Frequency Response Analysis vs. Flux Division Measurement in Detection of Transformer Winding Internal Short Circuit

Diagnosis of electrical equipment, particularly distribution and power transformers, which are considered as the heart of the electric power grid, has been quite important for quite a long time. Transformer diagnosis methods have been introduced and employed to recognize transformer internal defects since many years ago. Turn to turn and disc to disc short circuit in transformer windings are considered as one of the main problems in transformer active part. Flux Division Measurement (FDM) technique is employed specifically to realize internal short circuit in transformer windings. This test is performed as an on-site, non-destrnctive, fast and simple method to detect turn to turn or disc to disc short circuits in transformer windings. In this study, a 360 MVA, 230 kV/20 kV five-limb step up transformer has been taken as a case in order to clarify the capability of Frequency Response Analysis (FRA) in internal short circuit detection of transformer. Also, FRA tests were performed to elaborate that it is able to give further detailed information as well. Interpretation of test results on this giant transformer winding shows that FRA method is capable to provide significant information as to the healthy or defected condition of the windings.