SIST EN 60027-7:2010

Letter symbols to be used in electrical technology - Part 7: Power generation, transmission and distribution (IEC 60027-7:2010)

This part of IEC 60027 is applicable to generation, transmission, and distribution of electric energy. It gives names and letter symbols for quantities and units. In addition, rules for multiple subscripts and their succession are given. This part of IEC 60027 is an addition to IEC 60027-1. Therefore letter symbols already given in IEC 60027-1 are repeated only if they have a special meaning in the field of power generation, transmission, and distribution or if they are used in this field with special subscripts. Guidance on the use of capital and lower case letters, is given in IEC 60027-1, 2.1, and guidance on the representation of complex quantities,is given in IEC 60027-1, 1.6. Therefore in many cases only U is given instead of U, U =U or u.

Formelzeichen für die Elektrotechnik - Teil 7: Energieerzeugung, -übertragung und -verteilung (IEC 60027-7:2010)

Symboles littéraux à utiliser en électrotechnique - Partie 7: Production, transport et distribution de l’énergie électrique (CEI 60027-7:2010)

La CEI 60027-7:2010 s'applique à la production, au transport et à la distribution de l'énergie électrique. Elle donne les noms et les symboles littéraux des grandeurs et unités. Elle fixe en outre des règles concernant les indices multiples et leur succession. Elle est une extension de la CEI 60027-1. Les symboles littéraux figurant déjà dans la CEI 60027-1 ne sont donc répétés que s'ils ont une signification particulière dans le domaine de la production, du transport et de la distribution de l'énergie électrique ou s'ils sont utilisés avec des indices particuliers dans ce domaine.

Črkovne oznake za elektrotehniko - 7. del: Proizvodnja, prenos in distribucija električne energije (IEC 60027-7:2010)

Ta del IEC 60027 velja za proizvodnjo, prenos in distribucijo električne energije. Podaja imena in črkovne oznake za količine in enote. Poleg tega podaja pravila v primeru več podpisanega besedila in njihovo zaporedje. Ta del IEC 60027 je dodatek k IEC 60027-1. Zato so črkovne oznake, ki so že podane v IEC 60027-1, ponovljene samo, če imajo poseben pomen na področju proizvodnje, prenosa in distribucije električne energije ali če se na tem področju uporabljajo s posebnim podpisanim besedilom. Navodila glede uporabe velikih in malih črk so podana v IEC 60027-1, 2.1, in navodila glede predstavitve kompleksnih količin so podana v IEC 60027-1, 1.6. Zato je v številnih primerih podan samo U namesto U, U = U ali u.

General Information

• Status: Published
• Publication Date: 20-Oct-2010
• ICS: 01.075 - Character symbols
• ICS: 29.240.01 - Power transmission and distribution networks in general
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 05-Oct-2010
• Due Date: 10-Dec-2010
• Completion Date: 21-Oct-2010
• Ref Project: EN 60027-7:2010 - Letter symbols to be used in electrical technology - Part 7: Power generation, transmission and distribution

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60027-7:2010
01-december-2010
ýUNRYQHR]QDNH]DHOHNWURWHKQLNRGHO3URL]YRGQMDSUHQRVLQGLVWULEXFLMD
HOHNWULþQHHQHUJLMH,(&
Letter symbols to be used in electrical technology - Part 7: Power generation,
transmission and distribution (IEC 60027-7:2010)
Formelzeichen für die Elektrotechnik - Teil 7: Energieerzeugung, -übertragung und -
verteilung (IEC 60027-7:2010)
Symboles littéraux à utiliser en électrotechnique - Partie 7: Production, transport et
distribution de l’énergie électrique (CEI 60027-7:2010)
Ta slovenski standard je istoveten z: EN 60027-7:2010
ICS:
01.075 Simboli za znake Character symbols
29.240.01 2PUHåMD]DSUHQRVLQ Power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks in
QDVSORãQR general
SIST EN 60027-7:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60027-7:2010

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SIST EN 60027-7:2010

EUROPEAN STANDARD
EN 60027-7

NORME EUROPÉENNE
September 2010
EUROPÄISCHE NORM

ICS 01.060


English version


Letter symbols to be used in electrical technology -
Part 7: Power generation, transmission and distribution
(IEC 60027-7:2010)


Symboles littéraux à utiliser  Formelzeichen für die Elektrotechnik -
en électrotechnique - Teil 7: Energieerzeugung, -übertragung
Partie 7: Production, transport und -verteilung
et distribution de l’énergie électrique (IEC 60027-7:2010)
(CEI 60027-7:2010)




