Short-Circuit-Calculations.pdf

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Copyright Siemens AG 2008. All rights reserved.

Short Circuit Calculation

Sector Energy

D SE PTI NC

Steffen Schmidt


2/72Page 2 28.06.2008Copyright Siemens AG 2008. All rights reserved.

E D SE PTI NCSteffen Schmidt

Standards and Terms




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

)..


4/72Page * 28.06.2008Copyright Siemens AG 2008. All rights reserved.


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.igh o!tage Circ&it 9rea:ers ated on a Tota! C&rrent 9asis.




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





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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E D SE PTI NCSteffen SchmidtCopyright Siemens AG 200%. All rights reserved.


Types of Short Circuits

&phase

2phase

'phase




(ariation of short circuit current shapes

fa&!t at o!tage 'ea: fa&!t at o!tage=ero crossing

fa&!t !ocated inthe networ:

fa&!t !ocatednear generator


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)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





*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 poer 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 the

connection '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

=





*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 ipma





/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





*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 1rea-ing current I1r.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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Copyright Siemens AG 2008. All rights reserved.E D SE PTI NCSteffen Schmidt


Purpose of ShortCircuit (alues

(inim&m symmetrica! short-circ&it c&rrent I:Se!ectie detection of 'artia!short-circ&it c&rrents

Protection setting

(a

Potentia! rise;

(agnetic fie!ds

Earthing? Interference? E(C

Initia! symmetrica! short-circ&it c&rrent I:>

%a&!t d&ration

Tem'erat&re rise of e!ectrica!

deices "e.g. ca#!es$

Therma! stress to e&i'ment

Pea: short-circ&it c&rrenti'%orces to e!ectrica! deices

"e.g. #&s #ars? ca#!es)$(echanica! stress toe&i'ment

Symmetrica! short-circ&it#rea:ing c&rrent I#

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 (oltage 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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Short circuit in meshed grid

"uivalent voltage source at the shortcircuit location

rea! networ: e&ia!ent circ&it


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(oltage )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.

1.001.10(edi&m o!tage 1 : H 37 :

0.+70.+7

1.071.10

Fow o!tage 100 H 1000

-systems with a to!erance of 6-systems with a to!erance of 10

1.001.10igh o!tage 37 :

minim&m short circ&it c&rrentsma


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Short Circuit !mpedances and Correction )actors


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Short Circuit !mpedances

%or networ: feeders? transformer? oerhead !ines? ca#!e etc.

im'edance of 'ositie se&ence system K im'edance of negatiese&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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/etor- 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

E S

4c

I3

4c

C

=

=

2

EE

$ML"1

CM

+=


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/etor- 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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/etor- transformer

!mpact of Correction )actor

The Correction factor is 5T1.0 for transformers with


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Generator ith direct Connection to /etor-

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

ma

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