SIST EN 60076-4:2004
(Main)Power transformers -- Part 4: Guide to the lightning impulse and switching impulse testing - Power transformers and reactors
Power transformers -- Part 4: Guide to the lightning impulse and switching impulse testing - Power transformers and reactors
Gives guidance and explanatory comments on the existing procedures for lightning and switching impulse testing of power transformers to supplement the requirements of EN 60076-3. Also generally applicable to the testing of reactors (see EN 60289), modifications to power transformer procedures being indicated where required. Information is given on waveshapes, test circuits including test connections, earthing practices, failure detection methods, test procedures, measuring techniques and interpretation of results.
Leistungstransformatoren -- Teil 4: Leitfaden zur Blitz- und Schaltstoßspannungsprüfung von Leistungstransformatoren und Drosselspulen
Transformateurs de puissance -- Partie 4: Guide pour les essais au choc de foudre et au choc de manoeuvre - Transformateurs de puissance et bobines d'inductance
Donne des directives et des commentaires explicatifs sur les méthodes d'essais d'impulsions de choc de foudre et de manoeuvre existantes pour les transformateurs de puissance, afin de compléter les prescriptions de la EN 60076-3. Il est également généralement applicable aux essais des bobines d'inductance (voir la EN 60289): Les modifications aux méthodes des transformateurs de puissance sont indiquées, si nécessaire. Des informations sont données sur les formes d'onde, les circuits d'essai comprenant les connexions d'essai, les pratiques de mise à la terre, les méthodes de détection de défaillance, les méthodes d'essai, les techniques de mesurage et l'interprétation des résultats.
Power transformers - Part 4: Guide to the lightning impulse and switching impulse testing - Power transformers and reactors (IEC 60076-4:2002)
General Information
Relations
Standards Content (Sample)
SLOVENSKI SIST EN 60076-4:2004
STANDARD
februar 2004
Power transformers - Part 4: Guide to the lightning impulse and switching impulse
testing - Power transformers and reactors (IEC 60076-4:2002)
ICS 29.180 Referenčna številka
SIST EN 60076-4:2004(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60076-4
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2002
ICS 29.180
English version
Power transformers
Part 4: Guide to the lightning impulse and switching impulse testing -
Power transformers and reactors
(IEC 60076-4:2002)
Transformateurs de puissance Leistungstransformatoren
Partie 4: Guide pour les essais au choc Teil 4: Leitfaden zur Blitz-
de foudre et au choc de manoeuvre - und Schaltstoßspannungsprüfung
Transformateurs de puissance von Leistungstransformatoren
et bobines d'inductance und Drosselspulen
(CEI 60076-4:2002) (IEC 60076-4:2002)
This European Standard was approved by CENELEC on 2002-09-01. 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, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, 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
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60076-4:2002 E
---------------------- Page: 2 ----------------------
EN 60076-4:2002 - 2 -
Foreword
The text of document 14/413/FDIS, future edition 1 of IEC 60076-4, prepared by IEC TC 14, Power
transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60076-4 on 2002-09-01.
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) 2003-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-09-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A and B are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60076-4:2002 was approved by CENELEC as a European
Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60076-4:2002
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
1) 2)
IEC 60060-1 - High-voltage test techniques HD 588.1 S1 1991
Part 1: General definitions and test
requirements
1) 2)
IEC 60060-2 - Part 2: Measuring systems EN 60060-2 1994
1) 2)
IEC 60076-3 - Power transformers EN 60076-3 2001
Part 3: Insulation levels, dielectric tests
and external clearances in air
1) 2)
IEC 60289 - Reactors EN 60289 1994
1) 2)
IEC 61083-1 - Instruments and software used for EN 61083-1 2001
measurement in high-voltage impulse
tests
Part 1: Requirements for instruments
1) 2)
IEC 61083-2 - Digital recorders for measurements in EN 61083-2 1997
high-voltage impulse tests
Part 2: Evaluation of software used for
the determination of the parameters of
impulse waveforms
1)
Undated reference.
