EN 60909-0:2016
(Main)Short-circuit currents in three-phase a.c. systems - Part 0: Calculation of currents
Short-circuit currents in three-phase a.c. systems - Part 0: Calculation of currents
IEC 60909-0:2016 is applicable to the calculation of short-circuit currents in low-voltage three-phase AC systems, and in high-voltage three-phase AC systems, operating at a nominal frequency of 50 Hz or 60 Hz. It establishes a general, practicable and concise procedure leading to results which are generally of acceptable accuracy and deals with the calculation of short-circuit currents in the case of balanced or unbalanced short circuits. This second edition cancels and replaces the first edition published in 2001. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - contribution of windpower station units to the short-circuit current; - contribution of power station units with ful size converters to the short-circuit current; - new document structure.
Kurzschlussströme in Drehstromnetzen - Teil 0: Berechnung der Ströme
Courants de court-circuit dans les réseaux triphasés à courant alternatif - Partie 0: Calcul des courants
L'IEC 60909-0:2016 est applicable au calcul des courants de court-circuit dans les réseaux triphasés basse tension à courant alternatif, et dans les réseaux triphasés haute tension à courant alternatif, fonctionnant à une fréquence nominale de 50 Hz ou de 60 Hz. Elle établit une procédure générale, réalisable et concise conduisant à des résultats qui sont en général d'une précision acceptable. Et traite du calcul des courants de court-circuit dans le cas de courts-circuits symétriques et dissymétriques. Cette deuxième édition annule et remplace la première édition parue en 2001. Cette édition constitue une révision technique. Elle inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: - contribution des groupes de production éoliens au courant de court-circuit; - contribution des groupes de production avec convertisseurs grande capacité au courant de court-circuit; - nouvelle structure du document.
Kratkostični toki v izmeničnih trifaznih sistemih - 0. del: Računanje tokov
Standard IEC 60909-0:2016 se uporablja za izračun kratkostičnih tokov v nizkonapetostnih izmeničnih trifaznih sistemih in visokonapetostnih izmeničnih trifaznih sistemih, ki delujejo pri nominalni frekvenci 50 Hz ali 60 Hz. Uveljavlja splošen, izvedljiv in strnjen postopek z rezultati, ki so običajno sprejemljive natančnosti, ter obravnava izračun kratkostičnih tokov v primeru uravnovešenih in neuravnovešenih kratkih stikov. Druga izdaja razveljavlja in nadomešča prvo izdajo, objavljeno leta 2001. Ta izdaja je tehnično popravljena izdaja. Ta izdaja vključuje naslednje znatne tehnične spremembe glede na prejšnjo izdajo:
– prispevek enot vetrnih elektrarn h kratkostičnemu toku;
– prispevek enot elektrarn s pretvorniki polne velikosti h kratkostičnemu toku;
– nova struktura dokumentov.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2016
1DGRPHãþD
SIST EN 60909-0:2002
.UDWNRVWLþQLWRNLYL]PHQLþQLKWULID]QLKVLVWHPLKGHO 5DþXQDQMHWRNRY
Short-circuit currents in three-phase a.c. systems - Part 0: Calculation of currents
Kurzschlussströme in Drehstromnetzen - Teil 0: Berechnung der Ströme
Courants de court-circuit dans les réseaux triphasés à courant alternatif - Partie 0: Calcul
des courants
Ta slovenski standard je istoveten z: EN 60909-0:2016
ICS:
17.220.01 Elektrika. Magnetizem. Electricity. Magnetism.
Splošni vidiki General aspects
29.240.20 Daljnovodi Power transmission and
distribution lines
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN 60909-0
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2016
ICS 17.220.01; 29.240.20 Supersedes EN 60909-0:2001
English Version
Short-circuit currents in three-phase a.c. systems -
Part 0: Calculation of currents
(IEC 60909-0:2016)
Courants de court-circuit dans les réseaux triphasés à Kurzschlussströme in Drehstromnetzen -
courant alternatif - Teil 0: Berechnung der Ströme
Partie 0: Calcul des courants (IEC 60909-0:2016)
(IEC 60909-0:2016)
This European Standard was approved by CENELEC on 2016-03-03. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 60909-0:2016 E
European foreword
The text of document 73/172/CDV, future edition 2 of IEC 60909-0, prepared by IEC/TC 73
"Shortcircuit currents" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC
as EN 60909-0:2016.
