Using the Frequency Response Analysis (FRA) In Transformers Internal Fault Detection

This paper deals with diagnostic methods of the internal faults in power transformers. The diagnostic process uses some of the current diagnosis methods (e.g. oil test, dissolved gases analysis (DGA), partial discharge (PD), etc.) to determine the condition of the transformer. In this process, the most frequent diagnostic methods were listed and applied practically to be compared. A conventional faulty oil-immersed transformer 400 V / 10 kV, 100 kVA was diagnosed and tested with different methods. The parameters and results were compared with a normal working transformer with the same parameters and age. After that an opening of the transformer was performed to approve and to make a visual verification of the diagnostic methods and the used devices. Among the applied methods, the frequency response analysis FRA reflects the real situation of the internal faults such as short circuits, mechanical displacement and deformation of the transformer windings.