Iec Ts 60871-3-2015.Pdf

IEC TS 60871 3 Edition 2 0 201 5 06 TECHNICAL SPECIFICATION Shunt capacitors for AC power systems having a rated voltage above 1 000 V – Part 3 Protection of shunt capacitors and shunt capacitor banks[.]

I EC TS 60871 -3 ® Ed i ti on 201 5-06 TECH N I CAL SPECIFI CATI ON Sh u n t capaci tors for AC power systems h avi n g a rated vol tage above 000 V – I EC TS 60871 -3: 201 5-06(en ) Part 3: Protecti on of sh u n t capaci tors an d sh u n t capaci tor ban ks TH I S P U B L I C ATI O N I S C O P YRI G H T P RO TE C T E D C o p yri g h t © I E C , G e n e va , S w i tze rl a n d Al l or ri g h t s by re s e rv e d an y e i th e r m ean s, I EC c o p y ri g h t yo u r I EC 3, or or l o ca l IEC C e n t l ru e de CH -1 1 I E C's h a ve U n l ess o t h e rwi s e e l e c t ro n i c or m em ber an N a ti o n a l e n q u i ry m em ber s p e c i fi e d , m e ch a n i ca l , abou t N a ti o n a l no p a rt i n cl u d i n g C o m m i tte e o b ta i n i n g C o m m i tte e th e p u b l i ca ti o n c o u n t ry a d d i ti o n a l fo r O ffi c e in o f th i s p h o to co p yi n g fu rt h e r ri g h t s an d o f th e to th i s re p ro d u c e d re q u e s t e r If wi t h o u t yo u h a ve pl ease or u ti l i z e d p e rm i s s i o n an y co n ta c t in in an y q u e s ti o n s th e fo rm wri t i n g fro m abou t a d d re s s I EC bel ow or i n fo rm a t i o n Te l : +41 22 91 02 1 F a x: +41 22 91 03 00 G e n e va i n fo @ i e c c h 20 be p u b l i ca ti o n , V a re m b é S wi t z e rl a n d may m i c ro fi l m , ww w i e c c h Ab ou t th e I E C Th e I n t e rn a t i o n a l I n t e rn a t i o n a l E l e c t ro t e c h n i c a l S t a n d a rd s fo r al l Com m i ssi on e l e c t ri c a l , (I E C) e l e c t ro n i c and is th e re l a t e d l ead i n g g l obal o rg a n i z a t i o n th a t p re p a re s an d pu bl i sh es te ch n o l o g i e s Ab o u t I E C p u b l i c a ti o n s Th e te c h n i ca l l a te s t e d i ti o n , co n te n t a of IEC c o rri g e n d a p u b l i ca ti o n s or an is ke p t amend ment u n d er might co n s ta n t h a ve been I E C C atal og u e - webs tore i ec ch /catal og u e Th e s ta n d - a l o n e b i b l i o g p h i ca l Te ch n i ca l a p p l i ca ti o n i n fo rm a ti o n on S p e ci fi ca ti o n s , d o cu m e n ts Ava i l a b l e fo r fo r I EC PC, M ac th e I n te rn a ti o n a l An d ro i d e n ti re S ta n d a rd s , Re p o rts OS , an d o th e r Ta b l e ts an d i Pad a d va n ce d va ri e ty of s e a rch en abl es cri te ri a co m m i tte e , … ) an d th e Th e wo rl d ' s e l e ctri ca l wi th d wn It to ( re fe re n ce al so g i ve s fi n d I EC i n fo rm a ti o n on Pl ease m a ke s u re th a t yo u h a ve th e d e fi n i ti o n s in a d d i ti o n a l on l i n e co n ta i n i n g En g l i sh an d l an g u ag es d i cti o n a ry m o re F re n ch , Al s o th a n wi th e l e ctro n i c 000 as th e an d te rm s e q u i va l e n t kn o wn Vo ca b u l a ry ( I E V) of 30 te rm s an d in I n te rn a ti o n a l on l i n e I E C G l os s ary - s td i ec ch /g l os s ary p u b l i ca ti o n s n u m b e r, I E C l ead i n g te rm s E l e ctro te ch n i ca l I E C pu bl i cati on s s earch - www i ec ch /s earch pu b Th e by E l ectroped i a - www el ectroped i a org co n s u l ti n g Te ch n i ca l re v i e w pu bl i sh ed te xt, by a te ch n i ca l p ro j e cts , re p l a ce d M o re th a n E n g l i sh cl a u s e h a ve p u b l i ca ti o n s 77, 60 an d of I EC been 86 an d 000 F re n ch e l e ctro te ch n i ca l e xtra cte d p u b l i ca ti o n s co l l e cte d fro m fro m i ssu ed e a rl i e r te rm i n o l o g y th e Te rm s s i n ce an d 2002 p u b l i ca ti o n s e n tri e s S om e of in D e fi n i ti o n s I EC e n tri e s TC 37, C I S P R I E C J u s t P u bl i s h ed - webs tore i ec ch /j u s u bl i s h ed S ta y up d e ta i l s al so to al l o n ce d a te n ew a on al l n ew p u b l i ca ti o n s m o n th by em l I EC p u b l i ca ti o n s re l e a s e d J u st Ava i l a b l e Pu bl i sh ed on l i n e an d I E C C u s to m er S ervi ce C en tre - web s tore i ec ch /cs c If yo u n eed wi s h fu rth e r C e n tre : to g i ve us a s s i s ta n ce , cs c@ i e c ch yo u r fe e d b a ck pl ease co n ta ct on th e th i s p u b l i ca ti o n or C u s to m e r S e rvi ce I E C TS 60 871 -3 ® Ed i ti on 201 5-06 TE C H N I C AL S PE C I FI C ATI ON S h u n t capaci tors for AC power s ystem s h avi n g a rated vol tag e above 000 V – Part 3: Protecti on of sh u n t capaci tors an d sh u n t capaci tor ban ks I N TERN ATI ON AL ELECTROTECH N I CAL COM M I SSI ON I CS 29 240 99; 31 060 70 I SBN 978-2 -832 2-2755-8 Warn i n g ! M ake s u re th at you obtai n ed th i s pu bl i cati on from an au th ori zed d i stri bu tor ® Reg i stered trad em ark of th e I n tern ati on al El ectrotech n i cal Com m i ssi on – – I E C TS -3 : © I E C C O N TE N TS F O R E WO RD S co p e N o rm a ti ve re fe re n ce s T e rm s a n d d e fi n i ti o n s I n te rn a l fu s e s G e n e l F u s e ch a cte ri s ti cs 4 2 Ra te d d i s ch a rg e ca p a b i l i ty D i s c o n n e cti n g ca p a b i l i ty 4 Vo l ta g e wi th s ta n d ca p a b i l i ty a fte r o p e ti o n I n fl u e n ce o f ca p a ci to r e l e m e n t co n fi g u ti o n o n ca p a ci to r l i fe C a p a ci to r wi th a l l e l e m e n ts co n n e cte d i n p a l l e l C a p a ci to r wi th e l e m e n ts co n n e cte d i n s e ri e s a n d p a l l e l E xte rn a l fu s e s G e n e l F u s e ch a cte ri s ti cs Ra te d cu rre n t 2 Ra te d vo l ta g e Ti m e - cu rre n t ch a cte ri s ti cs 5 D i s c h a rg e ca p a b i l i ty F u s e typ e s G e n e l E xp u l s i o n fu s e s 3 C u rre n t- l i m i ti n g fu s e s 1 5 C o m b i n a ti o n cu rre n t- l i m i ti n g /e xp u l s i o n fu s e s 1 I n fl u e n ce o f ca p a ci to r b a n k co n fi g u ti o n o n fu s e s e l e cti o n 1 S i n g l e s e ri e s s e cti o n g ro u n d e d s ta r a n d d e l ta b a n ks 1 S i n g l e s e ri e s s e cti o n u n g ro u n d e d s ta r b a n ks 1 M u l ti p l e s e ri e s s e cti o n b a n ks 1 5 Ra te d cu rre n t C o o rd i n a ti o n wi th ca s e ru p tu re cu rve s 1 U n b a l a n ce d e te cti o n O p e ti o n T yp e s o f u n b a l a n ce p ro te cti o n N e u tra l cu rre n t ( F i g u re ) 2 N e u tra l vo l ta g e ( F i g u re ) C u rre n t u n b a l a n ce b e twe e n n e u tra l s ( F i g u re ) P h a s e vo l ta g e u n b a l a n ce ( F i g u re ) Vo l ta g e d i ffe re n ce ( F i g u re ) 6 