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.
This publication is to be read in conjunction with IEC TR 60909-1:2002, IEC TR 60909-2:2008, IEC 60909-3:2009 and IEC TR 60909-4:2000.

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.
Cette publication doit être lue conjointement avec l' IEC TR 60909-1:2002, l'IEC TR 60909-2:2008, l'IEC 60909-3:2009 et l'IEC TR 60909-4:2000.

General Information

Status
Published
Publication Date
27-Jan-2016
Technical Committee
Current Stage
PPUB - Publication issued
Start Date
28-Jan-2016
Completion Date
28-Jan-2016
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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
IEC 60909-0:2016-01(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
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

---------------------- Page: 5 ----------------------
– 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

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

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

---------------------- Page: 6 ----------------------
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

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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.
---------------------- Page: 7 ----------------------
– 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.
---------------------- Page: 8 ----------------------
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

equipme
...

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