The following dates are fixed:
(dop) 2016-12-10
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2019-06-10
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60909-0:2001.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.
Endorsement notice
The text of the International Standard IEC 60909-0:2016 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60865-1 NOTE Harmonized as EN 60865-1.
IEC 62428 NOTE Harmonized as EN 62428.
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu
Publication Year Title EN/HD Year
IEC 60038 (mod) 2009 IEC standard voltages EN 60038 2011
IEC 60050-131 - International Electrotechnical - -
Vocabulary (IEV) -
Part 131: Circuit theory
IEC/TR 60909-1 2002 Short-circuit currents in three-phase e.c. - -
systems -
Part 1: Factors for the calculation of short-
circuit currents according to IEC 60909-0
IEC/TR 60909-2 2008 Short-circuit currents in three-phase a.c. - -
systems -
Part 2: Data of electrical equipment for
short-circuit current calculations
IEC 60909-3 2009 Short-circuit currents in three-phase a.c EN 60909-3 2010
systems -
Part 3: Currents during two separate
simultaneous line-to-earth short-circuits
and partial short-circuit currents flowing
through earth
IEC/TR 60909-4 2000 Short-circuit currents in three-phase a.c. - -
systems -
Part 4: Examples for the calculation of
short-circuit currents
IEC 60909-0 ®
Edition 2.0 2016-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Short-circuit currents in three-phase a.c. systems –
Part 0: Calculation of currents
Courants de court-circuit dans les réseaux triphasés à courant alternatif –
Partie 0: Calcul des courants
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.01; 29.240.20 ISBN 978-2-8322-3158-6
– 2 – IEC 60909-0:2016 © IEC 2016
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 8
3 Terms and definitions . 8
4 Symbols, subscripts and superscripts . 13
4.1 General . 13
4.2 Symbols . 13
4.3 Subscripts . 15
4.4 Superscripts . 16
5 Characteristics of short-circuit currents: calculating method . 16
5.1 General . 16
5.2 Calculation assumptions . 19
5.3 Method of calculation . 20
5.3.1 Equivalent voltage source at the short-circuit location . 20
5.3.2 Symmetrical components . 22
6 Short-circuit impedances of electrical equipment . 23
6.1 General . 23
6.2 Network feeders . 23
6.3 Transformers . 25
6.3.1 Two-winding transformers . 25
6.3.2 Three-winding transformers . 25
6.3.3 Impedance correction factors for two- and three-winding network
transformers . 27
6.4 Overhead lines and cables . 28
6.5 Short-circuit current-limiting reactors . 29
6.6 Synchronous machines . 29
6.6.1 Synchronous generators . 29
6.6.2 Synchronous compensators and motors. 31
6.7 Power station units . 31
6.7.1 Power station units with on-load tap-changer . 31
6.7.2 Power station units without on-load tap-changer . 32
6.8 Wind power station units . 33
6.8.1 General . 33
6.8.2 Wind power station units with asynchronous generator . 33
6.8.3 Wind power station units with doubly fed asynchronous generator . 34
6.9 Power station units with full size converter . 35
6.10 Asynchronous motors . 35
6.11 Static converter fed drives . 36
6.12 Capacitors and non-rotating loads . 36
7 Calculation of initial short-circuit current . 36
7.1 General . 36
7.1.1 Overview . 36
7.1.2 Maximum and minimum short-circuit currents . 41
7.1.3 Contribution of asynchronous motors to the short-circuit current . 42
7.2 Three-phase initial short-circuit current . 43
7.2.1 General . 43
IEC 60909-0:2016 © IEC 2016 – 3 –
7.2.2 Short-circuit currents inside a power station unit with on-load tap-
changer . 44
7.2.3 Short-circuit currents inside a power station unit without on-load tap-
changer . 46
7.3 Line-to-line short circuit . 47
7.4 Line-to-line short circuit with earth connection . 47
7.5 Line-to-earth short circuit . 49
8 Calculation of peak short-circuit current . 49
8.1 Three-phase short circuit . 49
8.1.1 Single-fed and multiple single-fed short circuits . 49
8.1.2 Multiple-fed short circuit . 51
8.2 Line-to-line short circuit . 52
8.3 Line-to-line short circuit with earth connection . 52
8.4 Line-to-earth short circuit . 52
