SIST EN 61378-2:2002
(Main)Convertor transformers -- Part 2: Transformers for HVDC applications
Convertor transformers -- Part 2: Transformers for HVDC applications
This part of EN 61378 applies to oil-immersed three-phase and -single-phase convertor transformers for use in HVDC power transmission. It applies to transformers having two, three or multiple windings. This standard does not apply to convertor transformers for industrial applications (see EN 61378-1) and to convertor transformers for traction applications (see EN 60310).
Stromrichtertransformatoren -- Teil 2: Transformatoren für HGÜ-Anwendungen
Transformateurs de conversion -- Partie 2: Transformateurs pour applications CCHT
La présente partie de la EN 61378 s'applique aux transformateurs de conversion immergés dans l'huile triphasés et monophasés utilisés pour la transmission de puissance CCHT. Elle s'applique aux transformateurs possédant deux, trois ou de multiples enroulements. La présente norme ne s'applique pas aux transformateurs de conversion pour applications industrielles (voir EN 61378-1) et aux transformateurs de conversion pour applications de traction (voir EN 60310).
Convertor transformers - Part 2: Transformers for HVDC applications (IEC 61378-2:2001)
General Information
Standards Content (Sample)
SLOVENSKI SIST EN 61378-2:2002
prva izdaja
STANDARD
oktober 2002
Convertor transformers - Part 2: Transformers for HVDC applications (IEC 61378-
2:2001)
ICS 29.180 Referenčna številka
SIST EN 61378-2:2002(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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EUROPEAN STANDARD EN 61378-2
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2001
ICS 29.180
English version
Convertor transformers
Part 2: Transformers for HVDC applications
(IEC 61378-2:2001)
Transformateurs de conversion Stromrichtertransformatoren
Partie 2: Transformateurs pour Teil 2: Transformatoren für
applications CCHT HGÜ-Anwendungen
(CEI 61378-2:2001) (IEC 61378-2:2001)
This European Standard was approved by CENELEC on 2001-01-01. 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, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway,
Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61378-2:2001 E
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EN 61378-2:2001 - 2 -
Foreword
The text of document 14/384/FDIS, future edition 1 of IEC 61378-2, prepared by IEC TC 14, Power
transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61378-2 on 2001-01-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2001-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-01-01
Annexes designated "normative" are part of the body of the standard.
In this standard, annex ZA is normative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61378-2:2001 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60310 NOTE: Harmonized as EN 60310:1996 (not modified).
__________
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- 3 - EN 61378-2:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
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 60076-1 (mod) 1993 Power transformers EN 60076-1 1997
Part 1: General
IEC 60076-2 (mod) 1993 Part 2: Temperature rise EN 60076-2 1997
IEC 60076-3 2000 Part 3: Insulation levels, dielectric tests EN 60076-3 2001
and external clearances in air
1)
IEC 60076-5 (mod) 1976 Part 5: Ability to withstand short-circuit HD 398.5 S1 1983
IEC 60076-8 1997 Part 8: Application guide - -
2)
IEC 60076-10 Part 10: Determination of sound levels - -
IEC 60137 1995 Insulated bushings for alternating EN 60137 1996
voltages above 1 kV
IEC 60146-1-1 1991 Semiconductor convertors - General EN 60146-1-1 1993
requirements and line commutated
convertors
Part 1-1: Specifications of basic
requirements
IEC 60146-1-2 1991 Semiconductor convertors - General--
requirements and line commutated
convertors
Part 1-2: Application guide
IEC 60214 (mod) 1989 On-load tap-changers EN 60214 1997
IEC 60270 2000 High-voltage test techniques - Partial EN 60270 2001
discharge measurements
IEC 60354 1991 Loading guide for oil-immersed power--
transformers
1)
HD 398.5 S1 is superseded by EN 60076-5:2000 which is based on IEC 60076-5:2000.
2)
To be published.
