Diagnosis of Technical Condition of Power Transformers Based on the Analysis of Vibroacoustic Signals Measured in Transient Operating Conditions

The issue of an effective assessment of the technical condition of the mechanical structure of the power transformer core and windings originated the research work discussed in this paper. This publication presents the results which indicate the possibility of developing a new and noninvasive diagnostic method of the transformer active part. The method developed is based on the time-frequency analysis results of the mechanical vibrations measured of the monitored appliance. The registration of vibrations is performed during switching the transformer monitored into idle operation. This paper characterizes the power object under study, the measuring system applied, and discusses a new methodology of assessment of the technical condition of the core and windings using a modified vibroacoustic method. The original measurement results presented in this paper were obtained during switching on a 200-kVA transformer in laboratory conditions. The analysis of the signals measured was carried out for four operating conditions of the transformer under study: 1) with the core pressed by the manufacturer; 2) with the core with loose screws fixing the upper yoke; 3) with the core with loose screws fixing the upper and lower yokes; and 4) with the core with loose screws fixing the upper and lower yokes with a simultaneous unpressing of the windings of the upper voltage side.