This European Standard was approved by CENELEC on 2010-09-01. 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

Management Centre: 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 60027-7:2010 E

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SIST EN 60027-7:2010
EN 60027-7:2010 - 2 -
Foreword
The text of document 25/391/CDV, future edition 1 of IEC 60027-7, prepared by IEC TC 25, Quantities
and units, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60027-7 on 2010-09-01.
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) 2011-06-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2013-09-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60027-7:2010 was approved by CENELEC as a European
Standard without any modification.
__________

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SIST EN 60027-7:2010
- 3 - EN 60027-7:2010
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 60027-1 1995 Letter symbols to be used in electrical EN 60027-1 2006
+ A1 1997 technology - - -
1)
+ A2 2005 Part 1: General + A2 2007


2)
IEC 60027-2 2005 Letter symbols to be used in electrical EN 60027-2 2007
technology -
Part 2: Telecommunications and electronics


IEC 60038 2009 IEC standard voltages - -


IEC 60050-121 1998 International Electrotechnical Vocabulary - -
+ A1 2002 (IEV) - - -
Part 121: Electromagnetism


IEC 60050-131 2002 International Electrotechnical Vocabulary - -
+ A1 2008 (IEV) - - -
Part 131: Circuit theory


IEC 60050-141 2004 International electrotechnical vocabulary - - -
Part 141: Polyphase systems and circuits


IEC 60050-151 2001 International Electrotechnical Vocabulary - -
(IEV) -
Part 151: Electrical and magnetic devices


IEC 60050-195 1998 International Electrotechnical Vocabulary - -
+ A1 2001 (IEV) - - -
Chapter 195: Earthing and protection against
electric shock


IEC 60050-411 1996 International Electrotechnical Vocabulary - -
+ A1 2007 (IEV) - - -
Chapter 411: Rotating machinery


IEC 60050-421 1990 International electrotechnical vocabulary - -
(IEV) -
Chapter 421: Power transformers and
reactors


IEC 60050-441 1984 International Electrotechnical Vocabulary - -
+ A1 2000 (IEV) - - -
Chapter 441: Switchgear, controlgear and
fuses



1)
EN 60027-1 includes A1 to IEC 60027-1.
2)
EN 60027-2 is superseded by EN 80000-13:2008, which is based on IEC 80000-13:2008.

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SIST EN 60027-7:2010
EN 60027-7:2010 - 4 -
Publication Year Title EN/HD Year

IEC 60050-442 1998 International Electrotechnical Vocabulary - - -
Part 442: Electrical accessories


IEC 60050-448 1995 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 448: Power system protection


IEC 60050-466 1990 International electrotechnical vocabulary - -
(IEV) -
Chapter 466: Overhead lines


IEC 60050-601 1985 International Electrotechnical Vocabulary - -
+ A1 1998 (IEV) - - -
Chapter 601: Generation, transmission and
distribution of electricity - General


IEC 60050-603 1986 International electrotechnical vocabulary - - -
+ A1 1998 Chapter 603: Generation, transmission and - -
distribution of electricity - Power system
planning and management


IEC 60050-604 1987 International Electrotechnical Vocabulary - -
+ A1 1998 (IEV) - - -
Chapter 604: Generation, transmission and
distribution of electricity - Operation


IEC 60050-811 1991 International electrotechnical vocabulary - -
(IEV) -
Chapter 811: Electric traction


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


IEC/TR 60909-1 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


3)
IEC 60909-3 2003 Short-circuit currents in three-phase a.c EN 60909-3 2003
systems -
Part 3: Currents during two separate
simultaneous line-to-earth short-circuits and
partial short-circuit currents flowing through
earth


IEC 62428 2008 Electric power engineering - Modal EN 62428 2008
components in three-phase a.c. systems -
Quantities and transformations


IEC 80000-6 2008 Quantities and units - EN 80000-6 2008
Part 6: Electromagnetism








3)
EN 60909-3 is superseded by EN 60909-3:2010, which is based on IEC 60909-3:2009.

