IEC 62695:2014

Railway applications - Fixed installations - Traction transformers

IEC 62695:2014 covers specific characteristics of traction transformers used in traction substations or along the track for the supply of power to a.c. and d.c. traction systems or to provide power to auxiliary services.

Applications ferroviaires - Installations fixes - Transformateurs de traction

L'IEC 62695:2014 couvre les caractéristiques spécifiques des transformateurs de traction utilisés dans les sous-stations de traction ou le long de la voie pour l'alimentation de puissance des systèmes de traction à courant alternatif et à courant continu ou pour fournir de la puissance aux services auxiliaires.

General Information

• Status: Published
• Publication Date: 08-Jul-2014
• ICS: 45.060.01 - Railway rolling stock in general
• Technical Committee: TC 9 - Electrical equipment and systems for railways
• Drafting Committee: PT 62695 - TC 9/PT 62695
• Current Stage: PPUB - Publication issued
• Start Date: 09-Jul-2014
• Completion Date: 30-Jun-2014

Overview

IEC 62695:2014 sets out international requirements for traction transformers used in railway fixed installations. Developed by the International Electrotechnical Commission (IEC), this standard provides comprehensive guidance on the specific characteristics, performance criteria, and testing of traction transformers in both alternating current (a.c.) and direct current (d.c.) railway power supply systems. It addresses various transformer types delivering energy to traction systems or auxiliary railway services along the track or in substations. The standard ensures interoperability, safety, and quality in railway electrification projects around the world.

Key Topics

IEC 62695:2014 covers essential aspects of traction transformers for railway applications, including:

• Scope and Application: Applies to single-phase, three-phase to two-phase, rectifier/converter/inverter transformers, autotransformers, booster transformers, and auxiliary transformers used in railway fixed installations. On-board vehicle transformers are excluded.

• Service Conditions: Specifies environmental, electrical, thermal, and mechanical operating requirements for different transformer types.

• General and Specific Requirements:

  • Loading and rated characteristics (current, voltage, power)
  • Overvoltage protection and response to short-circuit stresses
  • Insulation characteristics and test values
  • Temperature rise limits and measurement methods for liquid-immersed and dry-type transformers

• Transformer Types and Test Methods:

  • Directly-coupled traction transformers
  • Traction converter and inverter transformers
  • Traction autotransformers
  • Special three-phase to two-phase conversion transformers (e.g., Scott and Woodbridge)
  • Auxiliary services transformers

• Simulation and Type Testing:

  • Dielectric testing (routine and type tests)
  • Overload and loss calculations
  • Tolerances, load cycles, and duty classes

• Compatibility and EMC: References electromagnetic compatibility (EMC) requirements as relevant to transformer accessories (according to IEC 62236-5).

Applications

Traction transformers are fundamental to reliable, efficient railway electrification and are used in several key applications:

• Traction Substations: Step down and distribute power from high-voltage supply grids to rail contact lines for train propulsion.
• Trackside Installations: Provide distributed power feed to a.c. or d.c. contact lines along the rail corridor.
• Auxiliary Services: Power essential ancillary systems such as signaling, lighting, and station services.
• Traction Converter Systems: Interface with power electronic converters for variable voltage and frequency supply, essential in modern railway operations.
• Voltage Regulation and Harmonic Mitigation: Improve power quality, manage system harmonics, and support stable operation under varying load conditions.

Proper specification and testing according to IEC 62695:2014 are vital for:

• System safety and compatibility
• Equipment interchangeability
• Ensuring life cycle durability and reliable performance
• Supporting global railway infrastructure development

Related Standards

IEC 62695:2014 is closely linked with several other international standards for railway electrification and transformer technology, including:

• IEC 60076 Series: General standards for power transformers (oil-immersed, dry-type, gas-filled)
• IEC 61378-1: Converter transformers for industrial applications
• IEC 62590: Fixed installations - Electronic power converters for substations
• IEC 62497-1: Insulation coordination for electrical and electronic railway equipment
• IEC 60850: Railway applications - Supply voltages of traction systems
• IEC 62236-5: EMC requirements for fixed railway installations

Reference to these standards ensures full compliance and optimal performance of railway traction transformers in international railway projects.

