!in* con"ition') T&i' t#e o+ /oint"ete!io!ation i' -e!# (uc& (o!e liel# to &aen %it& 'o+t (ate!ial', 'uc& a' E1E alu(iniu(,%&e!e t&e (ate!ial ela'tic li(it i' lo% co(a!e" %it& t&at o+ &i*& con"ucti-it# coe!)

'oint efficiency

T&e e++icienc# o+ a /oint (a# be (ea'u!e" in te!(' o+ t&e !atio o+ t&e !e'i'tance o+ t&e o!tion o+t&e con"ucto! co(!i'in* t&e /oint an" t&at o+ an e0ual len*t& o+ 't!ai*&t con"ucto!)

T&e !e'i'tance o+ a /oint, a' al!ea"# (entione", i' (a"e u o+ t%o a!t', one "ue to t&e "i'to!tion

o+ line' o+ cu!!ent +lo% an" t&e ot&e! to contact !e'i'tance) T&e !e'i'tance "ue to t&e 't!ea(linee++ect at an o-e!la /oint i' *i-en b#

%&e!e +o! a *i-en /oint a, b an" la!e t&e %i"t&, t&icne'' an" o-e!la len*t&, t&e'e all bein*con'tant, an" contact !e'i'tance o+ t&e /oint i'

%&e!e K contact !e'i'tance e! unit a!ea)

T&e total /oint !e'i'tance i'

an" t&e e++icienc# o+ t&e /oint i'

T&e !e'i'tance o+ an e0ual len*t& o+ 't!ai*&t con"ucto! i' *i-en b#


54/104

T&e !e'i'tance !atio e i' obtaine" +!o( :i*u!e 1>)

In (o't ca'e' it i' ina"-i'able to u'e contact !e''u!e' o+ le'' t&an N(( 2, 1$ N((2bein*!e+e!!e") T&e contact !e''u!e c&o'en i' in+luence" b# t&e 'ie an" nu(be! o+ bolt' o! cla(',t&e latte! *i-in* a (o!e e-en contact !e''u!e) :o! t&e 'ae o+ '#((et!# t&e len*t& o+ o-e!la i'o+ten (a"e e0ual to t&e %i"t& o+ t&e ba!, t&ou*& %it& t&ic an" na!!o% ba!' t&e o-e!la can be

inc!ea'e" to i(!o-e t&e o-e!all /oint e!+o!(ance)

O%in* to t&e la!*e! 'u!+ace a!ea +!o( %&ic& &eat (a# be "i''iate", e++icient /oint' bet%een'in*le coe! con"ucto!' u'uall# &a-e a lo%e! te(e!atu!e !i'e t&an t&e con"ucto!' t&e('el-e')It i' i(o!tant, in *ene!al, to en'u!e t&at all /oint' &a-e a !ea'onable (a!*in o+ 'a+et#) T&i' i'a!ticula!l# 'o %&e!e (ulti8con"ucto!' /oin at one /oint an"o! t&e con"ucto!' a!e no!(all# !unnin*clo'e to t&e 'eci+ie" (a.i(u( te(e!atu!e !i'e')

Bolting Arrange!ents

In "eci"in* t&e nu(be!, 'ie an" "i't!ibution o+ bolt' !e0ui!e" to !o"uce t&e nece''a!# contact!e''u!e to *i-e &i*& /oint e++icienc#, bot& elect!ical an" (ec&anical con'i"e!ation' &a-e to be

taen into account) T&e (et&o"' u'e" to "ete!(ine t&e'e !e0ui!e(ent' &a-e been *i-en in!e-iou' 'ection')