C u rre n t u n b a l a n ce i n b ri d g e co n n e cti o n ( F i g u re ) C u rre n t a n d vo l ta g e tra n s fo rm e rs C u rre n t tra n s fo rm e rs Vo l ta g e tra n s fo rm e rs Re l a ys a n d p ro te cti o n s e tti n g s S e n s i ti vi ty 6 I n i ti a l u n b a l a n ce I E C TS -3 : © I E C O ve rl o a d cu rre n t O p e ti o n P ro te cti ve a rra n g e m e n t C u rre n t tra n s fo rm e rs Re l a ys P ro te cti ve s e tti n g s O ve r a n d u n d e rvo l ta g e O p e ti o n O ve rvo l ta g e p ro te cti o n U n d e rvo l ta g e p ro te cti o n Re cl o s i n g O th e r p ro te cti o n S u rg e a rre s te rs G e n e l O p e ti o n L i g h tn i n g tra n s i e n ts S wi tch i n g tra n s i e n ts Te m p o ry o ve rvo l ta g e s Ra te d vo l ta g e E n e rg y a b s o rp ti o n D a m p i n g d e vi ce s C a p a ci to r s wi tch i n g 2 I n ru s h cu rre n ts Vo l ta g e tra n s i e n ts 9 10 – – Ra ti n g s S yn ch ro n i z e d s wi tch i n g 9 O p e ti o n 9 B re a ke r co n ta cts d e l a y S a fe ty 1 D i s ch a rg i n g d e vi ce s 1 G e n e l 1 I n te rn a l re s i s to rs 1 E xte rn a l d i s ch a rg e d e vi ce s 1 D i s ch a rg i n g a fte r d i s co n n e cti o n 2 D e a d m e ta l l i c p a rts B i b l i o g p h y F i g u re – F u s e typ e s F i g u re – Typ i ca l ca s e ru p tu re cu rve s fo r a p p ro xi m a te l y F i g u re – S ta r co n n e cti o n wi th th e n e u tra l 0 0 cm ³ ca s e vo l u m e g ro u n d e d th ro u g h a cu rre n t tra n s fo rm e r F i g u re – S ta r co n n e cti o n wi th vo l ta g e tra n s fo rm e r b e twe e n n e u tra l a n d g ro u n d F i g u re – S ta r co n n e cti o n wi th u n g ro u n d e d n e u tra l a n d vo l ta g e tra n s fo rm e rs co n n e cte d i n a n o p e n d e l ta 2 F i g u re – D o u b l e - s ta r co n n e cti o n wi th u n g ro u n d e d n e u tra l 2 F i g u re – S ta r co n n e cti o n wi th g ro u n d e d n e u tra l a n d vo l ta g e tra n s fo rm e rs co n n e cte d i n d i ffe re n ti a l m e a s u re m e n t 2 F i g u re – B ri d g e co n n e cti o n 2 – – I E C TS -3 : © I E C F i g u re – L i n e o ve rcu rre n t re l a ys fo r ca p a ci to r b a n k, g ro u n d e d 2 F i g u re – L i n e o ve rcu rre n t re l a ys fo r ca p a ci to r b a n k, u n g ro u n d e d Ta b l e – M e l ti n g cu rre n ts fo r typ e - K ( fa s t) fu s e l i n ks , i n a m p e re s Ta b l e – M e l ti n g cu rre n ts fo r typ e - T ( s l o w) fu s e l i n ks , i n a m p e re s I E C TS -3 : © I E C – – I N TE RN ATI O N AL E L E C TRO TE C H N I C AL C O M M I S S I O N SH U N T CAPACI TORS FOR AC POWER SYSTEM S H AVI N G A RATED VOLTAGE ABOVE 000 V – Part 3: Protecti on of shu n t capaci tors and shu n t capaci tor banks F O RE WO RD 1) T h e I n te rn a ti o n a l E l e c t ro t e c h n i c a l C o m m i s s i o n ( I E C ) i s a wo rl d wi d e o rg a n i z a ti o n fo r s ta n d a rd i z a ti o n c o m p ri s i n g al l n a ti o n a l e l e c tro te c h n i c a l c o m m i tte e s (I EC N a ti o n a l C o m m i t te e s ) Th e o b j e ct of IEC is to p ro m o te i n t e rn a ti o n a l c o - o p e ti o n o n a l l q u e s ti o n s c o n c e rn i n g s ta n d a rd i z a t i o n i n t h e e l e c tri c a l a n d e l e c tro n i c fi e l d s T o th i s end and Te ch n i ca l in a d d i ti o n R e p o rt s , t o o th e r a c ti v i ti e s , P u b l i cl y Av a i l a b l e I E C p u b l i s h e s I n te rn a ti o n a l S p e c i fi c a ti o n s ( P AS ) and S t a n d a rd s , Guides Te ch n i ca l ( h e re a fte r S p e c i fi c a t i o n s , re fe rre d to as “I E C P u b l i c a ti o n ( s ) ” ) T h e i r p re p a ti o n i s e n tru s te d to te c h n i c a l c o m m i tte e s ; a n y I E C N a ti o n a l C o m m i t te e i n te re s t e d in th e s u b j e ct d eal t wi th may p a rti c i p a t e in th i s p re p a to ry wo rk I n te rn a t i o n a l , g o v e rn m e n t a l and n on - g o v e rn m e n t a l o rg a n i z a ti o n s l i a i s i n g wi th th e I E C a l s o p a rti c i p a t e i n t h i s p re p a ti o n I E C c o l l a b o te s c l o s e l y wi t h th e I n t e rn a t i o n a l O rg a n i z a t i o n fo r S ta n d a rd i z a ti o n (I S O) in a c c o rd a n c e wi t h c o n d i ti o n s d e te rm i n e d by a g re e m e n t b e twe e n t h e two o rg a n i z a ti o n s 2) Th e fo rm a l d e ci s i o n s or a g re e m e n t s of IEC on te c h n i c a l m a t te rs e xp re s s , as n e a rl y as possi bl e, an i n te rn a ti o n a l c o n s e n s u s o f o p i n i o n o n th e re l e v a n t s u b j e c ts s i n c e e a c h t e c h n i c a l c o m m i tt e e h a s re p re s e n ta ti o n fro m a l l i n t e re s te d I E C N a t i o n a l C o m m i tte e s 3) I E C P u b l i c a t i o n s h a v e t h e fo rm o f re c o m m e n d a ti o n s fo r i n t e rn a ti o n a l u se an d a re a c c e p t e d b y I E C N a ti o n a l C o m m i tte e s i n th a t s e n s e W h i l e a l l re a s o n a b l e e ffo rt s a re m a d e to e n s u re t h a t th e te c h n i c a l c o n te n t o f I E C P u b l i ca ti o n s is a c c u te , IEC ca n n o t be held re s p o n s i b l e fo r th e wa y in wh i c h th e y a re u sed or fo r an y m i s i n te rp re t a ti o n b y a n y e n d u s e r 4) In o rd e r to p ro m o te tra n s p a re n tl y to i n t e rn a ti o n a l th e m a xi m u m u n i fo rm i t y, e xte n t IEC possi bl e in N a ti o n a l th e i r C o m m i t te e s n a ti o n a l and u n d e rta k e re g i o n a l to appl y IEC p u b l i ca ti o n s P u b l i c a ti o n s An y d i v e rg e n c e b e twe e n a n y I E C P u b l i c a t i o n a n d t h e c o rre s p o n d i n g n a t i o n a l o r re g i o n a l p u b l i c a ti o n s h a l l b e c l e a rl y i n d i c a te d i n th e l a tt e r 5) I E C i t s e l f d o e s n o t p ro v i d e a n y a tt e s ta t i o n o f c o n fo rm i ty a s s e s s m e n t s e rv i c e s a n d , i n s o m e a re a s , I n d e p e n d e n t c e rt i fi c a ti o n b o d i e s p ro v i d e c o n fo rm i t y a c c e s s to I E C m a rk s o f c o n fo rm i ty I E C i s n o t re s p o n s i b l e fo r a n y s e rv i c e s c a rri e d o u t b y i n d e p e n d e n t c e rti fi c a ti o n b o d i e s 6) Al l u s e rs s h o u l d e n s u re th a t t h e y h a v e th e l a te s t e d i ti o n o f th i s p u b l i c a ti o n 7) N o l i a b i l i ty s h a l l a tt a c h to I E C o r i ts d i re c to rs , e m p l o ye e s , s e rv a n t s o r a g e n ts i n c l u d i n g i n d i v i d u a l e xp e