---

Keywords: IEC 62695:2014, traction transformers, railway applications, fixed installations, a.c. railway power, d.c. railway power, traction substations, transformer testing, railway electrification standards, power quality, EMC, railway infrastructure.

Standards Content (Sample)

IEC 62695 ®
Edition 1.0 2014-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Railway applications – Fixed installations – Traction transformers

Applications ferroviaires – Installations fixes – Transformateurs de traction

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.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
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 corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing more than 30 000 terms and
Technical Specifications, Technical Reports and other definitions in English and French, with equivalent terms in 14
documents. Available for PC, Mac OS, Android Tablets and additional languages. Also known as the International
iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a More than 55 000 electrotechnical terminology entries in
variety of criteria (reference number, text, technical English and French extracted from the Terms and Definitions
committee,…). It also gives information on projects, replaced clause of IEC publications issued since 2002. Some entries
and withdrawn publications. have been collected from earlier publications of IEC TC 37,

77, 86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient plus de 30 000 termes et définitions en
Spécifications techniques, Rapports techniques et autres
anglais et en français, ainsi que les termes équivalents dans
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
14 langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
Plus de 55 000 entrées terminologiques électrotechniques, en
La recherche avancée permet de trouver des publications IEC
en utilisant différents critères (numéro de référence, texte, anglais et en français, extraites des articles Termes et
comité d’études,…). Elle donne aussi des informations sur les Définitions des publications IEC parues depuis 2002. Plus
projets et les publications remplacées ou retirées. certaines entrées antérieures extraites des publications des

CE 37, 77, 86 et CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
[e-mail].
IEC 62695 ®
Edition 1.0 2014-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Railway applications – Fixed installations – Traction transformers

Applications ferroviaires – Installations fixes – Transformateurs de traction

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 45.060 ISBN 978-2-8322-1645-3

– 2 – IEC 62695:2014 © IEC 2014
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and symbols . 9
3.1 Terms and definitions . 9
3.2 Symbols . 14
4 Service conditions . 15
5 General requirements for a traction transformer . 16
5.1 Loading . 16
5.1.1 General . 16
5.1.2 Rated current . 17
5.1.3 Rated current of accessories . 17
5.2 Checking of the capability of the transformer to sustain the stipulated load

cycle . 17
5.2.1 General . 17
5.2.2 Temperature rise measurement for liquid immersed transformers . 18
5.2.3 Temperature rise measurement for dry-type transformers . 18
5.2.4 Alternative criteria for determining temperature rise limits . 18
5.3 Transferred overvoltages . 19
5.4 Short circuit stresses . 19
5.4.1 General . 19
5.4.2 Short circuit withstand (when applicable) . 19
5.5 Insulation characteristics and test values . 20
5.6 Other particular features. 20
5.7 Requirements for the simulation test. 21
5.8 Rating plate. 21
6 Directly-coupled traction transformer . 22
6.1 General . 22
6.2 Dielectric tests for windings with U < 300 kV . 22
m
6.2.1 General . 22
6.2.2 Applied voltage test (routine test) . 22
6.2.3 Lightning impulse test (type test) . 22
6.2.4 Induced overvoltage withstand test (routine test) . 23
6.3 Dielectric tests for windings with U ≥ 300 kV . 23
m
6.3.1 General . 23
6.3.2 Applied voltage test (routine test) . 23
6.3.3 Lightning impulse test (routine test) . 23
6.3.4 Switching impulse test (routine test) . 23
6.3.5 Induced overvoltage withstand test (routine test) . 23
7 Traction converter transformers . 24
7.1 General . 24
7.2 Short-circuit impedance and load loss . 25
7.2.1 Total load loss calculation . 25
7.2.2 Impedance . 25
7.3 Tolerances . 26