A /oint no!(all# "ec!ea'e' in !e'i'tance %it& an inc!ea'e in t&e 'ie an" nu(be! o+ bolt' u'e")olt 'ie' u'uall# -a!# +!o( M6 to M2$ %it& bet%een +ou! an" 'i. bein* u'e" in eac& /oint %it& a!e+e!ence +o! +ou! bolt' in na!!o% con"ucto!' an" 'i. in la!*e con"ucto!') T&e to!0ue c&o'en +o!eac& bolt 'ie i' "een"ent on t&e bolt (ate!ial an" t&e (a.i(u( oe!atin* te(e!atu!ee.ecte") ecau'e o+ t&e 't!en*t& o+ coe!, "e+o!(ation o+ t&e con"ucto! un"e! t&e !e''u!e o+t&e /oint i' not no!(all# a con'i"e!ation)

Table 9 '&o%' t#ical boltin* a!!an*e(ent' +o! -a!iou' bu'ba! 'ie') T&e !eco((en"e" to!0ue'ettin*' a!e alicable to &i*&8ten'ile 'teel 7F)F o! alu(iniu( b!one 7C4@$, +o!(e!l# C#1$?+a'tene!' %it& unlub!icate" t&!ea"' o+ no!(al 'u!+ace +ini'&) In t&e ca'e o+ 'tainle'' 'teel bolt',t&e'e to!0ue 'ettin*' (a# be u'e", but t&e t&!ea"' (u't be lub!icate" !io! to u'e)

In a""ition to t&e !oo+ o! #iel" 't!e'' o+ t&e bolt (ate!ial an" t&e t&!ea" c&a!acte!i'tic', t&eco!!ect ti*&tenin* to!0ue "een"' on t&e "i++e!ential e.an'ion bet%een t&e bolt an" con"ucto!(ate!ial') al-ani'e" 'teel bolt' a!e no!(all# u'e" but b!a'' o! b!one bolt' &a-e been u'e"becau'e t&ei! coe++icient' o+ e.an'ion clo'el# (atc& t&e coe! con"ucto! an" &ence t&e contact!e''u!e "oe' not -a!# %i"el# %it& oe!atin* te(e!atu!e) Coe! allo# bolt' al'o &a-e t&ea"-anta*e t&at t&e o''ibilit# o+ "i''i(ila! (etal co!!o'ion i' a-oi"e") ecau'e t&e'e allo#' "onot &a-e an ea'il# "i'ce!nible #iel" 't!e'', &o%e-e!, ca!e &a' to be taen not to e.cee" t&eco!!ect ti*&tenin* to!0ue)

ecau'e o+ t&ei! non8(a*netic !oe!tie', coe! allo#' (a# al'o be !e+e!!e" to (il" o! &i*&8

ten'ile 'teel %&e!e &i*& (a*netic +iel"' a!e e.ecte") Alte!nati-el#, a non8(a*netic 'tainle'''teel (a# be u'e") In (o't ca'e' &o%e-e!, &i*&8ten'ile 'teel i' u'e" +o! it' -e!# &i*& #iel" 't!e'')

able ypical busbar bolting arrange!ents single face oerlap5

Bar /idt%!!

'ointoerlap!!

'oint area!!2

9u!ber ofbolts

)etric boltsiecoarset%read5

Bolttor*ue 9!

12 2 M6 )2 1? 1)F

2$ ?$ F$$ 2 M6 )2 1? 1)F

2> 6$ 1>$$ 2 MF 1 1$ 21 2)$


55/104

@$ 6$ 1F$$ 2 MF 1 1$ 21 2)$

?$ $ 2F$$ 2 M1$ 2F 11)> 2? 2)2

>$ $ @>$$ 2 M12 ?> 1? 2F 2)

6$ 6$ @6$$ ? M1$ 2F 11)> 2? 2)2

F$ F$ 6?$$ ? M12 ?> 1? 2F 2)

1$$ 1$$ 1$$$$ > M12 ?> 1> 2F 2)

12$ 12$ 1??$$ > M12 ?> 1> 2F 2)

16$ 16$ 2>6$$ 6 M16 91 2$ 2F 2)

2$$ 2$$ ?$$$$ F M16 91 2$ 2F 2)

&i*&8ten'ile 'teel o! alu(iniu( b!one 7C4@$, +o!(e!l# C1$?

