SIST EN 60076-18:2012

Power transformers - Part 18: Measurement of frequency response

This part of the IEC 60076 series covers the measurement technique and measuring equipment to be used when a frequency response measurement is required either on-site or in the factory either when the test object is new or at a later stage. Interpretation of the result is not part of the normative text but some guidance is given in Annex B. This standard is applicable to power transformers, reactors, phase shifting transformers and similar equipment.

Leistungstransformatoren - Teil 18: Messung des Frequenzübertragungsverhaltens

Transformateurs de puissance - Partie 18: Mesure de la réponse en fréquence

La CEI 60076-18:2012 couvre la technique de mesure et l'appareillage de mesure à utiliser lorsqu'une mesure de réponse en fréquence est requise, soit sur site, soit en usine, lorsque l'objet à soumettre à essai est neuf ou à un stade plus avancé. La présente norme est applicable aux transformateurs de puissance, bobines d'inductance, transformateurs déphaseurs et appareillages similaires.

Močnostni transformatorji - 18. del: Merjenje frekvenčne odzivnosti

Ta del serije standardov IEC 60076 pokriva metodo merjenja in merilno opremo za uporabo, ko je potrebno merjenje frekvenčnega odziva na mestu samem ali v tovarni, ne glede na to, ali je preizkušani predmet nov ali starejši. Interpretacija rezultata ni del normativnega besedila, vendar je v dodatku B navedenih nekaj napotkov. Ta standard velja za močnostne transformatorje, reaktorje, prečne transformatorje in podobno opremo.

General Information

• Status: Published
• Publication Date: 16-Oct-2012
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: ETR - Power transformers
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 12-Oct-2012
• Due Date: 17-Dec-2012
• Completion Date: 17-Oct-2012
• Ref Project: EN 60076-18:2012 - Power transformers - Part 18: Measurement of frequency response

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60076-18:2012
01-december-2012
0RþQRVWQLWUDQVIRUPDWRUMLGHO0HUMHQMHIUHNYHQþQHRG]LYQRVWL
Power transformers - Part 18: Measurement of frequency response
Transformateurs de puissance - Partie 18: Mesure de la réponse en fréquence
Ta slovenski standard je istoveten z: EN 60076-18:2012
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
SIST EN 60076-18:2012 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60076-18:2012

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SIST EN 60076-18:2012

EUROPEAN STANDARD
EN 60076-18

NORME EUROPÉENNE
September 2012
EUROPÄISCHE NORM

ICS 29.180


English version


Power transformers -
Part 18: Measurement of frequency response
(IEC 60076-18:2012)


Transformateurs de puissance -  Leistungstransformatoren -
Partie 18: Mesure de la réponse Teil 18: Messung des
en fréquence Frequenzübertragungsverhaltens
(CEI 60076-18:2012) (IEC 60076-18:2012)




This European Standard was approved by CENELEC on 2012-08-13. 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60076-18:2012 E

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SIST EN 60076-18:2012
EN 60076-18:2012 - 2 -
Foreword
The text of document 14/718/FDIS, future edition 1 of IEC 60076-18, prepared by IEC/TC 14 "Power
transformers" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN 60076-18:2012.
The following dates are fixed:
(dop) 2013-05-13
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2015-08-13
• latest date by which the national
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.

Endorsement notice
The text of the International Standard IEC 60076-18:2012 was approved by CENELEC as a European
Standard without any modification.

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SIST EN 60076-18:2012




IEC 60076-18

®


Edition 1.0 2012-07




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Power transformers –

Part 18: Measurement of frequency response




Transformateurs de puissance –

Partie 18: Mesure de la réponse en fréquence
















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX X


ICS 29.180 ISBN 978-2-83220-222-7



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 60076-18:2012
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CONTENTS