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SIST EN 60027-7:2010
IEC 60027-7
®
Edition 1.0 2010-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Letter symbols to be used in electrical technology –
Part 7: Power generation, transmission, and distribution

Symboles littéraux à utiliser en électrotechnique –
Partie 7: Production, transport et distribution de l’énergie électrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
U
CODE PRIX
ICS 01.060 ISBN 978-2-88910-921-0
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 60027-7:2010
– 2 – 60027-7 © IEC:2010
CONTENTS

FOREWORD.3
1 Scope.5
2 Normative references .5
3 Letter symbols for AC, three-phase AC, and other network quantities.7
4 Letter symbols for space and time .17
5 Letter symbols for numerical values and ratios of quantities .20
6 Subscripts and superscripts.24
6.1 Subscripts for natural quantities and components in three-phase AC systems.24
6.2 Subscripts for operating conditions.25
6.3 Subscripts for electrical equipment.25
6.4 Subscripts for locations, reference points, and fault locations.27
6.5 Superscripts .28
6.6 Multiple subscripts and their succession.28
Bibliography.29

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SIST EN 60027-7:2010
60027-7 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

LETTER SYMBOLS TO BE USED
IN ELECTRICAL TECHNOLOGY –

Part 7: Power generation, transmission, and distribution


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 60027-7 has been prepared by IEC technical committee 25:
Quantities and units.
The text of this standard is based on the following documents:
CDV Report on voting
25/391/CDV 25/406/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.

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SIST EN 60027-7:2010
– 4 – 60027-7 © IEC:2010
A list of all parts of the IEC 60027 series, under the general title Letter symbols to be used in
electrical technology can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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 60027-7:2010
60027-7 © IEC:2010 – 5 –
LETTER SYMBOLS TO BE USED
IN ELECTRICAL TECHNOLOGY –

Part 7: Power generation, transmission, and distribution



1 Scope
This part of IEC 60027 is applicable to generation, transmission, and distribution of electric
energy. It gives names and letter symbols for quantities and units. In addition, rules for
multiple subscripts and their succession are given.
This part of IEC 60027 is an addition to IEC 60027-1. Therefore letter symbols already given
in IEC 60027-1 are repeated only if they have a special meaning in the field of power
generation, transmission, and distribution or if they are used in this field with special
subscripts.
Guidance on the use of capital and lower case letters, is given in IEC 60027-1, 2.1, and
guidance on the representation of complex quantities,is given in IEC 60027-1, 1.6. Therefore
in many cases only U is given instead of U, U = U or u.
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 60027-1:1992, Letter symbols to be used in electrical technology – Part 1: General
Amendment 1:1997
Amendment 2:2005
IEC 60027-2:2005, Letter symbols to be used in electrical technology – Part 2: Telecom-
munications and electronics
IEC 60038:2009, IEC standard voltages
IEC 60050-121:1998, International Electrotechnical Vocabulary – Part 121: Electromagne-
tism
Amendment 1 (2002)
IEC 60050-131:2002, International Electrotechnical Vocabulary – Part 131: Circuit theory
Amendment 1 (2008)
IEC 60050-141:2004, International Electrotechnical Vocabulary – Part 141: Polyphase
systems and circuits
IEC 60050-151:2001, International Electrotechnical Vocabulary – Part 151: Electrical and
magnetic devices
IEC 60050-195:1998, International Electrotechnical Vocabulary – Part 195: Earthing and
protection against electric shock
Amendment 1 (1998)

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SIST EN 60027-7:2010
– 6 – 60027-7 © IEC:2010
IEC 60050-411:1996, International Electrotechnical Vocabulary – Chapter 411: Rotating
machines
Amendment 1 (2007)
IEC 60050-421:1990, International Electrotechnical Vocabulary – Chapter 421: Power trans-
formers and reactors
IEC 60050-441:1984, International Electrotechnical Vocabulary – Chapter 441: Switchgear,
controlgear and fuses
Amendment 1 (2000)
IEC 60050-442:1998, International Electrotechnical Vocabulary – Part 442: Electrical
accessories
IEC 60050-448:1995, International Electrotechnical Vocabulary – Chapter 448: Power
system protection
IEC 60050-466:1990, International Electrotechnical Vocabulary – Chapter 466: Overhead
lines
IEC 60050-601:1985, International Electrotechnical Vocabulary – Chapter 601: Generation,
transmission and distribution of electricity – General
Amendment 1 (1998)
IEC 60050-603:1986, International Electrotechnical Vocabulary – Chapter 603: Generation,
transmission and distribution of electricity – Power system planning and management
Amendment 1 (1998)
IEC 60050-604:1987, International Electrotechnical Vocabulary – Chapter 604: Generation,
transmission and distribution of electricity – Operation
Amendment 1 (1998)
IEC 60050-811:1991, International Electrotechnical Vocabulary – Chapter 811: Electric
traction
IEC 60909-0:2001, Short-circuit currents in three-phase AC systems – Part 0: Calculation of
currents
IEC/TR 60909-1:2002, Short-circuit currents in three-phase AC 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 AC systems – Part 2: Data of
electrical equipment for short-circuit current calculations
IEC 60909-3:2003, 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
IEC 62428:2008, Electric power engineering – Modal components in three-phase a.c.
systems – Quantities and transformations
IEC 80000-6:2008, Quantities and units – Part 6: Electromagnetism