9 Calculation of symmetrical breaking current . 53
9.1 Three-phase short circuit . 53
9.1.1 Symmetrical breaking current of synchronous machines. 53
9.1.2 Symmetrical breaking current of asynchronous machines . 54
9.1.3 Symmetrical breaking current of power station units with doubly fed
asynchronous generator . 55
9.1.4 Symmetrical breaking current of power station units with full size
converter . 55
9.1.5 Symmetrical breaking current of network feeder . 56
9.1.6 Symmetrical breaking current in case of multiple single-fed short-
circuits . 56
9.1.7 Symmetrical breaking current in case of multiple-fed short circuits . 56
9.2 Unbalanced short-circuits . 57
10 DC component of the short-circuit current . 57
11 Calculation of steady-state short-circuit current . 58
11.1 General . 58
11.2 Three-phase short circuit . 58
11.2.1 Steady-state short-circuit current of one synchronous generator or one
power station unit . 58
11.2.2 Steady-state short-circuit current of asynchronous motor or generator. 61
11.2.3 Steady-state short-circuit current of wind power station unit with doubly
fed asynchronous generator . 61
11.2.4 Steady-state short-circuit current of wind power station unit with full size
converter . 61
11.2.5 Steady-state short-circuit current of network feeder . 61
11.2.6 Steady-state short-circuit current in case of multiple single-fed short
circuits . 61
11.2.7 Steady-state short-circuit current in case of multiple-fed short circuits . 62
11.3 Unbalanced short circuits . 62
12 Short circuits at the low-voltage side of transformers, if one line conductor is
interrupted at the high-voltage side . 62
13 Terminal short circuit of asynchronous motors . 64
14 Joule integral and thermal equivalent short-circuit current. 65
Annex A (normative) Formulas for the calculation of the factors m and n . 68
Annex B (informative) Nodal admittance and nodal impedance matrices . 69
Bibliography . 73
– 4 – IEC 60909-0:2016 © IEC 2016
Figure 1 – Short-circuit current of a far-from-generator short circuit with constant AC
component (schematic diagram) . 17
Figure 2 – Short-circuit current of a near-to-generator short-circuit with decaying AC
component (schematic diagram) . 18
Figure 3 – Characterization of short-circuits and their currents . 19
"
Figure 4 – Illustration for calculating the initial symmetrical short-circuit current in
I
k
compliance with the procedure for the equivalent voltage source . 21
Figure 5 – System diagram and equivalent circuit diagram for network feeders . 24
Figure 6 – Three-winding transformer (example) . 27
Figure 7 – Diagram to determine the short-circuit type (Figure 3) for the highest initial
short-circuit current referred to the initial three-phase short-circuit current when the
impedance angles of the sequence impedances Z , Z , Z are identical . 38
(1) (2) (0)
Figure 8 – Examples of single-fed short-circuits . 40
Figure 9 – Example of a multiple single-fed short circuit . 40
Figure 10 – Example of multiple-fed short circuit . 41
Figure 11 – Short-circuit currents and partial short-circuit currents for three-phase
short circuits between generator and unit transformer with or without on-load tap-
changer, or at the connection to the auxiliary transformer of a power station unit and at
the auxiliary busbar A . 45
Figure 12 – Factor κ for series circuit as a function of ratio R/X or X/R . 50
Figure 13 – Factor µ for calculation of short-circuit breaking current I . 54
b
Figure 14 – Factor q for the calculation of the symmetrical short-circuit breaking
current of asynchronous motors . 55
Figure 15 – Factors λ and λ factors for cylindrical rotor generators . 60
min max
Figure 16 – Factors λ and λ for salient-pole generators . 60
min max
Figure 17 – Transformer secondary short-circuits, if one line (fuse) is opened on the
high-voltage side of a transformer Dyn5 . 63
Figure 18 – Factor m for the heat effect of the DC component of the short-circuit
current (for programming, the formula to calculate m is given in Annex A) . 66
Figure 19 – Factor n for the heat effect of the AC component of the short-circuit current
