SIST EN 61400-11:2013
(Main)Wind turbines - Part 11: Acoustic noise measurement techniques
Wind turbines - Part 11: Acoustic noise measurement techniques
IEC 61400-11:2012(E) presents measurement procedures that enable noise emissions of a wind turbine to be characterised. This involves using measurement methods appropriate to noise emission assessment at locations close to the machine, in order to avoid errors due to sound propagation, but far away enough to allow for the finite source size. The procedures described are different in some respects from those that would be adopted for noise assessment in community noise studies. They are intended to facilitate characterisation of wind turbine noise with respect to a range of wind speeds and directions. Standardisation of measurement procedures will also facilitate comparisons between different wind turbines. This new edition constitutes a technical revision, introducing new principles for data reduction procedures.
Windenergieanlagen - Teil 11: Schallmessverfahren
Aérogénérateurs - Partie 11: Techniques de mesure du bruit acoustique
l’IEC 61400-11:2012 spécifie les procédures de mesure qui permettent de caractériser les émissions sonores d’une éolienne. Cette démarche implique l’utilisation de méthodes de mesure appropriées à l’évaluation des émissions sonores à des emplacements proches de la machine, afin d’éviter les erreurs dues à la propagation du son, mais toutefois suffisamment éloignés pour permettre de déterminer la dimension des sources finies. Les procédures décrites sont différentes à certains égards de celles qui seraient adoptées pour l’évaluation du bruit dans le cadre des études portant sur le bruit ambiant. Ces procédures sont destinées à faciliter la caractérisation du bruit émis par une éolienne par rapport à une plage donnée de vitesses et de directions du vent. La normalisation des procédures de mesure facilite également les comparaisons entre différentes éoliennes. Cette nouvelle édition constitue une révision technique, introduisant de nouveaux principes concernant les procédures de traitement des données.
Vetrne turbine - 11. del: Tehnike merjenja hrupa
Ta del standarda IEC 61400 predstavlja postopke merjenja, ki omogočajo opredelitev emisij hrupa vetrnih turbin. To vključuje načine merjenja, ki so primerni za ocenjevanje emisij hrupa na lokacijah, ki so dovolj blizu naprave, da bi se izognili napakam zaradi širjenja zvoka na prostem, vendar dovolj daleč, da je mogoče pridobiti končno velikost vzorca. Nekateri vidiki opisanih postopkov so drugačni od postopkov, ki se uporabljajo za ocenjevanje hrupa v študijah hrupa v okolici. Namenjene so opredelitvi hrupa vetrnih turbin, pri čemer upoštevajo razpon hitrosti in smeri vetra. Standardizacija merilnih postopkov bo omogočila tudi primerjave različnih vetrnih turbin. Postopki predstavljajo metodologijo, ki bo omogočila usklajeno in pravilno opredelitev emisij hrupa vetrnih turbin. Ti postopki vključujejo naslednje:
• lokacijo položajev akustičnega merjenja;
• zahteve za pridobitev akustičnih, meteoroloških in drugih povezanih podatkov o delovanju vetrnih turbin;
• analizo pridobljenih podatkov in vsebino za poročila ter
• definicijo posebnih parametrov akustičnih emisij in povezanih deskriptorjev, ki se uporabljajo za izvajanje okoljskih ocen.
Ta mednarodni standard ni omejen na določene velikosti ali vrste vetrnih turbin. Postopki, ki so opisani v tem standardu, omogočajo temeljit opis emisij hrupa iz vetrnih turbin. Metoda za majhne vetrne turbine je opisana v dodatku F.
