Electrical Engineering

, Volume 101, Issue 4, pp 1189–1197 | Cite as

Effect of oil impregnated paper thickness and impulse waveshapes on voltage–number characteristics

  • Zeenath Ameena MubarakEmail author
  • Usa Savadamuthu
Original Paper


Inter-turn insulation plays a major role in the dielectric integrity of any transformer. Though the inter-turn insulation thickness is designed based on standard lightning impulse (LI) voltage distribution, the insulation fails due to various types of overvoltages from switching impulse (SI) to very fast transient overvoltages (VFTO). Moreover, the insulation gets degraded due to many factors such as service ageing, exposure to repeated applications of overvoltages due to various reasons, etc. The effect of the repeated impulses is characterized using the voltage–number (VN) characteristics recommended by CIGRE Working group C4.302. Based on the design and rating of the transformer, the thickness of the inter-turn insulation is normally changed. To quantify and compare the impulse breakdown strength and degradation due to repeated impulses under SI, LI and VFTO, different thicknesses of oil impregnated paper, ranging from 0.25 to 0.75 mm are considered. Experiments are carried out to obtain the VN characteristics for all the cases. VN characteristics are mathematically modeled by enhancing the existing exponential model to incorporate the thickness of insulation and are then validated experimentally. Based on the model parameters, the effect of the various waveshapes and the degradation due to repeated impulses are quantified and compared with the standard LI.


Inter-turn insulation thickness SI LI VFTO Repeated impulses VN characteristics 



  1. 1.
    CIGRE WG A2.37 (2015) Transformer reliability survey. Technical Brochure 642Google Scholar
  2. 2.
    Kulkarni SV, Khaparde SA (2004) Transformer engineering design and practice, chapter 8. Marcel Dekker Inc., New York, p 353Google Scholar
  3. 3.
    Karsai K, Kerenyi D, Kiss L (1987) Large power transformers, chapter 5. Elsevier, Amsterdam, p 302Google Scholar
  4. 4.
    Liu R, Jaksts A (2005) Breakdown processes in transformer insulation under LI voltages. In: IEEE international conference on dielectric liquids (ICDL), pp 75–78Google Scholar
  5. 5.
    Whitehead JB (1940) The dielectric strength and life of impregnated-paper insulation—II: the influence of the thickness of the paper. Trans Electr Eng 59:660–663Google Scholar
  6. 6.
    Li X, Li J, Xiang C, Zhang J, Bao L, Ran H (2016) The influence of oil-impregnated insulation paper’s thickness on electrical breakdown strength. In: IEEE conference on electrical insulation and dielectric phenomena (CEIDP), pp 392–395Google Scholar
  7. 7.
    CIGRE WG A2/C4.39 (2013) Electrical transient interaction between transformers and power system. Technical Brochure 577AGoogle Scholar
  8. 8.
    CIGRE WG D1.43 (2017) Insulation degradation under fast, repetitive voltage pulses. Technical Brochure 703Google Scholar
  9. 9.
    Bhoomaiah A, Mukherji S, Gupta SC, Murthy TSR, Singh BP (2005) Effect of repetitive impulse voltage on models of EHV transformer windings to determine ageing of paper insulation. In: IEEE report conference on electrical insulation & dielectric phenomena, pp 206–209Google Scholar
  10. 10.
    CIGRE WG 33.01 (1991) Guide to procedures for estimating the lightning performance of transmission lines. Technical Brochure 063Google Scholar
  11. 11.
    Naidu MS (2008) Gas insulated substations, chapter 7. I.K. International Publishing House Pvt. Ltd., Delhi, p 178Google Scholar
  12. 12.
    Vinod Kumar V, Joy Thomas M, Naidu MS (2001) Influence of switching conditions on the VFTO Magnitudes in a GIS. IEEE Trans Power Deliv 16(4):539–544CrossRefGoogle Scholar
  13. 13.
    CIGRE WG C4.302 (2008) Insulation co-ordination related to internal insulation of gas insulated systems with SF6 and Nitrogen/SF6 gas mixtures under AC condition. Electra no. 360 Google Scholar
  14. 14.
    Okabe S (2006) Voltage–time and voltage–number characteristics of insulation elements with oil-filled transformers in EHV and UHV classes. IEEE Trans Dielectr Electr Insul 13(2):436–444CrossRefGoogle Scholar
  15. 15.
    Balaji SP, Usa S, Merin Sheema IP, Kritika G (2011) Effect of repeated impulses on transformer insulation. IEEE Trans Dielectr Electr Insul 18(6):2069–2073CrossRefGoogle Scholar
  16. 16.
    Balaji SP (2016) Effect of repeated impulses on oil impregnated paper. Ph.D. thesis, Department of Electrical and Electronics Engineering, CEG, Anna UniversityGoogle Scholar
  17. 17.
    Stone GC, Van Heeswijk RG, Kurtz M (1979) The statistical analysis of HV endurance test on an epoxy insulation. IEEE Trans Electr Insul 14:315–326CrossRefGoogle Scholar
  18. 18.
    Bartnikas R, Eichhorn RM (1983) Engineering dielectrics, vol IIA. ASTM, PhiladelphiaGoogle Scholar
  19. 19.
    Sima W, Sun P, Yang M, Yang Q, Wu J (2015) Effect of space charge on the accumulative characteristics of oil paper insulation under repeated lightning impulses. IEEE Trans Dielectr Electr Insul 22(5):2483–2490CrossRefGoogle Scholar
  20. 20.
    Balaji SP, Lavanya L, Usa S (2012) Effect of repeated impulses on OIP. In: International conference on high voltage engineering and application ICHVE, Shanghai, China, pp 558–561Google Scholar
  21. 21.
    Sima W, Sun P, Yang Q, Yuan T, Lu C, Yang M (2014) Study on the accumulative effect of repeated lightning impulses on insulation characteristics of transformer oil impregnated paper. IEEE Trans Dielectr Electr Insul 21(4):1933–1941CrossRefGoogle Scholar
  22. 22.
    Balaji SP, Usa S (2013) Life estimation of transformer insulation under repeated impulses. In: IEEE 1st international conference on condition assessment techniques in electrical systems, pp 331–334Google Scholar
  23. 23.
    Bavisha T (2017) Characterization of degraded oil impregnated paper under transient overvoltages. Ph.D. thesis, Department of Electrical and Electronics Engineering,, CEG, Anna UniversityGoogle Scholar
  24. 24.
    Vandermaar AJ, Wang M, Neilson JB, Srivastava KD (1994) The electrical breakdown characteristics of oil-paper insulation under steep front impulse voltages. IEEE Trans Power Deliv 9(4):1926–1935CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Division of High Voltage Engineering, College of Engineering, GuindyAnna UniversityChennaiIndia

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