SIST EN 60909-3:2010

SLOVENSKI STANDARD
SIST EN 60909-3:2010
01-junij-2010
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SIST EN 60909-3:2004
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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 60909-3:2009)
Kurzschlussströme in Drehstromnetzen - Teil 3: Ströme bei Doppelerdkurzschluss und
Teilkurzschlussströme über Erde (IEC 60909-3:2009)
Courants de court-circuit dans les réseaux triphasés à courant alternatif - Partie 3:
Courants durant deux court-circuits monophasés simultanés séparés à la terre et
courants de court-circuit partiels s'écoulant à travers la terre (CEI 60909-3:2009)
Ta slovenski standard je istoveten z: EN 60909-3:2010
ICS:
17.220.01 Elektrika. Magnetizem. Electricity. Magnetism.
Splošni vidiki General aspects
29.240.20 Daljnovodi Power transmission and
distribution lines
SIST EN 60909-3:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60909-3:2010

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SIST EN 60909-3:2010

EUROPEAN STANDARD
EN 60909-3

NORME EUROPÉENNE
March 2010
EUROPÄISCHE NORM

ICS 17.220.01; 29.240.20 Supersedes EN 60909-3:2003


English version


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 60909-3:2009)


Courants de court-circuit dans les réseaux Kurzschlussströme in Drehstromnetzen -
triphasés à courant alternatif - Teil 3: Ströme bei Doppelerdkurzschluss
Partie 3: Courants durant deux und Teilkurzschlussströme über Erde
courts-circuits monophasés simultanés (IEC 60909-3:2009)
séparés à la terre et courants
de court-circuit partiels s'écoulant
à travers la terre
(CEI 60909-3:2009)




This European Standard was approved by CENELEC on 2010-03-01. 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 Central Secretariat 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 Central Secretariat 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60909-3:2010 E

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SIST EN 60909-3:2010
EN 60909-3:2010 - 2 -
Foreword
The text of document 73/148/FDIS, future edition 3 of IEC 60909-3, prepared by IEC TC 73, Short-circuit
currents, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60909-3 on 2010-03-01.
This standard is to be used in conjunction with EN 60909-0:2001.
This European Standard supersedes EN 60909-3:2003.
The main changes with respect to EN 60909-3:2003 are listed below:
– New procedures are introduced for the calculation of reduction factors of the sheaths or shields and in
addition the current distribution through earth and the sheaths or shields of three-core cables or of
three single-core cables with metallic non-magnetic sheaths or shields earthed at both ends;
– The information for the calculation of the reduction factor of overhead lines with earth wires are
corrected and given in the new Clause 7;
– A new Clause 8 is introduced for the calculation of current distribution and reduction factor of three-
core cables with metallic sheath or shield earthed at both ends;
– The new Annexes C and D provide examples for the calculation of reduction factors and current
distribution in case of cables with metallic sheath and shield earthed at both ends.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2010-12-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2013-03-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60909-3:2009 was approved by CENELEC as a European
Standard without any modification.
__________

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SIST EN 60909-3:2010
- 3 - EN 60909-3:2010
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60909-0 2001 Short-circuit currents in three-phase a.c. EN 60909-0 2001
systems -
Part 0: Calculation of currents


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

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SIST EN 60909-3:2010

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SIST EN 60909-3:2010
IEC 60909-3
®
Edition 3.0 2009-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Short-circuit currents in three-phase AC systems –
Part 3: Currents during two separate simultaneous line-to-earth short circuits
and partial short-circuit currents flowing through earth

Courants de court-circuit dans les réseaux triphasés à courant alternatif –
Partie 3: Courants durant deux courts-circuits monophasés simultanés séparés
à la terre et courants de court-circuit partiels s'écoulant à travers la terre

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XA
CODE PRIX
ICS 17.220.01; 29.240.20 ISBN 2-8318-1027-8
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 60909-3:2010
– 2 – 60909-3 © IEC:2009
CONTENTS
FOREWORD.5
1 Scope and object.7
2 Normative references .8
3 Terms and definitions .8
4 Symbols .10
5 Calculation of currents during two separate simultaneous line-to-earth short
circuits .12
5.1 Initial symmetrical short-circuit current .12
5.1.1 Determination of M and M .12
(1) (2)
5.1.2 Simple cases of two separate simultaneous line-to-earth short
circuits.13
5.2 Peak short-circuit current, symmetrical short circuit breaking current and
steady-state short-circuit current .13
5.3 Distribution of the currents during two separate simultaneous line-to-earth
short circuits.14
6 Calculation of partial short-circuit currents flowing through earth in case of an
unbalanced short circuit.14
6.1 General .14
6.2 Line-to-earth short circuit inside a station .15
6.3 Line-to-earth short circuit outside a station.16
6.4 Line-to-earth short circuit in the vicinity of a station.18
6.4.1 Earth potential U at the tower n outside station B .19
ETn
6.4.2 Earth potential of station B during a line-to earth short circuit at the
tower n .19
7 Reduction factor for overhead lines with earth wires .20
8 Calculation of current distribution and reduction factor in case of cables with
metallic sheath or shield earthed at both ends.21
8.1 Overview .21
8.2 Three-core cable .22
8.2.1 Line-to-earth short circuit in station B .22
8.2.2 Line-to-earth short circuit on the cable between station A and
station B .23
8.3 Three single-core cables .26
8.3.1 Line-to-earth short circuit in station B .26
8.3.2 Line-to-earth short circuit on the cable between station A and
station B .26
Annex A (informative) Example for the calculation of two separate simultaneous line-
to-earth short-circuit currents.30
Annex B (informative) Examples for the calculation of partial short-circuit currents
through earth .33
Annex C (informative) Example for the calculation of the reduction factor r and the
1
current distribution through earth in case of a three-core cable .43
Annex D (informative) Example for the calculation of the reduction factor r and the
3
current distribution through earth in case of three single-core cables .48

