Power transformers - Part 10: Determination of sound levels

Defines sound pressure and sound intensity measurement methods by which sound power levels of transformers, reactors and their associated cooling auxiliaries may be determined. The methods are applicable to transformers and reactors covered by the EN 60076 series, EN 60289, EN 60726 and the EN 61378 series, without limitation as regards size or voltage and when fitted with their normal cooling auxiliaries. This standard is primarily intended to apply to measurements made at the factory. Conditions on-site may be very different because of the proximity of objects, including other transformers. Nevertheless, the same general rules as are given in this standard may be followed when on-site measurements are made.

Leistungstransformatoren - Teil 10: Bestimmung der Geräuschpegel

Transformateurs de puissance - Partie 10: Détermination des niveaux de bruit

Disponible uniquement en anglais

Power transformers - Part 10: Determination of sound levels (IEC 60076-10:2001)

General Information

Status
Withdrawn
Publication Date
09-Jul-2001
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Start Date
10-Jul-2001
Completion Date
10-Jul-2001

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SLOVENSKI STANDARD
SIST EN 60076-10:2002
01-oktober-2002
1DGRPHãþD
SIST EN 60551:1997
SIST EN 60551:1997/A1:1998
Power transformers - Part 10: Determination of sound levels (IEC 60076-10:2001)
Power transformers -- Part 10: Determination of sound levels
Leistungstransformatoren -- Teil 10: Bestimmung der Geräuschpegel
Transformateurs de puissance -- Partie 10: Détermination des niveaux de bruit
Ta slovenski standard je istoveten z: EN 60076-10:2001
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
29.180 Transformatorji. Dušilke Transformers. Reactors
SIST EN 60076-10:2002 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60076-10
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2001
ICS 29.180 Supersedes EN 60551:1992 + A1:1997
English version
Power transformers
Part 10: Determination of sound levels
(IEC 60076-10:2001)
Transformateurs de puissance Leistungstransformatoren
Partie 10: Détermination des Teil 10: Bestimmung der Geräuschpegel
niveaux de bruit (IEC 60076-10:2001)
(CEI 60076-10:2001)

This European Standard was approved by CENELEC on 2001-06-01. 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 60076-10:2001 E
---------------------- Page: 2 ----------------------
EN 60076-10:2001 - 2 -
Foreword

The text of document 14/390/FDIS, future edition 1 of IEC 60076-10, prepared by IEC TC 14, Power

transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as

EN 60076-10 on 2001-06-01.
This European Standard supersedes EN 60551:1992 + A1:1997.
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) 2002-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-06-01
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 60076-10:2001 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60076-10:2001
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 Series Power transformers EN 60076 Series
IEC 60289 (mod) 1988 Reactors EN 60289 1994
IEC 60651 1979 Sound level meters EN 60651 1994
IEC 60726 (mod) 1982 Dry-type power transformers HD 464 S1 1988
+ A2 1991
+ A3 1992
+ A4 1995
IEC 61043 1993 Electroacoustics - Instruments for the EN 61043 1994
measurement of sound intensity -
Measurement with pairs of pressure
sensing microphones
IEC 61378 Series Convertor transformers EN 61378 Series
ISO 3746 1995 Acoustics - Determination of sound EN ISO 3746 1995
power levels of noise sources using
sound pressure - Survey method using
an enveloping measurement surface
over a reflecting plane
ISO 9614-1 1993 Acoustics - Determination of sound EN ISO 9614-1 1995
power levels of noise sources using
sound intensity - Part 1: Measurement
at discrete points
HD 464 S1 includes A1:1986 to IEC 60726:1982.
---------------------- Page: 4 ----------------------
NORME CEI
INTERNATIONALE IEC
60076-10
INTERNATIONAL
Première édition
STANDARD
First edition
2001-05
Transformateurs de puissance –
Partie 10:
Détermination des niveaux de bruit
Power transformers –
Part 10:
Determination of sound levels
© IEC 2005 Droits de reproduction réservés ⎯ Copyright - all rights reserved

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---------------------- Page: 5 ----------------------
60076-10 © IEC:2005 – 3 –
CONTENTS

FOREWORD...........................................................................................................................5

INTRODUCTION.....................................................................................................................9

1 Scope.............................................................................................................................13

2 Normative references .....................................................................................................13

3 Terms and definitions .....................................................................................................15

4 Instrumentation and calibration.......................................................................................17

5 Choice of test method.....................................................................................................17

