SFRA (Sweep Frequency Response Analysis Test)
This test is basically used for knowing the physical conditioning of the transformer winding. The transformer winding may be subjected to mechanical stresses due to transportation, transient switching impulses, and short circuit faults.

In this test, the input signal is applied to the winding while varying its input frequency and simultaneously output voltage is measured at different frequencies and the graph is recorded.

After transportation of transformer winding, SFRA test is done and the graph is captured.

Now the current graph is matched with the earlier graph and if any deviation is found between these two graphs then there must be a mechanical deformation of the transformer winding.