IEC TR 60909-4:2021
(Main)Short-circuit currents in three-phase AC systems - Part 4: Examples for the calculation of short-circuit currents
Short-circuit currents in three-phase AC systems - Part 4: Examples for the calculation of short-circuit currents
IEC TR 60909-4:2021 which is a Technical Report, is intended to give help for the application of IEC 60909-0 for the calculation of short-circuit currents in 50 Hz or 60 Hz three-phase AC systems.
This document does not include additional requirements but gives support for the modelling of electrical equipment in the positive-sequence, the negative-sequence and the zero-sequence system (Clause 4), the practical execution of calculations in a low-voltage system (Clause 5), a medium-voltage system with asynchronous motors (Clause 6) and a power station unit with its auxiliary network feeding a large number of medium-voltage asynchronous motors and low-voltage motor groups (Clause 7).
The three examples given in Clauses 5, 6 and 7 are similar to those given in IEC TR 60909-4:2000 but they are revised in accordance with IEC 60909-0, which replaces it. The example given in Clause 8 is new and mirrors the introduction of the new 6.8 of IEC 60909-0:2016.
Clause 9 gives the circuit diagram and the data of a test network and the results for a calculation carried out in accordance with IEC 60909-0, to offer the possibility for a comparison between the results found with a digital program for the calculation of short-circuit currents and the given results for and in a high-voltage network with power station units, generators, asynchronous motors and lines in four different voltage levels 380 kV, 110 kV, 30 kV and 10 kV.
This second edition cancels and replaces the first edition published in 2000. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) adaption to IEC 60909-0:2016;
b) addition of an example for the calculation of short-circuit currents of wind power station units;
c) correction of errors.
General Information
Relations
Standards Content (Sample)
IEC TR 60909-4 ®
Edition 2.0 2021-06
TECHNICAL
REPORT
colour
inside
Short-circuit currents in three-phase AC systems –
Part 4: Examples for the calculation of short-circuit currents
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC TR 60909-4 ®
Edition 2.0 2021-06
TECHNICAL
REPORT
colour
inside
Short-circuit currents in three-phase AC systems –
Part 4: Examples for the calculation of short-circuit currents
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.01; 29.240.20 ISBN 978-2-8322-9932-6
– 2 – IEC TR 60909-4:2021 © IEC 2021
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions, symbols and indices, and formulae . 8
4 Positive-sequence, negative-sequence and zero-sequence impedances of
electrical equipment . 9
4.1 General . 9
4.2 Overhead lines, cables and short-circuit current-limiting reactors . 9
4.3 Transformers . 10
4.3.1 General . 10
4.3.2 Example . 15
4.4 Generators and power station units . 17
4.4.1 General . 17
4.4.2 Example . 20
5 Calculation of short-circuit currents in a low-voltage system U = 400 V . 22
n
5.1 Problem . 22
5.2 Determination of the positive-sequence impedances . 22
5.2.1 Network feeder . 22
5.2.2 Transformers . 23
5.2.3 Lines (cables and overhead lines) . 24
5.3 Determination of the zero-sequence impedances . 24
5.3.1 Transformers . 24
5.3.2 Lines (cables and overhead lines) . 25
"
5.4 Calculation of I and i for three-phase short circuits . 25
k p
5.4.1 Short-circuit location F1 . 25
5.4.2 Short-circuit location F2 . 27
5.4.3 Short-circuit location F3 . 28
"
5.5 Calculation of I and i for line-to-earth short circuits . 28
k1 p1
5.5.1 Short-circuit location F1 . 28
5.5.2 Short-circuit location F2 . 29
5.5.3 Short-circuit location F3 . 29
5.6 Collection of results . 30
6 Calculation of three-phase short-circuit currents in a medium-voltage system –
Influence of asynchronous motors . 31
6.1 Problem . 31
6.2 Complex calculation with absolute quantities . 31
6.3 Calculation with per-unit quantities . 35
6.4 Calculation with the superposition method . 37
7 Calculation of three-phase short-circuit currents for a power station unit and the
auxiliary network. 40
7.1 Problem . 40
7.2 Short-circuit impedances of electrical equipment. 43
7.2.1 Network feeder . 43
7.2.2 Power station unit . 43
7.2.3 Auxiliary transformers . 44
7.2.4 Low-voltage transformers 2,5 MVA and 1,6 MVA . 45
7.2.5 Asynchronous motors . 49
7.3 Calculation of short-circuit currents . 49
7.3.1 Short-circuit location F1 . 49
7.3.2 Short-circuit location F2 . 50
7.3.3 Short-circuit location F3 . 51
7.3.4 Short-circuit location F4 . 55
7.3.5 Short-circuit location F5 . 57
8 Calculation of three-phase short-circuit currents in a wind power plant . 59
8.1 General . 59
8.2 Problem . 59
8.3 Data and short-circuit impedances of electrical equipment . 60
8.4 Nodal admittance and nodal impedance matrices . 62
8.5 Short-circuit currents for the wind power plant with ten wind power station
units WD . 63
8.6 Short-circuit currents for the wind power plant with ten wind power station
units WF . 65
8.7 Short-circuit currents for the wind power plant with five wind power station
units WD and five wind power station units WF . 68
9 Test network for the calculation of short-circuit currents with digital programs in
accordance with IEC 60909-0 . 72
9.1 General . 72
9.2 High-voltage test network 380 kV/110 kV/30 kV/10 kV . 73
9.2.1 Network topology and data . 73
9.2.2 Short-circuit impedances of electrical equipment . 76
9.3 Results . 77
9.3.1 General . 77
9.3.2 Three-phase short-circuit currents . 78
9.3.3 Line-to-earth short-circuit currents . 78
Bibliography . 80
Figure 1 – Positive-sequence and zero-sequence impedances of an overhead line
(one circuit) and cable (cross-bonded) . 9
Figure 2 – Positive-sequence and zero-sequence impedance of a short-circuit current-
limiting reactor . 10
Figure 3 – Positive-sequence and zero-sequence system impedances of a two-
winding transformer YNd5 . 11
Figure 4 – Equivalent circuits of a three-winding network transformer . 15
Figure 5 – Short circuit at the high-voltage side of a power station unit with on-load
tap changer . 19
Figure 6 – Low-voltage system Un = 400 V with short-circuit locations F1, F2, F3 . 22
"
Figure 7 – Positive-sequence system (according to Figure 6) for the calculation of I
k
at the short-circuit location F1 . 26
Figure 8 – Positive-sequence, negative-sequence and zero-sequence system with
"
connections at the short-circuit location F1 for the calculation of I . 29
k1
Figure 9 – Medium-voltage network 33 kV/6 kV: data . 32
– 4 – IEC TR 60909-4:2021 © IEC 2021
"
Figure 10 – Short-circuit current I calculated by the superposition method (S)
k(T1,T2)S
"
compared with I calculated by the IEC method of equivalent voltage source
k(T1,T2)IEC
b b
at the short-circuit location, depending on the load S and the voltage U . 39
"
Figure 11 – Short-circuit current I calculated by the superposition method (S)
kS
"
compared with I calculated by the IEC method of equivalent voltage source at the
kIEC
short-circuit location, depending on the transformation ratio t before the short circuit . 40
Figure 12 – Power station unit (generator and unit transformer with on-load tap-
changer) and auxiliary network with medium- and low-voltage asynchronous
motors: data . 42
Figure 13 – Positive-sequence system for the calculation of the short-circuit currents
at the location F3 (see Figure 12) . 52
Figure 14 – Positive-sequence system for the calculation of the short-circuit currents
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.