IEC 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

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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
– 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

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.

– 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.
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)
– 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
Amendm
...