The ageing rate of cellulose insulation materials (paper/pressboard) in oil-impregnated transformers is largely determined by moisture. In this paper, several experiments were conducted under controlled laboratory conditions to quantitatively diagnose the amount of moisture in cellulose insulation using frequency domain spectroscopy (FDS) technique, which has been proven to be an effective tool to predict the insulation condition in oil-impregnated power equipment. The frequency dielectric response in oil-impregnated pressboards, moisture content as well as test temperature, was monitored carefully, and a new dielectric characteristic parameter for the diagnosis of moisture content was proposed. In addition, the master curve technique was introduced to calibrate the temperature effect on FDS measurement results. These experiments revealed that a strong correlation exists between frequency dielectric parameter and moisture content in cellulose insulation. Such correlation can be utilised for better prediction of moisture content in paper–oil insulation. A modified assessment method for the diagnosis of moisture content in paper–oil insulation was investigated and its effectiveness was also demonstrated using a case.

References

1. 1)
  - T.K. Saha . Review of modern diagnostic techniques for assessing insulation condition aged transformers. IEEE Trans. Dielectr. Electr. Insul. , 903 - 917
2. 2)
  - 6. Jian, H., Ruijin, L., Chen, G., Zhiqin, M., Lijun, Y.: ‘Quantitative analysis ageing status of natural ester-paper insulation and mineral oil-paper insulation by polarization/depolarization current’, IEEE Trans. Dielectr. Electr. Insul., 2012, 19, (1), pp. 188–199 (doi: 10.1109/TDEI.2012.6148518).
3. 3)
  - 20. Du, Y., Zahn, M., Lesieutre, B.C., Mamishev, A.V., Lindgren, S.R.: ‘A review of moisture equilibrium in transformer paper-oil systems’, IEEE Electr. Insul. Mag., 1999, 15, (1), pp. 11–20 (doi: 10.1109/57.744585).
4. 4)
  - A. Seytashmehr , I. Fofana , C. Eichler , A. Akbari , H. Borsi , E. Gockenbach . Dielectric spectroscopic measurements on transformer oil-paper insulation under controlled laboratory conditions. IEEE Trans. Dielectr. Electr. Insul. , 1100 - 11
5. 5)
  - 29. Fofana, I., Hemmatjou, H., Meghnefi, F., et al: ‘On the frequency domain dielectric response of oil-paper insulation at low temperatures’, IEEE Trans. Dielectr. Electr. Insul., 2010, 17, (3), pp. 799–807 (doi: 10.1109/TDEI.2010.5492253).
6. 6)
  - 11. Saha, T.K., Purkait, P.: ‘Investigations of temperature effects on the dielectric response measurements of transformer oil-paper insulation system’, IEEE Trans. Power Deliv., 2008, 23, (1), pp. 252–260 (doi: 10.1109/TPWRD.2007.911123).
7. 7)
  - R. Neimanis , R. Eriksson . Diagnosis of moisture in oil/paper distribution cables-Part I: Estimation of moisture content using frequency-domain spectroscopy. IEEE Trans. Power Delivery , 1 , 9 - 14
8. 8)
  - 22. Chen, J.D., Liu, Z.Y.: ‘Dielectric physics’ (China Machine Press, 1982).
9. 9)
  - 20. Jonscher, A.K.: ‘Universal relaxation law’ (Chelsea Dielectrics Press, 1996).
10. 10)
  - 7. Garcia, B., Burgos, J.C., Alonso, A.M., Sanz, J.: ‘A moisture-in-oil model for power transformer monitoring – part I: theoretical foundation’, IEEE Trans. Power Deliv., 2005, 20, (2), pp. 1417–1422 (doi: 10.1109/TPWRD.2004.832366).
11. 11)
  - 9. Koch, M., Prevost, T.: ‘Analysis of dielectric response measurements for condition assessment of oil-paper transformer insulation’, IEEE Trans. Dielectr. Electr. Insul., 2012, 19, (6), pp. 1908–1915 (doi: 10.1109/TDEI.2012.6396947).
12. 12)
  - C. Ekanayake , S.M. Gubanski , A. Graczkowski , K. Walczak . Frequency response of oil impregnated pressboard and paper samples for estimating moisture in transformer insulation. IEEE Trans. Power Deliv. , 3 , 1309 - 1317
13. 13)
  - 4. Shi-Qiang, W., Guan-Jun, Z., Jian-Lin, W., Shuang-suo, Y., Ming, D., Xin-Bo, H.: ‘Investigation on dielectric response characteristics of thermally aged insulating pressboard in vacuum and oil-impregnated ambient’, IEEE Trans. Dielectr. Electr. Insul., 2010, 17, (6), pp. 1853–1862 (doi: 10.1109/TDEI.2010.5658238).
14. 14)