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Vetrne turbine - 11. del: Tehnike merjenja hrupaWindenergieanlagen - Teil 11: SchallmessverfahrenAérogénérateurs - Partie 11: Techniques de mesure du bruit acoustiqueWind turbines - Part 11: Acoustic noise measurement techniques27.180Sistemi turbin na veter in drugi alternativni viri energijeWind turbine systems and other alternative sources of energy17.140.20Emisija hrupa naprav in opremeNoise emitted by machines and equipmentICS:Ta slovenski standard je istoveten z:EN 61400-11:2013SIST EN 61400-11:2013en01-junij-2013SIST EN 61400-11:2013SLOVENSKI
STANDARD
EUROPEAN STANDARD EN 61400-11 NORME EUROPÉENNE
EUROPÄISCHE NORM March 2013
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2013 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61400-11:2013 E
ICS 27.180 Supersedes EN 61400-11:2003 + A1:2006
English version
Wind turbines -
Part 11: Acoustic noise measurement techniques (IEC 61400-11:2012)
Eoliennes -
Partie 11: Techniques de mesure
du bruit acoustique (CEI 61400-11:2012)
Windenergieanlagen -
Teil 11: Schallmessverfahren (IEC 61400-11:2012)
This European Standard was approved by CENELEC on 2012-12-12. 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.
This document supersedes EN 61400-11:2003 + A1:2006.
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 61400-11:2012 was approved by CENELEC as a European Standard without any modification.
- 3 - EN 61400-11:2013 Annex ZA
(normative)
Normative references to international publications with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
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 60688 - Electrical measuring transducers for converting A.C. and D.C. ectrical quantities to analogue or digital signals EN 60688 -
IEC 60942 2003 Electroacoustics - Sound calibrators EN 60942 2003
IEC 61260 1995 Electroacoustics - Octave-band and fractional-octave-band filters EN 61260 1995
IEC 61400-12-1 2005 Wind turbines -
Part 12-1: Power performance measurements of electricity producing
wind turbines EN 61400-12-1 2006
IEC 61400-12-2 - 1) Wind turbines -
Part 12-2: Power performance of electricity producing wind turbines based on nacelle anemometry EN 61400-12-2 -
IEC 61672 Series Electroacoustics - Sound level meters EN 61672 Series
ISO/IEC Guide 98-3 - Uncertainty of measurement -
Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) - -
1) To be published. SIST EN 61400-11:2013
IEC 61400-11 Edition 3.0 2012-11 INTERNATIONAL STANDARD Wind turbines –
Part 11: Acoustic noise measurement techniques
INTERNATIONAL ELECTROTECHNICAL COMMISSION XA ICS 27.180 PRICE CODE ISBN 978-2-83220-463-4
– 2 – 61400-11 © IEC:2012(E) CONTENTS FOREWORD . 5 INTRODUCTION . 7 1 Scope . 8 2 Normative references . 8 3 Terms and definitions . 9 4 Symbols and units . 12 5 Outline of method . 13 6 Instrumentation . 14 6.1 Acoustic instruments . 14 6.1.1 General . 14 6.1.2 Equipment for the determination of the equivalent continuous A-weighted sound pressure level. 14 6.1.3 Equipment for the determination of A-weighted 1/3-octave band spectra . 14 6.1.4 Equipment for the determination of narrow band spectra . 14 6.1.5 Microphone with measurement board and windscreen . 14 6.1.6 Acoustical calibrator . 16 6.1.7 Data recording/playback systems . 16 6.2 Non-acoustic Instruments . 16 6.2.1 General . 16 6.2.2 Anemometers . 16 6.2.3 Electric power transducer . 17 6.2.4 Other instrumentation . 17 6.3 Traceable calibration . 17 7 Acoustic measurements and measurement procedures . 17 7.1 Acoustic measurement positions . 17 7.2 Acoustic measurements . 20 7.2.1 General . 20 7.2.2 Acoustic measurement requirements . 20 7.2.3 A-weighted sound pressure level . 21 7.2.4 A-weighted 1/3-octave band measurements . 21 7.2.5 A-weighted narrow band measurements . 21 7.2.6 Optional acoustic measurements at positions 2, 3 and 4 . 21 7.2.7 Other optional measurements . 21 8 Non-acoustic measurements . 21 8.1 General . 21 8.2 Wind speed measurements . 22 8.2.1 Determination of the wind speed during wind turbine operation. 22 8.2.2 Wind speed measurements during background noise measurements . 23 8.3 Downwind direction . 24 8.4 Other atmospheric conditions . 24 8.5 Rotor speed and pitch angle measurement . 24 9 Data reduction procedures. 24 9.1 General methodology for sound power levels and 1/3-octave band levels . 24 9.2 Calculation of sound pressure levels . 27 SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 3 –
