AS 2374.6-1994

1 - AS 2374.6-1994 Power transformers - Determination of transformer and reactor sound levels
4 - PREFACE
5 - CONTENTS
7 - 1. Scope
7 - 2. Definitions
7 - 2.1 Sound pressure level, Lp
7 - 2.2 A-weighted surface sound pressure level, L pA
8 - 2.3 Sound power level, LW
8 - 2.4 Principal radiating surface
8 - 2.5 Prescribed contour
8 - 2.6 Measurement surface
8 - 2.7 Measurement distance
8 - 2.8 Background noise
8 - 3. Instruments
8 - 4. Conditions for measurement
8 - 4.1 Criteria for adequacy of the test environment
9 - 4.2 Operating conditions of equipment during measurement
9 - 4.3 Quantities to be measured
9 - 5. Measurement of sound pressure levels
9 - 5.1 Background noise measurement
10 - 5.2 Sound pressure level measurements for the transformer
12 - 5.3 Corrections for background noise
13 - 6. Calculation of surface sound pressure level and sound power level
13 - 6.1 Calculation of surface sound pressure level
13 - 6.2 Calculation of the area of the measurement surface
14 - 6.3 Calculation of sound power level
15 - 7. Presentation of results
24 - APPENDIX A - TEST ENVIRONMENT QUALIFICATION PROCEDURE
24 - A1. General
24 - A2. Environmental conditions
24 - A2.1 Types of reflecting planes
24 - A2.2 Reflecting objects
25 - A2.3 Precautions for outdoor measurements
25 - A3. Qualification procedure and requirements for test rooms
25 - A3.1 Test procedures
26 - A3.2 Qualification requirements for test rooms
27 - A4. Qualification requirements for outdoor spaces
27 - A5. Alternative test procedure
28 - APPENDIX AA - SPECIFIED SOUND LEVELS FOR TRANSFORMERS
28 - AA1 SCOPE
28 - AA2 STANDARD SOUND POWER LEVELS (A WEIGHTED SCALE)
28 - AA3 APPLICATION
28 - AA4 DERIVATION
30 - APPENDIX B - DERIVATION OF SOUND POWER LEVEL FROM SOUND INTENSITY MEASUREMENTS
30 - B.1 General
30 - B.2 Definitions
31 - B.3 Instruments
32 - B.4 Conditions for measurement
32 - B.5 Measurement of sound intensity
34 - B.6 Calculation of the sound power level from the surface sound intensity level
34 - B.7 Presentation
35 - APPENDIX C - DETERMINATION OF SOUND POWER LEVEL DUE TO LOAD CURRENTS
35 - C.1 General
35 - C.2 Operating conditions of the transformer during measurement
35 - C.3 Measurement of transformer sound power level
36 - C.4 Calculation of sound power level from measurement at reduced current
36 - C.5 Addition of no-load and load noise levels

Defines sound power versus sound pressure and sets out the methods by which the sound power levels of transformers, reactors, and their associated cooling equipment shall be determined. Standard and reduced sound power level limits for transformers only have been added in an Australian Appendix. Technically equivalent to IEC 551:1987, with the addition of Appendix AA.

This standard defines the methods by which the sound levels of transformers, reactors and their associated cooling equipment shall be determined so that compliance with any specification requirements may be confirmed and the characteristics of the noise emitted in service determined.This standard is intended to apply to measurements made in the manufacturer's works since conditions may be very different when measurements are made on site because of the proximity of other objects, background extraneous noises, etc. Nevertheless, the same general rules as are given herein may be followed when on-site measurements are made.In those cases where sufficient power is available in the factory to permit full energization of reactors, the methods to be followed are the same as for transformers. Such measurements shall be made by agreement between the manufacturer and the purchaser. Alternatively, measurements may be made on site where conditions are suitable.The methods are applicable to transformers and reactors covered by IEC Publications 76, 726 and 289, without further limitation as regards size or voltage and when fitted with their normal auxiliary equipment, inasmuch as it may influence the measurement result.Although the following text refers only to transformers, it is equally applicable to reactors provided that it is recognized that the current taken by a reactor is dependent on the voltage applied and, consequently, that a reactor cannot be tested at no-load.This standard provides a basis for calculation of sound power levels.The methods of measurement and the environmental qualification procedure given in Appendix A are in accordance with ISO Standard 3746. Measurements made in conformity with this IEC standard tend to result in standard deviations which are equal to or less than 3 dB.

First published as part of AS C61-1931.
Second edition 1946 (endorsement of BS 171-1936 with amendments).
Third edition 1963.
Fourth edition 1970.
Revised and redesignated in part as AS 2374.6-1982.
Second edition 1994.