Publications

The frequency response analysis (FRA) technique is undoubtedly a sensitive diagnostic tool for assessing the mechanical and electrical integrity of transformers. Despite FRA measurement procedures being standardized by international bodies such as IEEE, IEC, and CIGRE, there is comparatively limited literature for identifying particular phase winding with localized faults in three-phase transformer. In this context, this paper proposed a series of new FRA measurements followed by their interpretation with no post-processing for identifying the faulty phase in star-connected HV windings. The method identifies the specific phase winding with a localized incipient fault in two stages. In the first stage, it determines whether the fault is in the middle phase winding or in one of the two outer phase windings. If the fault is in an outer phase, the second stage is employed to distinctly identify which outer phase winding has gone faulty. The philosophy of the proposed method has been validated by experimental results on a real three-phase 1MVA, 33/11kV, YnYn0, 50 Hz transformer. Results are found promising and encouraging.