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Introduction to Switchyard
EquipmentAbhishek Kr. Jha
Sr. Engineer
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Switchyard Equipment
LA
CV
C Iso!ator
Circuit "reaker
rans#ormer and $eactor
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Substation %
Assemb!age o# switchyard eqpmt.&busbars& trans#ormers and reactors &au'i!iaries etc.
Incomer and outcomer based on the#ormu!a (
)*VS+V$,-/+sin 0
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INSULATION COORDINATION
Se!ection o# the die!ectric strength o#equipment in re!ation to theoperating 1o!tages and o1er1o!tage2swhich can appear on the system #orwhich the equipment is intended andtaking into account the ser1ice
en1ironment and the characteristicso# the a1ai!ab!e pre1enting andprotecti1e de1ices
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LI345I53 A$$ES6$
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T e m p o r a r y O v e r - v o lt a g e s S w i t c h i n g O v e r - v o l t a g e s O v e r - v o l t a g e s d u e t o l i g h t n i n g .
P o w e r S y s t e m s O v e r v o l t a g e s
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Temporary Over-Voltages
Typically due to faults
!"# pu
ms to te$s of seco$d or eve$ mi$utes
Not da$gerous to i$sulatio$
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S%itc&i$g Over-Voltages
Due to system s%itc&i$goperatio$s
!"' pu ( ' pu depe$ds o$ systemvoltage
mostly damped asymmetricsi$usoids
fro$t time of )rst pea* ( te$s ofs to a fe% ms"
decides e+ter$al i$sulatio$ i$,V.UV system
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Over-Voltages due toLig&t$i$g
Due to /direct0 or /i$direct0 lig&t$i$gstro*es"
*$o%$ to co$tri1ute to '23 of systemoutages i$ ,V 4 UV systems
fe% &u$dred *V to several te$s of 5V" 6e% *A to 722 *A
very s&ort duratio$ 8 times to fro$t 8 ! tofe% te$s of s
times to tail 8 fe% te$s to &u$dreds of s" Decides li$e i$sulatio$ 9:IL;
Severely i$
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Ad1antages o# 76SA
Impro1ed re!iabi!ity due to simp!icity o# thedesign.
Superior protecti1e characteristics.
7inimum energy absorptioncommensurate with the protecti1e !e1e!spro1ided.
Superior per#ormance on !ow impedancecircuits*e.g cab!e and capacitorapp!ication,
3ent!e operation due to absence o# spark
gaps
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The Zinc Oxide Arresters are made by mixing
ZnO with small amounts of additives such as
Bi2O3, CoO, Cr2O3, nO and !b2O3
"ranuling the mixture, then drying, #ressing
into discs and finally sintering
!3 TIRD AR5ONIC IN S=ST,5VOLTA>, 5A= INTRODUC, ,RRORU?TO !223 IN T, 5,ASUR,DVALU,
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CTION O6 RATIN>S O6
CONTINOUS VOLTA>, RATIN>
T,5?ORAR= OV,R VOLTA>,
LI>TIN> OV,R VOLTA>,
S@ITCIN> OV,R VOLTA>,
,N,R>= ANDLIN> CA?ACIT=
89
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Co$ti$uous Voltage rati$g8 - Arrester ca$ operate%it&out a$y type of restrictio$
At present& :;:kV has been speci
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Temporary Over Voltages8 - Capa1ility of Arrester toDeal %it& temporary over voltage of system
At present& :?;kV has been speci8*=, and a!so as per IEEE@C=.@@@& 61erVo!tages upto 8.9 p.u. ha1e been speci
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8
S.5 Characteristics Va!ue*#or D;; kV
System,8 $ated arrester 1o!tage :: kV
= 5omina! Fischarge current*-=; G Sec wa1e,
=; kA
: 7inimum discharge capabi!ity 8= kJ-kV
D Continues operating 1o!tage =>9 7in Switching surge residua! 1o!tage *=
kA,>; kVp
7a' residua! 1o!tage at
i, 8;kA nomina! discharge current ;; kVp
ii, =; kA nomina! discharge current 9; kVp
iii, Steep #ronted wa1e residua! 1o!tage ?=9 kVp
> Hressure re!ie# c!ass D;-9;-: kA*asapp!icab!e,
@ RATIN>S O6 #22 *V
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CV
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Capacitor voltage transformer
A voltage transformer com#rising a ca#acitor
divider unit and an electromagnetic unit so
designed and interconnected that the secondary
voltage of the electromagnetic unit is
substantially #ro#ortional to the #rimary
voltage, and differs in #hase from it by an anglewhich is a##roximately $ero for an a##ro#riate
direction of the connections
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EMU
H Terminal
Upper !apacitor Unit
"ellow#evel $ndicator
Sec.
