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Electrical SC analysis
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7/17/2019 04-shortcircuitcalculations
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Copyright Siemens AG 2008. All rights reserved.
Short Circuit Calculation
Sector Energy
D SE PTI NC
Steffen Schmidt
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Page 2 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Standards and Terms
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Page 3 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Purpose of ShortCircuit Calculations
Dimensioning of switching deices
Dynamic dimensioning of switchgear
Therma! rating of e!ectrica! deices "e.g. ca#!es$
Protection coordination
%a&!t diagnostic
In'&t data for
Earthing st&dies
Interference ca!c&!ations E(C '!anning
)..
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Page * 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
ShortCircuit Calculation
Standards
IEC 60+0+,Short-Circ&it C&rrent Ca!c&!ation in Three-Phase .C. Systems
E&ro'ean Standard EN 60+0+ /erman Nationa! Standard DIN DE 0102 f&rther Nationa! Standards
Engineering ecommendation /* "45$Proced&re to (eet the e&irements of IEC 60+0+ for theCa!c&!ation of Short-Circ&it C&rrents in Three-Phase C Power
Systems
NSI IIEEE Std. C3.7 "4S$IEEE /&ide for Ca!c&!ation of %a&!t C&rrents for ''!ication of a.c. igho!tage Circ&it 9rea:ers ated on a Tota! C&rrent 9asis.
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Page 7 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
ShortCircuit Calculations
Standard !"C #0$0$
IEC 60+0+ , Short-circ&it c&rrents in three-'hase a.c. systems
Part 0, Ca!c&!ation of c&rrentsPart 1, %actors for the ca!c&!ation of
short-circ&it c&rrentsPart 2, E!ectrica! e&i'ment; data for
short-circ&it c&rrent ca!c&!ationsPart 3, C&rrents d&ring two se'arate
sim&!taneo&s !ine-to-earth shortcirc&its and 'artia! short-circ&itc&rrents f!owing thro&gh earth
Part *, E
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Page 6 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
ShortCircuit Calculations
Scope of !"C #0$0$
three-'hase a.c. systems !ow o!tage and high o!tage systems &' to 700 : nomina! fre&ency of 70 = and 60 = #a!anced and &n#a!anced short circ&its
three 'hase short circ&its two 'hase short circ&its "with and witho&t earth connection$ sing!e 'hase !ine-to-earth short circ&its in systems with so!id!y
earthed or im'edance earthed ne&tra! two se'arate sim&!taneo&s sing!e-'hase !ine-to-earth short circ&its
in a systems with iso!ated ne&tra! or a resonance earthed ne&tra!"IEC 60+0+-3$ ma
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7/67Page 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt Copyright Siemens AG 200%. All rights reserved.
ShortCircuit Calculations
Types of Short Circuits
&phase
2phase
'phase
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ShortCircuit Calculations
(arfromgenerator short circuit
I:> Initia! symmetrica! short-circ&it c&rrenti' Pea: short-circ&it c&rrentI: Steady-state short-circ&it c&rrent
Initia! a!&e of the d.c com'onent
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ShortCircuit Calculations
)efinitions according !"C #0$0$ *!+
initial symmetrical shortcircuit current I,>r.m.s. a!&e of the a.c. symmetrica! com'onent of a 'ros'ectie"aai!a#!e$ short-circ&it c&rrent? a''!ica#!e at the instant of short circ&it ifthe im'edance remains at =ero-time a!&e
initial symmetrical shortcircuit po-er S,>fictitio&s a!&e determined as a 'rod&ct of the initia! symmetrica! short-circ&it c&rrent I:>? the nomina! system o!tage Unand the factor @3,
NATE, S:> is often &sed to ca!c&!ate the interna! im'edance of a networ: feeder at theconnection 'oint. In this case the definition gien sho&!d #e &sed in the fo!!owing form,
B:n
B: I43S =
B
:
2
n
S
4cC
=
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ShortCircuit Calculations
)efinitions according !"C #0$0$ *!!+
decaying *aperiodic+ component id.c.of shortcircuit current