2)
Valid edition at date of issue.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE IEC
60076-4
INTERNATIONAL
Première édition
STANDARD
First edition
2002-06
Transformateurs de puissance –
Partie 4:
Guide pour les essais au choc de foudre
et au choc de manoeuvre –
Transformateurs de puissance
et bobines d'inductance
Power transformers –
Part 4:
Guide to the lightning impulse and
switching impulse testing –
Power transformers and reactors
IEC 2002 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 any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
XB
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 5 ----------------------
60076-4 IEC:2002 – 3 –
CONTENTS
FOREWORD.7
1 Scope.11
2 Normative references .11
3 General .13
4 Specified waveshapes .13
5 Test circuit .13
6 Calibration.17
7 Lightning impulse tests .17
7.1 Waveshapes.17
7.2 Impulses chopped on the tail .19
7.3 Terminal connections and applicable methods of failure detection.21
7.4 Test procedures .23
7.5 Recording of tests .25
8 Switching impulse tests .31
8.1 Special requirements.31
8.2 Transformers.31
8.3 Reactors.39
9 Interpretation of oscillograms or digital recordings.43
9.1 Lightning impulse .43
9.2 Switching impulse.47
10 Digital processing, including transfer function analysis .49
11 Impulse test reports.53
Annex A (informative) Principles of waveshape control .63
Annex B (informative) Typical oscillograms and digital recordings.77
Figure 1 – Typical impulse test circuit .55
Figure 2 – Lightning impulse test terminal connections and applicable methods
of failure detection .57
Figure 3 – Transformer and reactor switching impulse waveshapes .59
Figure 4 – Switching impulse test terminal connections and methods
of failure detection .61
Figure A.1 – Waveshape control for high-impedance windings .63
Figure A.2 – Wavetail control for low impedance windings .67
Figure A.3 – Damped oscillation .69
Figure A.4 – Effects due to short length of wavetail.73
Figure A.5 – Winding earthed through a resistor .75
Figure A.6 – Resistance earthing of low-impedance windings .75
Figure B.1 – Lightning impulse, full-wave failure – Line-to-neutral breakdown
across high-voltage winding of 400 kV generator transformer .81
Figure B.2 – Lightning impulse, full-wave failure – Breakdown between discs
at entrance to high-voltage winding of 115 kV transformer .83
---------------------- Page: 6 ----------------------
60076-4 IEC:2002 – 5 –
Figure B.3 – Lightning impulse, interlayer breakdown in coarse-step tapping winding
of a 400/220 kV transformer.85
Figure B.4 – Lightning impulse, full-wave failure – Breakdown between leads
of two 1,1 % sections of outside tapping winding of 400 kV generator transformer .87
Figure B.5 – Lightning impulse, full-wave failure – Breakdown short-circuiting
one section of the fine-step tapping winding of a 220 kV transformer .89
Figure B.6 – Lightning impulse, full-wave failure – Breakdown between parallel
conductors in a multi-conductor main high-voltage winding of a 220/110 kV transformer.91
Figure B.7 – Lightning impulse, full-wave failure – Breakdown between foils of 66 kV
bushing on tested winding.93
Figure B.8 – Lightning impulse, chopped-wave failure – Breakdown between turns
in the main high-voltage winding of a 115 kV transformer .95
Figure B.9 – Lightning impulse, chopped-wave failure – Breakdown between turns
in a fine-step tapping winding of a 220 kV transformer .97
Figure B.10 – Chopped lightning impulse – Impulses at different voltage levels
with identical times to chopping when testing a 115 kV transformer .99
Figure B.11 – Chopped lightning impulse – Effects of differences in times to chopping
when testing a 220 kV transformer.101
Figure B.12 – Full lightning impulse – Effect of non-linear resistors embodied
in neutral end on-load tap-changer of a transformer with separate windings.103
Figure B.13 – Full lightning impulse – Effect of generator firing differences
at different voltage levels when testing a 400 kV transformer.105
Figure B.14 – Switching impulse – Satisfactory test on a 400 kV three-phase
generator transformer .107
Figure B.15 – Switching impulse – Breakdown by axial flashover of the main high-
voltage winding of a 525 kV single-phase, generator transformer.109
Figure B.16 – Switching impulse – Satisfactory test on a 33 Mvar, 525 kV
single-phase shunt reactor.111
Figure B.17 – Lightning impulse – Comparison of the transfer function
of a full wave and a chopped wave .113
Figure B.18 – Full lightning impulse – Evaluation of a non-standard waveshape –
Influence of in-built smoothing algorithms in digitizers .115
Figure B.19 – Full lightning impulse – Non-standard waveshape,
superimposed oscillations with >50 % amplitude and frequency <0,5 MHz .115
Figure B.20 – Chopped lightning impulse – Non-standard chopped wave
on a layer type winding .117
Figure B.21 – Full lightning impulse – Non-standard waveshape, comparison
of non-standard waveshapes by digitizers of different make from the same recording .119
Figure B.22 – Full lightning impulse – Test-circuit problem caused by a sparkover
to earth from a measuring cable.121
Figure B.23 – Full lightning impulse – Failure digital recordings of a flashover between
tap leads of a tap changer and of a flashover between coarse and fine tapping winding.123
Table B.1 – Summary of examples illustrated in oscillograms and digital recordings .77
---------------------- Page: 7 ----------------------
60076-4 IEC:2002 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 4: Guide to the lightning impulse and switching impulse testing –
Power transformers and reactors
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 60076-4 has been prepared by IEC technical committee 14: Power
transformers.