---------------------- Page: 12 ----------------------

SIST EN 60027-7:2010
60027-7 © IEC:2010                  – 7 –

3 Letter symbols for AC, three-phase AC, and other network quantities
Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
101 line-to-earth capacitance of a line
i = 1, 2, 3 in three-phase AC networks
C C farad F

Li LiE

102 line-to-line capacitance of a line i, k = 1, 2, 3 with i ≠ k in three-phase AC
C C
farad F
LiLk Lik
networks
103 131-14-29 hybrid matrix Names and symbols for the elements are one, ohm,
1,Ω, S
H
given in IEC 60027-2.
60027-2 siemens
104 electric current
The general symbol I is used in case of three-
ampere A
I
phase AC networks if the three currents are
equal or nearly equal.
105 441-17-06 prospective breaking current, Current of the first opening pole of a switching
device (circuit breaker) or a fuse.
I I
441-17-07 breaking current ampere A

b a
60909-0
106 capacitive charging current
U
n
IC
= ω where ω is the angular
C
3
I ampere A

C
frequency, C is the positive-sequence
capacity, and U is the nominal voltage of the
n
three-phase AC line.
107 capacitive earth-fault current
I is the capacitive single line-to-earth fault
Ce
I ampere A


Ce current in a network with isolated neutral
(IEV 601-02-24).
108 131-11-22 direct current average value, for instance in the case of a
direct current link
I I
ampere A
d DC
For the qualifier DC, see IEC 60050-151,
151-15-02
109 442-01-23 earth fault current See items 107 and 121.
I
ampere A

e
110 field (excitation) current Current in the field winding of a machine.
I I ampere A
F f

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SIST EN 60027-7:2010
– 8 –             60027-7 © IEC:2010

Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
111 no-load field (excitation) current
I I
ampere A

0F f0
112 60909-0 steady-state short-circuit current The steady state short-circuit current in the
at a short-circuit location r.m.s. value of a three-phase short-circuit
current at a short-circuit location in a network,
which remains after the decay of all transient
I I ampere A

phenomena.
k k3
Short-circuit currents with subscript k in solidly
earthed or impedance earthed networks
(IEV 601-02-25, IEV 601-02-26).
113 60909-1 transient short-circuit current at a The transient short circuit current is the r.m.s.
short-circuit location value of a three-phase short-circuit current at
' '
ampere A
I I
k k3
a short-circuit location after the decay of the
subtransient short-circuit current.
114 60909-0 subtransient short-circuit current The initial symmetrical short-circuit current at
at a short-circuit location a short-circuit location is the r.m.s. value of
" "
ampere A
I I
k k3
the AC component of a prospective three-
phase short-circuit current.
115 121-11-13 line conductor current
i = 1, 2, 3 in three-phase AC networks.
I
ampere A

Li
MOD
116 411-48-16 locked rotor current
I is the highest r.m.s. current of an
LR
asynchronous motor with locked rotor at the
60909-0 I I ampere A

LR an
most unfavourable postion fed with rated
voltage and frequency of the rotor.
117 magnetizing current I is the magnetizing current of a machine, a
m
I I ampere A
m μ reactor, a transformer, etc. IEC 60027-1,
Table 6, Subscript m, mag.
118 60909-0 peak short-circuit current at a The peak short circuit current is the maximum
short-circuit location i i possible instantaneous value of the ampere A

p p3
prospective three-phase short-circuit current.
119 thermal continuous permissible
I I
ampere A
per d
current

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SIST EN 60027-7:2010
60027-7 © IEC:2010                  – 9 –

Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
120 411-48-23 peak short-circuit current of a Peak value reached by the current in the
MOD generator armature winding within a half cycle after the
winding has been suddenly short circuited,
i ampere A


pG
when the conditions are such that the initial
value of any aperiodic component of current is
a maximum.
121 421-04-05 rated current Rated current, given from the manufacturer of
electrical equipment, for a generator, motor,
I ampere A


r
transformer, reactor, etc. If necessary with an
additional subscript from 6.3.
122 rated current of a current
I ampere A

rCT
transformer
123 411-54-07 rated field (excitation) current
I I ampere A

rF fr
124 60909-0 rated current of a generator
I
ampere A

rG
125 earth-fault residual current Current at the fault location of a resonant
I I ampere A

rsd Rest
earthed network (see IEV 601-02-27)
126 60909-0 rated current at the high-voltage
Use I and I , respectively, at the
rTMV rTLV
I ampere A


side of a transformer rTHV
medium-voltage and the low-voltage side.
127 448-11-30 inrush current Inrush current of a transformer.
I
ampere A
rush
128 rated current of a winding Transformer winding at the high-voltage side
(W) or the low-voltage side (w).
I I ampere A


rW, rw
In the case of three-winding transformers, see
item 253.

