Derating of distribution transformers under non-linear loads using a combined analytical-finite elements approach

Milad Ghazizadeh; Jawad Faiz; Hashem Oraee

Derating of distribution transformers under non-linear loads using a combined analytical-finite elements approach

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Author(s): Milad Ghazizadeh ¹ ; Jawad Faiz ² ; Hashem Oraee ¹
- Affiliations: 1: Department of Electrical Engineering, Sharif University of Technology, Tehran, Iran ;
  2: Centre of Excellence on Applied Electromagnetic Systems, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran
Source: Volume 10, Issue 8, September 2016, p. 779 – 787
DOI: 10.1049/iet-epa.2016.0103 , Print ISSN 1751-8660, Online ISSN 1751-8679

Received 29/02/2016, Accepted 16/05/2016, Revised 27/04/2016, Published 01/09/2016

Supplying non-linear loads causes increased losses in transformers which eventually leads to their reduced life spans. Therefore, transformers are derated in order to protect them against premature loss of life. To do this, load losses including ohmic loss and winding eddy current (WEC) loss need to be estimated. This study suggests an improved analytical approach using finite element method (FEM) which includes all material characteristics and geometrical structures in order to calculate WEC loss under non-sinusoidal load current in each winding individually. By adopting this procedure, harmonic loss factor as a dominant parameter in transformers derating is estimated. By emphasising the region in which the maximum WEC loss occurs, an additional factor (F _MECL) based on the physical phenomena involved is introduced using FEM. On the basis of the aforementioned concepts, a new relationship is presented for transformer derating. Ultimately, the suggested method and the IEEE standard are applied to derate a distribution transformer and the results are discussed. In addition, the proposed method is validated using a thermal model and its advantages over the IEEE derating method is presented.

