Frequency response analysis in diagnosing transformer winding movements - fundamental understandings

Frequency response analysis (FRA) is a powerful diagnostic method in detecting transformer winding deformation, which is difficult to detect by conventional measurements. FRA relies on the fact that transformer windings can be modelled as a network of capacitance, resistance, self-inductance and mutual inductance; the values of these parameters are altered when a fault occurs on the winding, and hence the frequency response of the winding will change accordingly. This method presently suffers a drawback due to the difficulties in result interpretation. Therefore, a reliable diagnostic method, which will enable inexperienced engineers to interpret the results, is needed. Many papers have been published on FRA techniques, however none of them described the fundamental studies of FRA measurements on the basic electrical components. Thus, this study is aimed at investigating the FRA results produced from various basic electrical circuits, which consist of simple inductors, capacitors and resistors. It is hoped that these simple FRA measurements could be used to interpret the complex FRA results from transformer windings.