9.2.1 General . 27 9.2.2 Calculation of average sound spectra and uncertainty per bin . 27 9.2.3 Calculation of average wind speed and uncertainty per bin . 29 9.2.4 Calculation of noise levels at bin centres including uncertainty . 30 9.3 Apparent sound power levels . 31 9.4 Apparent sound power levels with reference to wind speed in 10 m height . 32 9.5 Tonal audibility . 33 9.5.1 General methodology for tonality . 33 9.5.2 Identifying possible tones . 34 9.5.3 Classification of spectral lines within the critical band . 34 9.5.4 Identified tone . 37 9.5.5 Determination of the tone level . 37 9.5.6 Determination of the masking noise level . 37 9.5.7 Determination of tonality . 37 9.5.8 Determination of audibility . 38 9.5.9 Background noise . 38 10 Information to be reported . 39 10.1 General . 39 10.2 Characterisation of the wind turbine . 39 10.3 Physical environment . 39 10.4 Instrumentation . 40 10.5 Acoustic data . 40 10.6 Non-acoustic data . 41 10.7 Uncertainty . 41 Annex A (informative)
Other possible characteristics of wind turbine
noise emission and their quantification . 42 Annex B (informative)
Assessment of turbulence intensity . 44 Annex C (informative)
Assessment of measurement uncertainty . 45 Annex D (informative)
Apparent roughness length . 47 Annex E (informative)
Characterization of a secondary wind screen. 49 Annex F (normative)
Small wind turbines . 53 Annex G (informative)
Air absorption . 57 Bibliography . 58
Figure 1 – Mounting of the microphone . 15 Figure 2 – Picture of microphone and measurement board . 16 Figure 3 – Standard pattern for microphone measurement positions (plan view) . 18 Figure 4 – Illustration of the definitions of R0 and slant distance R1 . 19 Figure 5 – Acceptable meteorological mast position (hatched area) . 22 Figure 6 – Flowchart showing the data reduction procedure . 26 Figure 7 – Flowchart for determining tonal audibility for each wind speed bin . 33 Figure 8 – Illustration of L70 % level in the critical band . 35 Figure 9 – Illustration of lines below the L70 % + 6 dB criterion . 36 Figure 10 – Illustration of Lpn,avg level and lines classified as masking. 36 Figure 11 – Illustration of classifying all spectral lines . 37 Figure E.1 – Example 1 of a secondary wind screen . 50 SIST EN 61400-11:2013
– 4 – 61400-11 © IEC:2012(E) Figure E.2 – Example 2 of secondary wind screen . 51 Figure E.3 – Example on insertion loss from Table E.1 . 52 Figure F.1 – Allowable region for meteorological
mast position as a function of β – Plan view . 54 Figure F.2 – Example immission noise map . 56 Figure G.1 – Example of 1/3-octave spectrum . 57
Table C.1 – Examples of possible values of type B uncertainty components
relevant for apparent sound power spectra . 46 Table C.2 – Examples of possible values of type B uncertainty components
for wind speed determination relevant for apparent sound power spectra . 46 Table D.1 – Roughness length . 47 Table E.1 – Example on reporting of insertion loss. 51
61400-11 © IEC:2012(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
WIND TURBINES –
Part 11: Acoustic noise measurement techniques
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 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 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 61400-11 has been prepared by IEC technical committee 88: Wind turbines. This third edition of IEC 61400-11 cancels and replaces the second edition published in 2002 and its Amendment 1 (2006). It constitutes a technical revision, introducing new principles for data reduction procedures. The text of this standard is based on the following documents: FDIS Report on voting 88/436/FDIS 88/440/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. SIST EN 61400-11:2013
– 6 – 61400-11 © IEC:2012(E) This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. A list of all parts of the IEC 61400 series, under the general title Wind turbines, can be found on the IEC website. 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. A bilingual edition of this document may be issued at a later date.