(for programming, the formula to calculate n is given in Annex A) . 67
Figure B.1 – Formulation of the nodal admittance matrix . 70
Figure B.2 – Example . 71
Table 1 – Voltage factor c . 22
Table 2 – Importance of short-circuit currents . 37
Table 3 – Factors α and β for the calculation of short-circuit currents with Formula
(96), rated transformation ratio t = U /U . 64
r rTHV rTLV
Table 4 – Calculation of short-circuit currents of asynchronous motors in the case of a
short circuit at the terminals . 65
Table B.1 – Impedances of electrical equipment referred to the 110 kV side . 71
IEC 60909-0:2016 © IEC 2016 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SHORT-CIRCUIT CURRENTS IN THREE-PHASE AC SYSTEMS –
Part 0: Calculation of currents
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60909-0 has been prepared by IEC technical committee 73: Short-
circuit currents.
This second edition cancels and replaces the first edition published in 2001. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) contribution of windpower station units to the short-circuit current;
b) contribution of power station units with ful size converters to the short-circuit current;
c) new document structure.
– 6 – IEC 60909-0:2016 © IEC 2016
The text of this standard is based on the following documents:
CDV Report on voting
73/172/CDV 73/175A/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60909 series, published under the general title Short-circuit
currents in three-phase a.c. systems, can be found on the IEC website.
This part of IEC 60909 is to be read in conjunction with the following International Standards
and Technical Reports:
– IEC TR 60909-1:2002, Short-circuit currents in three-phase a.c. systems – Part 1: Factors
for the calculation of short-circuit currents according to IEC 60909-0
– IEC TR 60909-2:2008, Short-circuit currents in three-phase a.c. systems – Part 2: Data of
electrical equipment for short-circuit current calculations
– IEC 60909-3:2009, Short-circuit currents in three-phase a.c. systems – Part 3: Currents
during two separate simultaneous line-to-earth short circuits and partial short-circuit
currents flowing through earth
– IEC TR 60909-4:2000, Short-circuit currents in three-phase a.c. systems – Part 4:
Examples for the calculation of short-circuit currents
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IEC 60909-0:2016 © IEC 2016 – 7 –
SHORT-CIRCUIT CURRENTS IN THREE-PHASE AC SYSTEMS –
Part 0: Calculation of currents
1 Scope
This part of IEC 60909 is applicable to the calculation of short-circuit currents
• in low-voltage three-phase AC systems, and
• in high-voltage three-phase AC systems,
operating at a nominal frequency of 50 Hz or 60 Hz.
Systems at highest voltages of 550 kV and above with long transmission lines need special
consideration.
This part of IEC 60909 establishes a general, practicable and concise procedure leading to
results which are generally of acceptable accuracy. For this calculation method, an equivalent
voltage source at the short-circuit location is introduced. This does not exclude the use of
special methods, for example the superposition method, adjusted to particular circumstances,
if they give at least the same precision. The superposition method gives the short-circuit
current related to the one load flow presupposed. This method, therefore, does not
necessarily lead to the maximum short-circuit current.
This part of IEC 60909 deals with the calculation of short-circuit currents in the case of
balanced or unbalanced short circuits.
A single line-to-earth fault is beyond the scope of this part of IEC 60909.
For currents during two separate simultaneous single-phase line-to-earth short circuits in an
isolated neutral system or a resonance earthed neutral system, see IEC 60909-3.
Short-circuit currents and short-circuit impedances may also be determined by system tests,
by measurement on a network analyser, or with a digital computer. In existing low-voltage
systems it is possible to determine the short-circuit impedance on the basis of measurements
at the location of the prospective short circuit considered.
