Mechanical Condition Assessment of Vacuum On-load Tap-changer for Converter Transformer based on time-frequency domain characteristics of Vibration Signal

In this paper, according to the structural characteristics of vacuum on-load tap-changer for converter transformer, vibration test was carried out during switching process in the field. Vibration characteristics in the time domain and frequency domain were studied. Based on the time-frequency domain characteristics of the vibration signal, a method to evaluate the condition of vacuum on-load tap-changer(OL TC) for converter transformer is proposed, and its engineering validity is verified. This method was proved to be effectively detect mechanical defects of vacuum OLTC, such as abnormal motor-drive mechanism, broken supporting-plate and crack of base of shock absorber.