Sweep frequency response analysis based diagnosis of shorts within transformer windings

Sweep frequency response analysis (SFRA) is a diagnostic technique which can identify faults within transformers. Though SFRA approaches are used to identify faults, their effectiveness in discriminating two same level faults at two different locations within transformer is not much analysed and reported. Experiments were carried out on a 1 kVA, single phase, 240 V/240 V laboratory transformers and on a 315 kVA, three phase, 11 kV/433 V, Dyn11, ONAN, distribution transformer, to analyse the usefulness of SFRA in inter turn short identification and discriminations. Faulty conditions were created artificially in transformers, by shorting the tappings provided in one of their windings, at different levels and locations. Open circuit self‐impedance and transfer voltage transfer function approaches were experimented and transfer function plots representing winding impedance and voltage transfer ratios at various frequencies were developed for transformers, under normal and faulty conditions. Significant differences were identified at some frequencies while comparing normal case plots with faulty case plots. It was observed that the SFRA is effective in identifying shorts within transformer winding as well as, discriminating two same level shorts (i.e.) locating shorts. Statistical analysis using absolute difference and min–max ratio also confirmed the efficacy of these approaches.