Effect of Transformer Windings (Not Under The Test) on The Frequency Response (FR) of The Winding Under The Test

Sweep frequency response analysis (SFRA) is most conscious to changes in the electrical elements (R, L, C) related to the test setup and test object. Therefore, in order to monitor even the smallest winding movement in a transformer, SFRA testing is a very effective technique. The effect of changes in such electrical elements associated with the test setup (outside the test object) on the FR of the winding should be neglected. Similarly, the FR of the test object is affected by a factor located inside the transformer and unrelated to the test object. It is the transformer winding that is not being tested. All transformer windings are connected together. Even if one of the windings has a mechanical fault, it can interfere with the frequency response of the other healthy windings, even if it is not tested. In this article, experiment results are used to explore this idea.