This International Standard cancels and replaces IEC 60722 published in 1982 and
constitutes a technical revision of that document.
The text of this standard is based on the following documents:
FDIS Report on voting
14/413/FDIS 14/446/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.
Annexes A and B are for information only.
---------------------- Page: 8 ----------------------
60076-4 IEC:2002 – 9 –
IEC 60076 consists of the following parts, under the general title Power transformers:
Part 1: General
Part 2: Temperature rise
Part 3: Insulation levels, dielectric tests and external clearances in air
Part 4: Guide to lightning impulse and switching impulse testing – Power transformers and
reactors
Part 5: Ability to withstand short-circuit
Part 8: Application guide
Part 10: Determination of sound levels
The committee has decided that the contents of this publication will remain unchanged until 2007.
At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
---------------------- Page: 9 ----------------------
60076-4 IEC:2002 – 11 –
POWER TRANSFORMERS –
Part 4: Guide to the lightning impulse and switching impulse testing –
Power transformers and reactors
1 Scope
This part of IEC 60076 gives guidance and explanatory comments on the existing procedures for
lightning and switching impulse testing of power transformers to supplement the requirements of
IEC 60076-3. It is also generally applicable to the testing of reactors (see IEC 60289),
modifications to power transformer procedures being indicated where required.
Information is given on waveshapes, test circuits including test connections, earthing
practices, failure detection methods, test procedures, measuring techniques and interpretation
of results.
Where applicable, the test techniques are as recommended in IEC 60060-1 and IEC 60060-2.
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 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60060-2, High-voltage test techniques – Part 2: Measuring systems
IEC 60076-3, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60289, Reactors
IEC 61083-1, Instruments and software used for measurement in high-voltage impulse tests –
Part 1: Requirements for instruments
IEC 61083-2, Digital recorders for measurements in high-voltage impulse tests – Part 2:
Evaluation of software used for the determination of the parameters of impulse waveforms
---------------------- Page: 10 ----------------------
60076-4 IEC:2002 – 13 –
3 General
This standard is primarily based on the use of conventional impulse generators for both
lightning and switching impulse testing of transformers and reactors. The practice of switching
impulse generation with discharge of a separate capacitor into an intermediate or low-voltage
winding is also applicable. However, the method which employs an additional inductance in
series with the capacitor to provide slightly damped oscillations transferred into the high-
voltage winding is not applicable.
Alternative means of switching impulse generation or simulation such as d.c. current
interruption on an intermediate or low-voltage winding or the application of a part-period of
power frequency voltage are not discussed since these methods are not as generally
applicable.
Different considerations in the choice of test circuits (terminal connections) for lightning and
switching impulse tests apply for transformers and reactors. On transformers, all terminals
and windings can be lightning impulse tested to specific and independent levels. In switching
impulse testing, however, because of the magnetically transferred voltage, a specified test
level may only be obtained on one winding (see IEC 60076-3).
Whilst, on reactors, lightning impulse testing is similar to that on transformers, i.e., all
terminals can be tested separately, different considerations apply and different problems arise
in switching impulse testing. Hence, in this standard, lightning impulse testing is covered by a
common text for both transformers and reactors whilst switching impulse testing is dealt with
separately for the two types of equipment.
4 Specified waveshapes
The voltage waveshapes to be used normally during lightning and switching impulse testing of
transformers and reactors are given in IEC 60076-3 and the methods for their determination
are given in IEC 60060-1.
5 Test circuit
The physical arrangement of test equipment, test object and measuring circuits can be divided
into three major circuits:
– the main circuit including the impulse generator, additional waveshaping components and
the test object;
– the voltage measuring circuit;
– the chopping circuit where applicable.
This basic arrangement is shown in figure 1.
---------------------- Page: 11 ----------------------
60076-4 IEC:2002 – 15 –
The following parameters influence the impulse waveshape;
a) the effective capacitance C , and inductance of the test object, L ; C is constant for any
t t t
given design and any given waveshape, L is also a constant for any given design.
t
The effective L , however, may be influenced by the terminal treatment. It varies between
t
the leakage inductance L for short-circuited terminals and L for open-circuited terminals.
s o
More details in this respect are given in 7.1 and 7.3 and in annex A;
b) the generator capacitance C ;
g
c) waveshaping components, both internal and external to the generator, R , R , R , C
si se p L
(plus, where applicable, the impedance of a voltage divider Z );
1
d) the stray inductance and capacitance of the generator and the complete test circuit;
e) chopping equipment, where applicable.