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SIST EN 60909-3:2010
60909-3 © IEC:2009 – 3 –
Figure 1 – Driving point impedance Z of an infinite chain, composed of the earth wire
P
'
impedance Z =Zd and the footing resistance R of the towers, with equal
T
QQ T
distances d between the towers.9
T
Figure 2 – Driving point impedance Z of a finite chain with n towers, composed of the
Pn
'
earth wire impedance Z =Z d , the footing resistance R of the towers, with equal
T
Q Q T
distances d between the towers and the earthing impedance Z of station B from
T EB
Equation (29) .10
Figure 3 – Characterisation of two separate simultaneous line-to earth short circuits
"
and the currents I .12
kEE
Figure 4 – Partial short-circuit currents in case of a line-to-earth short circuit inside
15
station B .
Figure 5 – Partial short-circuit currents in case of a line-to-earth short circuit at a
tower T of an overhead line .16
Figure 6 – Distribution of the total current to earth I .17
ETtot
Figure 7 – Partial short–circuit currents in the case of a line-to-earth short circuit at a
tower n of an overhead line in the vicinity of station B .18
Figure 8 – Reduction factor r for overhead lines with non-magnetic earth wires
depending on soil resistivity ρ .21
Figure 9 – Reduction factor of three-core power cables .23
Figure 10 – Reduction factors for three single-core power cables .27
Figure A.1 – Two separate simultaneous line-to-earth short circuits on a single fed
overhead line (see Table 1) .30
Figure B.1 – Line-to-earth short circuit inside station B – System diagram for stations
A, B and C .34
Figure B.2 – Line-to-earth short circuit inside station B – Positive-, negative- and zero-
sequence systems with connections at the short-circuit location F within station B.34
Figure B.3 – Line-to-earth short circuit outside stations B and C at the tower T of an
overhead line – System diagram for stations A, B and C .36
Figure B.4 – Line-to-earth short circuit outside stations B and C at the tower T of an
overhead line – Positive-, negative- and zero-sequence systems with connections at
the short-circuit location F.37
Figure B.5 – Earth potentials u = U /U with U = 1,912 kV and u = U /U
ETn Etn ET ET EBn Ebn EB
with U = 0,972 kV, if the line-to-earth short circuit occurs at the towers n = 1, 2, 3, .
EB
in the vicinity of station B .42
Figure C.1 – Example for the calculation of the cable reduction factor and the current
distribution through earth in a 10-kV-network, U = 10 kV; c = 1,1; f = 50 Hz .44
n
Figure C.2 – Short-circuit currents and partial short-circuit currents through earth for
the example in Figure C.1.45
Figure C.3 – Example for the calculation of current distribution in a 10-kV-network with
a short circuit on the cable between A and B (data given in C.2.1 and Figure C.1).46
Figure C.4 – Line-to-earth short-circuit currents, partial currents in the shield and
partial currents through earth.47
Figure D.1 – Example for the calculation of the reduction factor and the current
distribution in case of three single-core cables and a line-to-earth short circuit in
station B .49
Figure D.2 – Positive-, negative- and zero-sequence system of the network in Figure
D.1 with connections at the short-circuit location (station B) .50
Figure D.3 – Current distribution for the network in Figure D.1, depending on the
length, ℓ, of the single-core cables between the stations A and B.51

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SIST EN 60909-3:2010
– 4 – 60909-3 © IEC:2009
r and the current
Figure D.4 – Example for the calculation of the reduction factors
3
distribution in case of three single-core cables and a line-to-earth short circuit
between the stations A and B .52
Figure D.5 – Positive-, negative- and zero-sequence system of the network in Figure D.4
with connections at the short-circuit location (anywhere between the stations A and B) .52
Figure D.6 – Current distribution for the cable in Figure D.4 depending on ℓ , R →∞ .54
A EF
Figure D.7 – Current distribution for the cable in Figure D.4 depending on ℓ , R = 5 Ω .56
A EF

Table 1 – Calculation of initial line-to-earth short-circuit currents in simple cases .13
Table 2 – Resistivity of the soil and equivalent earth penetration depth .20
Table C.1 – Results for the example in Figure C.1 .45
Table C.2 – Results for the example in Figure C.3, l = 5 km .47
Table C.3 – Results for the example in Figure C.3, l = 10 km .47