8 Auxiliary transformers . 27
9 Traction auto-transformers . 27
9.1 General . 27
9.2 Loading . 29
9.3 Checking of the capability of the auto-transformer to sustain the stipulated
load cycle . 29
9.4 Short-circuit stresses . 29
10 Three-phase to two-phase conversion transformers . 29
10.1 General . 29
10.2 Scott connection transformer . 30
10.2.1 General . 30
10.2.2 Loading . 31
10.2.3 Checking of the capability of the Scott connection transformer to
sustain the stipulated load cycle . 31
10.2.4 Short-circuit stresses . 31
10.3 Modified Woodbridge transformer . 31
10.3.1 General . 31
10.3.2 Loading . 34
10.3.3 Checking of the capability of the modified Woodbridge transformer to

sustain the stipulated load cycle . 34
10.3.4 Short-circuit stresses . 34
10.4 Roof-delta connection transformer . 34
10.4.1 General . 34
10.4.2 Loading . 36
10.4.3 Checking of the capability of the roof-delta connection transformer to
sustain the stipulated load cycle . 36
10.4.4 Short-circuit stresses . 36
11 Other traction transformers . 37
11.1 General . 37
11.2 Booster transformer . 37
11.3 Scalene Scott connection transformer . 37
Annex A (informative) Preferred duty classes . 39
Annex B (normative) Insulation characteristics and test values . 44
Annex C (normative) Determination of losses and of equivalent current by means of
alternative methods . 45
C.1 General . 45
C.2 Definition of symbols used in loss calculation . 45
C.3 Ratios between rated current and rated service current for traction converter
transformers . 45
C.4 Calculation of load losses based on loss measurements at two different
frequencies for oil immersed transformers . 48
C.5 Calculation of load losses based on two frequencies for dry type transformers . 49
Annex D (informative) Evaluation of traction transformer behaviour . 50
D.1 Evaluation of losses . 50
D.2 Magnetic information . 50
Annex E (informative) Information for tenders and orders . 51
E.1 Information to be provided in a tender enquiry . 51
E.1.1 General . 51
E.1.2 Characteristics . 51
E.1.3 Service conditions . 51

– 4 – IEC 62695:2014 © IEC 2014
E.1.4 Auxiliaries . 52
E.1.5 Operation and fitting . 52
E.1.6 Tests . 52
E.2 Information to be provided in a tender . 52
Bibliography . 53

Figure 1 – Example of scheme for connection Dd0y11 with earthed screen . 22
Figure 2 – Typical arrangement of a traction auto-transformer . 28
Figure 3 – Vector groups of traction auto-transformers . 28
Figure 4 – Connection of Scott connection transformers . 30
Figure 5 – Connection of modified Woodbridge transformers . 32
Figure 6 – Phase A currents on modified Woodbridge transformer . 33
Figure 7 – Phase B currents on modified Woodbridge transformer . 33
Figure 8 – Connection of roof-delta connection transformers . 35
Figure 9 – Phase currents on roof-delta connection transformer . 36
Figure 10 – Booster transformer . 37
Figure 11 – Scalene Scott connection transformer . 38
Figure A.1 – Test cycle for duty classes IA to IF . 40
Figure A.2 – Test cycle for duty classes V, VI, VII . 41
Figure A.3 – Test cycle for duty classes VIII, IX and JP . 42
Figure A.4 – Test cycle for duty class CN . 43
Figure C.1 – Service current versus fundamental current . 48

Table 1 – Tolerances for voltage ratio and impedances of traction converter
transformers . 26
Table A.1 – Preferred duty classes . 39
Table B.1 – Insulation voltages and test values. 44
Table C.1 – Connections of converter transformers . 46
Table C.2 – Main harmonic contents for various converter connections . 47
Table C.3 – Service current over rated current . 47

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS –
FIXED INSTALLATIONS –
TRACTION TRANSFORMERS
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 62695 has been prepared by IEC technical committee 9: Electrical
equipment and systems for railways.
This standard is derived from EN 50329:2003 and its amendment 1(2010).
The text of this standard is based on the following documents:
FDIS Report on voting
9/1916FDIS 9/1943/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.

