Extrapolation of transformer equipment noise from excessive background noise environment

Dynamic, high relative background noise environments present challenging measurement conditions for discerning the noise level contributions for equipment of interest, particularly in circumstances where equipment cannot ideally be shut down for baseline measurement comparison. This paper considers the evaluation of large transformer noise emissions contributions in excessive background noise conditions for purposes of property line compliance assessment, exemplifying such an occurrence. While often insufficient alone, typical field measurements may be accompanied by fundamental, but powerful, narrowband signal analysis techniques to estimate and demonstrate equipment noise contributions, especially for sources containing prominent tonal components, such as those that are common to electrical equipment. This simple and straightforward approach focusing on calculation of average spectral densities and use of spectrograms, supplemented by other analysis tools including three-dimensional environmental noise modeling as was employed in this case study, offers an efficient and effective equipment noise assessment strategy that may be readily applied by the practitioner.