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.
61400-11 © IEC:2012(E) – 7 –
INTRODUCTION The purpose of this part of IEC 61400 is to provide a uniform methodology that will ensure consistency and accuracy in the measurement and analysis of acoustical emissions by wind turbine generator systems. This International Standard has been prepared with the anticipation that it would be applied by: • wind turbine manufacturers striving to meet well defined acoustic emission performance requirements and/or a possible declaration system (e.g. IEC/TS 61400-14); • wind turbine purchasers for specifying performance requirements; • wind turbine operators who may be required to verify that stated, or required, acoustic performance specifications are met for new or refurbished units; • wind turbine planners or regulators who must be able to accurately and fairly define acoustical emission characteristics of a wind turbine in response to environmental regulations or permit requirements for new or modified installations. This standard provides guidance in the measurement, analysis and reporting of complex acoustic emissions from wind turbine generator systems. The standard will benefit those parties involved in the manufacture, installation, planning and permitting, operation, utilization, and regulation of wind turbines. The measurement and analysis techniques recommended in this document should be applied by all parties to ensure that continuing development and operation of wind turbines is carried out in an atmosphere of consistent and accurate communication relative to environmental concerns. This standard presents measurement and reporting procedures expected to provide accurate results that can be replicated by others. SIST EN 61400-11:2013
– 8 – 61400-11 © IEC:2012(E) WIND TURBINES –
Part 11: Acoustic noise measurement techniques
1 Scope This part of IEC 61400 presents measurement procedures that enable noise emissions of a wind turbine to be characterised. This involves using measurement methods appropriate to noise emission assessment at locations close to the machine, in order to avoid errors due to sound propagation, but far away enough to allow for the finite source size. The procedures described are different in some respects from those that would be adopted for noise assessment in community noise studies. They are intended to facilitate characterisation of wind turbine noise with respect to a range of wind speeds and directions. Standardisation of measurement procedures will also facilitate comparisons between different wind turbines. The procedures present methodologies that will enable the noise emissions of a single wind turbine to be characterised in a consistent and accurate manner. These procedures include the following: • location of acoustic measurement positions; • requirements for the acquisition of acoustic, meteorological, and associated wind turbine operational data; • analysis of the data obtained and the content for the data report; and • definition of specific acoustic emission parameters, and associated descriptors which are used for making environmental assessments. This International Standard is not restricted to wind turbines of a particular size or type. The procedures described in this standard allow for the thorough description of the noise emission from a wind turbine. A method for small wind turbines is described in Annex F. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60688, Electrical measuring transducers for converting a.c. electrical quantities to analogue or digital signals
IEC 60942:2003, Electroacoustics – Sound calibrators IEC 61260:1995, Electroacoustics – Octave-band and fractional-octave-band filters IEC 61400-12-1:2005, Wind turbines – Part 12-1: Power performance measurements of electricity producing wind turbines IEC 61400-12-2, Wind turbines – Part 12-2: Power performance verification of electricity producing wind turbines1 ____________ 1 To be published. SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 9 –
IEC 61672 (all parts), Electroacoustics – Sound level meters ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) 3 Terms and definitions For the purposes of this standard, the following terms and definitions apply. 3.1
apparent sound power level LWA A-weighted sound power level re. 1 pW of a point source at the rotor centre with the same emission in the downwind direction as the wind turbine being measured, LWA is determined at bin centre wind speeds at hub height Note 1 to entry: Apparent sound power level is expressed in dB re. 1 pW. 3.2
