Power transformer modelling to support the interpretation of frequency response analysis

A power transformer will yield a frequency response which is unique to its mechanical geometry and electrical properties. Changes in the frequency response of a transformer can be potential indicators of winding deformation, as well as other structural and electrical problems. A diagnostic tool which can be used to detect such changes is Frequency Response Analysis (FRA). To date, FRA has provided only limited insight into the underlying physical cause of the change. There is now a growing research interest in identifying the physical change in a transformer directly from its FRA signature. The aim of the research in this thesis is to support the physical interpretation of FRA through the development of a wide-band three phase transformer model. The resulting model can be used for parameter sensitivity analysis, hence providing greater insight into the effects geometric change can have on transformer FRA. The research validates the proposed modelling approach by fitting the model to FRA data, without a priori knowledge of the internal dimensions, and then quantitatively assessing the accuracy of key geometric parameters. Finally, the ability of the model to support the interpretation of FRA is demonstrated. This is achieved by modifying a power transformer to emulate winding deformation and using the model to detect and quantify the degree of change.