mean a!&e #etween the to' and #ottom ene!o'e of a short-circ&itc&rrent decaying from an initia! a!&e to =ero
pea, shortcircuit current ip
ma
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ShortCircuit Calculations
eartogenerator short circuit
I:> Initia! symmetrica! short-circ&it c&rrenti' Pea: short-circ&it c&rrentI: Steady-state short-circ&it c&rrent
Initia! a!&e of the d.c com'onentI9 Symmetrica! short-circ&it #rea:ing c&rrent
t/
9I22
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ShortCircuit Calculations
)efinitions according !"C #0$0$ *!!!+
steadystate shortcircuit currentI,r.m.s. a!&e of the short-circ&it c&rrent which remains after the decay ofthe transient 'henomena
symmetrical shortcircuit rea,ing current I
r.m.s. a!&e of an integra! cyc!e of the symmetrica! a.c. com'onent of the'ros'ectie short-circ&it c&rrent at the instant of contact se'aration ofthe first 'o!e to o'en of a switching deice
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ShortCircuit Calculations
Purpose of ShortCircuit 1alues
Design Criterion Physica! Effect e!eant short-circ&it c&rrent
9rea:ing ca'acity of circ&it
#rea:ers
Therma! stress to arcing
cham#er; arc e
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Standard !"C #0$0$
Simplifications and Assumption
ss&m'tions &asi-static state instead of dynamic ca!c&!ation
no change in the ty'e of short circ&it d&ring fa&!t d&ration
no change in the networ: d&ring fa&!t d&ration
arc resistances are not ta:en into acco&nt im'edance of transformers is referred to ta' changer in main 'osition
neg!ecting of a!! sh&nt im'edances e
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"uivalent 1oltage Source
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Shortcircuit
"uivalent voltage source at the shortcircuit location
E
E CFCTC.
%
G
IB33
.n
Uc
rea! networ:
e&ia!ent circ&it
A'erationa! data and the 'assie !oad of cons&mers are neg!ectedTa'-changer 'osition of transformers is dis'ensa#!eE
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Page 18 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Short circuit in meshed grid
"uivalent voltage source at the shortcircuit location
rea! networ: e&ia!ent circ&it
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Page 1+ 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
1oltage (actor c
c is a safety factorto consider the fo!!owing effects, o!tage ariations de'ending on time and '!ace? changing of transformer ta's? neg!ecting !oads and ca'acitances #y ca!c&!ations? the stransient #ehaio&r of generators and motors.
Nomina! o!tage
o!tage factor c for ca!c&!ation of
ma
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Page 20 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
4a5imum and minimum ShortCircuit Currents
ma
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Page 21 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Short Circuit !mpedances and Correction (actors
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Page 22 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Short Circuit !mpedances
%or networ: feeders? transformer? oerhead !ines? ca#!e etc.
im'edance of 'ositie se&ence system K im'edance of negatie se&ence system
im'edance of =ero se&ence system &s&a!!y different
to'o!ogy can #e different for =ero se&ence system
Correction factors for
generators? generator #!oc:s?
networ: transformer
factors are a!id in =ero? 'ositie? negatie se&ence system
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Page 23 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
et-or, feeders
t a feeder connection 'oint &s&a!!y one of the fo!!owing a!&es is gien, the initia! symmetrica! short circ&it c&rrent I:> the initia! short-circ&it 'ower S:>
If LM of the networ: feeder is &n:nown? one of the fo!!owing a!&es can#e &sed, LM K 0.1 LM K 0.0 for high o!tage systems 37 : fed #y oerhead !ines
B:
2n
B:
n
S
4c
I3
4c
C
=
=
2
EE
$ML"1
CM
+
=
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Page 2* 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
et-or, transformer
Correction of !mpedance
T5K T5T
genera!