rt s a n d m e m b e rs o f i t s te c h n i c a l c o m m i tt e e s a n d I E C N a t i o n a l C o m m i tte e s fo r a n y p e rs o n a l i n j u ry, p ro p e rt y d a m a g e o r o th e r d a m a g e e xp e n s e s o f a n y n a tu re a ri s i n g ou t of th e wh a ts o e v e r, wh e t h e r d i re c t p u b l i ca ti o n , use o f, or o r i n d i re c t , re l i a n c e u pon , o r fo r c o s t s th i s IEC ( i n cl u d i n g P u b l i ca ti o n or legal fe e s ) and any o th e r IEC P u b l i c a ti o n s 8) Att e n t i o n i s d wn to t h e N o rm a ti v e re fe re n c e s c i te d i n th i s p u b l i c a ti o n U s e o f th e re fe re n c e d p u b l i c a t i o n s i s i n d i s p e n s a b l e fo r t h e c o rre c t a p p l i c a t i o n o f th i s p u b l i c a ti o n 9) Att e n t i o n i s d wn to th e p o s s i b i l i ty th a t s o m e o f th e e l e m e n ts o f th i s I E C P u b l i c a ti o n m a y b e th e s u b j e c t o f p a t e n t ri g h ts I E C s h a l l n o t b e h e l d re s p o n s i b l e fo r i d e n ti fyi n g a n y o r a l l s u c h p a t e n t ri g h ts Th e main ta s k of I EC te ch n i ca l co m m i tte e s is to p re p a re I n te rn a ti o n a l S ta n d a rd s In e xce p ti o n a l ci rcu m s ta n ce s , a te ch n i ca l co m m i tte e m a y p ro p o s e th e p u b l i ca ti o n o f a te ch n i ca l s p e ci fi ca ti o n wh e n • th e re q u i re d s u p p o rt ca n n o t b e o b ta i n e d fo r th e p u b l i ca ti o n o f a n I n te rn a ti o n a l S ta n d a rd , d e s p i te re p e a te d e ffo rts , o r • th e s u b j e ct i s s ti l l u n d e r te ch n i ca l d e ve l o p m e n t o r wh e re , fo r a n y o th e r re a s o n , th e re i s th e fu tu re b u t n o i m m e d i a te p o s s i b i l i ty o f a n a g re e m e n t o n a n I n te rn a ti o n a l S ta n d a rd I n te rn a ti o n a l S ta n d a rd I E C - , wh i ch i s a te ch n i ca l s p e ci fi ca ti o n , h a s b e e n p re p a re d b y I E C te ch n i ca l co m m i tte e 3 : P o we r ca p a ci to rs a n d th e i r a p p l i ca ti o n s Th i s s e co n d e d i ti o n ca n ce l s an d co n s ti tu te s a te ch n i ca l re vi s i o n re p l a ce s th e fi rs t e d i ti o n pu bl ish ed in 996 Th i s e d i ti o n – – I E C TS -3 : © I E C Th i s e d i ti o n i n cl u d e s th e fo l l o wi n g s i g n i fi ca n t te ch n i ca l ch a n g e s wi th re s p e ct to th e p re vi o u s e d i ti o n : a) C l e a re r wri ti n g o f fo rm u l a s o n e n e rg y l i m i ta ti o n fo r e xp u l s i o n fu s e s ; b) U p d a te d n o rm a ti ve re fe re n ce s a n d b i b l i o g p h y; c) A n e w cl a u s e fo r s yn ch ro n i z e d s wi tch i n g h a s b e e n a d d e d Th e te xt o f th i s te ch n i ca l s p e ci fi ca ti o n i s b a s e d o n th e fo l l o wi n g d o cu m e n ts : E n q u i ry d ft R e p o rt o n vo ti n g 3 /5 /D T S 3 /5 /R V C F u l l i n fo rm a ti o n o n th e vo ti n g fo r th e a p p ro va l o f th i s te ch n i ca l s p e ci fi ca ti o n ca n b e fo u n d i n th e re p o rt o n vo ti n g i n d i ca te d i n th e a b o ve ta b l e Th i s p u b l i ca ti o n h a s b e e n d fte d i n a cco rd a n ce wi th th e I S O /I E C D i re cti ve s , P a rt A l i s t o f a l l p a rts i n th e I E C , p u b l i s h e d u n d e r th e g e n e l ti tl e p o we r s ys te m s h a vin g a te d vo lta g e a b o ve Sh un t ca p a cito rs fo r a c , ca n b e fo u n d o n th e I E C we b s i te 000 V Th e co m m i tte e h a s d e ci d e d th a t th e co n te n ts o f th i s p u b l i ca ti o n wi l l re m a i n u n ch a n g e d u n ti l th e s ta b i l i ty d a te i n d i ca te d on th e I EC we b s i te u n d e r " h ttp : //we b s to re i e c ch " re l a te d to th e s p e ci fi c p u b l i ca ti o n At th i s d a te , th e p u b l i ca ti o n wi l l b e • tra n s fo rm e d i n to a n I n te rn a ti o n a l s ta n d a rd , • re co n fi rm e d , • wi th d wn , • re p l a ce d b y a re vi s e d e d i ti o n , o r • amend ed A b i l i n g u a l ve rs i o n o f th i s p u b l i ca ti o n m a y b e i s s u e d a t a l a te r d a te in th e d a ta I E C TS -3 : © I E C – – S H U N T C AP AC I T O RS F O R AC P O WE R S YS T E M S H AVI N G A RAT E D VO L T AG E AB O VE P a rt : P ro t e c t i o n 000 V – o f s h u n t c a p a c i t o rs a n d s h u n t c a p a ci to r b a n ks Scope Th i s p a rt o f I E C , wh i ch i s a te ch n i ca l s p e ci fi ca ti o n , g i ve s g u i d a n ce o n th e p ro te cti o n o f s h u n t ca p a ci to rs a n d s h u n t ca p a ci to r b a n ks i t a p p l i e s to ca p a ci to rs a cco rd i n g to I E C 1 N o rm a t i v e re fe re n c e s Th e fo l l o wi n g d o cu m e n ts , i n wh o l e o r i n p a rt, a re n o rm a ti ve l y re fe re n ce d i n th i s d o cu m e n t a n d a re i n d i s p e n s a b l e fo r i ts a p p l i ca ti o n F o r d a te d re fe re n ce s , o n l y th e e d i ti o n ci te d a p p l i e s For u n d a te d re fe re n ce s , th e l a te s t e d i ti o n of th e re fe re n ce d d o cu m e n t ( i n cl u d i n g an y a m e n d m e n ts ) a p p l i e s I E C , High -volta ge fuses for th e externa l protection of sh unt ca pa citors I E C - , Sh unt ca pa citors for a c power systems h a ving a ted volta ge a b ove 000 V –Pa rt : Genera l I E C - , Sh unt ca pa citors for A C power systems h a ving a ted volta ge a b ove 000 V – Pa rt 4: Interna l fuses T e rm s a n d d e fi n i t i o n s F o r th e p u rp o s e s o f th i s d o cu m e n t, th e te rm s a n d d e fi n i ti o n s g i ve n i n I E C , I E C 1 a n d I E C - a p p l y 4 I n t e rn a l fu s e s G e n e l I n te rn a l fu s e s fo r sh u n t ca p a ci to rs a re s e l e cti ve cu rre n t- l i m i ti n g fu s e s a rra n g e d in si d e a ca p a ci to r As d e fi n e d i n I E C - , th e y a re d e s i g n e d to i s o l a te fa u l te d ca p a ci to r e l e m e n ts o r ca p a ci to r u n i t, to a l l o w o p e ti o n o f th e re m a i n i n g p a rts o f th a t ca p a ci to r u n i t a n d th e b a n k i n wh i ch th e ca p a ci to r u n i t i s co n n e cte d Th e o p e ti o n o f a n i n te rn a l fu s e i s i n i ti a te d b y th e b re a kd o wn o f a ca p a ci to r e l e m e n t T h e a ffe cte d element is i n s ta n ta n e o u s l y d i s co n n e cte d by th e o p e ti o n of th e element fu s e wi th o u t i n te rru p ti o n i n th e o p e ti o n o f th e ca p a ci to r Th e n u m b e r o f e xte rn a l l y p a l l e l co n n e cte d ca p a ci to rs a n d th e a va i