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EN 61378-2:2001 - 4 -
Publication Year Title EN/HD Year
IEC 60567 1992 Guide for the sampling of gases and of oil EN 60567 1992
from oil-filled electrical equipment and for
the analysis of free and dissolved gases
IEC 61378-1 1997 Convertor transformers EN 61378-1 1998
Part 1: Transformers for industrial + corr. November 1998
applications
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NORME
CEI
INTERNATIONALE IEC
61378-2
INTERNATIONAL
Première édition
STANDARD
First edition
2001-02
Transformateurs de conversion –
Partie 2:
Transformateurs pour applications CCHT
Convertor transformers –
Part 2:
Transformers for HVDC applications
© IEC 2001 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun procédé, any form or by any means, electronic or mechanical,
électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission in
microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
S
PRICE CODE
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61378-2 © IEC:2001 – 3 –
CONTENTS
Page
FOREWORD . 7
Clause
1 General. 11
1.1 Scope . 11
1.2 Service conditions. 11
2 Normative references. 11
3 Definitions. 13
4 List of variables . 15
5 Ratings . 17
5.1 General. 17
5.2 Rated voltage . 17
5.3 Rated current. 17
5.4 Rated frequency . 17
5.5 Rated power . 17
6 Tolerances.17
6.1 General. 17
6.2 Short-circuit impedance tolerances . 17
6.3 Guarantees. 19
7 Losses . 19
7.1 General. 19
7.2 No-load loss . 19
7.3 Load loss under rated power-frequency conditions. 19
7.4 Load loss under service conditions . 21
7.5 Determination of hot-spot temperature. 23
8 Insulation levels . 23
8.1 Line windings. 23
8.2 Valve windings. 23
8.3 Induced voltage level with partial discharge measurements . 25
9 Sound level.25
9.1 General. 25
9.2 Guaranteed sound-power levels. 25
9.3 Sound-power level at site. 27
10 Testing. 27
10.1 General. 27
10.2 Tests . 27
10.3 Load-loss measurements . 29
10.4 Factory dielectric tests. 31
10.5 Temperature-rise test . 37
10.6 Load-current test . 41
10.7 Determination of transformer sound-power level . 41
11 High-frequency modelling. 41
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61378-2 © IEC:2001 – 5 –
Clause Page
12 Loading of transformer above rating. 41
13 Bushings. 41
13.1 AC bushings . 41
13.2 Valve winding bushings. 41
14 Tap-changer . 43
14.1 General. 43
14.2 Current wave shape. 43
Bibliography . 45
Figure 1 – Profile of short-circuit impedance tolerances for tapping ranges ≤30 %. 19
Figure 2 – Double reversal test voltage profile. 35
Table 1 – Test conditions for three-winding transformers. 39
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61378-2 © IEC:2001 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONVERTOR TRANSFORMERS –
Part 2: Transformers for HVDC applications
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61378-2 has been prepared by IEC technical committee 14: Power
transformers.
The text of this standard is based on the following documents:
FDIS Report on voting
14/384/FDIS 14/386/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 3.
IEC 61378 consists of the following parts, under the general title: Convertor transformers:
– Part 1: Transformers for industrial applications;
– Part 2: Transformers for HVDC applications;
– Part 3: Application guide (under consideration).
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61378-2 © IEC:2001 – 9 –
The committee has decided that the contents of this publication will remain unchanged until
2004. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
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61378-2 © IEC:2001 – 11 –
CONVERTOR TRANSFORMERS –
Part 2: Transformers for HVDC applications
1 General
1.1 Scope
This part of IEC 61378 applies to oil-immersed three-phase and single-phase convertor
transformers for use in HVDC power transmission. It applies to transformers having two, three
or multiple windings.
This standard does not apply to
– convertor transformers for industrial applications (see IEC 61378-1);
– convertor transformers for traction applications (see IEC 60310).
1.2 Service conditions
1.2.1 General
Convertor transformers in this standard shall comply with the service conditions stated in
IEC 60076-1, except where it is clearly not applicable to convertor transformers or when other
requirements are specified herein. It is assumed that the transformer operates in an
approximately symmetrical three-phase system, unless otherwise stated.
1.2.2 Temperature
If any part of the transformer (for example, the valve bushings) protrudes into the valve hall,
the maximum temperature in the valve hall shall be specified in addition to the normal ambient
temperature.
1.2.3 Load current
The currents flowing through the transformers contain harmonics. Residual d.c. currents also
flow through the valve windings. The supplier shall be provided with the harmonic content and
the magnitude of the residual d.c. currents in the enquiry and have it confirmed during the
contract stage.