Cla!ps

T&e c&oice o+ cla( (ate!ial an" (et&o" o+ (anu+actu!e "een"' on t&e a)c) o! ")c) cu!!ent!e0ui!e(ent', an" on t&e nu(be! o+ cla(' o+ a *i-en 'ie !e0ui!e") T&e (anu+actu!in* (et&o"'u'e" inclu"e (ac&inin* +!o( late, 'an" o! "ie ca'tin*, o! 'ta(in* +!o( late) In t&e ca'e o+ lo%cu!!ent a)c) 7le'' t&an @$$$ A an" ")c) '#'te(' t&e cla(' '&oul" be (a"e +!o( a &i*&8't!en*t&(ate!ial co(atible %it& t&e !e0ui!e" contact !e''u!e) T&e# can t&e!e+o!e be (a"e +!o( 'teel inca't, +o!*e" o! 'ta(e" +o!() 4&e!e a)c) cu!!ent' in e.ce'' o+ @$$$ A a!e conce!ne", t&e c&oiceo+ (ate!ial i' bet%een t&e lo% o! non8(a*netic 'teel' o! a b!a'' o! b!one) Steel cla(' a!e*ene!all# un'uitable becau'e o+ t&e 'te!e'i' lo''e' in"uce" in t&e()

elded 'oints

T&e ine!t *a' '&iel"e" a!c !oce''e', tun*'ten ine!t *a' 7TI an" (etal ine!t *a' 7MI a!e t&e!e+e!!e" %el"in* (et&o"' +o! &i*& con"ucti-it# coe!' an" a!e caable o+ !o"ucin* e.cellentbu'ba! /oint') T&e %el"in* "ata *i-en in Table 1$ a!e !o-i"e" a' a *ui"e to *oo" !actice, butt&e actual %el"in* con"ition' t&at %ill *i-e t&e be't !e'ult' +o! a a!ticula! /oint (u't be"ete!(ine" +!o( e.e!ience) Ce!tain 'ical an" (etallu!*ical !oe!tie' o+ coe! (u't,&o%e-e!, be taen account o+ %&en %el"in*) T&e &i*& t&e!(al "i++u'i-it# o+ coe! 8 +ou! o! +i-eti(e' t&at o+ (il" 'teel 8 oo'e' t&e +o!(ation o+ an a"e0uate %el" ool nece''a!# +o! *oo"+u'ion an" "eo.i"ation %&ic& can *i-e !i'e to lac o+ +u'ion "e+ect' an" o!o'it#) T&e !ai" &eat'in e++ect, %&ic& i' a!ticula!l# !onounce" in t&ice! 'ection', (u't t&e!e+o!e be o-e!co(e)P!e&eatin* o+ t&e coe! be+o!e %el"in* i' nece''a!# +o! t&icne'' abo-e about @ (( a'

in"icate" in Table 1$)

A' e.laine" in Section 2, t&e tou*& itc& *!a"e' o+ coe!, C4$$?A an" C4$$>A 7+o!(e!l#C1$1 an" C1$2, contain a!ticle' o+ cu!ou' o.i"e %&ic& a!e no!(all# in a +o!( %&ic& &a' a(ini(al e++ect on elect!ical an" (ec&anical !oe!tie') P!olon*e" &eatin* o+ t&e coe! &o%e-e!,allo%' t&e o.i"e a!ticle' to "i++u'e to *!ain boun"a!ie' %&e!e t&e# can 'e!iou'l# a++ect t&e!oe!tie') T&i' "i++u'ion e++ect i' bot& ti(e an" te(e!atu!e "een"ent an" i' (ini(i'e" b#e!+o!(in* t&e %el"in* oe!ation a' 0uicl# a' o''ible an" b# !e't!ictin* t&e o-e!all &eatin* o+t&e co(onent a' +a! a' o''ible con'i'tent %it& a"e0uate +u'ion an" a 'ati'+acto!# %el" !o+ile)T&i' con'i"e!ation ob-iou'l# "oe' not al# to o.#*en8+!ee coe!' %&ic& "o not contain t&eo.i"e a!ticle')

able 1 elding data for


56/104

a5 "eco!!ended usage of B$ 21 filler alloys for , and ), /elding of %ig%conductiity copper.