l a b l e s h o rt- ci rcu i t cu rre n t o f th e s u p p l y s ys te m s h o u l d n o t a ffe ct th e cu rre n t- l i m i ti n g o f i n te rn a l fu s e s I t s h o u l d b e n o te d th a t i n te rn a l fu s e s d o n o t p ro vi d e p ro te cti o n a g a i n s t a s h o rt ci rcu i t b e twe e n i n te rn a l co n n e cti o n s o r a s h o rt ci rcu i t b e twe e n a cti ve p a rts a n d ca s i n g , b o th o f wh i ch m a y l e a d to ca s e ru p tu re – – I E C TS -3 : © I E C F u s e c h a c t e ri s t i c s Ra te d c u rre n t Th e re i s n o d e fi n i ti o n o r te s t m e th o d e xi s ti n g fo r e l e m e n t fu s e s El emen t fu s e s a re , in g e n e l , d esi g ned fo r m u ch h igh er cu rre n ts th a n th e m a xi m u m p e rm i s s i b l e e l e m e n t cu rre n t Th e y a re m e a n t to d i s co n n e ct o n l y fa u l ty e l e m e n ts Th e fa u l ty e l e m e n ts a n d th e i r fu s e s a re n o t i n te n d e d to b e re p l a ce d Ra te d I EC 60871 -4 d i s c h a rg e c a p a b i l i t y an d I EC 60871 -1 s p e ci fy th a t d i s ch a rg e s fro m a d c ch a rg e l e ve l o f , U N th e ca p a ci to r be s u b j e ct to fi ve u n d am ped F o r s p e ci a l a p p l i ca ti o n s , wh e re i n ru s h cu rre n ts a n d /o r p e a k vo l ta g e s a re l i m i te d , l o we r d i s ch a rg e re q u i re m e n ts a re a p p l i ca b l e D i s c o n n e c ti n g ca p ab i l i ty Re q u i re m e n ts a n d te s t p ro ce d u re s a re g i ve n i n I E C - Th e s e te s ts ve ri fy th a t th e fu s e h a s a cu rre n t- l i m i ti n g a cti o n Vo l t a g e w i t h s t a n d c a p a b i l i t y a ft e r o p e t i o n Re q u i re m e n ts a n d te s t p ro ce d u re s a re g i ve n i n I E C - I n fl u e n c e o f c a p a c i t o r e l e m e n t c o n fi g u t i o n C a p a ci tor wi th al l e l e m e n ts c o n n e cte d in on c a p a c i t o r l i fe p a l l e l Afte r th e b re a kd o wn o f a n e l e m e n t, th e re s p e cti ve fu s e wi l l m e l t i n l e s s th a n a m i l l i s e co n d o wi n g to th e d i s ch a rg e cu rre n t fro m th e p a l l e l co n n e cte d e l e m e n ts a n d ca p a ci to rs a n d th e p o we r fre q u e n cy cu rre n t fro m th e s u p p l y T h e ca p a ci to r m a y, h o we ve r, co n ti n u e o p e ti n g wi th a co rre s p o n d i n g l y re d u ce d o u u t I f th e ca p a ci to r i s o p e te d a t a fi xe d b u s vo l ta g e , n o va ri a ti o n i n o p e ti n g vo l ta g e o n th e re m a i n i n g h e a l th y e l e m e n ts wi l l o ccu r C a p a ci tor wi th Afte r th e b re a kd o wn e l e m e n ts c o n n e cte d of an e l e m e n t, al l in s e ri e s a n d p a l l e l e n e rg y o r p a rt o f i t i n to th e fa u l ty e l e m e n t co n n e cte d p a l l e l e l e m e n ts d i s ch a rg e th e i r s to re d T h e p o we r fre q u e n cy cu rre n t i s l i m i te d b y th e re m a i n i n g h e a l th y e l e m e n ts co n n e cte d i n s e ri e s Afte r th e d i s co n n e cti o n co rre s p o n d i n g l y re d u ce d of th e o u u t fa u l ty Th e s tre s s e d wi th a vo l ta g e a p p ro xi m a te l y is th e n umber of p a l l e l co n n e cte d e l e m e n t, th e re m a i n i n g m n/m n × [ e l e m e n ts ( ca p a ci to r h e a l th y co n ti n u e s e l e m e n ts of th e o p e ti n g g ro u p wi th a re – ) + ] ti m e s th e i n i ti a l vo l ta g e , wh e re per g ro u p an d m th e n umber of a th e n n s e ri e s - co n n e cte d s e cti o n s p e r u n i t I n ce rta i n ca s e s th e vo l ta g e m a y b e h i g h e r, fo r e xa m p l e d u e to n e u tra l s h i ft wi th a n u n g ro u n d e d s ta r co n fi g u ti o n 5 E x t e rn a l fu s e s G e n e l E xte rn a l fu s e s fo r s h u n t ca p a ci to rs a re d e fi n e d i n I E C a s i n te n d e d to cl e a r fa u l ts i n s i d e a ca p a ci to r u n i t a n d to p e rm i t co n ti n u e d o p e ti o n o f th e re m a i n i n g p a rts o f th e b a n k i n wh i ch th e u n i t i s co n n e cte d T h e y wi l l a l s o cl e a r a n e xte rn a l ca p a ci to r b u s h i n g fl a s h o ve r – 14 – IEC TS 60871 -3:201 © IEC 201 The current transformer should be capable of withstanding currents during abnormal conditions such as short circuits Such failures may lead to a high peak transient and high power frequency currents during the delay of the overcurrent protection Switching current transient should also be taken into account The current transformer may be protected at its primary by means of spark gaps or surge arresters The accuracy requirement is generally quite low Class P would normally be sufficient providing the measuring error of the current transformer at the protection setting current is less than % (see IEC 60044-1 ) Should the maximum unbalance be much lower than the rated current of the current transformer, a better accuracy class is required V o l t a g e t n s fo rm e rs The rated primary voltage of the voltage transformer should correspond to the calculated maximum unbalance For ungrounded banks the insulation class also applies to the voltage transformer For grounded banks, voltage transformers with reduced insulation may be used When the primary winding forms a discharge path for the capacitor, the capability to withstand the discharge energy and peak current at disconnection from the line has to be considered Standard voltage transformers of accuracy class 0,5 are normally used (see IEC 60044-2) For connection schemes according to Figures and 7, special attention should be paid to matching the voltage transformers in different phases R e l a ys a n d p ro t e c t i o n s e tti n g s To avoid false operations due to switching or other transients, the unbalance relay should have a certain time delay Typical delay-settings are about 0,1 s to s; for external fuses, the coordination with fuses is of special importance The relaying should also incorporate features for blocking of automatic reclosure if such a system is used Relays used for unbalance protection should normally have reduced sensitivity for frequencies other than the fundamental to prevent undesired operation and to simplify calculation of the relay setting When defining settings for the unbalance relay, one has to consider the overvoltage limit (1 %) for adjacent capacitors, i.e alarm for overvoltages less than %, trip when in excess of % For internally fused capacitors there may be different restrictions on voltage rise across parallel non-failed internal elements