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SIST EN 60027-7:2010
– 10 –             60027-7 © IEC:2010

Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
129 60909-0 thermal equivalent short-circuit r.m.s. value of a current having the same
current thermal effect and the same duration as the
actual short-circuit current, which may contain
a DC component and may subside in time,
"
I=+Im n ,
th k
I ampere A
′′
where I is the subtransient short-circuit
th
k
current (item 113), m is the factor for the heat
(thermal) effect of the DC component in a
short-circuit current (item 229), and n the
factor for the (thermal) effect of the AC
component in a short-circuit current (item
232).
130 currents at the terminals of three- Subscripts for the high-voltage side: U, V, W
I I I
, ,
U V W
phase AC transformers with two
ampere A
Subscripts for the low-voltage side: u, v, w
windings
I I I
, ,
u v w
131 currents at the terminals of the The subscripts x, y, z should be used in case
I I I
tertiary winding of a three-phase of transformer windings in delta connection. ampere A
, ,
x y z
AC transformer
132 winding current i = 1, 2, 3 in three-phase AC networks
For instance index W for the high-voltage side
I , I
ampere A

Wi wi
and index w for the low-voltage side (see
item 252).
133 harmonic current component
I ν = (2), 3, (4), 5, . ≠ 1; f = ν f ampere A

ν ν
134 131-11-42 active power In a three-phase AC network with symmetric In practice mostly
sinusoidal voltages and currents: in kW or MW Is
P watt W
used.
P = 3UI cosϕ
135 DC power
PU= I ,
ddd
P watt W
where U is the line-to-line voltage of of a SC-
P d
d
DC
line (item 149) and I the DC-current at the
d
same location (item 108).
136 121-12-11 dielectric loss
watt W
P P
diel ε

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SIST EN 60027-7:2010
60027-7 © IEC:2010                  – 11 –

Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
137 421-06-03 total load loss in transformer In case of a two-winding three-phase
MOD windings at rated current transformer (T) one side is short circuited (k)
and the other side is fed with the rated current
(r) of this side of the main tapping.
P watt W


krT
In case of three-winding transformers three
measurements or calculations are necessary
(see IEC 60909-0 and IEC 60909-2).
138 surge-impedance load of a line Surge-impedance load of a three-phase AC
line in case of U
n
2

PU= /Z
nat n W
P watt W

nat
where U is the nominal value of the line-to-
n
line voltage (item 159) and Z = Z is the
W W1
surge impedance of a line in the positive-
sequence system (item 186).

139 rated mechanical power of a For a three-phase asynchronous motor use:
motor

PU=3cIosϕ η
rM rM rM rM rM
P
watt W

rM
where U is the rated voltage, I the rated
rM rM
current, ϕ the phase difference and η
rM rM
the efficiency of the motor.

140 131-11-43 non-active power
2 2
Q
= S − P
~
80000-6,
Q , Q′
volt ampere VA
~
6-61
where S is the apparent power (item 142) und
P the active power (item 134)

---------------------- Page: 17 ----------------------

SIST EN 60027-7:2010
– 12 –             60027-7 © IEC:2010

Quantities Units
Item Unit, coherent
IEV and/or
Chief Reserve
number with the SI
IEC Name of quantity Remarks Remarks
symbol symbol
number
Name Symbol
141 131-11-44 reactive power Shall be used only in three-phase AC In practice mostly
networks with symmetric sinusoidal voltages var, kvar, Mvar is
used.
and currents:
QU==3sIinϕϕSsin
where S is the apparent power (item 142) and
Q volt ampere VA

ϕϕ=−ϕ the phase difference with ϕ as
ui u
the initial phase of the voltage and ϕ the
i
initial phase of the current (IEC 80000-6, 6-
48).
142 131-11-41 apparent power In a symmetrical three-phase AC network use: In practice mostly
kVA, MVA is used.
S = 3UI , where U is the line-to-line
S volt ampere VA
voltage (item 147) and I the line current
(item 104).
143 601-01-14 short-circuit power The short-circuit apparent power in a sym- In practice mostly
MOD met
...