Diagnosis of the Non-Concurrent Operation of the On-Load Tap Changer Contacts by the Acoustic Emission Method

Abstract

On-load tap changers (OLTC) are some of the main transformer elements that make voltage adjustment in a power network possible. Their failures often cause shutdowns of distribution transformers. The paper presents research work aimed at the assessment of the technical condition of OLTCs by the acoustic emission method (EA). This method makes the OLTC diagnosis possible without the need of disconnecting the transformer from the system. The measurements were taken in laboratory conditions. The influence on the operation non-concurrence of the power tap changer contacts on the AE registered signals has been investigated. The signals registered were subjected to analyses in the time and time-frequency domains. The result analysis in the time domain was carried out using the Hilbert transform and calculating characteristic times for the particular runs. A short-time Fourier transform was used for the assessment of results in the time-frequency domain.

Vibro-Acoustic Methods in the Condition Assessment of Power Transformers: A Survey

“…These methods were used to tackle the problems of highly non-stationary nature of the signals and to improve the precision of the diagnostics. CWT, DWT and STFT have also been used in [20], [21], [71], and [72] for the extraction of the diagnostic material. Li et al [73] reported the shortcomings of the existing vibro-acoustic diagnostic methods when electrical faults without obvious mechanical vibration are being diagnosed, such as contact terminals fault and contact resistance anomaly.…”

Comparative Analysis of Acoustic Emission Signals from On-Load Tap-Changers for Potential Detecting of Non-Simultaneous Operations

“…This makes it possible to record acoustic emission (AE) signals using piezoelectric transducers. The recorded AE signals provide information characterizing the operation of the OLTC, enabling the diagnosis of the device using these signals (Cichoń et al, 2011a;2011b;Li et al, 2012).…”