Depending on bank size, one or more fuses may be allowed to operate before an alarm is initiated The protective relaying should trip the bank once the overvoltage limit is exceeded S e n s i t i vi t y The sensitivity of the protection depends upon the size of the capacitor bank or that part of the bank which is incorporated in one particular protection zone For large banks a method that allows one separate relay (in rare cases even more) per phase is necessary When defining the number of relays based on sensitivity requirements, the influence of factors such as temperature differences within the bank should be considered Sensitivity analysis, i.e the relation between number of failed elements, fuses and current or voltage outputs, is usually made by the capacitor manufacturer Higher sensitivity is generally IEC TS 60871 -3:201 © IEC 201 – 15 – needed with internally fused than with externally fused capacitors Special computer programs are often available for sensitivity analysis 6 I n i ti a l u n bal an ce Due to normal capacitance variation between capacitors, an initial unbalance may exist in a bank This unbalance should be limited to a magnitude that allows for a clear definition of the criteria for relay operation and should normally not exceed % of the relay setting As an alternative to initial balancing of capacitors, the unbalance may be compensated by means of suitable relays 7 O v e rl o a d c u rre n t O p e t i o n Excessive capacitor currents may be obtained in connection with system voltage disturbances, harmonics and short-circuit failures To protect the capacitors, current transformers with associated relays are used to detect current overloads and provide tripping operation of the bank As protection for short-circuit currents due to line-to-line and line-to-ground faults in moderately sized banks, power fuses may also be used P ro t e c t i ve a rra n g e m e n t For effectively grounded banks, the protection is normally arranged with a current transformer and its relay in each phase (Figure 9) If the bank is ungrounded, protection in two of the three phases is sufficient (Figure 0) For smaller banks (typically less than Mvar) without switched parallel sections, where the inrush transients are of short duration, a common relay for overload protection and shortcircuit protection may be used The setting will be an immediate trip at a relatively low current magnitude The current transients obtained with larger single banks, or when parallel banks are switched, lead to separate overload and short-circuit protection being required The current settings are considerably higher for the short-circuit protection to avoid false operations at switching In the case of separate short-circuit protection, and if the bank is ungrounded, the current for line-to-line faults may not be sufficient to obtain instantaneous protection of the bank However, the unbalance protection will always detect this kind of failure within a reasonable time delay C u rre n t t n s fo rm e rs Current transformers for overload protection should have a rated primary of at least ,4 times rated current of the bank Standard accuracy classes P and P would normally be sufficient for this application (see IEC 60044-1 ) If a common current transformer is used for both metering and protection purposes, it will have two secondary windings, one for measuring devices and the other for relays 7.4 Re l a ys The accuracy of the relays used for overload protection should be valid within the frequency range 50 Hz to 000 Hz The resetting ratio should be at least 95 %; this ratio defines the – 16 – I E C TS -3 : © I E C l o a d l e ve l b e l o w th e p ro te cti o n s e tti n g a t wh i ch th e re l a y i s re s e t i f th e l o a d d e cre a s e s d u ri n g th e d e l a ye d fu n cti o n i n g ti m e For P ro t e c t i ve s e t t i n g s small p ro te cti o n , b a n ks ( typ i ca l l y l ess th a n 10 M va r) wi th co m m o n o ve rl o a d and s h o rt- ci rcu i t th e re l a y s e tti n g s a re n o rm a l l y i n th e n g e o f , a n d , ti m e s te d cu rre n t Th e o p e ti o n d e l a y i s s e t fo r a fe w cycl e s ( m a xi m u m o f cycl e s ) For b a n ks wi th s e p a te o ve rl o a d an d s h o rt- ci rcu i t p ro te cti o n , th e o ve rl o a d p ro te cti o n is n o rm a l l y s e t i n th e n g e o f , a n d , ti m e s te d cu rre n t T h e o p e ti o n d e l a y i s s e t l o n g e n o u g h to a vo i d fa l s e tri p s d u ri n g s wi tch i n g Th e s h o rt- ci rcu i t p ro te cti o n i s s e t a b o ve IN a n d a fe w cycl e s d e l a y T h e s e s e tti n g s h a ve to b e ch o s e n wi th s p e ci a l a tte n ti o n to th e i n ru s h cu rre n ts 8 For O ve r a n d u n d e rv o l t a g e O p e t i o n m o d e rn p o we r ca p a ci to rs , vo l ta g e wi th s ta n d is o fte n th e d e ci s i ve fa cto r th e r th a n th e rm a l l i m i ta ti o n I t m a y th e re fo re b e n e ce s s a ry to u s e o ve rvo l ta g e p ro te cti o n to co m p l e m e n t th e co n ve n ti o n a l o ve rl o a d p ro te cti o n b a s e d o n cu rre n t m e a s u re m e n t O ve rvo l ta g e p ro te cti o n m a y b e a rra n g e d b y m e a n s o f p e a k va l u e s e n s i ti ve vo l ta g e re l a ys wi th i n ve rs e vo l ta g e - ti m e ch a cte ri s ti cs C u rre n t re l a ys wi th i n te g ti n g fu n cti o n s to o b ta i n th e i n s ta n ta n e o u s p e a k vo l ta g e m a y a l s o b e u s e d Th e vo l ta g e p ro te cti o n re l a y is al so u sed to a cco m p l i s h u n d e rvo l ta g e p ro te cti o n an d i n te rl o cki n g fu n cti o n s a t re cl o s i n g Typ i ca l l y th e vo l ta g e s o u rce fo r th i s p ro te cti o n s ys te m i s d e ri ve d fro m vo l ta g e tra n s fo rm e rs co n n e cte d on th e bu s si d e o f th e ca p a ci to r s wi tch I t sh ou l d n ot be d e ri ve d fro m vo l ta g e tra n s fo rm e rs co n n e cte d l i n e - to - e a rth o n th e ca p a ci to r s i d e o f th e s wi tch O ve rvo l t a g e p ro t e c t i o n P ro te cti o n a g a i n s t o ve rvo l ta g e s h o u l d ta ke i n to a cco u n t l e ve l s a cco rd i n g to I E C - a n d th e p a rti cu l a r a p p l i ca ti o n I f th e h a rm o n i c co n te n t i s h i g h , a s p e ci a l re l a y th a t m e a s u re s th e p e a k vo l ta g e s h o u l d b e u s e d To a vo i d u n d e s i re d re l a y o p e ti o n s , th e re s e tti n g ti o s h o u l d b e a s h i g h a s p o s s i b l e U n d e rvo l t a g e p ro t