A diagnostic method for determining deformations in a transformer winding including the steps of representing the winding as a lumped parameter circuit and dividing the winding into at least two sections; generating a first set of fingerprint values based on capacitive values of the winding; the first set of finger print values indicating the location and extent of radial deformation in the winding; generating a second set of fingerprint values based on capacitive values of the winding; the second set of finger prints indicating the location and extent of axial deformation in the winding and determining the location and extent of radial or axial deformation or combination of both radial and axial deformation in the winding by comparing the measured values with the first set and second set of finger print values.