The calculation of the short-circuit impedance is in general based on the rated data of the
electrical equipment and the topological arrangement of the system and has the advantage of
being possible both for existing systems and for systems at the planning stage.
In general, two types short-circuit currents, which differ in their magnitude, are considered:
• the maximum short-circuit current which determines the capacity or rating of electrical
equipment; and
• the minimum short-circuit current which can be a basis, for example, for the selection of
fuses, for the setting of protective devices, and for checking the run-up of motors.
NOTE The current in a three-phase short circuit is assumed to be made simultaneously in all poles. Investigations
of non-simultaneous short circuits, which may lead to higher aperiodic components of short-circuit current, are
beyond the scope of this part of IEC 60909.
This part of IEC 60909 does not cover short-circuit currents deliberately created under
controlled conditions (short-circuit testing stations).
– 8 – IEC 60909-0:2016 © IEC 2016
This part of IEC 60909 does not deal with the calculation of short-circuit currents in
installations on board ships and aeroplanes.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60038:2009, IEC standard voltages
IEC 60050-131, International Electrotechnical Vocabulary – Part 131: Circuit theory (available
at: www.electropedia.org)
IEC TR 60909-1:2002, Short-circuit currents in three-phase a.c. systems – Part 1: Factors for
the calculation of short-circuit currents according to IEC 60909-0
IEC TR 60909-2:2008, Short-circuit currents in three-phase a.c. systems – Data of electrical
equipment for short-circuit current calculations
IEC 60909-3:2009, Short-circuit currents in three-phase a.c. systems – Part 3: Currents
during two separate simultaneous line-to-earth short circuits and partial short-circuit currents
flowing through earth
IEC TR 60909-4:2000, Short-circuit currents in three-phase a.c. systems – Part 4: Examples
for the calculation of short-circuit currents
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-131 and the
following apply.
3.1
short circuit
accidental or intentional conductive path between two or more conductive parts (e.g. three-
phase short circuit) forcing the electric potential differences between these conductive parts
to be equal or close to zero
3.1.1
line-to-line short circuit
two-phase short circuit
accidental or intentional conductive path between two line conductors with or without earth
connection
3.1.2
line-to-earth short circuit
single-phase short circuit
accidental or intentional conductive path in a solidly earthed neutral system or an impedance
earthed neutral system between a line conductor and local earth
3.2
short-circuit current
over-current resulting from a short circuit in an electric system
IEC 60909-0:2016 © IEC 2016 – 9 –
Note 1 to entry: It is necessary to distinguish between the short-circuit current at the short-circuit location and
partial short-circuit currents in the network branches (see Figure 3) at any point of the network.
3.3
prospective short-circuit current
current that would flow if the short circuit were replaced by an ideal connection of negligible
impedance without any change of the supply
Note 1 to entry: The current in a three-phase short circuit is assumed to be made simultaneously in all poles.
Investigations of non-simultaneous short circuits, which may lead to higher aperiodic components of short-circuit
current, are beyond the scope of this part of IEC 60909.
3.4
symmetrical short-circuit current
rms value of the AC symmetrical component of a prospective short-circuit current (see 3.3),
the aperiodic component of current, if any, being neglected
3.5
initial symmetrical short-circuit current
"
I
k
rms value of the AC symmetrical component of a prospective short-circuit current (see 3.3),
applicable at the instant of short circuit if the impedance remains at zero-time value
SEE: Figures 1 and 2
3.6
initial symmetrical short-circuit power
"
S
k
"
fictitious value determined as a product of the initial symmetrical short-circuit current I (see
k
" "
3.5), the nominal system voltage U (see 3.13) and the factor 3 : S = 3 ⋅U ⋅ I
k n k
n
"
Note 1 to entry: The initial symmetrical short-circuit power S is not used for the calculation procedure in this part
k
"
of IEC 60909. If S is used in spite of this in connection with short-circuit calculations, for instance to calculate the
k
internal impedance of a network feeder at the connection point Q, then the definition given should be used in the
" " 2 "
following form: S = 3 ⋅U ⋅ I or Z = c ⋅U / S .
kQ nQ kQ Q kQ
nQ
3.7
decaying (aperiodic) component of short-circuit current or DC component
i
DC
mean value between the top and bottom envelope of a short-circuit current decaying from an
initial value to zero according to Figures 1 and 2
3.8
peak short-circuit current
i
p
maximum possible instantaneous value of the prospective short-circuit current
SEE: Figures 1 and 2
Note 1 to entry: Sequential short circuits are not considered.
