Measuring no — load and load noise of power transformers using the sound pressure and sound intensity methods — Part - II: Indoors measurements

As mentioned earlier, this paper presents results of a comprehensive study conducted to identify magnitudes of contributors to the inherent difference between sound pressure and sound intensity measurements of transformer noise. From this study, appropriate conditions for accurate indoors measurement of transformer noise, when using the sound intensity method, have been derived. Also, magnitudes of the inherent inaccuracies in the measurements using the sound pressure method have been determined. Finally, modifications to the existing IEC and IEEE Industry Standards of measuring transformer noise are proposed. Part - I of the paper presented results of the outdoors measurements while this Part - II presents results of the indoors measurements made of no-load and load noise of 48 power transformers of 12 - 336 MVA power ratings, using both the sound pressure and sound intensity methods.