apparent sound power level with reference to wind speed at 10 m height LWA,10m A-weighted sound power level re. 1 pW of a point source at the rotor centre with the same emission in the downwind direction as the wind turbine being measured, LWA,10m are determined at bin centre wind speeds at 10 m height within the measured wind speed range Note 1 to entry: Apparent sound power level with reference to wind speed at 10 m height is expressed in dB re. 1 pW. 3.3
audibility criterion La frequency dependent criterion curve determined from listening tests, and reflecting the subjective response of a “typical” listener to tones of different frequencies Note 1 to entry: Audibility criterion is expressed in dB re. 20 µPa. 3.4 sound pressure levels 3.4.1 A-weighted sound pressure levels LA sound pressure levels measured with the A frequency weighting networks specified in IEC 61672 Note 1 to entry: A-weighted sound pressure levels are expressed in dB re. 20 µPa. 3.4.2 C-weighted sound pressure levels LC
sound pressure levels measured with the C frequency weighting networks specified in IEC 61672 Note 1 to entry: C-weighted sound pressure levels are expressed in dB re. 20 µPa. 3.5
bin centre centre value of a wind speed bin SIST EN 61400-11:2013
– 10 – 61400-11 © IEC:2012(E) 3.6
inclination angle
φ angle between the plane of the measurement board and a line from the microphone to the rotor centre Note 1 to entry: Inclination angle is expressed in °. 3.7
maximum power maximum value of the binned power curve for the power optimised mode of operation Note 1 to entry: Maximum power is expressed in kW. 3.8
measured wind speed at height Z VZ,m wind speed measured at height Z with a mast mounted anemometer Note 1 to entry: Measured wind speed at height Z is expressed in m/s. 3.9
measured nacelle wind speed at hub height Vnac,m wind speed measured at hub height with a nacelle anemometer Note 1 to entry: Measured nacelle wind speed at hub height is expressed in m/s. 3.10
normalised nacelle wind speed at hub height Vnac,n normalised wind speed measured at hub height with a nacelle anemometer corrected to standard meteorological conditions Note 1 to entry: Normalised nacelle wind speed at hub height is expressed in m/s. 3.11
normalised wind speed derived from power curve VP,n normalised wind speed derived from power curve under standard meteorological conditions Note 1 to entry: Normalised wind speed derived from power curve is expressed in m/s. 3.12
normalised wind speed at hub height during background noise measurements VB,n normalised wind speed at hub height from anemometer Note 1 to entry: Normalised wind speed at hub height during background noise measurements is expressed in m/s. 3.13
normalised wind speed at hub height VH,n normalised wind speed at hub height Note 1 to entry: Normalised wind speed at hub height is expressed in m/s. 3.14
normalised wind speed at height Z VZ,n normalised wind speed at height Z from mast mounted anemometer SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 11 –
Note 1 to entry: Normalised wind speed at height Z is expressed in m/s. 3.15
reference distance
R0 nominal horizontal distance from the centre of the base of the wind turbine to each of the prescribed microphone positions Note 1 to entry: Reference distance is expressed in m. 3.16
reference roughness length
z0ref roughness length of 0,05 m used for converting wind speed to meteorological reference conditions Note 1 to entry: Reference roughness length is expressed in m. 3.17
sound pressure level Lp 10 times the log10 of the ratio of the square mean sound pressure to the square of the reference sound pressure of 20 µPa Note 1 to entry: Sound pressure level is expressed in dB re. 20 µPa. 3.18
tonal audibility ∆La,k difference between the tonality and the audibility criterion in each wind speed bin, where k is the centre value of the wind speed bin Note 1 to entry: Tonal audibility is expressed in dB. 3.19
tonality ûLk difference between the tone level and the level of the masking noise in the critical band around the tone in each wind speed bin where k is the centre value of the wind speed bin Note 1 to entry: Tonality is expressed in dB. 3.20
wind speed bin wind speed interval, 0,5 m/s wide, centred around integer and half-integer wind speeds open at the low end, and closed at the high end 3.21
wind speed at 10 m height V10 wind speed at 10 m height for reporting apparent sound power levels and spectra with reference to 10 m height Note 1 to entry: Wind speed at 10 m height is expressed in m/s. SIST EN 61400-11:2013
