Patent ID: 8278939
Filing Date: 2012-10-02
Classification: G01B

Abstract:
1. A diagnostic method for determining deformations in a transformer winding, comprising the steps of: A. representing the winding as a lumped parameter circuit and dividing the winding into at least two sections; B. 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 is as follows: (i) measuring a terminal capacitance C (ii) calculating the sectional series capacitance (Cs) and the sectional ground capacitance (Cg) of each of the different sections of the winding using the values of C (iii) simulating a range of deformations in each of the sections of the winding by changing the sectional ground capacitance Cg obtained in step B(ii) by predetermined percentages and generating simulated terminal capacitance values C (iv) calculating a deformation coefficient which is a non-limiting function of (C (iva) forming the first set of finger prints using the deformation coefficients obtained in the step above, the first set of finger prints indicating the location of the radially deformed section of the winding; and (v) calculating the difference between C C. 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 as follows: (vi) simulating a range of deformations in each of the sections of the winding by changing the sectional series capacitance Cs obtained in step B(ii) by predetermined percentages and generating simulated terminal capacitance values C (vii) calculating the deformation coefficient which is a non-limiting function of (C (viia) forming one part of the second set of finger prints using the deformation coefficients obtained in the step above, the one part of the second set of fingerprints indicating the location of the axially deformed section of the winding; (viii) calculating the difference between C (viiia) forming a second part of the second set of finger prints using the differences obtained in the step above, the second part of the second set of fingerprints indicating the extent of the axial deformation in the deformed section of the winding; D. determining the location and extent of radial or axial deformation or combination of both radial and axial deformation in the winding as follows: (i) measuring the terminal capacitance values C (ii) comparing the values of C (iii) comparing the values of C (iv) comparing the difference between C (v) wherein no difference between the values of C (vi) comparing C