3.9
symmetrical short-circuit breaking current
I
b
rms value of an integral cycle of the symmetrical AC component of the prospective short-
circuit current at the instant of contact separation of the first pole to open of a switching
device
– 10 – IEC 60909-0:2016 © IEC 2016
3.10
steady-state short-circuit current
I
k
rms value of the short-circuit current which remains after the decay of the transient
phenomena
SEE: Figures 1 and 2
3.11
symmetrical locked-rotor current
I
LR
symmetrical rms current of an asynchronous motor with locked rotor fed with rated voltage
U at rated frequency
rM
3.12
equivalent electric circuit
model to describe the behaviour of a circuit by means of a network of ideal elements
3.13
nominal system voltage
U
n
voltage (line-to-line) by which a system is designated, and to which certain operating
characteristics are referred
Note 1 to entry: Values are given in IEC 60038.
3.14
equivalent voltage source
cU / 3
n
voltage of an ideal source applied at the short-circuit location for calculating the short-circuit
current according to 5.3.1
Note 1 to entry: This is the only active voltage of the network.
3.15
voltage factor
c
ratio between the equivalent voltage source and the nominal system voltage U divided by
n
Note 1 to entry: The values are given in Table 1.
Note 2 to entry: The introduction of a voltage factor c is necessary for various reasons. These are:
– voltage variations depending on time and place,
– changing of transformer taps,
– neglecting loads and capacitances by calculations according to 5.2,
– the subtransient behaviour of generators and motors.
3.16
far-from-generator short circuit
short circuit during which the magnitude of the symmetrical AC component of the prospective
short-circuit current remains essentially constant
SEE: Figure 1
3.17
near-to-generator short circuit
short circuit during which the magnitude of the symmetrical AC component of the prospective
short-circuit current decreases
IEC 60909-0:2016 © IEC 2016 – 11 –
SEE: Figure 2
Note 1 to entry: A near-to-generator short circuit can be assumed if at least one synchronous machine contributes
a prospective initial symmetrical short-circuit current which is more than twice the machine's rated current, or a
short circuit to which asynchronous motors contribute more than 5 % of the initial symmetrical short-circuit current
without motors.
3.18
short-circuit impedances at the short-circuit location F
3.18.1
positive-sequence short-circuit impedance
Z
(1)
impedance of the positive-sequence system as viewed from the
short-circuit location
Note 1 to entry: See 5.3.2.
3.18.2
short-circuit impedance
Z
k
abbreviated expression for the positive-sequence short-circuit
impedance Z according to 3.18.1 for the calculation of three-phase short-circuit currents
(1)
3.18.3
negative-sequence short-circuit impedance
Z
(2)
impedance of the negative-sequence system as viewed from the
short-circuit location
Note 1 to entry: See 5.3.2.
3.18.4
zero-sequence short-circuit impedance
Z
(0)
impedance of the zero-sequence system as viewed from the short-
circuit location (see 5.3.2)
Note 1 to entry: It includes three times the neutral-to-earth impedance Z .
N
3.19
short-circuit impedances of electrical equipment
3.19.1
positive-sequence short-circuit impedance
Z
(1)
ratio of the line-to-neutral voltage to the short-circuit current of the
corresponding line conductor of electrical equipment when fed by a symmetrical positive-
sequence system of voltages
Note 1 to entry: See Clause 6 and IEC TR 60909-4.
Note 2 to entry: The index of symbol Z may be omitted if there is no possibility of confusion with the negative-
(1)
sequence and the zero-sequence short-circuit impedances.
3.19.2
negative-sequence short-circuit impedance
Z
(2)
ratio of the line-to-neutral voltage to the short-circuit current of the
corresponding line conductor of electrical equipment when fed by a symmetrical negative-
sequence system of voltages
Note 1 to entry: See Clause 6 and IEC TR 60909-4.