6 Load conditions ..............................................................................................................19

6.1 General .................................................................................................................19

6.2 No-load current and rated voltage .........................................................................19

6.3 Rated current and short-circuit voltage ..................................................................19

6.4 Reduced-load current ............................................................................................21

7 Principal radiating surface ..............................................................................................21

7.1 General .................................................................................................................21

7.2 Transformers with or without cooling auxiliaries, dry-type transformers in
enclosures and dry-type transformers with cooling auxiliaries inside the

enclosure ..............................................................................................................21

7.3 Cooling auxiliaries mounted on a separate structure spaced ≥3 m away from

the principal radiating surface of the transformer...................................................23

7.4 Dry-type transformers without enclosures..............................................................23

8 Prescribed contour .........................................................................................................23

9 Microphone positions......................................................................................................23

10 Calculation of the area of the measurement surface .......................................................25

10.1 Measurements made at 0,3 m from the principal radiating surface.........................25

10.2 Measurements made at 2 m from the principal radiating surface............................25

10.3 Measurements made at 1 m from the principal radiating surface............................25

10.4 Measurements on test objects where safety clearance considerations require
a measurement distance which for all or part of the prescribed contour(s)

exceeds the provisions of 10.1 to 10.3 ..................................................................25

11 Sound pressure method..................................................................................................27

11.1 Test environment...................................................................................................27

11.2 Sound pressure level measurements .....................................................................31

11.3 Calculation of average sound pressure level .........................................................33

12 Sound intensity method ..................................................................................................35

12.1 Test environment...................................................................................................35

12.2 Sound intensity level measurements .....................................................................37

12.3 Calculation of average sound intensity level ..........................................................37

13 Calculation of sound power level ....................................................................................39

14 Addition of no-load and load current sound power levels ................................................39

15 Far-field calculations ......................................................................................................41

16 Presentation of results....................................................................................................41

Annex A (informative) Narrow-band and time-synchronous measurements ..........................57

Annex B (informative) Typical report of sound level determination .......................................61

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60076-10 © IEC:2005 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 10: Determination of sound levels
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60076-10 has been prepared by IEC technical committee 14:

Power transformers.

This first edition of IEC 60076-10 cancels and replaces IEC 60551, published in 1987 and its

amendment 1 (1995), and constitutes a technical revision.
This bilingual version (2005-07) replaces the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
14/390/FDIS 14/394/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.
---------------------- Page: 7 ----------------------
60076-10 © IEC:2005 – 7 –
The French version of this standard has not been voted upon.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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 the lightning impulse and switching impulse testing – Power transformers

and reactors
Part 5: Ability to withstand short circuit
Part 6: Reactors
Part 7: Loading guide for oil-immersed power transformers
Part 8: Application guide
Part 10: Determination of sound levels
Part 11: Dry-type transformers
Part 13: Self protected liquid filled transformers

Part 14: Design and application of liquid-immersed power transformers using high-

temperature insulation materials

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result 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.
---------------------- Page: 8 ----------------------
60076-10 © IEC:2005 – 9 –
INTRODUCTION

One of the many parameters to be considered when designing and siting transformers,

reactors and their associated cooling equipment is the amount of sound that the equipment is

likely to emit under normal operating conditions on site.
Sources of sound

The audible sound radiated by transformers is generated by a combination of magnetostrictive

deformation of the core and electromagnetic forces in the windings, tank walls and magnetic

shields. Historically, the sound generated by the magnetic field inducing longitudinal

vibrations in the core laminations has been dominant. The amplitude of these vibrations

depends on the flux density in the laminations and the magnetic properties of the core steel,

and is therefore independent of the load current. Recent advances in core design, combined

with the use of low induction levels, have reduced the amount of sound generated in the core

such that the sound caused by the electromagnetic forces may become significant.

Current flowing in the winding conductors produces electromagnetic forces in the windings. In

addition, stray magnetic fields may induce vibrations in structural components. The force (and

therefore the amplitude of the vibrations) is proportional to the square of the current, and the

radiated sound power is proportional to the square of the vibrational amplitude. Consequently,

the radiated sound power is strongly dependent on the load current. Vibrations in core and

winding assemblies can then induce sympathetic vibrations in tank walls, magnetic shields

and air ducts (if present).

In the case of dry-type, air-cored shunt or series reactors, sound is generated by

electromagnetic forces acting on the windings in a similar manner to that described above.