at :nown conditions of o'eration
no correction for im'edances #etween star 'oint and gro&nd
T
ma
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Page 27 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
et-or, transformer
!mpact of Correction (actor
The Correction factor is 5T1.0 for transformers with
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Page 26 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Generator -ith direct Connection to et-or,
Correction of !mpedance
/5K /5/
genera!
for contin&o&s o'eration a#oe rated o!tage,
4r/"1O'/$ instead of 4r/
t&r#ine generator, M"2$ K M"1$
sa!ient 'o!e generator, M"2$ K 1L2 "MdBO MB$
r/d
manearW or WfarW from generator
Definition short circ&it >nearW to generator
for at !east one synchrono&s machine is, I:> 2 X Ir?/eneratoror I:>with motor 1.07 X I:>witho&t motor
9rea:ing c&rrent I#for short circ&it WfarW from generator
I#K I:>
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Page 61 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
/rea,ing Current
Calculation in nonmeshed et-or,s
The #rea:ing c&rrent I9at a short-circ&it !ocation? fed from so&rces whichare not meshed is the s&m of the 'artia! short-circ&it c&rrents,
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Page 62 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
/rea,ing current
)ecay of Current fed from Generators
I9K Y X IW:
%actor Y to consider the decay of short circ&it c&rrent fed fromgenerators.
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Page 63 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
/rea,ing current
)ecay of Current fed from Asynchronous 4otors
I9K Y X X IW:
%actor to consider the decay of short circ&it c&rrent fed fromasynchrono&s motors.
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/rea,ing Current
Calculation in meshed et-or,s
Sim'!ified ca!c&!ation,
I#K I:>
%or increased acc&racy can #e &sed,
MWdi5 stransient reactance of the synchrono&s machine "i$MW(V reactance of the asynchrono&s motors "V$IW:/i ? IW:(V contri#&tion to initia! symmetrica! short-circ&it c&rrent from the synchrono&s machines "i$
and the asynchrono&s motors "V$ as meas&red at the machine termina!s
B
:(VVVV n
(VB
:/iii n
/iB
:# I$1"3L4c
B4I$1"
3L4c
B4II
=
B
:/iB
di5
B
/i IVM4 =B:(V
B(V
B(V IVM4 =
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Page 67 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Continuous short circuit current
Contin&o&s short circ&it c&rrent I:
r.m.s. a!&e of short circ&it c&rrent after decay of a!! transienteffects
de'ending on ty'e and e
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Page 66 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Shortcircuit -ith preload
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Page 6 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Shortcircuit -ith preload
Principle
Foad f!ow ca!c&!ation that considers a!! networ: 'arameters?s&ch as !oads? ta' 'ositions? etc.
9 P!ace o!tage so&rce with the o!tage that was determined #y
the !oad f!ow ca!c&!ation at the fa&!t !ocation.
C S&'er'osition of and 9
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Page 68 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Shortcircuit -ith preload
"5ample
Foad f!ow ca!c&!ation
9 Short circ&it ca!c&!ation
S
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Page 6+ 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Shortcircuit -ith preload
7esults
203367+2.11
1000
1+2.01681+.3203.+7
Shortcircuit -ith preload
G G
367.3
20
-0
2000
-36*
336
+00.
-30.8+
7+2.11
1000
-0
1000
10
182
1+2
*0
208
168
*0.
17.3
1+.3
70.
173.+7
203.+7
Superposition< 9oad flo- = feed 0ac,
G G
367.3
2*6.78
201000
*0*070
9oad flo-
G G
7010
2 3 2 10 2
1*80+00
+000
00208.0
367.3173.+7
Shortcircuit< feed 0ac,
263.*2
182
8030.8+ 36*
17.3
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Page 0 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
/rea, time>
Copyright Siemens AG 2008. All rights reserved.
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Page 1 28.06.2008 Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt
Contact
Steffen SchmidtSenior Cons&!tantSiemens /? Energy SectorE D SE PTI NC
%reyes!e#enstr. 1+1078 Er!angen
Phone, O*+ +131 - 326*%a
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Than, you for your attention>