– 12 – 61400-11 © IEC:2012(E) 4 Symbols and units D rotor diameter (horizontal axis turbine) or equatorial diameter (vertical axis turbine) (m) H height of rotor centre (horizontal axis turbine) or height of rotor equatorial plane (vertical axis turbine) above local ground near the wind turbine (m) LA or LC A or C-weighted sound pressure level (dB) LAeq equivalent continuous A-weighted sound pressure level (dB) Lpn,j,k sound pressure level of masking noise within a critical band in the “jth” spectra at the “kth” wind speed bin (dB) Lpn,avg,j,k average of analysis bandwidth sound pressure levels of masking noise in the “jth” spectra at the “kth” wind speed bin (dB) Lpt,j,k sound pressure level of the tone or tones in the “jth” spectra at the “kth” wind speed bin (dB) LWA,k apparent sound power level, where k is a wind speed bin centre value (dB) log logarithm to base 10
Pm measured electric power (kW) Pn normalised electric power (kW) R1 slant distance, from rotor centre to actual measurement position (m) R0 reference distance (m) S0 reference area, S0 = 1 m2 (m2) TC air temperature (°C) TK absolute air temperature (K) UA type A uncertainty (-) UB type B uncertainty (-) VH wind speed at hub height, H (m/s) VP derived wind speed from power curve (m/s) Vz wind speed at height, z (m/s) Vnac wind speed from nacelle anemometer (m/s) f frequency of the tone (Hz) fc centre frequency of critical band (Hz) p atmospheric pressure (kPa) z0 roughness length (m) z0ref reference roughness length, 0,05 m (m) SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 13 –
z anemometer height (m) κ ratio of normalised wind speed and measured wind speed (-) ∆Ltn,j,k tonality of the “jth” spectra at “kth” wind speed (dB) φ inclination angle (°) 5 Outline of method This part of IEC 61400 defines the procedures to be used in the measurement, analysis and reporting of acoustic emissions of a wind turbine. Instrumentation and calibration requirements are specified to ensure accuracy and consistency of acoustic and non-acoustic measurements. Non-acoustic measurements required defining the atmospheric conditions relevant to determining the acoustic emissions are also specified. All parameters to be measured and reported are identified, as are the data reduction methods required for obtaining these parameters. Application of the method described in this International Standard provides the apparent A-weighted sound power levels, spectra, and tonal audibility at bin centre wind speeds at hub height and 10 m height of an individual wind turbine. The tonal audibility is included to give information on the presence of tones in the noise. The tonality determined is not giving information on the tonality at other distances. Optionally, measurements can be made in supplementary positions to give information on the directional characteristics. The method applies to all wind speeds. The wind speed range for documentation is related to the specific wind turbine. As a minimum it is defined as the hub height wind speed from 0,8 to 1,3 times the wind speed at 85 % of maximum power rounded to bin centres. Indicatively, this is a wind speed range of approximately 6 to 10 m/s at 10 m height, depending on the turbine type. The wind speed range may be expanded for instance to comply with national requirements. The measurements are made at locations close to the turbine in order to minimise the influence of terrain effects, atmospheric conditions or wind-induced noise. To account for the size of the wind turbine under test, a reference distance R0 based on the wind turbine dimensions is used. Measurements are taken with a microphone positioned on a measurement board placed on the ground to reduce the wind noise generated at the microphone and to minimise the influence of different ground types. Measurements of sound pressure levels, sound pressure spectra, wind speeds, electrical power, rotor rotational speed and, if measured, pitch angle are made simultaneously over short periods of time and over a wide range of hub height wind speeds. The sound pressure levels and spectra at bin centre wind speeds are determined and used for calculating the apparent A-weighted sound power spectra and levels. Annexes are included that cover: – other possible characteristics of wind turbine noise emission and their quantification (Annex A informative); – assessment of turbulence intensity (Annex B informative); – assessment of measurement uncertainty (Annex C informative); – apparent roughness length (Annex D informative); – classification of a secondary wind screen (Annex E informative); – small wind turbines (Annex F normative); SIST EN 61400-11:2013