1.2.4 Direction of power flow
Unless otherwise specified, the transformer shall be designed for both rectifier and inverter
operation.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61378. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this part of IEC 61378 are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
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61378-2 © IEC:2001 – 13 –
IEC 60076-1:1993, Power transformers – Part 1: General
IEC 60076-2:1993, Power transformers – Part 2: Temperature rise
IEC 60076-3:2000, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60076-5:1976, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60076-8:1997, Power transformers – Part 8: Application guide
1)
IEC 60076-10:—, Power transformers and reactors – Part 10: Determination of sound levels
IEC 60137:1995, Insulated bushings for alternating voltages above 1 000 V
IEC 60146-1-1:1991, Semiconductor convertors – General requirements and line commutated
converters – Part 1-1: Specifications of basic requirements
IEC/TR 60146-1-2:1991, Semiconductor convertors – General requirements and line
commutated convertors – Part 1-2: Application guide
IEC 60214:1989, On-load tap-changers
1)
IEC 60270:⎯, Partial discharge measurements
IEC 60354:1991, Loading guide for oil-immersed power transformers
IEC 60567:1992, Guide for the sampling of gases and of oil from oil-filled electrical equipment
and for the analysis of free and dissolved gases
IEC 61378-1:1997, Convertor transformers – Part 1: Transformers for industrial application
3 Definitions
For the purpose of this part of IEC 61378, the definitions of IEC 60050 (IEV) apply. Additional
definitions of more specific transformer and convertor terms are given in IEC 60076-1 and
IEC 60146-1-1, respectively. Where some of these terms are at variance with earlier
definitions of the same terms, found in the IEV, the terms specified in IEC 60076-1 and
IEC 60146-1-1 will take precedence.
___________
1)
To be published.
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61378-2 © IEC:2001 – 15 –
4 List of variables
I rated current
1
I load-loss test current at frequency f
x x
I r.m.s. value of the in-service load current in the winding under consideration
LN
I current at harmonic order number h
h
I equivalent sinusoidal r.m.s. current giving the winding in-service load loss
eq
h harmonic order number
U rated voltage
1
S rated power
R
P total load losses at fundamental frequency (50 Hz or 60 Hz)
1
P load loss measured at frequency f
x x
2
IR ohmic losses at rated current
1
d.c. resistance of windings including internal leads
R
P eddy losses in windings at fundamental frequency
WE1
P stray losses in structural parts (excluding windings) at fundamental frequency
SE1
P total service load loss
N
f rated frequency and also the fundamental frequency
1
f frequency ≥150 Hz used to determine the distribution of eddy losses
x
f frequency at harmonic order number h
h
F enhancement factor for winding eddy losses
WE
F enhancement factor for stray losses in structural parts
SE
K ratio of the current I to the rated current I
h h 1
U a.c. separate source test voltage for the valve windings (r.m.s. value)
ac
U highest system voltage of the line winding
m
U highest d.c. voltage per valve bridge
dm
U d.c. separate source test voltage for the valve windings
dc
U polarity-reversal test voltage for the valve windings (d.c. voltage)
pr
U maximum phase to phase a.c. operating voltage of the valve windings of the
vm
convertor transformer
N number of six-pulse bridges in series from the neutral of the d.c. line to the rectifier
bridge connected to the transformer
"Valve side" and "line side" define the external connections of the transformer windings. Line
side refers to the winding connected to the a.c. network and valve side to the winding
connected to the convertor.
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61378-2 © IEC:2001 – 17 –
5 Ratings
5.1 General
The rating characteristics of the transformer are expressed in steady-state sinusoidal
quantities of current and voltages at rated fundamental frequency. The guaranteed losses,
impedances and noise level shall correspond to these values.
NOTE North American practice establishes nameplate rating in kVA based on both r.m.s. and fundamental
frequency.
5.2 Rated voltage
The rated voltage is the r.m.s. value of the fundamental component of the line-to-line voltage.
5.3 Rated current
The rated current is the r.m.s. value of the fundamental component of the line current.
5.4 Rated frequency
The rated frequency is the fundamental frequency of either 50 Hz or 60 Hz for which the
transformer is designed.
5.5 Rated power
The rated power is the product of the rated voltage and rated current, hence the rated three-
phase power is as follows:
SU=×3 ×I
R 11
6 Tolerances
6.1 General
The tolerances shall be in accordance with table 1 of IEC 60076-1, with the exceptions given
in 6.2.
6.2 Short-circuit impedance tolerances
The impedance at the principal tap shall not deviate by more than ±5 % of the guaranteed
value.
For transformers having a tapping range not exceeding 30 %, the impedance over the usual
operating part of the range shall not exceed ±5 % of the value at the principal tapping and not
more than ±10 % of the value at the principal tapping over all other parts of the range. The
usual part of the tapping range shall be agreed between the supplier and the purchaser.
The tolerances on impedance over the tapping range for transformers having a tapping range
greater than 30 % shall be agreed between supplier and purchaser before contract.
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61378-2 © IEC:2001 – 19 –
The impedance at the principal tapping and the variation of impedance over tapping range for
transformers of duplicate or similar design for the purpose of identical application in service or
interchangeability shall not exceed ±3 % of the mean test values.