Designation rade, ),

Argon or


57/104

2? u to $$ @?$8?6$ 2F8@2 >)>86)> 1?82$

T&e!(al e.an'ion '&oul" be allo%e" +o! "u!in* %el"in* a' t&i' lea"' to t&e clo'in* o+ !oot *a'a' t&e te(e!atu!e o+ t&e (etal !i'e') T&e !oot *a' in"icate" in Table 11 '&oul" t&e!e+o!e beallo%e")

O.#8acet#lene an" o.#8!oane %el"in* (et&o"' can be u'e" %it& o.#*en8+!ee coe! but t&e#a!e not !eco((en"e" +o! %el"in* tou*& itc& coe!' a' t&e !e"ucin* at(o'&e!e !o"uce" int&e +la(e can !eact %it& t&e cu!ou' o.i"e a!ticle' to !o"uce 'tea( in'i"e t&e (etal) T&i' *i-e'!i'e to o!o'it# an" i' no%n a'


58/104


59/104

(. )ec%anical $trengt% "e*uire!ents

All bu'ba! '#'te(' &a-e to be "e'i*ne" to %it&'tan" t&e (ec&anical +o!ce' to %&ic& t&e# (a# be'ub/ecte", %&et&e! t&e'e be "ue to t&ei! o%n %ei*&t, %in" an" ice loa"', o! '&o!t8ci!cuit +o!ce')T&i' +o!ce beco(e' (o!e one!ou' %it& inc!ea'in* -olta*e an" "ec!ea'in* cu!!ent "ue to!e'ecti-el# lon*e! in'ulato!' an" '(alle! con"ucto!')

T&e con"ucto! it'el+ '&oul" &a-e 'u++icient (ate!ial 't!en*t& un"e! all oe!ational con"ition') It(u't be able to 'uo!t it'el+ %it&out un"ue "e+lection un"e! no!(al %o!in* con"ition', an" not'u++e! e!(anent "a(a*e un"e! abno!(al con"ition') T&e +ollo%in* 'ection enable' t&e(ec&anical 't!en*t& !e0ui!e(ent o+ a con"ucto! to be calculate" u'in* t&e '&o!t8ci!cuit +o!ce'obtaine" +!o( t&e +o!(ulae *i-en !e-iou'l#)

Deflection

9atural 0re*uency

ind and ,ce oadings

)a;i!u! Per!issible $tress

%er!al E;pansion

Deflection

T&e (a.i(u( "e+lection o+ a bea( ca!!#in* a uni+o!(l# "i't!ibute" loa" an" +!eel# 'uo!te" ateac& en" i' *i-en b# t&e +o!(ula

%&e!eK (a.i(u( "e+lection, ((%K %ei*&t e! unit len*t& o+ loa"e" bea(, N((

L K bea( len*t& bet%een 'uo!t', ((

E K (o"ulu' o+ ela'ticit# 712? . 1$@N((2

I K (o(ent o+ ine!tia o+ bea( 'ection, ((

I+ one en" o+ a bea( i' !i*i"l# +i.e" in a &o!iontal o'ition t&e "e+lection i' $)?1> ti(e' t&at *i-enb# t&e abo-e +o!(ula an" it +ollo%' t&at i+ a +!eel# 'uo!te" bea( i' al'o 'uo!te" at it' (i"8oint t&en it' (a.i(u( "e+lection i' !e"uce" to $)$2> o+ it' +o!(e! -alue) I+ bot& en"' o+ a bea(a!e !i*i"l# +i.e" in a &o!iontal o'ition t&e "e+lection i' $)2 ti(e' t&at *i-en b# t&e abo-e +o!(ula)

