IEC 60076-19-1:2023

IEC 60076-19-1
®

Edition 1.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Power transformers –
Part 19-1: Rules for the determination of uncertainties in the measurement of the
losses of power transformers

Transformateurs de puissance –
Partie 19-1: Règles pour la détermination des incertitudes de mesure des pertes
des transformateurs de puissance
IEC 60076-19-1:2023-05(en-fr)

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IEC 60076-19-1

®


Edition 1.0 2023-05




INTERNATIONAL



STANDARD




NORME


INTERNATIONALE
colour

inside










Power transformers –

Part 19-1: Rules for the determination of uncertainties in the measurement of the

losses of power transformers



Transformateurs de puissance –

Partie 19-1: Règles pour la détermination des incertitudes de mesure des pertes


des transformateurs de puissance












INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE





ICS 29.180  ISBN 978-2-8322-7024-0




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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– 2 – IEC 60076-19-1:2023 © IEC 2023
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
4 Symbols . 11
4.1 General symbols . 11
4.2 Symbols for uncertainty . 12
4.2.1 General designations . 12
4.2.2 Specific designations . 12
5 Power measurement, systematic deviation and uncertainty . 12
5.1 General . 12
5.2 Traceability . 13
5.3 Model function . 13
5.4 Measuring systems . 13
6 Procedures for no-load loss measurement . 13
6.1 General . 13
6.2 Model function for no-load losses at reference conditions . 14
6.3 Uncertainty budget for no-load loss . 15
7 Procedures for load loss measurement . 16
7.1 General . 16
7.2 Model function for load loss measurement at rated current . 16
7.3 Model function for load loss at rated current and reference temperature . 17
7.4 Uncertainty budget for the measured power P recalculated to rated current . 18
2
7.4.1 General . 18
7.4.2 Uncertainties of measured load loss power P at ambient temperature θ . 18
2 2
7.5 Uncertainty budget for reported load loss at reference temperature . 18
8 Three-phase power calculations . 19
9 Reporting. 20
10 Estimate of corrections and uncertainty contributions . 20
10.1 Instrument transformers . 20
10.1.1 General . 20
10.1.2 Ratio error of instrument transformers . 21
10.1.3 Phase displacement of instrument transformers . 22
10.2 Voltage and current measurements . 24
10.3 Power meter . 25
10.4 Advanced system with specified system uncertainty . 25
10.5 Correction to sinusoidal waveform . 26
10.6 Winding resistance measurement . 26
10.7 Winding temperature at load loss measurement . 27
10.7.1 General . 27
10.7.2 R and θ determined from temperature measurement . 27
2 2
10.7.3 R and θ determined by resistance measurement . 28
2 2
Annex A (informative) Example of no-load loss uncertainty evaluation – Advanced
measuring system . 30

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IEC 60076-19-1:2023 © IEC 2023 – 3 –
A.1 General (intent of example) . 30
A.2 Transformer specification . 30
A.3 Measuring system . 30
A.4 Measurements . 31
A.5 Correction of measured values. 31
A.6 Calculation of uncertainty . 31
A.7 Reported loss and uncertainty estimate . 32
Annex B (informative) Example of no-load loss uncertainty evaluation – Calibration
based procedure . 33
B.1 General . 33
B.2 Transformer specification . 33
B.3 Measuring system . 33
B.4 Measurements . 34
B.5 Correction of measured values. 35
B.6 Uncertainty calculation . 35
B.7 Reported loss and uncertainty estimate . 36
Annex C (informative) Example of load loss uncertainty evaluation class index
procedure . 37
C.1 General . 37
C.2 Transformer specification . 37
C.3 Measuring system . 37
C.4 Measurements . 38
C.5 Calculation in accordance with IEC 60076-1 . 39
C.6 Uncertainty calculation . 39
C.7 Reported loss and uncertainty estimate . 41
Annex D (informative) Determination of exponent n in expression for no-load loss . 42
Annex E (informative) Measurement uncertainty and test results . 44
E.1 General . 44
E.2 Test results, guarantees, tolerances, uncertainty limits . 44
E.3 Traceability as tool for quality assurance . 44
E.4 Means and methods to prove uncertainty claims and traceability . 45
E.4.1 Calibration . 45
E.4.2 Calibration certificate . 46
E.4.3 Guidance on scope of a calibration . 47
Annex F (normative) Calculation of uncertainty of losses with different reference
temperatures and/or winding material . 48
Bibliography . 49

Figure D.1 – Evaluation of exponent n from data in Table D.1 . 43

Table 1 – Measured no-load loss uncertainties . 16
Table 2 – Measured load loss uncertainties at ambient temperature . 18
Table 3 – Absolute uncertainty of load losses P reported at reference temperature θ . 19
LL r
Table 4 – Measured no-load loss uncertainties, advanced system . 25
Table 5 – Measured load loss uncertainties at ambient temperature, advanced system . 26
Table A.1 – Three-phase transformer oil immersed transformer . 30
Table A.2 – Uncertainty specification of the power measuring system . 30