– 6 – IEC 62695:2014 © IEC 2014
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

INTRODUCTION
Transformers used in fixed installations of traction systems differ from other transformers. The
transformer standards of IEC technical committee 14 deal mainly with three-phase
transformers or single-phase units assembled to a three-phase bank.
Application of such standards to single- or bi-phase transformers as used in traction systems is
not evident.
Moreover, IEC 61378-1 deals with converter transformers for industrial use which have loading
characteristics different from traction transformers for converters.
Therefore, this standard is set up to clarify the particular aspects of traction transformers.

– 8 – IEC 62695:2014 © IEC 2014
RAILWAY APPLICATIONS –
FIXED INSTALLATIONS –
TRACTION TRANSFORMERS
1 Scope
This International Standard covers specific characteristics of traction transformers as defined
in 3.1.1, used in traction substations or along the track for the supply of power to a.c. and d.c.
traction systems or to provide power to auxiliary services. Traction transformers are either
– single-phase traction transformers, or
– three-phase to two-phase traction transformers, or
– single-, three- or poly-phase rectifier-transformers or converter-/inverter-transformers for
d.c. or a.c. traction systems, or
– single phase auto-transformers for traction power supply, or
– single-phase booster transformers, or
– single- or three-phase auxiliary transformers at traction supply voltage.
Traction transformers are generally covered by the Standards of the IEC 60076 series. The
requirements given in IEC 60076 apply together with the additional requirements given in this
standard.
Dependent on the selected technology specific parts of IEC 60076 apply:
– IEC 60076-1: Oil immersed transformers
– IEC 60076-11: Dry-type transformers
– IEC 60076-15: Gas-filled transformers
For transformers feeding contact lines through static converters IEC 61378-1 may assist, but
modified or additional requirements are given in this standard.
Transformers mounted on-board traction vehicles are covered by IEC 60310 and are excluded
from the scope of this standard.
Electromagnetic compatibility is ruled by IEC 60076-1, which states that a transformer may be
considered a passive element in this respect. Some accessories, however, are subject to EMC
requirements given in IEC 62236-5.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
IEC 60076-1:2011, Power transformers – Part 1: General
IEC 60076-2:2011, Power transformers – Part 2: Temperature rise for liquid-immersed
transformers
IEC 60076-3:2013, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60076-5:2006, Power transformers – Part 5: Ability to withstand short circuit
IEC 60076-7:2005, Power transformers – Part 7: Loading guide for oil-immersed power
transformers
IEC 60076-11:2004, Power transformers – Part 11: Dry-type transformers
IEC 60076-12:2008, Power transformers – Part 12: Loading guide for dry-type power
transformers
IEC 60076-14:2013, Power transformers – Part 14: Liquid-immersed power transformers using
high-temperature insulation materials
IEC 60076-15:2008, Power transformers – Part 15: Gas-filled power transformers
IEC TR 60146-1-2:2011, Semiconductor converters – General requirements and line
commutated converters – Part 1-2: Application guide
IEC 60850:2007, Railway applications – Supply voltages of traction systems
IEC 61000-2-12:2003, Electromagnetic Compatibility (EMC) – Part 2-12: Environment –
Compatibility levels for low-frequency conducted disturbances and signalling in public medium-
voltage power supply systems
IEC 61378-1:2011, Converter transformers – Part 1: Transformers for industrial applications
IEC 62497-1:2010, Railway applications – Insulation coordination – Part 1: Basic requirements
– Clearances and creepage distances for all electrical and electronic equipment
IEC 62498-2:2010, Railway applications – Environmental conditions for equipment – Part 2:
Fixed electrical installations
IEC 62505-1:2009, Railway applications – Fixed installations – Particular requirements for a.c.
switchgear – Part 1: Single-phase circuit-breakers with U above 1 kV
m
IEC 62589:2010, Railway applications – Fixed installations – Harmonisation of the rated values
for converter groups and tests on converter groups
IEC 62590:2010, Railway applications – Fixed installations – Electronic power converters for
substations
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60076-1 and
IEC 62590, as well as the following apply.
3.1.1
traction transformer
transformer (with separate or auto-connected windings) connected to an a.c. or d.c. contact
line, directly or through a converter, used in fixed installations of railway applications
Note 1 to entry: The above definition relates to the contents of this standard and is introduced to simplify the
following definitions, which, in most cases, are not valid for all transformers and autotransformers.