FOREWORD . 5
1 Scope . 7
2 Terms and definitions . 7
3 Purpose of frequency response measurements . 8
4 Measurement method . 9
4.1 General . 9
4.2 Condition of the test object during measurement . 10
4.3 Measurement connection and checks . 11
4.3.1 Measurement connection and earthing . 11
4.3.2 Zero-check measurement . 11
4.3.3 Repeatability check . 11
4.3.4 Instrument performance check . 11
4.4 Measurement configuration . 12
4.4.1 General . 12
4.4.2 Principles for choosing the measurement configuration . 12
4.4.3 Star- and auto-connected windings with a neutral terminal . 13
4.4.4 Delta windings and other windings without an accessible neutral . 13
4.4.5 Zig-zag connected windings. 14
4.4.6 Two-winding three-phase transformers . 14
4.4.7 Three-phase auto-transformers . 14
4.4.8 Phase shifting transformers . 14
4.4.9 Reactors . 14
4.4.10 Method for specifying additional measurements . 14
4.5 Frequency range and measurement points for the measurement . 15
5 Measuring equipment . 15
5.1 Measuring instrument . 15
5.1.1 Dynamic range . 15
5.1.2 Amplitude measurement accuracy . 16
5.1.3 Phase measurement accuracy . 16
5.1.4 Frequency range . 16
5.1.5 Frequency accuracy . 16
5.1.6 Measurement resolution bandwidth . 16
5.1.7 Operating temperature range . 16
5.1.8 Smoothing of recorded data . 16
5.1.9 Calibration . 16
5.2 Measurement leads . 16
5.3 Impedance . 17
6 Measurement records . 17
6.1 Data to be recorded for each measurement . 17
6.2 Additional information to be recorded for each set of measurements . 18
Annex A (normative) Measurement lead connections . 20
Annex B (informative) Frequency response and factors that influence the
measurement . 23
Annex C (informative) Applications of frequency response measurements . 37

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SIST EN 60076-18:2012
60076-18 © IEC:2012 – 3 –
Annex D (informative) Examples of measurement configurations . 39
Annex E (informative) XML data format . 43
Bibliography . 44

Figure 1 – Example schematic of the frequency response measurement circuit. 10
Figure A.1 – Method 1 connection . 21
Figure A.2 – Method 3 connection . 22
Figure B.1 – Presentation of frequency response measurements . 23
Figure B.2 – Comparison with a baseline measurement . 24
Figure B.3 – Comparison of the frequency responses of twin transformers . 24
Figure B.4 – Comparison of the frequency responses from sister transformers . 25
Figure B.5 – Comparison of the frequency responses of three phases of a winding. 25
Figure B.6 – General relationships between frequency response and transformer
structure and measurement set-up for HV windings of large auto-transformer . 27
Figure B.7 – Effect of tertiary delta connection on the frequency response of a series
winding . 28
Figure B.8 – Effect of star neutral connection on the tertiary winding response . 29
Figure B.9 – Effect of star neutral termination on series winding response . 29
Figure B.10 – Measurement results showing the effect of differences between phases
in internal leads connecting the tap winding and OLTC . 30
Figure B.11 – Effect of measurement direction on frequency response . 30
Figure B.12 – Effect of different types of insulating fluid on frequency response . 31
Figure B.13 – Effect of oil filling on frequency response . 31
Figure B.14 – Effect of a DC injection test on the frequency response . 32
Figure B.15 – Effect of bushings on frequency response . 32
Figure B.16 – Effect of temperature on frequency response . 33
Figure B.17 – Examples of bad measurement practice . 34
Figure B.18 – Frequency response of a tap winding before and after partial axial
collapse and localised inter-turn short-circuit with a photograph of the damage . 34
Figure B.19 – Frequency response of an LV winding before and after axial collapse
due to clamping failure with a photograph of the damage [8] . 35
Figure B.20 – Frequency response of a tap winding with conductor tilting with a
photograph of the damage [1] . 36
Figure D.1 – Winding diagram of an auto-transformer with a line-end tap changer . 40
Figure D.2 – Connection diagram of an inductive inter-winding measurement on a
three-phase YNd1 transformer . 41
Figure D.3 – Connection diagram for a capacitive inter-winding measurement on a
three-phase YNd1 transformer . 42
Figure D.4 – Connection diagram for an end-to-end short-circuit measurement on a
three-phase YNd1 transformer . 42

Table 1 – Standard measurements for a star connected winding with taps . 13
Table 2 – Standard measurements for delta connected winding without tap . 14
Table 3 – Format for specifying additional measurements . 15
Table D.1 – Standard end-to-end measurements on a three-phase auto-transformer . 39
Table D.2 – Tap-changer connections . 40

