Experimental Investigations to Aid Interpretation of Frequency Response Analysis Measurements for Diagnosing Transformers

Frequency Response Analysis (FRA) is an emerging diagnostic tool to assess the mechanical integrity of the transformer. Proper guidelines on using FRA data for declaring the integrity of transformer windings or indicating the extent of displacement/deformations are not yet available. Interpretations of the Sweep Frequency Response Analysis (SFRA) data for diagnosing the condition of the transformer windings are not yet clear. Experimental investigations were carried out on a model transformer to obtain SFRA data for various simulated conditions like axial and radial displacements, winding displacements and deformation, core faults, etc. for different test configurations. The paper presents the results of these investigations and analyze them to form the guidelines in interpreting the SFRA data for various test conditions to detect various types of faults. It is observed from the analysis of results that SFRA with different test confi gurations needs to be applied to detect the type of fault and faulty phase winding. The information presented in the paper, from the simulated faults on transformers with SFRA measurements, will be useful in the interpretation of FRA results to assess and diagnose the condition of transformer windings and core.