– 12 – IEC 60909-0:2016 © IEC 2016
3.19.3
zero-sequence short-circuit impedance
Z
(0)
ratio of the line-to-earth voltage to the short-circuit current of one line
conductor of electrical equipment when fed by an AC voltage source, if the three paralleled
line conductors are used for the outgoing current and a fourth line and/or earth as a joint
return
Note 1 to entry: See Clause 6 and IEC TR 60909-4.
3.20
subtransient reactance
"
X
d
effective reactance of a synchronous machine at the moment of short circuit
"
Note 1 to entry: For the calculation of short-circuit currents the saturated value of X is taken.
d
3.21
minimum time delay
t
min
shortest time between the beginning of the short-circuit current and the contact separation of
the first pole to open of the switching device
Note 1 to entry: The time t is the sum of the shortest possible operating time of a protective relay and the
min
shortest opening time of a circuit-breaker. It does not take into account adjustable time delays of tripping devices.
3.22
thermal equivalent short-circuit current
I
th
the rms value of a current having the same thermal effect and the same duration as the actual
short-circuit current, which may contain a DC component and may subside in time
3.23
maximum short-circuit current
i
kWDmax
instantaneous maximum short-circuit current of a wind
power station unit with doubly fed asynchronous generator in case of a three-phase short-
circuit at the high-voltage side of the unit transformer
3.24
maximum short-circuit current
I
kPFmax
maximum steady state current of a power station unit with full size
converter in case of a three-phase short-circuit at the high-voltage side of the unit transformer
3.25
maximum source current
I
skPF
rms value of the maximum source current of a power station
unit with full size converter and current regulation in case of three-phase short circuit at the
high-voltage side of the unit transformer
3.26
maximum source current
I
(1)sk2PF
rms value of the maximum source current (positive-sequence
system) of a power station unit with full size converter and current regulation in case of a line-
to-line short circuit or a line-to-line short circuit with earth connection at the high-voltage side
of the unit transformer
IEC 60909-0:2016 © IEC 2016 – 13 –
3.27
maximum source current
I
(1)sk1PF
rms value of the maximum source current (positive-
sequence system) of a power station unit with full size converter and current regulation in
case of a line-to-earth short-circuit at the high-voltage side of the unit transformer
3.28
impedance of the nodal impedances matrix
Z , Z , Z
(1)ii (2)ii (0)ii
diagonal elements of the positive-sequence, or negative-sequence or zero-
sequence nodal impedance matrix for the short-circuit location i
Note 1 to entry: See Annex B.
3.29
impedance of the nodal impedances matrix
Z
(1)ij
elements of the positive-sequence nodal impedance matrix, where i is
the node of the short circuit and j the node where the high-voltage side of a power station unit
with full size converter is connected
Note 1 to entry: See Annex B.
4 Symbols, subscripts and superscripts
4.1 General
The formulas given in this standard are written without specifying units. The symbols
represent physical quantities possessing both numerical values and dimensions that are
independent of units, provided a consistent unit system is chosen, for example the
international system of units (SI). Symbols of complex quantities are underlined, for example
Z = R + jX.
4.2 Symbols
A Initial value of the DC component i
DC
a Complex operator
a Ratio between unbalanced short-circuit current and three-phase
short-circuit current
c Voltage factor
U / 3 Equivalent voltage source (rms)
n
f Frequency (50 Hz or 60 Hz)
I Symmetrical short-circuit breaking current (rms)
b
I Steady-state short-circuit current (rms)
k
I Steady-state short-circuit current at the terminals (poles) of a generator
kP
with compound excitation
"
I Initial symmetrical short-circuit current (rms)
k
I Symmetrical locked-rotor current of an asynchronous generator or motor
LR
I Rated current of electrical equipment
r
I Thermal equivalent short-circuit current
th
i DC component of short-circuit current
DC
i Peak short-circuit current
p
– 14 – IEC 60909-0:2016 © IEC 2016
K Correction factor for impedances
m Factor for the heat effect of the DC component
n Factor for the heat effect of th
...
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