Diagnosis of Power Transformer Cores Based on the Vibroacoustic Signals Measurement in a Transient State

The subject matter of the paper concerns the evaluation of power transformer cores technical conditions based on the measurement and the analysis of vibroacoustic signal registered in the transient state, when the transformer is switch on to the idle. The issues taken constitute a development in research work on application and effective use of the so-called modified vibroacoustic method. The main objective of the performed tests, whose results are presented in this paper, is evaluation of effectiveness in applying the developed diagnostic method in power transformer operational conditions. The paper presents the research results concerning technical verification of the noninvasive power transformer cores mechanical structure diagnostics method being developed at Opole University of Technology, Poland. The paper characterizes the proposed diagnostic methodology and presents the research results obtained from two power transformers with power 63 MVA, which were characterized by a similar exploitation time. The authors were in a position to make a preliminary diagnosis of the present live part technical condition of the devices under test based on data on the DGA analysis results of electro-insulation oil taken from their tanks. A correlation of the characteristic gas concentration values with the vibroacoustic signal parameters determined in time and frequency domain enabled to estimate the interpretation effectiveness and correctness of the registered data using the measurement method under development. The vibration analysis results, presented in the paper, of the power transformers in operating conditions proved the possible industrial application of the measurement method presented by the authors. Taking the results obtained via the modified vibroacoustic method in comparison to those obtained via the DGA analysis of electro-insulation oil, it was possible to prove the correctness of a diagnosis made based on their results.