Terminal
"o%
#ower !apacitor
Unit
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There are a##roximately 2%& ' 3(& elements
in
C( about () * 2) elements in C2
+ +oltage Ta# +s- C(./C(0C21
where, +s ' rimary +oltage
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n the event of an element failure in C2, Ca#acitance C2 increases4 5ence, Ca#acitor 6ivider 7atio ncreases4
+ Ta# . ntermediate +oltage 7educes4
5ence !econdary +oltage 7educes4
n the event of an element failure in C( , Ca#acitance C( increases4 Ca#acitor 6ivider 7atio 7educes4
+ Ta# . ntermediate +oltage ncreases4
5ence !econdary +oltage ncreases4
8umber of C2 9lements are lesser , e4g4 2& : hence change in C2 due toone element failure is /(.2&1 x (&& );4
8umber of C( 9lements are more e4g4
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Electromagnetic UnitThe com#onent of a ca#acitor voltage transformer,
connected across the intermediate terminal and the earthterminal of the ca#acitor divider which su##lies the
secondary voltage4 An electromagnetic unit com#rises
essentially a transformer to reduce the intermediate
voltage to the re>uired value to secondary voltage, and aninductive reactance, a##roximately e>ual, at rated
fre>uency, to the ca#acitive reactance of the two #arts of
the divider connected in #arallel4
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Com#ensating 7eactor is #rovided to
com#ensate for the #hase dis#lacement in
Ca#acitor elements
w? (.w /c(0c21
? (. w2/c(0c21
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@erro resonance in C+Ts is due to the
Ca#acitance in +oltage 6ivider in series with
the inductance of the Transformer and series
reactor4 This circuit is brought to resonance byvarious disturbances in the networ that may
saturate the iron core of the transformer, over
heat electro magnetic unit and lead toinsulation breadown4
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erro resonance in CVs is due to the Capacitance in Vo!tageFi1ider in series with the inductance o# the rans#ormer andseries reactor. his circuit is brought to resonance by 1arious
disturbances in the network that may saturate the iron core o#the trans#ormer& o1er heat e!ectro magnetic unit and !ead toinsu!ation breakdown.
@erro resonance su##ression circuit is #rovided in C+T !econdary to su##ress
@erro resonance oscillations4
The ferro*resonance su##ression device /@!61 contains a saturable reactor, whichacts lie a switch, #resenting a very high im#edance under normal conditions and
switching on a dam#ing resistor across the secondary at a #rescribed voltage, and
switching off the dam#ing load when voltage has normali$ed4 The voltage
sensitive switching strategy effectively su##resses ferroresonance without
im#osing a heavy #ermanently connected stabili$ing burden on the unit4
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Current rans#ormer
As per IEC ;;DD@8
@unctions 4* etering 4
* onitoring 4
* 7elaying.rotection
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Live Ta$* CTs
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Dead ta$* CTs
Hairpin design and Eye Bolt design
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ech Harameters
E'tended Current $ating( I# C has an e'tended current rating& in percentage
o# the rated primary current& it sha!! be treated as$ated continuous therma! current. *8=;,
$ated Short time therma! current( $7S1a!ue o# the primary current& which a C wi!!
withstand #or one second& without suering harms&the secondary winding being short@circuited.
D;kA #or 8 sec.
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$ated dynamic current( Heak 1a!ue o# the primary current& which a
C wi!! withstand& without suering harms&
the secondary winding being short@circuited. n!ess speci
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"urden( It is the impedance o# the secondary circuit in ohms and
p#.
$ated output( he 1a!ue o# apparent power *in VA at speci
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echnica! Harameters
Accuracy C!ass #or 7easuring Cs(4ighest permissib!e percentage current error atrated current prescribed #or concerned accuracyc!ass.
Standard c!asses@ ;.8& ;.=& ;.9& 8& :& 9or =9 to 8;; o# rated burden
Accuracy c!ass #or Hrotecti1e C(4ighest permissib!e percentage composite errorat rated accuracy !imit primary currentprescribed#or concerned accuracy c!ass.
9H=;& !omposite Error
Protection !lass'#(
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$ated Instrument Limit Hrimary Current(or measuring Cs& the minimum primary current atwhich the composite error N 8;& secondary burdenbeing equa! to rated burden.
Instrument Security actor *IS,(IS rated IHL - rated primary currentSecondary apparatus sa#ety is greatest when the 1a!ue o#IS is sma!!.