These oscillatory forces cause the reactor to vibrate both axially and radially, and the axial

and radial supports and manufacturing tolerances may result in the excitation of modes in

addition to those of rotational symmetry. In the case of iron-cored reactors, further vibrations

are induced by forces acting in the magnetic circuit.

For all electrical plants, the consequence of the presence of higher harmonics on the power

supply should be understood. Normally, vibrations occur at even harmonics of the power

frequency, with the first harmonic being dominant. If other frequencies are present in the

power supply, other forces may be induced. For certain applications, this may be significant,

particularly because the human ear is more sensitive to these higher frequencies.

Any associated cooling equipment will also generate noise when operating. Fans and pumps

both tend to generate broad-band noise due to the forced flow of air or oil.
Measurement of sound

Sound level measurements have been developed to quantify pressure variations in air that a

human ear can detect. The smallest pressure variation that a healthy human ear can detect is

20 µPa. This is the reference level (0 dB) to which all the other levels are compared. The

perceived loudness of a signal is dependent upon the sensitivity of the human ear to its

frequency spectrum. Modern measuring instruments process sound signals through electronic

networks, the sensitivity of which varies with frequency in a manner similar to the human ear.

This has resulted in a number of internationally standardized weightings of which the A-

weighting network is the most common.
---------------------- Page: 9 ----------------------
60076-10 © IEC:2005 – 11 –

Sound intensity is defined as the rate of energy flow per unit area and is measured in watts

per square metre. It is a vector quantity whereas, sound pressure is a scalar quantity and is

defined only by its magnitude.

Sound power is the parameter which is used for rating and comparing sound sources. It is a

basic descriptor of a source’s acoustic output, and therefore an absolute physical property of

the source alone which is independent of any external factors such as environment and

distance to the receiver.

Sound power can be calculated from sound pressure or sound intensity determinations.

Sound intensity measurements have the following advantages over sound pressure
measurements:

• an intensity meter responds only to the propagating part of a sound field and ignores any

non-propagating part, for example, standing waves and reflections;

• the intensity method reduces the influence of external sound sources, as long as their

sound level is approximately constant.
The sound pressure method takes the above factors into account by correcting for
background noise and reflections.

For a detailed discussion of these measuring techniques, see IEC 60076-10-1: Determination

of sound levels – Application guide.
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60076-10 © IEC:2005 – 13 –
POWER TRANSFORMERS –
Part 10: Determination of sound levels
1 Scope

This part of IEC 60076 defines sound pressure and sound intensity measurement methods by

which sound power levels of transformers, reactors and their associated cooling auxiliaries

may be determined.

NOTE For the purpose of this standard, the term "transformer" means "transformer or reactor".

The methods are applicable to transformers and reactors covered by the IEC 60076 series,

IEC 60289, IEC 60076-11 and the IEC 61378 series, without limitation as regards size or

voltage and when fitted with their normal cooling auxiliaries.

This standard is primarily intended to apply to measurements made at the factory. Conditions

on-site may be very different because of the proximity of objects, including other trans-

formers. Nevertheless, the same general rules as are given in this standard may be followed

when on-site measurements are made.
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 60076 (all parts), Power transformers
IEC 60076-1:1993, Power transformers – Part 1: General
IEC 60076-11, Power transformers – Part 11: Dry-type transformers
IEC 60289:1988, Reactors

IEC 61043:1993, Electroacoustics – Instruments for the measurement of sound intensity –

Measurement with pairs of pressure sensing microphones
IEC 61378 (all parts), Convertor transformers
IEC 61672-1, Electroacoustics – Sound level meters – Part 1: Specifications

IEC 61672-2, Electroacoustics – Sound level meters – Part 2: Pattern evaluation tests

ISO 3746:1995, Acoustics – Determination of sound power levels of noise sources using

sound pressure – Survey method using an enveloping measurement surface over a reflecting

plane

ISO 9614-1:1993, Acoustics – Determination of sound power levels of noise sources using

sound intensity – Part 1: Measurement at discrete points
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60076-10 © IEC:2005 – 15 –
3 Terms and definitions

For the purpose of this document, the definitions in IEC 60076-1, as well as the following

definitions, apply.
3.1
sound pressure

fluctuating pressure superimposed on the static pressure by the presence of sound. It is

expressed in pascals
3.2
sound pressure level

ten times the logarithm to the base 10 of the ratio of the square of the sound pressure to the

square of the reference sound pressure (p = 20 × 10 Pa). It is measured in decibels