References

1. 1)
  - 1. Fuchs, E.F., Masoum, M.A.S.: ‘Power quality in power systems and electrical machines’ (Academic Press/Elsevier, Amsterdam, Boston, 2008).
2. 2)
  - 50. Fuchs, E.F., Lin, D., Martynaitis, J.: ‘Measurement of three-phase transformer derating and reactive power demand under nonlinear loading conditions’, IEEE Trans. Power Deliv., 2006, 21, (2), pp. 665–672 (doi: 10.1109/TPWRD.2005.858744).
3. 3)
  - 17. Massey, G.W.: ‘Estimation methods for power system harmonic effects on power distribution transformers’, IEEE Trans. Ind. Appl., 1994, 30, (2), pp. 485–489 (doi: 10.1109/28.287505).
4. 4)
  - 23. IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators, ANSI/IEEE C57.91-2011 (Revision of IEEE Std C57.91-1995), IEEE Standards, 2012.
5. 5)
  - 55. Delaiba, A.C., De Oliveira, J.C., Cardoso, J.R., Nabeta, S.Y.: ‘Behavior of three-phase transformers supplying non linear loads using time domain representation and finite element analysis’, IEEE Trans. Magn., 1998, 34, (5), pp. 3174–3177 (doi: 10.1109/20.717744).
6. 6)
  - 58. Faiz, J., Ebrahimi, B.M., Ghofrani, M.: ‘Mixed derating of distribution transformers under unbalanced supply voltage and nonlinear load conditions using TSFEM’, IEEE Trans. Power Deliv., 2010, 25, (2), pp. 780–789 (doi: 10.1109/TPWRD.2009.2032837).
7. 7)
  - 9. Yildirim, D., Fuchs, E.F.: ‘Measured transformer derating and comparison with harmonic loss factor (FHL) approach’, IEEE Trans. Power Deliv., 2000, 15, (1), pp. 186–191 (doi: 10.1109/61.847249).
8. 8)
  - 30. Masoum, M.A.S., Fuchs, E.F.: ‘Derating of anisotropic transformers under nonsinusoidal operating conditions’, Electr. Power Energy Syst., 2003, 25, pp. 1–12 (doi: 10.1016/S0142-0615(01)00091-6).
9. 9)
  - 29. Opera-2D Software, Vector Field Co., U.K.
10. 10)
  - 42. Staats, P.T., Grady, W.M., Arapostathis, A., Thallam, R.S.: ‘A procedure for derating a substation transformer in the presence of widespread electric vehicle battery charging’, IEEE Trans. Power Deliv., 1997, 12, (4), pp. 1562–1568 (doi: 10.1109/61.634176).
11. 11)
  - 49. Fuchs, E.F., Yildirim, D., Grady, W.M.: ‘Measurement of eddy-current loss coefficient PEC-R, derating of single-phase transformers, and comparison with K-factor approach’, IEEE Trans. Power Deliv., 2000, 15, (1), pp. 148–154 (doi: 10.1109/61.847243).
12. 12)
  - 3. IEEE Recommended Practice for Establishing Transformer Capability When Supplying Non-sinusoidal Load Currents, ANSI/IEEE C57.110-1998, IEEE Standards, 1998.
13. 13)
  - 52. Faiz, J., Ebrahimi, B.M., Noori, T.: ‘Three- and two-dimensional finite-element computation of inrush current and short-circuit electromagnetic forces on windings of a three-phase core-type power transformer’, IEEE Trans. Magn., 2008, 44, (5), pp. 590–597 (doi: 10.1109/TMAG.2008.917819).
14. 14)
  - 48. Kelley, A.W., Edwards, S.W., Rhode, J.P., Baran, M.E.: ‘Transformer derating for harmonic currents: a wide-band measurement approach for energized transformers’, IEEE Trans. Ind. Appl., 1999, 35, (6), pp. 1450–1457 (doi: 10.1109/28.806061).
15. 15)
  - 4. IEEE Recommended Practice for Establishing Liquid-Filled and Dry-Type Power and Distribution Transformer Capability When Supplying Nonsinusoidal Load Currents, ANSI/IEEE C57.110-2008 (Revision of IEEE Std C57.110-1998), IEEE Standards, 2008.
16. 16)
  - 25. IEEE Standard Test Code for Dry-Type Distribution and Power Transformers, ANSI/IEEE C57.12.91-2011 (Revision of IEEE Std C57.12.91-2001), IEEE Standards, 2012.
17. 17)
  - 51. Lin, D., Fuchs, E.F.: ‘Real-time monitoring of iron-core and copper losses of transformers under (non)sinusoidal operation’, IEEE Trans. Power Deliv., 2006, 21, (3), pp. 1333–1341 (doi: 10.1109/TPWRD.2006.874118).
18. 18)
  - 35. Masoum, M.A.S., Moses, P.S., Masoum, A.S.: ‘Derating of asymmetric three-phase transformers serving unbalanced nonlinear loads’, IEEE Trans. Power Deliv., 2008, 23, (4), pp. 2033–2041 (doi: 10.1109/TPWRD.2008.923057).
19. 19)
  - 22. Faiz, J., Ghazizadeh, M., Oraee, H.: ‘Derating of transformers under non-linear load current and non-sinusoidal voltage – an overview’, IET Electr. Power Appl., 2015, 9, (7), pp. 486–495 (doi: 10.1049/iet-epa.2014.0377).
20. 20)
  - 8. Podoltsev, A.D., Kucheryavaya, I.N., Lebedev, B.B.: ‘Analysis of effective resistance and eddy-current losses in multiturn winding of high-frequency magnetic components’, IEEE Trans. Magn., 2003, 39, (1), pp. 539–548 (doi: 10.1109/TMAG.2002.806337).
21. 21)
  - 53. Ebrahimi, B.M., Fereidunian, A., Saffari, S., Faiz, J.: ‘Analytical estimation of short circuit axial and radial forces on power transformers windings’, IET Gener. Transm. Distrib., 2014, 8, (2), pp. 250–260 (doi: 10.1049/iet-gtd.2013.0268).
22. 22)
  - 20. Yazdani-Asrami, M., Mirzaie, M., Shayegani Akmal, A., et al: ‘Life estimation of distribution transformers under non- linear loads using calculated loss by 2D-FEM’, J. Electr. Syst. (JES), 2010, 7, (1), pp. 1444–1451.
23. 23)
  - 46. Lin, D., Fuchs, E.F., Doyle, M.: ‘Computer-aided testing of electrical apparatus supplying nonlinear loads’, IEEE Trans. Power Syst., 1997, 12, (1), pp. 11–21 (doi: 10.1109/59.574918).
24. 24)
  - 19. Faiz, J., Sharifian, M.B.B., Fakheri, S.A., et al: ‘Derating of distribution transformers for non-sinusoidal load currents using finite element method’, Trans. B Iran. J. Sci. Technol., 2004, 28, (B3), pp. 315–322.
25. 25)
  - 2. IEEE Recommended Practice for Establishing Transformer Capability When Supplying Non-sinusoidal Load Currents, ANSI/IEEE C57.110-1986, IEEE Standards, 1988.
26. 26)
  - 7. Fuchs, E.F., Yildirim, D., Batan, T.: ‘Innovative procedure for measurement of losses of transformers supplying nonsinusoidal loads’, IEE Proc. Gener. Transm. Distrib., 1999, 146, (6), pp. 617–625 (doi: 10.1049/ip-gtd:19990684).
27. 27)
  - 24. IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers, ANSI/IEEE C57.12.90-2010 (Revision of IEEE Std C57.12.90-2006), IEEE Standards, 2010.
28. 28)
  - 18. Driesen, J., Belmans, R., Hameyer, K.: ‘The computation of the effects of harmonic currents on transformers using a coupled electromagnetic-thermal FEM approach’. Proc. Ninth Int. Conf. on Harmonics and Quality of Power, Orlando, USA, October 2000, vol. 2, pp. 720–725.
29. 29)
  - 15. Savaghebi, M., Jalilian, A., Gholami, A.: ‘A new approach for transformer loading capability assessment under non-linear load currents’. IEEE Int. Conf. on Industrial Technology(ICIT), Chengdu, China, April 2008, pp. 1–5.

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Derating of distribution transformers under non-linear loads using a combined analytical-finite elements approach

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