T&u' %it& a continuou' bea( +!eel# 'uo!te" at +ou! o! (o!e oint' t&e (a.i(u( "e+lection int&e cent!e 'an' (a# be a''u(e" to be $)2 ti(e' t&at *i-en b# t&e +o!(ula, %&ile t&e "e+lectionin t&e en" 'an' i' $)?1> ti(e') T&e "e+lection in t&e en" 'an', t&e!e+o!e, (a# be a''u(e" tobe t%ice t&at in t&e cent!e 'an', a''u(in* e0ual 'an "i'tance')
http://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Deflectionhttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Natural%20Frequencyhttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Wind%20and%20Ice%20Loadingshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Maximum%20Permissible%20Stresshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Maximum%20Permissible%20Stresshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Deflectionhttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Natural%20Frequencyhttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Wind%20and%20Ice%20Loadingshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Maximum%20Permissible%20Stresshttp://www.cda.org.uk/megab2/elecapps/pub22/sec8.htm#Maximum%20Permissible%20Stress


60/104

)o!ents of inertia

In t&e abo-e +o!(ula t&e (o(ent o+ ine!tia I +o! t&e 'ection o+ t&e bea( &a' to be calculate"about t&e neut!al a.i' %&ic& !un' a!allel to t&e bea( %&e!e t&e bea( &a' e!o ten'ile +o!ce') In(o't ca'e' t&i' i' t&e 'a(e a.i' o+ t&e cent!e o+ c!o''8'ection)

:o! a !ectan*ula! 'ection o+ "et& D an" b!ea"t&

:o! a ci!cula! 'ection o+ "ia(ete! D

:o! a tubula! 'ection o+ inte!nal "ia(ete! " an" e.te!nal "ia(ete! D

It '&oul" be note" t&at t&e -alue o+ I +o! a *i-en c!o''8'ection i' "een"ent on t&e "i!ection in%&ic& eac& in"i-i"ual +o!ce i' alie") Mo(ent' o+ ine!tia +o! a !an*e o+ coe! !o"', ba!','ection' an" tube' a!e *i-en in Table' 12 16 7Aen"i. 2)

9atural 0re*uency

T&e natu!al +!e0uenc# o+ a bea( 'i(l# 'uo!te" at it' en" i'

an" +o! a bea( %it& bot& en"' +i.e" &o!iontall# it i'

%&e!e+nK natu!al +!e0uenc#, ;K "e+lection, ((

A' t&e "e+lection %it& +i.e" en"' i' $)2 ti(e' t&e -alue %it& +!eel# 'uo!te" en"' it +ollo%' t&att&e natu!al +!e0uenc# i' inc!ea'e" b# 2)2> ti(e' b# en"8+i.in*= +i.in* one en" onl# inc!ea'e' t&enatu!al +!e0uenc# b# about >$G) 4&e!e e0ui(ent i' to be (ounte" out'i"e, natu!al +!e0uencie'o+ le'' t&an 2)> ; '&oul" be a-oi"e" to !e-ent -ib!ation "ue to %in" e""ie')

ind and ,ce oadings


61/104

In con'i"e!in* t&e loa"in* o+ a con"ucto! +o! out"oo! 'e!-ice not onl# (u't t&e %ei*&t o+ t&econ"ucto! it'el+ be taen into account but al'o t&e %ei*&t o+ a coatin* o+ ice %&ic& it (a# ca!!#,to*et&e! %it& t&e %in" !e''u!e on t&e ice loa"e" con"ucto!)

T&e (a.i(u( t&icne'' o+ t&e ice an" t&e (a.i(u( %in" 'ee" a!e no!(all# 'eci+ie" b# t&eu!c&a'e! o+ t&e bu'ba!' but %&e!e t&e'e a!e not 'eci+ie" t&e# a!e u'uall# a-ailable +!o(

national 'tan"a!"' bo"ie' %it&in t&e count!# %&e!e t&e e0ui(ent i' to be in'talle")