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SIST EN 60909-3:2010
60909-3 © IEC:2009 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________

SHORT-CIRCUIT CURRENTS IN THREE-PHASE AC SYSTEMS –

Part 3: Currents during two separate simultaneous
line-to-earth short circuits and partial short-circuit
currents flowing through earth


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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60909-3 has been prepared by IEC technical committee 73: Short-
circuit currents.
This International Standard is to be read in conjunction with IEC 60909-0.
This third edition cancels and replaces the second edition published in 2003. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are listed below:
– New procedures are introduced for the calculation of reduction factors of the sheaths
or shields and in addition the current distribution through earth and the sheaths or
shields of three-core cables or of three single-core cables with metallic non-magnetic
sheaths or shields earthed at both ends;
– The information for the calculation of the reduction factor of overhead lines with earth
wires are corrected and given in the new Clause 7;

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SIST EN 60909-3:2010
– 6 – 60909-3 © IEC:2009
– A new Clause 8 is introduced for the calculation of current distribution and reduction
factor of three-core cables with metallic sheath or shield earthed at both ends;
– The new Annexes C and D provide examples for the calculation of reduction factors
and current distribution in case of cables with metallic sheath and shield earthed at
both ends.
The text of this standard is based on the following documents:
FDIS Report on voting
73/148/FDIS 73/149/RVD

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 of 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.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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.

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SIST EN 60909-3:2010
60909-3 © IEC:2009 – 7 –
SHORT-CIRCUIT CURRENTS IN THREE-PHASE AC SYSTEMS –

Part 3: Currents during two separate simultaneous
line-to-earth short circuits and partial short-circuit
currents flowing through earth



1 Scope and object
This part of IEC 60909 specifies procedures for calculation of the prospective short-circuit
currents with an unbalanced short circuit in high-voltage three-phase a.c. systems operating
at nominal frequency 50 Hz or 60 Hz, i. e.:
a) currents during two separate simultaneous line-to-earth short circuits in isolated neutral or
resonant earthed neutral systems;
b) partial short-circuit currents flowing through earth in case of single line-to-earth short
circuit in solidly earthed or low-impedance earthed neutral systems.
The currents calculated by these procedures are used when determining induced voltages or
touch or step voltages and rise of earth potential at a station (power station or substation) and
the towers of overhead lines.
Procedures are given for the calculation of reduction factors of overhead lines with one or two
earth wires.
The standard does not cover:
a) short-circuit currents deliberately created under controlled conditions as in short circuit
testing stations, or
b) short-circuit currents in the electrical installations on board ships or aeroplanes, or
c) single line-to-earth fault currents in isolated or resonant earthed systems.
The object of this standard is to establish practical and concise procedures for the calculation
of line-to-earth short-circuit currents during two separate simultaneous line-to-earth short
circuits and partial short-circuit currents through earth, earth wires of overhead lines and
sheaths or shields of cables leading to conservative results with sufficient accuracy. For this
purpose, the short-circuit currents are determined by considering an equivalent voltage
source at the short-circuit location with all other voltage sources set to zero. Resistances of
earth grids in stations or footing resistances of overhead line towers are neglected, when
calculating the short-circuit currents at the short-circuit location.
This standard is an addition to IEC 60909-0. General definitions, symbols and calculation
assumptions refer to that publication. Special items only are defined or specified in this
standard.
The calculation of the short-circuit currents based on the rated data of the electrical
equipment and the topological arrangement of the system has the advantage of being
possible both for existing systems and for systems at the planning stage. The procedure is
suitable for determination by manual methods or digital computation. This does not exclude
the use of special methods, for example the super-position method, adjusted to particular
circumstances, if they give at least the same precision.
As stated in IEC 60909-0, short-circuit currents and their parameters may also be determined
by system tests.

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SIST EN 60909-3:2010
– 8 – 60909-3 © IEC:2009
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60909-0:2001, Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of
currents
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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
two separate simultaneous line-to earth short circuits
line-to-earth short circuits at different locations at the same time on different conductors of a
three-phase a.c. network having a resonant earthed or an isolated neutral
3.2
initial short-circuit currents during two separate simultaneous line-to-earth
"
short circuits I
kEE
r.m.s value of the initial short-circuit currents flowing at both short-circuit locations with the
same magnitude
3.3
partial short-circuit current through earth I
Eδ
r.m.s. value of the current flowing through earth in a fictive line in the equivalent earth
penetration depth δ
NOTE In case of overhead lines remote from the short-circuit location and the earthing system of a station, where
the distribution of the current between earthed conductors and earth is nearly constant, the current through earth
depends on the reduction factor of the overhead line (Figures 4 and 5). In case of cables with metallic sheaths or
shields, earthed at both ends in the stations A and B, current through earth between the stations A and B (Figures
9a) and 10a)), respectively between the short-circuit location and the stations A or B (Figures 9b) and 10b)).
3.4
total current to earth I at the short-circuit location on the tower T of an overhead
ETtot
line
r. m. s. value of the current flowing to earth through the footing res
...