– 10 – IEC 62695:2014 © IEC 2014
3.1.2
traction converter transformer
traction transformer on the supply side of a converter group and supplying contact line(s)
through static converter(s)
3.1.3
traction inverter transformer
traction transformer on the traction (contact) line side of a converter group and supplied by a
static converter(s) (inverter)
3.1.4
directly-coupled traction transformer
traction transformer supplying contact line(s) without the interposition of static converter(s)
3.1.5
rated value
numerical value for the electrical, thermal, mechanical and environmental rating assigned to
the quantities which define the operation of a traction transformer in the conditions specified in
accordance with this International Standard and on which the manufacturer’s guarantees and
tests are based
3.1.6
rated frequency
f
N
frequency at which the traction transformer is designed to operate
3.1.7
rated voltage on the supply side of a traction transformer
U
NL
r.m.s. value of the sinusoidal no-load voltage assigned to be applied to the supply side
terminals of a traction transformer (for traction converter transformers)
3.1.8
rated voltage of a traction autotransformer
U
OHL
r.m.s. value of the sinusoidal no-load voltage between the overhead contact line and the line
feeder in a traction autotransformer
3.1.9
rated intermediate voltage of a traction autotransformer
U
rail
r.m.s. value of the sinusoidal no-load voltage between the overhead contact line and the
connection to the rail
3.1.10
rated voltage on the converter side(s) of a traction converter transformer and on the
traction side of a directly-coupled traction transformer
U
NS
r.m.s. value of the no-load voltage at the line-to-line terminals of the converter side(s) of a
traction converter transformer or of the traction side of a directly-coupled traction transformer,
at the rated voltage on the supply side of the traction transformer
3.1.11
rated voltage on the inverter side of a traction inverter transformer
U
NP
r.m.s. value of the sinusoidal no-load voltage resulting at the inverter side terminals of a
traction transformer
3.1.12
rated voltage on the traction side(s) of an inverter transformer
U
NV
r.m.s. value of the no-load voltage at the line-to-line terminals of the traction side(s) of an
inverter transformer at the rated voltage on its inverter side
3.1.13
rated power of a winding
S , S , S , S
NL NP NSn NV
conventional value of apparent power assigned to a winding, which, together with the rated
voltage of the winding, determines its rated current. It is based on the fundamental components
of voltage and current (see 3.1.7, 3.1.10, 3.1.12 and 3.1.14)
Note 1 to entry: “primary” and “secondary” are referred to the normal flow of energy from the supply side to the
traction side.
Note 2 to entry: In the suffix “S ” for secondary windings “n” is the assigned order number of the secondary
n
winding. In a formula where any winding is separately considered, S indicates the rated power of the winding
N
considered.
3.1.14
rated current on the primary side of the traction transformer
I , I
NL NP
r.m.s. value of the fundamental component of the current flowing through a line terminal of the
primary winding which is derived from the rated power S and rated voltage U for the winding
N N
Note 1 to entry: The generic r.m.s. of fundamental component of an a.c. current is indicated as I and the generic
rated current as I .
N
3.1.15
rated current in the series winding of a traction autotransformer