  - 25. Blennow, J., Ekanayake, C., Walczak, K., García, B., Gubanski, S.M.: ‘Field experiences with measurements of dielectric response in frequency domain for power transformer diagnostics’, IEEE Trans. Power Deliv., 2006, 21, (2), pp. 681–688 (doi: 10.1109/TPWRD.2005.861231).
15. 15)
  - C.D. Paraskevas , P. Vassiliou , C.T. Dervos . Temperature dependent dielectric spectroscopy in frequency domain of high voltage transformer oils compared to physicochemical results. IEEE Trans. Dielectr. Electr. Insul. , 3 , 539 - 546
16. 16)
  - S.M. Gubanski , P. Boss . Dielectric response methods for diagnostics of power transformers. IEEE Electr. Insul. Mag. , 12 - 18
17. 17)
  - 19. Aradhana, R., Sridhar, S., Papneja, G.S.: ‘Moisture and dielectric properties analysis of power transformer by DIRANA measurement’, Water Energy Int., 2010, 67, (1), pp. 333–344.
18. 18)
  - 3. Liao, R.J., Liang, S.W., Sun, C.X., Yang, L.J., Sun, H.G.: ‘A comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil’, Eur. Trans. Electr. Power, 2010, 20, (4), pp. 518–533.
19. 19)
  - 7. Saha, T.K., ZhengTong, Y.: ‘Experience with return voltage measurements for assessing insulation conditions in service-aged transformers’, IEEE Trans. Power Deliv., 2003, 18, (1), pp. 128–135 (doi: 10.1109/TPWRD.2002.803722).
20. 20)
  - A.M. Emsley , G.C. Stevens . Kinetics and mechanisms of the low temperature degradation of cellulose. Cellulose , 1 , 26 - 56
21. 21)
  - D. Linhjell , L.E. Lundgaard , U. Gafvert . Dielectric response of mineral oil impregnated cellulose and the impact of ageing. IEEE Trans. Dielectr. Electr. Insul. , 156 - 169
22. 22)
  - 28. Koch, M., Krüger, M.: ‘A fast and reliable dielectric diagnostic method to determine moisture in power transformers’. Proc. Int. Conf. on Condition Monitoring and Diagnosis, Beijing, China, April 2008, pp. 467–470.
23. 23)
  - 32. Fofana, I., Hemmatjou, H., Meghnefi, F.: ‘Effect of thermal transient on the polarization and depolarization current measurements of oil-paper insulation’, IEEE Trans. Dielectr. Electr. Insul., 2011, 18, (2), pp. 513–520 (doi: 10.1109/TDEI.2011.5739457).
24. 24)
  - W.S. Zaengl . Applications of dielectric spectroscopy in time and frequency domain for HV power equipment. IEEE Electr. Insul. Mag. , 6 , 9 - 22
25. 25)
  - 20. Ruijin, L., Jian, H., Chen, G., Lijun, Y.: ‘Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy’, IEEE Trans. Dielectr. Electr. Insul., 2012, 19, (3), pp. 821–830 (doi: 10.1109/TDEI.2012.6215085).
26. 26)
  - 26. Pahlavanpour, B., Martins, M., Eklund, : ‘Study of moisture equilibrium in oil-paper system with temperature variation’. Proc. Int. Conf. on Properties Applications of Dielectric Materials, June 2003, pp. 1124–1129.
27. 27)
  - 1. Fofana, I., Hemmatjou, H., Farzaneh, M.: ‘Low temperature and moisture effects on polarization and depolarization currents of oil-paper insulation’, Electr. Power Syst. Res., 2010, 80, pp. 91–97 (doi: 10.1016/j.epsr.2009.08.008).
28. 28)
  - 24. Jonscher, A.K.: ‘Dielectric relaxation in solids’ (Chelsea Dielectrics Press, London, UK, 1983).
29. 29)
  - 15. Jadav, R.B., Ekanayake, C., Saha, T.K.: ‘Understanding the impact of moisture and ageing of transformer insulation on frequency domain spectroscopy’, IEEE Trans. Dielectr. Electr. Insul., 2014, 21, (1), pp. 369–379 (doi: 10.1109/TDEI.2013.003984).
30. 30)
  - 21. Liao, R.J., Hao, J., Yang, L.J., Yuan, Q., Tang, C.: ‘Relationship between frequency domain dielectric characteristic quantity and aging status of transformer oil-paper insulation’, Trans. Chin. Electrotechn. Soc., 2012, 27, (5), pp. 43–76.
31. 31)
  - T.K. Saha , P. Purkait . Understanding the impacts of moisture and thermal ageing on transformer's insulation by dielectric response and molecular weight measurements. IEEE Trans. Dielectr. Electr. Insul. , 568 - 582
32. 32)
  - 8. Przybylek, P.: ‘The influence of cellulose insulation aging degree on its water sorption properties and bubble evolution’, IEEE Trans. Dielectr. Electr. Insul., 2010, 17, (3), pp. 906–912 (doi: 10.1109/TDEI.2010.5492265).

Understanding and analysis on frequency dielectric parameter for quantitative diagnosis of moisture content in paper–oil insulation system

References

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