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Composite Error(nder steady@state& the rms 1a!ue o# dierencebetween(a, Instantaneous 1a!ue o# primary current& ip.
b, Instantaneous 1a!ue o# secondary current ' rated
trans#ormation ratio& Kn' is
Oc *8;;-Ip,' P*8-,'Q;*ip@Knis,=dtCurrent error *Knis@ ip,'8;;-ip
Composite Error R Current Error Hhase ang!e errorR
Siemens makes S
SIE7E5S
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SIE7E5S
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Iso!ator
H$6VIFE ELEC$ICAL IS6LAI65 VISI"LE IS6LAI65 ACILIT 6$ EA$4I53 S7ALL C$$E5 I5E$$HI65 CA$$T S46$ CI$CI C$$E5 "
56 6$ "$EAKI53 SC C$$E5
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HA$S 6 FISC655EC6$S
C$$E5 CA$$TI53 A$7S
SHH6$ I5SLA6$S
"ASE $A7E
6HE$AI53 7EC4A5IS7
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THES 6 FISC655EC6$S
46$IU65AL@ CE5$E "$EAK 6$F6"LE "$EAK
VE$ICAL VE$ICAL SWIC4& K5EETHE 6$ HA563$AH4 THE
andem type
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FEHE5FS 65
@5CI65AL $EXI$E7E5
@SWIC4I53 SC4E7E
@EA$4I53 $EXI$E7E5
@C67HAC5ESS *space a1ai!ab!e,
@EC6567T
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EA$4 SWIC4
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Host Insu!ators
A #ost insulator consists of one #ost insulator unit or an
assembly of such units and is intended to give rigid su##ort to
a live #art which is to be insulated from earth or from another
live #art4
@8CTO8!
"us Supports 7echanica! Load Sharing Support Insu!ators #or Iso!ators Insu!ators #or C& CV& C"& IV etc. Support Insu!ators #or Wa1e raps
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Circuit "reaker
Circuit "reakers *C"s, are the switching andcurrent interrupting de1ices.
he C"s are necessary at e1ery switching
point in the substation.A Circuit breaker diers #rom a disconnector
switch main!y in three aspects(
@ au!t current interruption.
@ Arc e'tinction
@ Speed o# operation
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:asically a circuit 1rea*er9C:; comprises ofa set of )+ed a$d mova1le co$tacts"
Co$tacts ca$ 1e operated 1y mea$s of a$operati$g mec&a$ism"
Separatio$ of curre$t carryi$g co$tactsproduces t&e arc t&e arc is e+ti$guis&ed 1ysuita1le media suc& as dielectric oilairsfgas a$d vacuum"
Arc is e+ti$guis&ed 1y le$gt&e$i$g cooli$gsplitti$g or rotatio$"
I$ some 1rea*ers arc is dra%$ i$ t&edirectio$ of splitters 1y mag$etic )eld"
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Rated Voltage
he rated 1o!tage o# the circuit breaker is thehighest system 1o!tage in which the circuit breakeris to be used. his is phase to phase 1o!tage #or
three phase circuit e'pressed in kVrms. Rated Curre$t
he rated norma! current o# a circuit breaker is ther.m.s. 1a!ue o# the current which the circuit
breaker can carry continuous!y without e'ceedingthe !imits o# temperature rise in 1arious parts. he!imits are speci8@8.
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Rated s&ort Circuit :rea*i$g Curre$t 8 he rated short circuit breaking current o# a
circuit breaker is the highest rms 1a!ue o# shortcircuit current which the circuit breaker iscapab!e o# breaking at a stated reco1ery
1o!tage *most!y equa! to the rated 1o!tage, anda stated re#erence restriking 1o!tage underprescribed conditions o# use and beha1ior.
Symmetrica! breaking current is the rms 1a!ueo# a.c. component o# the short circuit currentat the instant o# contact separation. he
asymmetrica! breaking current is the rms 1a!ueo# the tota! current Y comprising a.c. and d.c.components o# the current& at the instant o#contact separation
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5a*i$g Capacity he making capacity is de
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Rated Operati$g seue$ce 9Duty cycle; he $ated 6perating Sequence *Futy Cyc!e, o# the circuit
breaker denotes the sequence o# opening and c!osingoperations which the circuit breaker can per#orm underspeci
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A ransient reco1ery 1o!tage re#ers to the 1o!tageacross the po!e immediate!y a#ter the arc e'tinction.Such 1o!tage has power #requency component p!usan osci!!atory transient component. he osci!!atorytransient component is due to the inductance andcapacitance. he power power #requency
component is due to the system 1o!tage. he heosci!!atory component subsides a#ter a #ew micro@seconds and the power #requency componentcontinues
he #requency o# the transient component is gi1enby (
# 8 -*=ZPLC,# requency o# transient reco1ery 1o!tage & 4[L Equi1a!ent inductance. henryC Equi1a!ent capacitance& arad
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au!t 6ccurs ( As the #au!t occurs the #au!timpedance being !ow& the currents increase andre!ay gets actuated. he re!ay contacts c!ose& thetrip circuit o# the circuit breaker c!oses and trip
coi! is energi[ed. he operating mechanism startsoperating #or opening operation. he circuitbreaker contacts separate.