I
OHL
r.m.s. value of the current flowing between the contact line terminal of a traction
autotransformer and rail terminal
3.1.16
rated current in the common winding of a traction autotransformer
I
feed
r.m.s. value of the current flowing between the line feeder terminal of a traction
autotransformer and rail
3.1.17
rated service current on the primary side of the traction converter transformer
I
NGL
r.m.s. value of the current flowing through a line terminal of the supply side winding of a
traction converter transformer which contains all harmonic components and whose
fundamental component is the rated current I
NL
Note 1 to entry: In case of traction inverter transformers it is assumed that the service current is not sensibly
different from sinusoidal current in all windings.
Note 2 to entry: The generic r.m.s. value of the service current is indicated as I .
G
Note 3 to entry: The generic r.m.s. value of the harmonic current of order h of an a.c. current is indicated as I .
h
Note 4 to entry: In formulas where any winding is separately considered, I indicates the rated current of the
N
winding considered and I its rated service current.
NG
– 12 – IEC 62695:2014 © IEC 2014
3.1.18
rated current on the secondary side of a traction transformer
I , I
NS NV
r.m.s value of the fundamental component of the current flowing at the terminals of the
secondary winding(s) of a traction transformer, which is derived from the rated power S and
N
rated voltage U for the winding
N
Note 1 to entry: When the secondary windings of a converter transformer are more than one, even if the
secondaries are intended to feed a single conversion bridge, the rated secondary current of each winding may differ
from that of other winding(s) by small quantities. The tolerances in any case should be observed.
Note 2 to entry: In some cases, the secondary current(s) of a traction converter transformer are not equal to the
input current of the converter due to the presence of an auxiliary transformer (see Clause 3 of IEC 62589:2010).
3.1.19
rated service current on the converter (valve) side of a traction converter transformer
I
NGSn
r.m.s value of the current flowing at the terminals of the secondary winding(s) of a traction
converter transformer which contains all harmonic components and whose fundamental
component is the rated current I
NS
Note 1 to entry: I differs from I . The latter is taken into account to determine loadability of given accessories
NGS NS
such as bushing insulators. Loss and temperature rise calculations are based on the rated service current,
considering also the additional eddy losses in the windings and structural parts produced by the harmonics.
Note 2 to entry: In some cases, the secondary current(s) of a traction converter transformer are not equal to the
input current of the converter due to the presence of an auxiliary transformer (see Clause 3 of IEC 62589:2010).
Note 3 to entry: In a formula where any winding is separately considered, I indicates the rated current of the
N
winding considered and I its rated service current.
NG
3.1.20
basic current
I , I , I , I , I , I
BL BP BS BV BGL BGS
current value in a winding which, according to a given duty class (see 3.1.31), is assumed to
last for longer periods and represents the load carried out continuously by the traction
transformer and on which the overloads are imposed.
3.1.21
basic current on the primary side of a traction transformer
I , I
BL BP
r.m.s. value of the fundamental component of the current flowing through a line terminal of the
primary winding which is derived from the basic power S and rated voltage U for the winding
B N
3.1.22
basic service current on the primary side of the traction converter transformer
I
BGL
r.m.s. value of the current flowing through a line terminal of the supply side winding of a
traction converter transformer which contains all harmonic components and whose
fundamental component is the basic current I
BL
3.1.23
basic current on the secondary side of a traction transformer
I , I
BS BV
r.m.s. value of the fundamental component of the current flowing at the terminals of the
secondary winding(s) of a traction transformer, which is derived from the basic power S and
B
rated voltage U for the winding
N
3.1.24
basic service current on the converter (valve) side of a traction converter transformer
I
BGSn
r.m.s value of the current flowing at the terminals of the secondary winding(s) of a traction
converter transformer which contains all harmonic components and whose fundamental
component is the basic current I
BS
3.1.25
leakage reactance related to the primary winding
X
p
difference between the mean of the short circuit reactance
values measured between the primary winding and each secondary winding and one half of the
short circuit reactance measured between the two secondary windings
X + X X
ccP/S1 ccP/S2 ccS1/S2
X = −
p
2 2
3.1.26
leakage reactance related to each of the secondary windings
X , X
S1 S2
sum of the half difference of the short circuit reactance values
measured between the primary winding and each secondary winding and one half of the short
circuit reactance measured between the two secondary windings
X − X X
ccP/S1 ccP/S2 ccS1/S2
X = +
S1
2 2
X − X X
ccP/S2 ccP/S1 ccS1/S2
X = +
S2
2 2
3.1.27
reactance ratio
coupling factor
K
ratio between the leakage reactance from primary side and the sum of the leakage reactance
from primary and secondary side
Note 1 to entry: In case of a traction transformer with two secondary windings, used for a twelve-pulse reaction
converter, the reactance ratio is designed to have the same no-load secondary voltages and the same impedance
between the primary and each secondary winding, in order to obtain an even sharing of the current on both bridges
in case the d.c. outputs are paralleled. Then X = X = X and
S1 S2 S
K = X / (X + X )
p S p
3.1.28
current demand
actual or expected load variation of the current absorbed by a traction line, whose root mean
square value is the rated current. It is expressed by a load diagram
3.1.29
load diagram
true demand of current by the traction circuit in the worse expected condition