T&e %in" an" ice loa"in* can be calculate" u'in* t&e +ollo%in* +o!(ulae

4in" loa"in*

4% K 7D2t . 1$>

Ice loa"in*

%&e!e%%K %in" loa"in*, N(%iK ice loa"in*, N(

K %in" !e''u!e, N((2

D K "ia(ete!, ((

t K ice t&icne'', ((

It i' a''u(e" t&at t&e %in" loa" i' at !i*&t an*le' to t&e -e!tical loa" o+ t&e con"ucto! %ei*&t, an"t&at it' ice loa" an" &ence t&e !e'ultant loa" on t&e con"ucto! &a' to be a""e" -e!ticall#) T&e!e'ultant loa" i' *i-en b#

%&e!eR K !e'ultant loa", N(% K con"ucto! %ei*&t e! unit len*t&, N(

an" %&e!e R act' at an an*le H to t&e -e!tical *i-en b# t&e +o!(ula

T&e -e!tical 'a* o! "e+lection in t&e con"ucto! 'an i' *i-en b#

%&e!e ii' t&e 'a* in (( in a lane incline" at an an*le to t&e -e!tical)


62/104


63/104

:o! a 'in*le bea( o+ len*t& L 7(( uni+o!(l# loa"e" an" +!eel# 'uo!te" at bot& en"' o! +!eel#'uo!te" at one en" an" +i.e" at t&e ot&e!,

%&e!e4 K loa", N((L K 'an, ((

:o! a ci!cula! 'ection o+ e.te!nal "ia(ete! D o! +o! a !ectan*ula! 'ection o+ "et& D,

%&e!eI K (o(ent o+ ine!tia, ((D K "ia(ete!, ((

T&en t&e (a.i(u( 't!e''

T&e (a.i(u( e!(i''ible 't!e'' i' "een"ent on t&e con"ucto! (ate!ial, te(e!, etc), but (u'tnot e.cee" t&e (ate!ial !oo+ 't!e'' o! e!(anent "e+o!(ation %ill occu!) :o! a con"ucto!(anu+actu!e" +!o( &a!" "!a%n coe! t&e -alue i' a!o.i(atel# 2?> N((2)

:o! a bea( %&ic& i' &o!iontall# +i.e" at bot& en"' t&e ben"in* (o(ent at t&e cent!e i' !e"uce"to one t&i!" an" t&at at it' en"' to t%o8t&i!"' o+ t&o'e +o! a 'i(le 'uo!te" bea()

%er!al E;pansion

I+ t&e c&an*e' in len*t& t&at occu! in a con"ucto! a' it e.an"' an" cont!act' %it& te(e!atu!e-a!iation' a!e not allo%e" +o!, un"ue +o!ce' %ill be 'et u in t&e con"ucto! 'uo!t '#'te( o! int&e e0ui(ent to %&ic& t&e bu'ba! i' connecte")

T&e coe++icient o+ linea! e.an'ion +o! coe! (a# be taen a' 1 . 1$6HC 7+o! te(e!atu!e'+!o( a(bient u to 2$$HC co(a!e" %it& 2@ . 1$6HC +o! alu(iniu() T&e lo%e! -alue +o! coe!i' o+ *!eat i(o!tance %&en allo%in* +o! t&e!(al e.an'ion un"e! bot& no!(al an" t!an'ito!#con"ition', a' u to 2>G le'' e.an'ion nee" be acco((o"ate" +o! a a!ticula! len*t& o+ bu'ba!)I+ a len*t& o+ coe! ba! %e!e to be et +!o( e.an"in* o! cont!actin*, a +o!ce o+ nea!l# 2 N e!((2o+ c!o''8'ectional a!ea %oul" be "e-eloe" +o! a te(e!atu!e c&an*e o+ 1HC)

