Interpretation of transformer FRA measurement results using winding equivalent circuit modelling technique

Diagnosis of transformer winding movement through frequency response analysis (FRA) depends on the interpretation of the raw FRA results. At present this is normally done by visual inspection of the FRA plot. In this paper a technique which converts the FRA measurement results into a transformer equivalent circuit model is studied. Laboratory and site examples are used to provide "healthy" and "deformed" FRA results, which are converted into the transformer equivalent circuits so that the circuit components affected by the deformation can be determined. The advantage with this technique is that the FRA data can be reduced to a small set of meaningful parameters that can aid interpretation and classification of FRA results.