Experience of Using the Frequency Response Analysis Method in Interpreting Defects of 10–500 kV Transformers

This paper presents a methodology for evaluating Frequency Response Analysis (FRA) results based on the standard deviation (SD) coefficient. The methodology is applied to a case study involving the evaluation of FRA results for a power transformer with a voltage of 10–500 kV. The paper also presents a method of dynamic division of the frequency region for the determination of winding and core zones based on the analysis of local extrema. The results of transformer measurements in the presence of radial and axial winding deformations, short-circuited in the winding, and deformation of the core are presented. The possibilities of analysis by capacitive inter-winding measurement schemes are shown. It is demonstrated that the application of the DL/T-911 method can lead to erroneous estimation of FRA results.