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– 4 – IEC 60076-19-1:2023 © IEC 2023
Table A.3 – Measured data . 31
Table A.4 – Corrected values . 31
Table A.5 – Uncertainty of no-load loss (according to Table 1) . 32
Table B.1 – Three-phase transformer oil immersed transformer . 33
Table B.2 – Uncertainties of measuring system current and voltage transducers. 34
Table B.3 – Uncertainties of power meter . 34
Table B.4 – Measured data . 34
Table B.5 – Corrected values . 35
Table B.6 – Uncertainty of no-load loss (according to Table 1) . 35
Table C.1 – Three-phase transformer dry type transformer . 37
Table C.2 – Uncertainties of measuring system current and voltage transducers . 38
Table C.3 – Measured data . 38
Table C.4 – Results based on measured data . 39
Table C.5 – Derivation of standard uncertainty contributions . 39
Table C.6 – Uncertainty budget for measured load loss at ambient temperature
(Table 2) . 40
Table C.7 – Uncertainty budget for absolute uncertainty of load loss reported at

reference temperature (Table 3) . 40
Table D.1 – Example of measured no-load loss versus applied voltage . 42

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IEC 60076-19-1:2023 © IEC 2023 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

POWER TRANSFORMERS –

Part 19-1: Rules for the determination of uncertainties in
the measurement of the losses of power 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
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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.
IEC 60076-19-1 has been prepared by IEC technical committee 14: Power transformers. It is
an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
14/1105/FDIS 14/1107/RVD

Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

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– 6 – IEC 60076-19-1:2023 © IEC 2023
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 60076 series, published under the general title Power transformers,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The "colour inside" logo on the cover page of this document 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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IEC 60076-19-1:2023 © IEC 2023 – 7 –
INTRODUCTION
The losses of power transformers (no-load and load losses) are the object of guarantee and
penalty in many contracts and play an important role in the evaluation of the total (service)
costs and therefore in the investments involved. Furthermore, regional regulations, such as the
Ecodesign Directive of the European Union (Directive 2009/125/EC), can also pose
requirements on the establishment of reliable values for losses.
According to ISO/IEC 17025 and ISO/IEC Guide 98-3, the result of any measurement should
be qualified with the evaluation of its uncertainty. A further requirement of those documents is
that known corrections shall have been applied before evaluation of uncertainty. These
provisions have been applied in this document.
Corrections and uncertainties are also considered in IEC 60076-8 where some general
indications are given for their determination.
This document deals with the measurement of the losses, which from a measuring point of view
consist of the estimate of a measurand and the evaluation of the uncertainty that affects the
measurand itself. The procedures can also be applied to loss measurements of power
transformers:
• as evaluation of the achievable performance of a test facility in the course of prequalification
processes,
• as estimations of achievable uncertainty in the enquiry stage of an order or prior to beginning
final testing at the manufacturer's premises; and for
• evaluations of market surveillance measurements.
Evaluation of uncertainty in testing is often characterized as "top-down" or "bottom-up", where
the first one relies on inter-laboratory comparisons on a circulated test object to estimate the
dispersion and hence the uncertainty. The latter method instead relies on the formulation of a
model function, where the test result y is expressed as a function of input quantities. This
function is often the formula used for the calculation of the result. The "bottom-up" method is
applied in this document.
The uncertainty range depends on the quality of the test installation and measuring system, on
the skill of the staff and on the intrinsic measurement difficulties presented by the tested objects.
The procedures developed in this document for evaluation of measurement uncertainty are
provided as a tool to assess the soundness of results of loss measurements. Uncertainty is
understood as a "parameter, associated with the result of a measurement, that characterizes
the dispersion of the values that could reasonably be attributed to the measurand" [SOURCE:
IEV 311-01-02].
In cases where the losses are required to conform to stated tolerance limits, it is recommended
that measurement systems are of such quality that their estimated uncertainty is less than the
tolerance limit. (As an example, a measurement with a 5 % uncertainty on a test where the
tolerance limit is 5 % is acceptable if the measured value lies within the tolerance limit.) This
situation can occur for example in market surveillance activities. It can be noted that an
uncertainty 3 % is regarded as state-of-the-art for uncertainty of loss.
Treatment of measurement results is defined as follows in IEC 60076-8:1997, 10.1: "The
submitted test result shall contain the most correct estimate that is possible, based on the
measurements that have been carried out. This value shall be accepted as it stands. The
uncertainty margin shall not be involved in the judgement of compliance for guarantees with no
positive tolerance or tolerance ranges for performance data of the test object."

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– 8 – IEC 60076-19-1:2023 © IEC 2023
In Annex A to Annex C of this document, examples of uncertainty calculations are reported for
no-load and load loss measurements on large power and distribution transformers. Annex D
provides information on determination of the exponent for applied voltage in no-load loss
measurement. Annex E provides information on uncertainty in measurement. Annex F provides
information on calculation of uncertainty of losses with different reference temperatures and/or
winding material.
International Standards, Technical Reports and Guides which are mentioned in the text of this
document, but which are not indispensable to its application, are listed in the Bibliography at
the end of this document.
Loss of reactors is not within the scope of this document. A separate part of IEC IEC60076-19
to handle loss of reactors is under consideration.
A problem with symbols has been rectified, where the symbol for voltage has been changed
from U to V to avoid confusion with expanded uncertainty. The new symbol is accepted in
IEC 60050-121:2002, 121-11-27 for the case when the corresponding electric field is
irrotational.

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IEC 60076-19-1:2023 © IEC 2023 – 9 –
POWER TRANSFORMERS –

Part 19-1: Rules for the determination of uncertainties in
the measurement of the losses of power transformers



1 Scope
This part of IEC 60076 defines the procedures that are applied to evaluate the uncertainty
affecting the measurements of no-load and load losses during the routine tests on power
transformers.
This document centres on measuring systems utilizing digital instruments, although the
procedures can be adapted to evaluation of systems with analogue instruments where further
uncertainty sources have to be taken into account.
This document specifies how to determine measurement uncertainty and how to apply
corrections for known errors in the measur
...