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SIST EN 60076-18:2012
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Table D.3 – Inductive inter-winding measurements on a three-phase YNd1 transformer . 41
Table D.4 – Capacitive inter-winding measurements on a three-phase YNd1
transformer . 41
Table D.5 – End-to-end short-circuit measurements on a three-phase YNd1
transformer . 42

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SIST EN 60076-18:2012
60076-18 © IEC:2012 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

POWER TRANSFORMERS –

Part 18: Measurement of frequency response


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
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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
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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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
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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 60076-18 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
14/718/FDIS 14/728/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.
A list of all parts of the IEC 60076 series can be found, under the general title Power
transformers, on the IEC website.

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SIST EN 60076-18:2012
– 6 – 60076-18 © IEC:2012
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.

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SIST EN 60076-18:2012
60076-18 © IEC:2012 – 7 –
POWER TRANSFORMERS –

Part 18: Measurement of frequency response



1 Scope
This part of the IEC 60076 series covers the measurement technique and measuring
equipment to be used when a frequency response measurement is required either on-site or
in the factory either when the test object is new or at a later stage. Interpretation of the result
is not part of the normative text but some guidance is given in Annex B. This standard is
applicable to power transformers, reactors, phase shifting transformers and similar
equipment.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
frequency response
amplitude ratio and phase difference between the voltages measured at two terminals of the
test object over a range of frequencies when one of the terminals is excited by a voltage
source
Note 1 to entry: The frequency response measurement result is a series of amplitude ratios and phase differences
at specific frequencies over a range of frequency.
Note 2 to entry: The measured voltage is the voltage developed across an impedance and so it is also related to
current.
2.2
frequency response analysis
FRA
technique used to detect damage by the use of frequency response measurements
Note 1 to entry: The terms SFRA and IFRA are commonly used and refer to the use of either a swept frequency
voltage source or an impulse voltage source. Provided the measuring equipment complies with the requirements of
Clause 5, this standard can be applied to both techniques.
2.3
source lead
lead connected to the voltage source of the measuring instrument used to supply an input
voltage to the test object
2.4
reference lead
V
in
lead connected to the reference channel of the measuring instrument used to measure the
input voltage to the test object
2.5
response lead
V
out
lead connected to the response channel of the measuring instrument used to measure the
output voltage of the test object

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SIST EN 60076-18:2012
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2.6
end-to-end measurement
frequency response measurement made on a single coil (phase winding) with the source and
reference (V ) leads connected to one end and the response (V ) lead connected to the
in out
other end
2.7
сapacitive inter-winding measurement
frequency response measurement made on two adjacent coils (windings of the same phase)
with the source and reference (V ) leads connected to one end of a winding, the response
in
(V ) lead connected to one end of another winding and with the other winding ends floating
out
Note 1 to entry: This type of measurement is not applicable to windings which have common part or connection
between them.
2.8
inductive inter-winding measurement
frequency response measurement made on two adjacent coils (windings of the same phase)
with the source and reference (V ) leads connected to one end of the higher voltage winding,
in
the response (V ) lead connected to one end of the other winding and with the other ends of
out
both windings grounded
2.9
end-to-end short circuit measurement
frequency response measurement made on a single coil (phase winding) with the source and
reference (V ) leads connected to one end, the response (V ) lead connected to the other
in out
end, and another winding of the same phase short-circuited
2.10
baseline measurement
frequency response measurement made on a test object to provide a basis for comparison
with a future measurement on the same test object in the same configuration
3 Purpose of frequency response measurements
Frequency response measurements are made so that Frequency Response Analysis (FRA)
can be carried out. FRA can be used to detect changes to the active part of the test object
(windings, leads and core).
NOTE FRA is generally used to detect geometrical changes and electrical short-circuits in the windings, see
Annex B.
Some examples of conditions that FRA can be used to assess are:
• damage following a through fault or other high current event (including short-circuit
testing),
• damage following a tap-changer fault,
• damage during transportation, and
• damage following a seismic event.
Further information on the application of frequency response measurements is given in
Annex C.
The detection of damage using FRA is most effective when frequency response measurement
data is available from the transformer when it is in a known good condition (baseline
measurement), so it is preferable to carry out the measurement on all large transformers
either in the factory or when the transformer is commissioned at site or both. If a baseline