– 14 – IEC 62695:2014 © IEC 2014
3.1.30
load cycle
conventional representation of the current demand to a traction transformer expressed in per
unit of the rated currents. It shows the repetitive variation of the loads with the time and, hence,
the overloads and underloads the traction transformer is expected to carry, as well as the
duration and intervals assumed
Note 1 to entry: Load cycles and duty classes are intended to allow testing of the traction transformers.
3.1.31
duty class
conventional classification of the current capability of a traction transformer expressed in per
unit of the basic currents I .
B
Note 1 to entry: The duty classes, associated with other rated values, define the characteristics of a traction
transformer.
Note 2 to entry: Annex A indicates preferred duty classes and the corresponding basic and rated values.
Note 3 to entry: The indication of a duty class is not compulsory.
3.1.32
long time overload
peak load in the load cycle lasting from 480 s up to 7 200 s
3.1.33
short time overload
peak load in the load cycle lasting up to and including 480 s
3.1.34
additional winding
winding required for connection of auxiliary devices such as harmonic filters
3.2 Symbols
See also Figure 1 of IEC 62589:2010.
f rated frequency
N
I basic current
B
I basic current on the supply side of a traction converter transformer
BL
I basic current on the supply side of a traction inverter transformer
BP
I basic current on the secondary side of a traction converter transformer
BS
I basic service current on the primary side of a traction converter transformer
BGL
I basic service current on the converter (valve) side of a traction converter
BGS
transformer
I basic service current on the converter (valve) side of a traction converter
BGSn
transformer
I basic current on the secondary side of a traction inverter transformer
BV
I rated current in the common winding of a traction autotransformer
feed
I generic r.m.s. value of the service current
G
I generic r.m.s. value of the harmonic current
h
I r.m.s. value of the rated service current
NG
I rated service current on the primary side of a traction converter transformer
NGL
I rated service current on the converter (valve) side of a traction converter transformer
NGSn
I rated current on the supply side of a traction converter transformer
NL
I rated current on the supply side of a traction inverter transformer
NP
I rated current on the secondary side of a traction converter transformer
NS
I rated current on the secondary side of a traction inverter transformer
NV
I rated current in the series winding of a traction autotransformer
OHL
K coupling factor
q continuous level of apparent charges
S rated power of the supply side winding of a traction transformer
NL
S rated power on the inverter side winding of a traction inverter transformer
NP
S rated powe
...