L = 10 lg (1)
3.3
sound intensity

vector quantity describing the amount and direction of the net flow of sound energy at a given

position. The unit is Wm
3.4
normal sound intensity

component of the sound intensity in the direction normal to a measurement surface

3.5
normal sound intensity level

ten times the logarithm to the base 10 of the ratio of the normal sound intensity to the

–12 –2
reference sound intensity (I = 1 × 10 Wm ). It is expressed in decibels
L = 10 lg (2)
NOTE When I is negative, the level is expressed as –XX dB.
3.6
sound power

rate at which airborne sound energy is radiated by a source. It is expressed in watts

3.7
sound power level

ten times the logarithm to the base 10 of the ratio of a given sound power to the reference

–12
sound power (W = 1 × 10 W). It is expressed in decibels
L = 10lg (3)
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60076-10 © IEC:2005 – 17 –
3.8
principal radiating surface

hypothetical surface surrounding the test object which is assumed to be the surface from

which sound is radiated
3.9
prescribed contour

horizontal line on which the measuring positions are located, spaced at a definite horizontal

distance (the "measurement distance") from the principal radiating surface
3.10
measurement distance

horizontal distance between the principal radiating surface and the "measurement surface"

3.11
measurement surface

hypothetical surface enveloping the source and on which the measurement points are located

3.12
background noise
A-weighted sound pressure level with the test object inoperative
4 Instrumentation and calibration

Sound pressure measurements shall be made using a type 1 sound level meter complying

with IEC 61672-1 and IEC 61672-2 and calibrated in accordance with 5.2 of ISO 3746.

Sound intensity measurements shall be made using a class 1 sound intensity instrument

complying with IEC 61043 and calibrated in accordance with 6.2 of ISO 9614-1. The

frequency range of the measuring equipment shall be adapted to the frequency spectrum of

the test object, that is, an appropriate microphone spacer system shall be chosen in order to

minimize systematic errors.

The measuring equipment shall be calibrated immediately before and after the measurement

sequence. If the calibration changes by more than 0,3 dB, the measurements shall be

declared invalid and the test repeated.
5 Choice of test method

Either sound pressure or sound intensity measurements may be used to determine the value

of the sound power level. Both methods are valid and either can be used, as agreed between

manufacturer and purchaser at the time of placing the order.

The sound pressure method of measurement described in this standard is in accordance with

ISO 3746. Measurements made in conformity with this standard tend to result in standard

deviations of reproducibility between determinations made in different laboratories which are

less than or equal to 3 dB.

The sound intensity method of measurement described in this standard is in accordance with

ISO 9614-1. Measurements made in conformity with this standard tend to result in standard

deviations of reproducibility between determinations made in different laboratories which are

less than or equal to 3 dB.
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60076-10 © IEC:2005 – 19 –
6 Load conditions
6.1 General

Load condition(s) shall be agreed between the manufacturer and purchaser at the time of

placing the order. If a transformer has a very low no-load sound level, the sound due to load

current can influence the total sound level in service. The method to be used for summing the

no-load and load current sound levels is given in Clause 14.

Current taken by a reactor is dependent on the voltage applied and consequently, a reactor

cannot be tested at no-load. Where sufficient power is available in the factory to permit full

energization of reactors, the methods to be followed are the same as those for transformers.

Alternatively, measurements may be made on-site if conditions are suitable.

Unless otherwise specified, the tests shall be carried out with the tap-changer (if any) on the

principal tapping. However, this tap position may not give the maximum sound level in

service. In addition, when the transformer is in service, a superposition of the flux at no-load

conditions and the stray flux occurs which causes a change in the flux density in certain parts

of the core. Therefore, under special conditions of intended application of a transformer

(particularly variable flux voltage variation), it may be agreed to measure the sound levels on

a tapping other than the principal tapping, or with a voltage other than the rated voltage on an

untapped winding. This shall be clearly indicated in the test report.
6.2 No-load current and rated voltage

For measurements made on the test object with or without its auxiliary cooling plant, the test

object shall be on no-load and excited at the rated voltage of sinusoidal or practically

sinusoidal waveform and rated frequency. The voltage shall be in accordance with 10.5 of

IEC 60076-1. If a transformer is fitted with reactor-type on-load tap-changer equipment where

the reactor may on certain tap-change positions be permanently energized, the measure-

ments shall be made with the transformer on a tapping which involves this condition and

which is as near to the principal tapping as possible. The excitation voltage shall be

appropriate to the tapping in use.
...

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