Vibro-Acoustic On-Load Tap Changer Diagnostic – A Sister Unit Comparison

Abstract:
This paper reports on the diagnostic electrical and vibro-acoustic routine measurements of two sister transformer on-load tap changers (OLTCs). The electrical diagnostic of OLTCs is an established diagnostic tool, whereas the vibro-acoustic measurement is not established everywhere. One reason might be the need for a fingerprint measurement to guarantee the highest accuracy of the assessment. The availability of fingerprints, especially for older units is rare to-day. If no fingerprint is available, a sister unit comparison can increase the assessment accuracy and quality. For the as-sessment of routine tests on two transformers, the vibro-acoustic signature of their OLTCs were recorded and compared together with the electrical measurements, revealing a good condition of both OLTCs.