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SIST EN 60076-18:2012
60076-18 © IEC:2012 – 9 –
measurement is not available for a particular transformer, reference results may be obtained
from either a similar transformer or another phase of the same transformer (see Annex B).
Frequency response measurements can also be used for power system modelling including
transient overvoltage studies.
4 Measurement method
4.1 General
To make a frequency response measurement, a low voltage signal is applied to one terminal
of the test object with respect to the tank. The voltage measured at this input terminal is used
as the reference signal and a second voltage signal (the response signal) is measured at a
second terminal with reference to the tank. The frequency response amplitude is the scalar
ratio between the response signal (V ) and the reference voltage (V ) (presented in dB) as
out in
a function of the frequency. The phase of the frequency response is the phase difference
between V and V (presented in degrees).
in out
The response voltage measurement is made across an impedance of 50 Ω. Any coaxial lead
connected between the test object terminal and the voltage measuring instrument shall have a
matched impedance. To make an accurate ratio measurement, the technical parameters of
the reference and response channels of the measuring instrument and any measurement
leads shall be identical.
NOTE 1 The characteristic impedance of the coaxial measuring leads is chosen to match the measuring channel
input impedance to minimise signal reflections and reduce the influence of the coaxial lead on the measurement to
the point where it has little or no practical effect on the measurement within the measurement frequency range.
With a matched impedance lead, the measuring impedance is effectively applied at the test object terminal.
NOTE 2 As V /V varies over a wide range, it is expressed in decibels (dB). The relative voltage response in dB
out in
is calculated as 20 × log (V /V ), where (V /V ) is the scalar ratio.
10 out in out in
An example of the general layout of the measurement method using coaxial measuring leads
is shown in Figure 1.

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SIST EN 60076-18:2012
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B

A
C

D

50 Ω

50 Ω
V V
out
in

IEC  1370/12
A source lead
B reference lead
C response lead
D earth connection
Figure 1 – Example schematic of the frequency response measurement circuit
4.2 Condition of the test object during measurement
For factory and site measurements, the test object shall be fully assembled as for service
complete with all bushings, but coolers and related auxiliaries do not need to be assembled.
Liquid or gas filled transformers and reactors shall be filled with liquid or gas of the same type
(similar relative permittivity) as that which is to be used in service. All busbars or other system
or test connections shall be removed and there shall be no connections to the test object
other than those being used for the specific measurement being performed. If internal current
transformers are installed but not connected to a protection or measurement system, the
secondary terminals shall be shorted and earthed. The core and frame to tank connections
shall be complete and the tank shall be connected to earth.
If the transformer is not assembled in the factory in the service condition, for example if oil/air
bushings are used in the factory and oil/SF bushings are to be used in service then the FRA
6
baseline measurement can only be performed at site. Transport configuration measurements
may still be possible see below.
If special connections have been specified by the purchaser and are provided on the test
object to enable a frequency response measurement to be made when it is arranged for
transport, then additional measurements shall be made in the transport configuration (drained
if required for transport) before transport and when delivered to site or as specified by the
purchaser.
For site measurements, the test object shall be disconnected from the associated electrical
system at all winding terminals and made safe for testing. Line, neutral and any tertiary line
connections shall be disconnected but tank earth, auxiliary equipment and current transformer
service connections shall remain connected. In the case where two connections to one corner
of a delta winding are brought out, the transformer shall be measured with the delta closed
(see also 4.4.4). In instances where it is impossible to connect directly to the terminal, then
the connection details shall be recorded with the measurement data since the additional bus
bars connected to the terminals may impact on the measurement results.

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SIST EN 60076-18:2012
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NOTE There may be a difference in the connection of current transformers (CTs) between measurements made
on-site and those made in the factory, the change in frequency response between a transformer with shorted and
earthed CTs and one with the CTs connected to a low impedance protection system is normally negligible.
If the transformer is directly
...