– 14 – 61400-11 © IEC:2012(E) – air absorption (Annex G informative). 6 Instrumentation 6.1 Acoustic instruments 6.1.1 General The following equipment is necessary to perform the acoustic measurements as set forth in this standard. 6.1.2 Equipment for the determination of the equivalent continuous A-weighted sound pressure level The equipment shall meet the requirements of an IEC 61672 class 1 sound level meter. The diameter of the microphone diaphragm shall be no greater than 13 mm. 6.1.3 Equipment for the determination of A-weighted 1/3-octave band spectra In addition to the requirements given for class 1 sound level meters, the equipment shall have a constant frequency response over at least the frequency range given by the 1/3-octave bands with centre frequencies from 20 Hz to 10 kHz. The filters shall meet the requirements of IEC 61260 for class 1 filters. The equivalent A-weighted continuous sound pressure levels in 1/3-octave bands with centre frequencies from 20 Hz to 10 kHz shall be determined simultaneously. 6.1.4 Equipment for the determination of narrow band spectra The equipment shall fulfil the relevant requirements for IEC 61672 series class 1 instrumentation in the 20 Hz to 11 200 Hz frequency range. 6.1.5 Microphone with measurement board and windscreen The microphone shall be mounted at the centre of a flat hard board with the diaphragm of the microphone in a plane normal to the board and with the axis of the microphone pointing towards the wind turbine, as in Figure 1 and Figure 2. The measurement board shall be circular with a diameter of at least 1,0 m and made from material that is acoustically hard, such as plywood or hard chip-board with a thickness of at least 12,0 mm or metal with a thickness of at least 2,5 mm. In the exceptional case that the board is split (i.e. not in one piece) there are considerations; the pieces shall be level within the same plane, the gap less than 1 mm, and the split shall be off the centre line and parallel with the microphone axis as shown in Figure 1a. The windscreen to be used with the ground-mounted microphone shall consist of a primary and, where necessary, a secondary windscreen. The primary windscreen shall consist of one half of an open cell foam sphere with a diameter of approximately 90 mm, which is centred around the diaphragm of the microphone, as in Figure 2. The secondary windscreen may be used when it is necessary to obtain an adequate signal-to-noise ratio at low frequencies in high winds. If the secondary windscreen is used, the influence of the secondary windscreen on the frequency response shall be documented and corrected for in 1/3-octave bands. A procedure for calibration of the secondary windscreen can be found in Annex E together with suggestions for design and demands on the insertion loss. SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 15 –
Figure 1a – Mounting of the microphone – Plan view
Figure 1b – Mounting of the microphone – Vertical cross-section Figure 1 – Mounting of the microphone SIST EN 61400-11:2013
– 16 – 61400-11 © IEC:2012(E)
Figure 2 – Picture of microphone and measurement board 6.1.6 Acoustical calibrator The complete sound measurement system, including any recording, data logging or computing systems, shall be calibrated immediately before and after the measurement session at one or more frequencies using an acoustical calibrator on the microphone. The calibrator shall fulfil the requirements of IEC 60942:2003 class 1, and shall be used within its specified environmental conditions. 6.1.7 Data recording/playback systems A data recording/playback system is a required part of the measurement instrumentation. If used for analysis (other than re-listening), the entire chain of measurement instruments shall fulfil the relevant requirements of IEC 61672 series, for class 1 instrumentation. 6.2 Non-acoustic Instruments 6.2.1 General The following equipment is necessary to perform the non-acoustic measurements set forth in this standard. 6.2.2 Anemometers The mast mounted anemometer and its signal processing equipment shall have a maximum deviation from the calibration value of ±0,2 m/s in the wind speed range from 4 m/s to 12 m/s. It shall be capable of measuring the average wind speed over time intervals synchronized with the acoustic measurements. IEC