Arc is drawn between the breaker contacts. he
arc is e'tinguished in the Circuit "reaker bysuitab!e techniques. he current reaches
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CLASSI6ICATION :AS,D ON ARCEU,NCIN> 5,DIU5
AIR :R,AF CIRCUIT :R,AF,R
OIL CIRCUIT :R,AF,R
5INI5U5 OIL CIRCUIT :R,AF,R
AIR :LAST CIRCUIT :R,AF,R SUL?,R ,GA6LOURID,
CIRCUIT :R,AF,R
VACUU5 CIRCUIT :R,AF,R
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$eco er Vo!tage and bui!d up o#
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$eco1ery Vo!tage and bui!d up o#die!ectric strength o# the medium
5AHOR ?ARTS O6 A CIRCUIT
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5AHOR ?ARTS O6 A CIRCUIT:R,AF,R
INT,RRU?TOR
SU??ORT COLU5N
O?,RATIN> 5,CANIS5
CONTROL 4 5ONITORIN>D,VIC,S
?U5?S 4 CO5?R,SSORS
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INTERRUPTOR
Interrupter houses the
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6HE$AI53 7EC4A5IS7
A. Spring assisted motormechanism
". Hneumatic operating
mechanism C. 4ydrau!ic mechanism
F. Combination o# abo1e
SH$I53 6HE$AI53
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SH$I53 6HE$AI537EC4A5IS7
O#ening s#ring and closing s#ring with limitswitch for automatic charging4Breaer o#eration shall be inde#endent of the
motor used for com#ressing the closing.o#enings#ring4Closing action of circuit breaer shall com#ressthe o#ening s#ring ready for tri##ing4Dhen closing s#rings are discharged after closinga breaer, closing s#rings shall be automaticallycharged for the next o#eration
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?OL, D,SCRI?ANC= his #eature is introduced to detect cases in which one or morepo!es o# a : phase C" remains in open condition where as the otherpo!es are c!osed. his may arise due to ma!@operation or s!uggishoperation o# one or more po!es. It essentia!!y is a timer connectedto a series para!!e! connection o# Au'i!iary switch
ANTI ?U5?IN>
Anti pumping #eature b!ocks the c!osing o# a C" more than once*mu!tip!e c!osing, with a sing!e pro@!onged c!osing impu!se *say&the operator keeps on gi1ing a c!osing impu!se without re!easingthe c!osing hand!e,.
AUTO R,CLOS, Circuit "reaker sha!! be capab!e o# per#orming auto@rec!ose
operation in case o# a transient #au!t. LOCF OUTS AND ALAR5S) S a!arm and L-6) 6perating mechanism a!arm - !ock out) rip circuit super1ision
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) 3uaranteed S !eakage ;.9 per year.) Separate S monitoring #or each po!es #or 8D9kV and
abo1e.) 6perating duty ;@;.:S C6 : min. C6.) S.C. rating D;-9;-:KA *#or D;;kV M ==;KV,
:8.9 kA #or 8D9KV@ Line charging interruption Capabi!ity ;;A
#or D=;kV& 8=9A #or =D9kV*IEC,& 9;A #or8D9kV*IEC,.)
6p. 7echanism Hneumatic-Spring-4ydrau!ic.) Au'. FC*==;V, supp!y 1ariation >; @88; #or trip o# 9 88; #or c!ose.
) = Independent trip circuits& each ha1ing separatepressure switches.
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CSF
C65$6LLE$ IS SEF 6 6HE5 *6$CL6SE,4E C" A IS 76S AV6$A"LEC65FII65
C65$6LLE$ 765I6$S 4ESTSE7HA$A7EE$S*LIKE V6LA3EWAVE6$7,
A5F FECIFE 6HI77 SWIC4I53C65FII65 A5F 4E5CE K56W5 ASH6I565 4E WAVE SWIC4I53
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Circuit "reaker 3A Frg W-o
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Circuit "reaker 3A Frg W-oHI$
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TANF =OU