IEC 60076-10:2001 pdf Power transformers – Part 10: Determination of sound levels

IEC 60076-10:2001 pdf 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 60076-1 1 and the IEC 61 378 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 :1 993, Power transformers – Part 1: General
IEC 60076-1 1 , Power transformers – Part 11: Dry-type transformers
IEC 60289:1 988, Reactors
IEC 61 043:1 993, Electroacoustics – Instruments for the measurement of sound intensity –
Measurement with pairs of pressure sensing microphones
IEC 61 378 (all parts), Convertor transformers
IEC 61 672-1 , Electroacoustics – Sound level meters – Part 1: Specifications
IEC 61 672-2, Electroacoustics – Sound level meters – Part 2: Pattern evaluation tests
ISO 3746:1 995, Acoustics – Determination of sound power levels of noise sources using
sound pressure – Survey method using an enveloping measurement surface over a reflecting plane
ISO 961 4-1 :1 993, Acoustics – Determination of sound power levels of noise sources using
sound intensity – Part 1: Measurement at discrete points
4 Instrumentation and calibration
Sound pressure measurements shall be made using a type 1 sound level meter complying with IEC 61 672-1 and IEC 61 672-2 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 61 043 and calibrated in accordance with 6.2 of ISO 961 4-1 . 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 961 4-1 . 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.
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 1 4. 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.