2092/12 SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 17 –
Because the nacelle anemometer is calibrated in-situ (8.2.1.2) during measurements, the demand for calibration does not apply to the nacelle anemometer. The measurements from the nacelle anemometer may be supplied from the wind turbine control system. The nacelle anemometer shall not be used for background noise measurements. 6.2.3 Electric power transducer The electric power transducer, including current and voltage transformers, shall meet the accuracy requirements of IEC 60688 class 1. If a calibrated system is not available for the power signal, an additional uncertainty of the electrical power shall be included. The power signal may be supplied by the manufacturer if the uncertainty of the measurement chain can be documented by a detailed description of the entire power measurement chain and the corresponding uncertainty components. 6.2.4 Other instrumentation A camera and instruments to measure distance are required. The temperature shall be measured with an accuracy of ±1 °C. The atmospheric pressure shall be measured with an accuracy of ±1 kPa. 6.3 Traceable calibration The following equipment shall be checked regularly and be calibrated with traceability to a national or primary standards laboratory. The maximum time from the last calibration shall be as stated for each item of equipment: • acoustic calibrator (12 months); • microphone (24 months); • integrating sound level meter (24 months); • spectrum analyzer (36 months); • data recording/playback system (24 months), if used for analysis; • anemometer (24 months); • electric power transducer (24 months); • temperature transducer (24 months); • atmospheric pressure transducer (24 months). Where temperature and atmospheric pressure measurements are made only to give general information about the meteorological conditions during the measurement, an internal verification of the instrument is sufficient. An instrument shall always be recalibrated if it has been repaired or is suspected of fault or damage. 7 Acoustic measurements and measurement procedures 7.1 Acoustic measurement positions To fully characterize the noise emission of a wind turbine, the following measurement positions are required. One, and optionally another three, microphone positions are to be used. The positions shall be laid out in a pattern around the vertical centreline of the wind turbine tower as indicated in the plan view shown in Figure 3. The required downwind measurement position is identified as the reference position, as shown in Figure 3. The direction of the positions shall be within ±15° relative to the downwind direction of the wind turbine at the time of measurement. The SIST EN 61400-11:2013
– 18 – 61400-11 © IEC:2012(E) downwind direction can be derived from the yaw position. The horizontal distance R0 from the wind turbine tower vertical centreline to each microphone position shall be as shown in Figure 3, with a tolerance of ±20 %, maximum ±30 m, and shall be measured with an accuracy of ±2 %.
Figure 3 – Standard pattern for microphone measurement positions (plan view) As shown in Figure 4a, the reference distance R0 for horizontal axis turbines is given by:
2DHR+=0 (1) where H
is the vertical distance from the ground to the rotor centre; and D is the diameter of the rotor. SIST EN 61400-11:2013
61400-11 © IEC:2012(E) – 19 –
As shown in Figure 4b, the reference distance R0 for vertical axis wind turbines is given by:
DHR+=0 (2) where H
is the vertical distance from the ground to the rotor equatorial plane; and D
is the equatorial diameter.
D H = H +
D
2 R0 R1 φ IEC
2094/12
Figure 4a – Horizontal axis turbine
H D R1 φ R0= H + D IEC
2095/12
Figure 4b – Vertical axis turbine Figure 4 – Illustration of the definitions of R0 and slant distance R1 SIST EN 61400-11:2013
– 20 – 61400-11 © IEC:2012(E) To minimize influence due to the edges of the measurement board on the measurement results, it shall be ensured that the board is positioned flat on the ground. Any edges or gaps under the board should be levelled out by means of soil. The inclination angle φ, as shown in Figure 4, shall be between 25° and 40°. This may require adjustment of the measurement position within the tolerances stated above. Additional considerations shall be made for measurements in complex terrain to avoid influence such as screening or reflections from obstructions or terrain. The measurement
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...