e c t i o n I f th e vo l ta g e i s z e ro o r a b n o rm a l l y l o w ( e g , UN ) , th e ci rcu i t- b re a ke r o f th e ca p a ci to r b a n k s h o u l d b e o p e n e d a n d i n te rl o cke d u n ti l th e vo l ta g e re tu rn s to n o rm a l l e ve l T h i s i s b e ca u s e u p o n re - e n e rg i z a ti o n th e m a g n e ti z a ti o n i n ru s h cu rre n t o f p o we r tra n s fo rm e rs co n ta i n s a l o t o f h a rm o n i cs and th e ca p a ci to r may be in re s o n a n ce wi th th e n e two rk at on e of th e s e fre q u e n ci e s T h e ci rcu i t- b re a ke rs o f p o we r tra n s fo rm e rs a n d ca p a ci to r b a n ks m a y a l s o b e co o rd i n a te d to a vo i d th e s e o ve rvo l ta g e s a n d s u rg e cu rre n ts 8.4 Re c l o s i n g I f a ca p a ci to r b a n k i s n o t p ro vi d e d wi th d i s ch a rg e re a cto rs ( m o s t u s u a l ca s e ) , re co n n e cti o n o f th e b a n k a fte r d i s co n n e cti o n fro m th e n e two rk s h o u l d b e d e l a ye d fo r th e p e ri o d d e fi n e d b y th e I E C TS -3 : © I E C – 17 – m a n u fa ctu re r, u s u a l l y m i n to m i n B e fo re re co n n e cti o n , th e re s i d u a l vo l ta g e s h o u l d b e l e s s th a n , U N O t h e r p ro t e c t i o n S u rg e a rre s t e rs 1 G e n e l Th e g u i d e l i n e s b e l o w a re a p p l i ca b l e m a i n l y to s u rg e a rre s te rs o f m e ta l o xi d e va ri s to r ( M O V) typ e s ( s e e I E C 0 9 - ) 9.1 O p e t i o n Th e p u rp o s e o f th e s u rg e a rre s te rs i s to l i m i t p o s s i b l e o ve rvo l ta g e s to l e ve l s n o t e xce s s i ve to th e p ro te cte d s e ve l e q u i p m e n t o rd e rs of Th e m a g n i tu d e M OV wh e n a rre s te r th e h as vo l ta g e a n on -l i n ear re s i s ta n ce re a ch e s a ce rta i n s ys te m s co n n e cte d th a t l e ve l d e cre a s e s Th i s l i m i ts th e i n s ta n ta n e o u s vo l ta g e to a d e s i re d p ro te cti ve l e ve l 9.1 S u rg e Li g h tn i n g a rre s te rs n e u tra l - g ro u n d t n s i e n t s a re tra d i ti o n a l l y Th e i r p u rp o s e u sed is in main ly p o we r to p ro te ct agai n st p h a s e - g ro u n d l i g h tn i n g s u rg e s , a n d /o r an d th e e va l u a ti o n o f n e ce s s a ry a rre s te r p e rfo rm a n ce i s b a s e d o n l i g h tn i n g p e a k cu rre n t a n d s ys te m ch a cte ri s ti cs s u ch as line i m p e d a n ce , line i n s u l a ti o n l e ve l , e tc S u rg e a rre s te rs a re n ot m a i n l y i n te n d e d fo r ca p a ci to r p ro te cti o n a s a ca p a ci to r b a n k i ts e l f re d u ce s tra n s i e n t vo l ta g e s ca u s e d b y l i g h tn i n g s u rg e s If S wi tch i n g ci rcu i t- b re a ke rs ca p a ci to rs may t n s i e n t s re s tri ke or e xp e ri e n ce if m i s fi ri n g s e ve re fa i l u re s o ve rvo l ta g e s o ccu r In th i s in th yri s to r ca s e , co n tro l l e d a rre s te r s ys te m s , p ro te cti o n wi l l be b e n e fi ci a l I f th e ri s k o f re s tri ki n g a t s wi tch i n g i s to b e co n s i d e re d , a th o ro u g h i n ve s ti g a ti o n o f vo l ta g e co n d i ti o n s a n d a rre s te r ca p a b i l i ty s h o u l d b e ca rri e d o u t b e fo re s e l e cti n g th e co m p o n e n ts 9.1 T e m p o ry o ve rv o l t a g e s C a p a ci to r b a n ks e xp o s e d to te m p o ry o ve rvo l ta g e s o f p o we r fre q u e n cy (an d h a rm o n i cs ) m a y b e p ro te cte d b y co n n e cti o n o f a rre s te rs d i re ctl y i n p a l l e l to e a ch ca p a ci to r b n c h Te m p o ry o ve rvo l ta g e s may be ca u s e d by si n g l e-ph ase g ro u n d fa u l ts or s wi tch i n g in o s ci l l a ti o n s i n l o w o rd e r tu n e d fi l te rs T h e y a re ch a cte ri z e d b y fa i rl y l o n g d u ti o n ( n u m b e r of cycl e s ) G e n e l l y d e ta i l e d e va l u a ti o n of d yn a m i c vo l ta g e s an d e n e rg y l oad i n g o f th e a rre s te r co m p o n e n ts s h o u l d b e ca rri e d o u t i n th e s e ca s e s D a ta o n p e rm i s s i b l e te m p o ry o ve rvo l ta g e s ve rs u s ti m e fo r M O Vs a re g i ve n b y th e s u p p l i e rs 9.1 Ra te d vo l ta g e Th e te d vo l ta g e o f a n a rre s te r i s u s e d a s a re fe re n ce p a m e te r to co rre l a te o p e ti n g a n d p ro te cti ve ch a cte ri s ti cs I t i s d e fi n e d a s th e l e ve l wh e re a ce rta i n cu rre n t fl o ws th ro u g h th e a rre s te r; th i s co n d i ti o n i s u s u a l l y p e rm i tte d fo r d u ti o n s i n th e o rd e r o f m i n u te s o n l y Th e ch o i ce o f th e a rre s te r ti n g i s a co m p ro m i s e b e twe e n p ro te cti ve l e ve l a n d te m p o ry o ve rvo l ta g e ca p a b i l i ty By i n cre a s i n g th e te d vo l ta g e o f th e a rre s te r, wi th s ta n d o ve rvo l ta g e i s i n cre a s e d , b u t th e m a rg i n o f p ro te cti o n i s re d u ce d th e p ro b a b i l i ty to – 18 – IEC TS 60871 -3:201 © IEC 201 Normally the continuous operating voltage across the equipment should not exceed 80 % of the rated voltage for a MOV arrester Duration and frequency of the overvoltages may require the continuous operating voltage to be less than 80 % of the arrester rating 9.1 E n e rg y a b s o rp t i o n For proper selection of MOV arresters, the maximum energy developed during a discharge should be checked For lightning duties, the evaluation is directly based on estimates on lightning charges and arrester voltage characteristics For switching and temporary overvoltage conditions, a more detailed evaluation of arrester energy development should be carried out The energy absorption capability is usually specified by the supplier in terms of kilojoules per kilovolt of rating 9 2.1 Dampi n g d e vi c e s C a p a ci tor s wi tch i n g Damping devices, reactors and/or resistors, connected in series with a capacitor branch, are sometimes used for limiting the magnitude of switching transients The transient phenomena at energization of a capacitor bank are characterized by a very high inrush current through the capacitor and a transient overvoltage with a magnitude up to two times rated voltage 2 I n ru s h c u rre n t s The inrush currents may affect performance of the capacitor or the switching device Capacitors may withstand current surges up to 00 times rated current, but the circuitbreakers are often limited to lower values The reactance of current-limiting reactors is normally less than % of the bank impedance The maximum