Audio-based On-Load Tap Changer diagnostics: correlation of sound and vibration fingerprints

Over the years, non-invasive vibration-based On Load Tap Changer (OLTC) diagnostic methods have become a part of standard monitoring systems. On the other hand, audio-based diagnostics did not receive much attention. Despite the above, since signal-processing techniques are constantly evolving, audio-based machinery diagnostics is getting more and more interesting. The obvious advantage compared to the vibration based techniques lies in the fact that the audio signal can be recorded without any physical contact with the tested object. The aim of this paper is to show that there is a high linear correlation between vibration and sound signals that are produced by the OLTC, which then means that the experiences gained in the field of the vibration analysis can be transferred to the domain of the audio-based diagnostics. Another goal is to point to problems that may arise due to the environment in which the signal is being recorded.