Impedance
deviation %
+10
+5
–5
–10
–15 +15 Tap position %
Usual operating range
IEC 2676/2000
Figure 1 – Profile of short-circuit impedance tolerances for tapping ranges ≤30 %
6.3 Guarantees
The value of impedance at the principal tap shall be guaranteed. Impedances at other tap
positions may also be guaranteed by agreement between purchaser and supplier.
7 Losses
7.1 General
The total losses of a convertor transformer shall be the sum of the no-load loss and the load
loss at rated values. The guaranteed losses shall be within the tolerances of table 1 of
IEC 60076-1.
7.2 No-load loss
No-load loss and no-load current are measured in the same way as for conventional a.c.
transformers according to 10.5 of IEC 60076-1. This shall be the guaranteed no-load loss.
NOTE The harmonic voltages and d.c. bias currents have an effect on no-load loss and no-load current. However,
in practice the differences due to this effect can be disregarded in comparison to the total losses of the
transformer.
7.3 Load loss under rated power-frequency conditions
The load loss shall be measured in accordance with 10.4 of IEC 60076-1.
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61378-2 © IEC:2001 – 21 –
7.4 Load loss under service conditions
The currents flowing through the windings of convertor transformers contain certain harmonics
whose magnitudes depend on the parameters of the convertor station. The determination of
actual load loss in service cannot be deduced from one single load-loss measurement. The
procedure to determine the load loss in accordance with this standard includes two load-loss
measurements, certain assumptions on loss distribution and a specific calculation scheme
(see 10.3).
The supplier shall calculate the value of the actual service total load loss based on a given
harmonic spectrum for the load current. This spectrum shall be provided by the purchaser.
The calculation shall be made for the principal and the extreme tap positions. The calculated
losses may form a basis for guarantee for the purpose of loss evaluation.
According to IEC 61378-1,
– eddy and stray losses are assumed to be proportional to the square of the current;
– winding eddy losses are assumed to depend on the frequency with the exponent 2, and
stray losses in structural parts are assumed to follow the frequency with the exponent 0,8.
Eddy loss and stray loss:
2 k
∆P ∝ I × f
where
⎧2 for winding eddy losses,
k =
⎨
0,8 for stray losses.
⎩
Based on a given harmonic spectrum, the total service load loss can be calculated as follows:
2
P=+IRPFP× + ×F
N LN WE1 WE SE1 SE
where
25
2
I = I (25 is the highest harmonic to be evaluated)
∑
LN h
h=1
25
2 2
F = k ×h and
∑
WE h
h=1
25
2 0,8
F = k × h
∑
SE h
h=1
I f
h h
with k = and h =
h
I f
1 1
In case of three-winding transformers, the winding arrangement shall be considered for the
calculation of the eddy current losses in windings and of the stray losses in structural parts;
see also IEC 60146-1-1, IEC 60146-1-2 and IEC 60076-8.
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61378-2 © IEC:2001 – 23 –
7.5 Determination of hot-spot temperature
The procedure to determine the hot-spot temperature shall be in accordance with section 2 of
IEC 60354. It should be noted that the hot-spot temperature rise determined by this procedure
may not be the same as the value likely to be obtained in normal service because the extra
losses in service due to the harmonic current are mainly concentrated at the ends of the
windings whereas those occurring during the test are distributed throughout the winding. As a
result, the hot-spot generated during the test may be less than that developed in normal
convertor operation. In order to compensate for this difference in performance, an
enhancement factor for eddy losses will be calculated for the specific harmonic content of the
load current.
8 Insulation levels
8.1 Line windings
The insulation levels for the line terminals, windings and neutrals are defined in clause 5 of
IEC 60076-3:
– highest voltage for equipment applicable to a transformer winding, U ;
m
– rated insulation level: rated lightning and switching impulse withstand voltages (phase to
earth);
– separate source a.c. corresponding to insulation level of neutral terminal.
NOTE It is important that the transferred voltage does not exceed the specified switching impulse level of the
valve winding.
8.2 Valve windings
The purchaser shall specify the lightning and switching impulse levels in accordance with
tables 2, 3 and 4 of IEC 60076-3.
NOTE The insulation levels should be coordinated in such a way that there is an adequate margin in excess of
the dielectric stresses that appear in actual service.
8.2.1 Lightning impulse levels
The lightning impulse level of the valve winding shall be specified for each terminal to earth
and across the winding(s).
If chopped wave tests are required, the test voltage shall be as prescribed in clause 14 of
IEC 60076-3.
8.2.2 Switching impulse levels
The switching impulse level of the valve winding shall be specified for each terminal to earth.
However, windings for back-to-back schemes should not be tested, because they are normally
low-voltage windings, and there is no possibility for transferred switching impulse from the
d.c. system.
The valve windings are subjected to a transferred switching impulse during
...
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