In (o't ca'e' t&e 'uo!t' e.an" +a! le'' "ue to (uc& '(alle! te(e!atu!e c&an*e' an" lo%e!t&e!(al e.an'ion coe++icient') It i' t&e!e+o!e no!(al !actice to allo% +o! t&e +ull e.an'ion u'in*+le.ible con"ucto! connection' at 'uitable oint')

ypes of e;pansion Goints


64/104

In t&e ca'e o+ '&o!t ba!' it i' u'uall# not nece''a!# to (ae an# 'ecial !o-i'ion toacco((o"ate e.an'ion) T&e!e %ill no!(all# be one o! t%o !ea'onabl# +le.ible ben"' caable o+!elie-in* an# un"ue 't!e''e' %&ic& (a# be 'et u)

0igure 1& ypes of e;pansion Goints in copper conductors

To !elie-e inte!(e"iate 'uo!t' o+ 't!e'', cla(' %&ic& allo% t&e con"ucto! to (o-e +!eel# in t&elon*itu"inal "i!ection '&oul" be !o-i"e") T&e'e cla(' (u't be "e'i*ne" an" a!!an*e" %it& ca!eto a-oi" t&e "an*e! o+ 't!e''e' buil"in* u at an# oint at %&ic& t&e ba! (a# beco(e %e"*e" o!!e-ente" +!o( (o-in* +!eel#)

In t&e ca'e o+ lon* 't!ai*&t !un' it i' a"-i'able t&at e.an'ion /oint' '&oul" be int!o"uce") T&e/oint' (a# u'e la(inate" t&in coe! 't!i' o! lea-e' an" &a-e t&e 'a(e total cu!!ent !atin* a' t&ebu'ba! it'el+)

A' an alte!nati-e to la(inate" +le.ible /oint', coe! b!ai" (a# be u'e") T&i' t#e o+ /oint i'u'uall# (o!e e.en'i-e to (anu+actu!e but &a' t&e a"-anta*e t&at it can acco((o"atee.an'ion in (o!e t&an one "i!ection 7in (o't ca'e' t&!ee "i!ection' an" al'o ten"' to eli(inate

-ib!ation +o!ce' bein* a''e" +!o( one iece o+ e0ui(ent to anot&e!) It i' i(o!tant t&at t&e+e!!ule into %&ic& t&e coe! b!ai" i' cla(e" i' o+ 'u++icient t&icne'' to en'u!e con'i'tent &i*&con"ucti-it# a+te! (anu+actu!e an" "u!in* it' 'e!-ice li+e) 4&e!e &i*& !e'i'tance' "e-elo in t&e/oint a+te! (anu+actu!e, o-e!&eatin* an" ulti(atel# b!ai" +ailu!e "ue to o.i"ation o+ t&e b!ai"(ate!ial (a# !e'ult


65/104

. Busbar ,!pedance

FoltDrop

,nductance 0or!ulae

Capacitance 0or!ulae

eo!etric )ean Distance 0or!ulae

T&e bu'ba! !eactance i' not no!(all# 'u++icientl# la!*e to a++ect t&e total !eactance o+ a o%e!'#'te( an" &ence i' not inclu"e" in t&e calculation' %&en e'tabli'&in* t&e '&o!t8ci!cuit cu!!ent'an" !eacti-e -olt "!o' %it&in a o%e! '#'te() T&e e.cetion to t&i' i' %&en con'i"e!in* ce!tain&ea-# cu!!ent in"u't!ial alication' 'uc& a' +u!nace', %el"in* 'et', o! !oll &eatin* e0ui(ent +o!'teel (ill') In t&e'e ca'e' t&e !eactance (a# be !e0ui!e" to be no%n +o! cont!ol u!o'e', o! toobtain bu'ba! a!!an*e(ent' to *i-e (ini(u( o! balance" !eactance) T&i' (a# be i(o!tantbecau'e o+ it' e++ect on bot& -olt "!o an" o%e! +acto!, an" &ence on t&e *ene!atin* lant VA!e0ui!e(ent e! 4 o+ loa", o! on t&e ta!i++' a#able %&e!e t&e o%e! i' u!c&a'e" +!o( out'i"e)

T&e bu'ba! i(e"ance i' (a"e u o+ t&!ee co(onent' !e'i'tance, in"uctance an" c

103574321 copper for busbars

Documents