Electromechanical Joint Analysis for Switching Procedure of Vacuum On-load Tap Changer in UHV Converter Transformer

As one of the key components of a UHV converter transformer, the suitable switching condition of the vacuum on-load tap changer (OLTC) is essential for the stability of the power system. It is highly desirable to interpret OLTC’s switching procedure to assess OLTC’s switching condition. However, such work can’t be solved by vibration analysis alone. Therefore, this paper proposes an innovative electromechanical comprehensive analysis method. First, a joint motor drive current, vibration, and electromagnetic signals online monitoring system is established and deployed in a VRG type OLTC in ±800 kV converter station. Second, independent component analysis (ICA), dynamic time warping (DTW), and wavelet transform (WT) are used for processing motor current, UHFCT, and vibration signals, respectively, to extract electromechanical pulses corresponding to OLTC’s contact actions. Third, the switching procedure of OLTC is revealed by comprehensively analyzing the corresponding time relationship between these extracted pulses, combined with OLTC’s timing sequence. The methodologies developed in this paper can help to interpret OLTC’s switching procedure for deeper and finer online condition assessment.