The front time T is determined mainly by combination of the effective surge capacitance of
1
the test object, including C , and the generator internal and external series resistances.
L
The time to half-value T is, for lightning impulses, primarily determined by the generator
2
capacitance, the inductance of the test object and the generator discharge resistance or any
other parallel resistance. However, there are cases, for example, windings of extremely low
inductance, where the series resistance will have a significant effect also on the wavetail.
For switching impulses, other parameters apply; these are dealt with in clause 8.
The test equipment used in lightning and switching impulse applications is basically the same.
Differences are in details only, such as values of resistors and capacitors (and the terminal
connections of the test object).
To meet the different requirements of the waveshape for lightning and switching impulses,
due consideration has to be given to the selection of the impulse generator parameters, such
as capacitance and series and discharge (parallel) resistances. For switching impulses, large
values of series resistors and/or load capacitors may be necessary, which will result in
significant reduction of the efficiency.
While the output voltage of the impulse generator is determined by the test levels of the
windings with respect to their highest voltage for equipment U for the test object, the
m
required energy storage capability is essentially dependent on the inherent impedances of
the test object.
A brief explanation of the principles of waveshape control is given in annex A.
The arrangement of the test plant, test object and the interconnecting cables, earthing strips,
and other equipment is limited by the space in the test room and, particularly, the proximity
effect of any structures. During impulse testing, zero potential cannot be assumed throughout
the earthing systems due to the high values and rates of change of impulse currents and
voltages and the finite impedances involved. Therefore, the selection of a proper reference
earth is important.
---------------------- Page: 12 ----------------------
60076-4 IEC:2002 – 17 –
The current return path between the test object and the impulse generator should be of low
impedance. It is good practice to firmly connect this current return path to the general earth
system of the test room, preferably close to the test object. This point of connection should be
used as reference earth and to attain good earthing of the test object it should be connected
to the reference earth by one or several conductors of low impedance (see IEC 60060-2).
The voltage measuring circuit, which is a separate loop of the test object carrying only the
measuring current and not any major portion of the impulse current flowing through the
windings under test, should also be effectively connected to the same reference earth.
In switching impulse testing, since the rates of change of the impulse voltages and currents
are much reduced compared with those in a lightning impulse test and no chopping circuit is
involved, the problems of potential gradients around the test circuit and with respect to the
reference earth are less critical. Nevertheless, it is suggested that, as a precaution, the same
earthing practices should be followed as used for lightning impulse testing.
6 Calibration
It is not the intention of this standard to give any recommendation on measuring systems or
their calibration but, of course, the apparatus which is used should be approved in
accordance with IEC 60060. Before a test, an overall check of the test circuit and the
measuring system may be performed at a voltage lower than the reduced voltage level. In this
check, voltage may be determined by means of a sphere gap or by comparative measurement
with another approved device. When using a sphere gap, it should be recognized that this is
only a check and does not replace the periodically performed calibration of the approved
measuring system. After any check has been made, it is essential that neither the measuring
nor the test circuit is altered except for the removal of any devices for checking.
Information on types of voltage dividers, their applications, accuracy, calibration and checking
is given in IEC 60060-2.
7 Lightning impulse tests
7.1 Waveshapes
The values of waveshape specified may not always be obtainable. In the impulse testing of
large power transformers and reactors, of low winding inductance and/or high surge
capacitance, wider tolerances may have to be accepted.
The surge capacitance of the transformer under test being constant, the series resistance
may have to be reduced in an attempt to obtain the correct front time T or rate of rise, but the
1
reduction should not be to the extent that oscillations on the crest of the voltage wave become
excessive. If it is considered desirable to have a short front time (preferably within the
specified limits) then oscillations and/or overshoots greater than ±5 % of the peak voltage,
allowed in IEC 60060-1, may have to be accepted. In such an event, a compromise between
the extent of allowable oscillations and the obtainable front time is necessary. In general,
oscillations not greater than ±10 % should be aimed at, even with extensions to the front time
as necessary and as agreed between manufacturer and purchaser. The value of the test
voltage is determined according to the principles of IEC 60060-1.
---------------------- Page: 13 ----------------------
60076-4 IEC:2002 – 19 –
For large power transformers and particularly the intermediate and low-voltage windings
thereof, the virtual time to half-value T may not be achievable within the value set by the
2
tolerance. The inductance of such windings may be so low that the resulting waveshape is
oscillat
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.