inrush peak current when switching a bank to the power supply may be calculated as shown in IEC 60871 -1 : Ỵ s ≈I N S Q where is the peak inrush bank current, in amperes; s N is the rated capacitor bank current (r.m.s.), in amperes; is the short-circuit power (MVA) at the point where the capacitor is to be connected; is the output of the bank, in megavars For calculating peak current when switching parallel banks the following formula may be used: Ỵ I S Q ì s= U X C XL where  C = U  X  Q1 + Q   × −  where is the peak inrush bank current, in amperes; s is the phase-to-earth voltage, in volts (r.m.s.); c is the series-connected capacitive reactance per phase, in ohms; L is the inductive reactance per phase between the banks, in ohms; Ỵ U X X I E C TS -3 : © I E C Q Q – 19 – i s th e o u u t o f th e b a n k to b e s wi tch e d i n , i n m e g a va rs ; i s th e s u m o f th e o u u t( s ) o f th e b a n k( s ) a l re a d y e n e rg i z e d , i n m e g a va rs 9.2.3 V o l t a g e t n s i e n t s Ad e q u a te l y s e l e cte d s e ri e s re a cto rs m a y re d u ce th e m a g n i tu d e o f tra n s i e n t o ve rvo l ta g e s to a cce p ta b l e l e ve l s O th e r m e a n s fo r d a m p i n g o f tra n s i e n ts a re a co m b i n a ti o n o f re s i s to rs a n d re a cto rs o r d a m p i n g re s i s to rs o n l y 9.2.4 Ra ti n g s Besi d es th e d e s i re d i n d u cta n ce va l u e , th e co n ti n u o u s cu rre n t l oad ( r m s ) as we l l as m a xi m u m tra n s i e n t p e a k cu rre n t s h o u l d b e s p e ci fi e d fo r th e d a m p i n g re a cto r F o r co n ti n u o u s ti n g th e m a xi m u m p e rm i s s i b l e cu rre n t fo r th e ca p a ci to r s h o u l d b e ta ke n i n to a cco u n t Acco rd i n g to I E C 60871 -1 th i s m a xi m u m is ,3 to ,5 ti m e s th e te d ca p a ci to r cu rre n t S yn c h ro n i z e d s w i tc h i n g O p e t i o n N o rm a l s wi tch i n g o f a ca p a ci to r b a n k m a y ca u s e s e ve re tra n s i e n ts E n e rg i z i n g a d i s ch a rg e d ca p a ci to r is si mil ar to a m o m e n ta ry s h o rt ci rcu i t an d it re s u l ts in vo l ta g e and cu rre n t tra n s i e n ts th a t m a y ca u s e p ro b l e m s C o n tro l l i n g th e ci rcu i t b re a ke r to e n e rg i z e a ca p a ci ti ve l o a d a t z e ro vo l ta g e a cro s s th e co n ta cts wi l l e l i m i n a te h a rm fu l tra n s i e n ts Re d u cti o n o f s wi tch i n g tra n s i e n ts wi l l re d u ce s tre s s e s i n th e s ys te m a n d i ts co m p o n e n ts I n a d d i ti o n , th e ci rcu i t b re a ke r i ts e l f wi l l e xp e ri e n ce l e s s e n e rg i z a ti o n cu rre n ts , wh i ch wi l l e xte n t i ts s e rvi ce l i fe F o r ca p a ci to r b a n ks th e n u m b e r o f l o a d s wi tch i n g o p e ti o n s ca n th e re fo re b e s i g n i fi ca n tl y i n cre a s e d b e fo re s ch e d u l e d o ve rh a u l i s re q u i re d B re a k e r c o n t a c t s d e l a y T h e m a g n i tu d e o f th e tra n s i e n ts d e p e n d s o n th e p o i n t- o n - wa ve wh e re cl o s i n g ( o r o p e n i n g ) o f th e ci rcu i t b re a ke r co n ta cts o ccu r Th e co m m a n d s to th e ci rcu i t b re a ke r a re d e l a ye d i n s u ch a wa y th a t m a ki n g o r co n ta ct s e p a ti o n wi l l o ccu r a t th e o p ti m u m ti m e i n s ta n t re l a te d to th e p h a s e a n g l e T h e ti m e d i ffe re n ce s b e twe e n p h a s e s d e p e n d o n th e a p p l i ca ti o n F o r ca p a ci to r b a n ks wi th g ro u n d e d n e u tra l , th e th re e pol es sh ou l d cl o s e in s u cce s s i o n wi th a ti m e s e p a ti o n o f /6 cycl e Wi th u n g ro u n d e d n e u tra l , two p o l e s s h o u l d cl o s e s i m u l ta n e o u s l y a t p h a s e – p h a s e vo l ta g e z e ro , a n d th e l a s t o n e /4 cycl e l a te r S a fe t y 0.1 D i s c h a rg i n g 0.1 E a ch d e vi c e s G e n e l ca p a ci to r ban k sh ou l d be p ro vi d e d wi th mean s fo r d i s ch a rg i n g th e ban k a fte r d i s co n n e cti o n fro m th e n e two rk Th e s p e ci fi e d d i s ch a rg i n g ti m e s may be met by a p p l yi n g e i th e r i n te rn a l ( i n co rp o te d ) d i s ch a rg e re s i s to rs p e r ca p a ci to r o r, e xte rn a l d i s ch a rg e d e vi ce s te d fo r th e e n ti re ca p a ci to r e q u i p m e n t B e fo re to u ch i n g a n y l i ve p a rts , a l l o w a t l e a s t m i n fo r th e b a n k to s e l f- d i s ch a rg e a n d th e n s h o rt- ci rcu i t e a ch ca p a ci to r te rm i n a l to g e th e r a n d to g ro u n d – 20 – 0.1 I n t e rn a l I n te rn a l re s i s to rs I E C TS -3 : © I E C re s i s t o rs a re g e n e l l y bu ilt i n to th e i n d i vi d u a l ca p a ci to rs Th e y a re d esi gn ed to i n s u re th e d i s ch a rg e o f e a ch ca p a ci to r, a n d th e re fo re th e wh o l e b a n k I n a b a n k wi th s e ve l s e cti o n s o f ca p a ci to rs i n s e ri e s , th e re s i d u a l vo l ta g e o n th e b a n k te rm i n a l i s e q u a l to th e s u m o f th e re s i d u a l vo l ta g e i n e a ch s e cti o n 0.1 E x t e rn a l d i s c h a rg e d e v i c e s E xte rn a l d i s ch a rg e d e vi ce s a re u s e d i n s p e ci a l ca s e s E a ch d e vi ce s h o u l d b e a d a p te d to th e co n d i ti o n s e xi s ti n g a t th e s i te o f e re cti o n o f th e e q u i p m e n t a n d h a ve s u i ta b l e s tri ke d i s ta n ce , cre e p a g e p a th an d i n s u l a ti o n l e ve l I f th e ca p a ci to rs h a ve n o i n te rn a l d i s ch a rg e re s i s to rs , th e re s h o u l d b e n o i s o l a ti n g d e vi ce b e twe e n th e ca p a ci to r b a n k a n d th e d i s ch a rg e d e vi ce D i s ch a rg e re a cto rs may be u sed , co n n e cte d U s u a l l y two re a cto rs a re co n n e cte d d i re ctl y i n p a l l e l wi th th e ca p a ci to r b a n ks l i n e - to - l i n e a cro s s two p h a s e s b e ca u s e o f e co n o m i ca l re a s o n s U n d e r o p e ti o n co n d i ti o n s , o n l y th e m a g n e ti z i n g cu rre n t fl o ws i n th e re a cto r Wh e n s wi tch i n g o ff th e ca p a ci to r e q u i p m e n t, a l l th e s to re d e n e rg y ci rcu l a te s th ro u g h th e co i l i n a fe w s e co n d s M o s t o f th e e n e rg y i s d i s s i p a te d i n th e re a cto r Th e n u m b e r o f d i s ch a rg e s p e r u n i t o f ti m e s h o u l d b e re s tri cte d s o th a t n o o ve rh e a ti n g o f th e d i s ch a rg e re a cto r o ccu rs Wi n d i n g s o f tra n s fo rm e rs