INGETRAF, has expertise engineers in the measurement and interpretation for sound emissions test on Power and Distribution transformers, in electrical substations, power plants, indoors substations with transformers in cabinet and in photovoltaics generation systems.
The Noise emissions in the transformers come from three kinds of sources:
- From the Core by magnetostriction effect, which is the dimensional change of the sheets during the hysteresis loop (magnetostrictive forces).
- By effect of current flowing through the windings in the presence of a magnetic field (magnetostrictive forces), these sources transmit the noise through the dielectric fluid and the mechanical structure of the transformer, where is radiated to the environment through the air.
- The other source of noise in transformers, are the accessories such as fans and pumps.
The spectrum of audible sound, consisting of tones, which are multiples of the fundamental frequency 120 HZ, 240 HZ, 360 HZ, 480 HZ….
The possible causes for the abnormal noise in the transformers are:
- Static discharge problems due to parts of the transformer that are floating, and do not are equipotential grounding, or damage to the grounding system.
- Tank and radiators resonance, due to changes in the frequency of the source.
- Structural defects, such as mismatch in the core clamping, flange bolts and presses may be loose.
- For the short circuit efforts that has to withstand the structure of the active part of the transformer during events or faults.
- Damage or misalignment in some accessories such as fans, pumps and radiators.
The test is performed under the standards IEC 60076-10, IEEE C.57.12.90, NTC 5978. The method is the measurement of levels of sound pressure level (PL) in terms of the consideration type "A”. This method applies to measurements in the factory or on-site where the transformer is installed.
The noise level study is performed in the environment for compliance with the Technical Control and Industrial Hygiene (sound measurement) under the resolutions that apply to assessing the level of noise, resolution 08321 from 1983 Article 42, “exposure time to continuous or intermittent noise” resolution 2400 of 1979, Article 92, Paragraph 1, “In offices and workplaces, where intellectual work predominates, sound levels (noise) cannot be higher than 70 dB (A), independent of frequency and exposure time”