An on-line method to detect radial mechanical deformations of power transformer winding turns is presented. First-order perturbation theory is applied to a transformer winding surrounded by the transformer tank wall and the iron core. The transformer winding is modeled as thin conducting cylindrical rings (winding segments or turns) situated within a coaxial waveguide, where the outer conducting cylinder represents the transformer tank wall while the inner conducting cylinder represents the iron core. Antennas which radiate and measure microwave fields are proposed inside the transformer tank in order to identify and quantify the mechanical deformations of winding turns. The direct propagation problem is solved using conventional waveguide theory with mode-matching and cascading techniques. An optimization algorithm is then used to solve the inverse problem whereby a good agreement between the reconstructed and true deformations of the winding segments is obtained.
2. Vaessen, P. T. M. and E. Hanique, "A new frequency response analysis method for power transformers," IEEE Transactions on Power Delivery, Vol. 7, No. 1, 384-391, January 1992.
3. Shao, Y., Z. Rao, and Z. Jin, "Online state diagnosis of transformer windings based on time-frequency analysis," WSEAS Transactions on Circuits and Systems, Vol. 8, No. 2, 227-236, February 2009.
4. Abeywickrama, N., Y. V. Serdyuk, and S. M. Gubanski, "High-frequency modeling of power transformers for use in frequency response analysis (FRA)," IEEE Transactions on Power Delivery, Vol. 23, No. 4, 2042-2049, 2008.
5. Dalarsson, M., A. Motevasselian, and M. Norgren, "On using multiple modes to reconstruct conductor locations in a power transformer winding," PIERS Proceedings, 516-523, Kuala Lumpur, Malaysia, March 27-30, 2012.
6. Dalarsson, M., A. Motevasselian, and M. Norgren, "Using multiple modes to reconstruct conductor locations in a cylindrical model of a power transformer winding," International Journal of Applied Electromagnetics and Mechanics, Vol. 41, No. 3, 279-291, 2013.
7. Myska, R. and P. Drexler, "Simulation and verification of methods for partial discharge source localization," PIERS Proceedings, 704-708, Kuala Lumpur, Malaysia, March 27-30, 2012.
8. Colton, D. and R. Kress, "Inverse Acoustic and Electromagnetic Scattering Theory," Springer, Berlin, 1992.
9. Masterman, P. H. and P. J. B. Clarricoats, "Computer field-matching solution of waveguide transverse discontinuities," Proc. IEEE, Vol. 118, 51-63, 1971.
10. Jackson, J. D., Classical Electrodynamics, 3rd Ed., Wiley, New York, 1999.
11. Schelkunoff, S. A., Electromagnetic Waves,, D. Van Nostrand Company, Inc., New York, 1943.
12. ABB, Transformer Handbook, 2004.
13. Li, Y., G. Liu, L. Zhang, L. Zhang, and Z. Lin, "Transformer winding deformation diagnosis using middle band frequency response analysis," 2007 International Conference on Solid Dielectrics, 677-680, Winchester, UK, July 8-13, 2007.
14. Omar , A. and K. Schonemann, "Transmission matrix representation of finline discontinuities," IEEE Transactions on Microwave Theory and Techniques, Vol. 33, 765-770, 1985.