o r m o to rs a re co n s i d e re d a s s u i ta b l e d i s ch a rg e i m p e d a n ce s a s we l l a s th e p ri m a ry o f vo l ta g e tra n s fo rm e rs 0.1 D i s c h a rg i n g a ft e r d i s c o n n e c t i o n D i s co n n e cte d ca p a ci to r e q u i p m e n ts s h o u l d co m p l e te l y s e l f- d i s ch a rg e , n o m a tte r wh e re th e d i s ch a rg e d e vi ce i s l o ca te d , b e i t d i re ctl y a t e a ch ca p a ci to r o r a t th e co n n e cti n g te rm i n a l s o f th e e q u i p m e n t H o we ve r, ca p a ci to r e q u i p m e n t co m p ri s i n g s e ri e s co n n e cti o n s a n d s ta r co n n e cti o n s , wh i ch h a ve u n d e rg o n e p u n ctu ri n g o f e l e m e n ts o r i n te rn a l o r e xte rn a l a rci n g , m a y n o t b e d i s ch a rg e d co m p l e te l y th ro u g h d i s ch a rg e d e vi ce s co n n e cte d to th e te rm i n a l s o f th e ca p a ci to r e q u i p m e n t Al th o u g h th e re i s n o vo l ta g e m e a s u b l e a t th e e q u i p m e n t te rm i n a l s , d a n g e ro u s a m o u n ts o f s to re d e n e rg y, wi th o p p o s i n g ch a rg e s , m a y e xi s t i n th e ca p a ci to r e q u i p m e n t Th e s e s o - ca l l e d " tra p p e d ch a rg e s " m a y p e rs i s t o ve r a p e ri o d o f s e ve l m o n th s a n d ca n o n l y b e d i s ch a rg e d b y i n d i vi d u a l l y d i s ch a rg i n g e a ch s e cti o n o f th e b a n k Al l th e a b o ve - d e s cri b e d d i s ch a rg e re s i s to rs ri s ks H o we ve r, a re th e re n o rm a l l y a vo i d e d is th a t a ri s k a by u si n g ca p a ci to rs re s i s to r m a y be wi th d e s tro ye d i n te rn a l d u ri n g a ca p a ci to r fa i l u re l e a vi n g a ch a rg e o n th e ca p a ci to r I t i s i m p o rta n t to n o te th a t a d i s ch a rg i n g d e vi ce i s n o t a s u b s ti tu te fo r s h o rt- ci rcu i ti n g th e ca p a ci to r te rm i n a l s to g e th e r a n d to g ro u n d b e fo re a n d d u ri n g h a n d l i n g 0.2 Dead m e t a l l i c p a rt s Th e vo l ta g e o f e ve ry m e ta l l i c p a rt o f th e b a n k ( fra m e a n d /o r ca p a ci to r co n ta i n e r) s h o u l d b e fi xe d Th e vo l ta g e co n ti n u i ty is co n d u cti n g wi re o f a d e q u a te s i z e o b ta i n e d by co n n e cti n g th e co n ta i n e rs an d fra m e wi th I E C TS -3 : © I E C – 21 – 000 Al l fi l m d i el ectri c Paper or paper/fi l m d i el ectri c 00 H i g h probabi l i ty Ti m e i n secon d s of case ru ptu re 10 Low probabi l i ty of case ru ptu re 0, 0, 01 ,0 10 00 000 000 Cu rren t i n am peres (r m s ) IEC Fi g u re – Typi cal case ru ptu re cu rves for approxi m atel y 30 000 cm ³ case vol u m e N O TE Th e i n fo rm a t i o n I EEE 8-1 992, IEEE co n ta i n e d s t a n d a rd fo r in F i g u re shunt p o we r is c o p yri g h te d c a p a c i to rs i n fo rm a t i o n c o p yri g h t o f th e ©1 9 by IEEE th e e xtra c te d I n s ti tu t e of fro m s t a n d a rd E l e c tri c a l and E l e c tro n i c E n g i n e e rs , I n c ( I E E E ) T h i s i n fo rm a ti o n wa s wri tt e n wi t h i n th e c o n t e xt o f I E E E s t a n d a rd I E E E - 9 Th e IEEE ta k e s no re s p o n s i b i l i t y or l i a b i l i ty an d wi l l assu m e no l i a b i l i ty fo r an y d amag es re s u l ti n g fro m th e p l a c e m e n t a n d c o n te xt i n th i s p u b l i c a ti o n I n fo rm a ti o n i s re p ro d u c e d wi th th e p e rm i s s i o n o f t h e I E E E IEC IEC Fi g u re – Star n ecti on wi th th e n eu tral g rou n d ed th rou g h a cu rren t tran sformer Fi g u re – Star n ecti on wi th vol tag e tran sformer between n eu tral an d g rou n d – 22 – I E C TS -3 : © I E C IEC IEC F i g u re – S t a r c o n n e c t i o n n e u t l an d wi th F i g u re – D o u b l e - s t a r c o n n e c t i o n u n g ro u n d e d vo l t a g e t n s fo rm e rs c o n n e c t e d in an open w i th u n g ro u n d e d n e u t l d e l ta IEC IEC F i g u re – S t a r c o n n e c t i o n an d w i th g ro u n d e d vo l t a g e t n s fo rm e rs c o n n e c t e d d i ffe re n t i a l n e u t l F i g u re – B ri d g e c o n n e c t i o n in m e a s u re m e n t IEC F i g u re – L i n e o v e rc u rre n t re l a ys fo r c a p a c i t o r b a n k , g ro u n d e d I E C TS -3 : © I E C – 23 – IEC F i g u re – L i n e o ve rc u rre n t re l a ys fo r c a p a c i to r b a n k, u n g ro u n d e d T a b l e – M e l ti n g c u rre n ts fo r typ e -K ( fa s t) fu s e l i n ks , i n a m p e re s Ra t e d co n ti n u ou s 300 s or 600 s m e l t i n g c u rre n t s m e l ti n g , s m e l ti n g Speed c u rre n t c u rre n t ti o 1) c u rre n t M i n i m al M a xi m a l M i n i m al M a xi m a l M i ni mal M a xi m a l P re fe rre d ti n g s 2, 4, 3, 20, 72 86 6, 1 9, 23, 22, 34 28 54 6, 31 , 37, 37, 55 21 258 6, 25 50 60 60 90 350 420 7, 40 80 96 98 48 565 680 7, 65 28 53 59 237 91 1 00 7, 00 200 240 258 388 520 820 7, 40 31 372 430 650 470 970 8, 200 480 576 760 1 50 880 650 8, 97 16 6, I n t e rm e d i a te t i n g s 18 18 27 25 30 29, 44 66 99 6, 20 39 47 48, 71 273 328 7, 30 63 76 77, 115 447 546 7, 50 01 21 26 88 71 862 7, 80 60 92 205 307 1 80 420 7, 58 – 58 – 58 – R a ti n g s b e l o w N O TE 2,4 4, 7, I n fo rm a ti o n i n T a b l e i s fro m T a b l e i n 2) 2) 2) A 10 10 10 2) 2) 2) American National Standard C – 9 ( s e e b i b l i o g p h y) a n d i s re p ro d u c e d wi t h th e p e rm i s s i o n o f th e AN S I ) 2) 0 s fo r fu s e l i n ks te d 0 A a n d l e s s ; 0 s fo r fu s e l i n k s te d A a n d 0 A N o m i n i m u m v a l u e i s i n d i c a te d , s i n c e th e re q u i re m e n t i s th a t A, A, A t i n g s s h a l l c o o rd i n a te wi th th e A ti n g b u t n o t n e c e s s a ri l y wi th e a c h o th e r – 24 – I E C TS -3 : © I E C T a b l e – M e l ti n g c u rre n ts fo r typ e -T ( s l o w ) fu s e l i n ks , i n a m p e re s Ra t e d co n ti n u ou s 300 s or 600 s m e l ti n g c u rre n t s m e l ti n g , s m e l ti n g Speed c u rre n t c u rre n t t i o 1) c u rre n t M i ni mal M a xi m a l M i n i m al M axi m al M i n i mal M a xi m a l P re fe rre d ti n g s 2,0 4, 5, 23, 20 44 0, 10 9, 23, 26, 40, 224 269 1 ,5 15 31 , 37, 44, 67, 388 466 2, 25 50 60 73, 09 635 762 2,7 40 80 96 20 78 040 240 3, 65 28 53 95 291 650 975 2, 00 200 240 31 475 620 50 3, 1 40 31 372 520 775 000 800 2, 200 480 576 850 275 250 470 3, I n t e rm e d i a t e ti n g s 5, 8, 20, 31 , 66 99 1 ,1 12 25, 30, 34, 52, 296 355 1 ,8 20 39, 47, 57, 85, 496 595 2,