Field experience of small quasi-DC bias on power transformers

A first classification of low-frequency current patterns and identification of sources


Low-frequency currents (LFC) or quasi-DC (QDC) in the electrical power transmission network, and especially in power transformers, are causing negative effects such as an increase in noise level, in reactive power consumption and in power losses.

Currently, no classification of LFC is available to identify a possible source. In order to identify the origin of undesired LFC, classifications of LFC in current and audio measurements are defined. They are based on a spectrum analysis of current and audio measurements. These classifications are successfully tested in laboratory and field measurements.

Consequently, LFC sources are identified by field and laboratory measurements and analytical approaches. For power transformer operators, a user-friendly and fast method is presented to identify LFC in the transformers. The method is based on audible measurements and serves as a first estimator for low-frequency currents in power transformers.

This is a preview of subscription content, access via your institution.

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.
Fig. 10.
Fig. 11.


  1. 1.

    Halbedl, T., Renner, H., Bailey, R. L., Leonhardt, R., Achleitner, G. (2016): Analysis of the impact of geomagnetic disturbances on the Austrian transmission grid. In 19th power systems computation conference, Genoa, Italy (S. 1–5).

    Google Scholar 

  2. 2.

    Bailey, R. L. Modelling geomagnetically induced currents in Austria. Available.

  3. 3.

    Bailey, R. L., et al. (2017): Modelling geomagnetically induced currents in midlatitude central Europe using a thin-sheet approach. Ann. Geophys., 35(3), 751–761.

    Article  Google Scholar 

  4. 4.

    Bailey, R. L., Halbedl, T., Schattauer, I., Achleitner, G., Leonhardt, R. (2018): Validating GIC models with measurements in Austria: evaluation of accuracy and sensitivity to input parameters. Space Weather, 16(7), 887–902.

    Article  Google Scholar 

  5. 5.

    Halbedl, T. (2019): Low frequency neutral point currents on transformer in the Austrian power transmission network. Doctoral Thesis, TU Graz.

  6. 6.

    GEOMAGICA. Available:

  7. 7.

    Albert, D., Halbedl, T., Renner, H., Bailey, R. L., Achleitner, G. (2019): Geomagnetically induced currents and space weather – a review of current and future research in Austria. In 2019 54th international universities power engineering conference (UPEC): proceedings: 3-6 September 2019, Bucharest, Romania, Bucharest, Romania (S. 1–6).

    Google Scholar 

  8. 8.

    Albertson, V., Kappenman, J. G., Mohan, N., Skarbakka, G. (1981): Load-flow studies in the presence of geomagnetically-induced currents. IEEE Trans. Power Appar. Syst., PAS–100 (2), 594–607.

    Article  Google Scholar 

  9. 9.

    Pirjola, R. J. (1982): Electromagnetic induction in the earth by a plane wave or by fields of line currents harmonic in time and space. Dissertation.

  10. 10.

    Bailey, R. L. (2018): Space weather and geomagnetically induced currents in Austria. Doctoral Thesis.

  11. 11.

    NERC (2012): Effects of geomagnetic disturbances on the bulk power system.

  12. 12.

    Dong, X., Liu, Y., Kappenman, J. G. (2001): Comparative analysis of exciting current harmonics and reactive power consumption from GIC saturated transformers. In 2001 IEEE power engineering society winter meeting conference proceedings: 28 January–1 February 2001, Columbus, Ohio USA (S. 318–322).

    Google Scholar 

  13. 13.

    Walling, R. A., Khan, A. N. (1991): Characteristics of transformer exciting-current during geomagnetic disturbances. IEEE Trans. Power Deliv., 6(4), 1707–1714.

    Article  Google Scholar 

  14. 14.

    Bachinger, F., et al. (2012): Direct current in transformers: effects and compensation. In 44th international conference on large high voltage electric systems.

    Google Scholar 

  15. 15.

    Demiray, T., Beccuti, G. (2012): Geomagnetisch induzierte Ströme im Schweizer Übertragungsnetz: Geomagnetically induced currents in the Swiss Transmission Network.

  16. 16.

    Hofbauer, F., et al. (2014): Rise-of-temperature method for building factor distribution in 1-phase model transformer core interior considering high DC bias. JAE, 44(3–4), 349–354.

    Article  Google Scholar 

  17. 17.

    Boteler, D. H., Pirjola, R. J. (2017): Modeling geomagnetically induced currents. Space Weather, 15(1), 258–276.

    Article  Google Scholar 

  18. 18.

    Boteler, D. H., Pirjola, R. J. (2019): Numerical calculation of geoelectric fields that affect critical infrastructure. IJG, 10(10), 930–949.

    Article  Google Scholar 

  19. 19.

    Marshall, R. A., et al. (2017): Modeling geomagnetic induced currents in Australian power networks. Space Weather, 15(7), 895–916.

    Article  Google Scholar 

  20. 20.

    Bachinger, F., Hamberger, P., Leikermoser, A., Leber, G., Passath, H. (2013): Direct current in transformers – experience, compensation: Paper PS1-34. CIGRE SC A2 & C4 JOINT COLLOQUIUM, Cigre, Zurich, Switzerland.

  21. 21.

    Prechtl, A. (1983): Dynamik elektromechanischer Systeme: Vorlesung im Wintersemester 1983/84, TU Wien. Available

  22. 22.

    Meyer, M. (2017): Signalverarbeitung: analoge und digitale signale, systeme und filter. 8. ed. Wiesbaden: Springer.

    Book  Google Scholar 

  23. 23.

    ZAMG Jahrbuch — ZAMG. Available:

  24. 24.

    Pfeiffer, M., Franck, C. M., Schmutz, J. (2015): DC ion-currents in AC conductors in hybrid AC/DC transmission systems. AC and DC power transmission.

    Book  Google Scholar 

  25. 25.

    Pfeiffer, M., Hedtke, S., Franck, C. M. (2018): Corona current coupling in bipolar HVDC and hybrid HVAC/HVDC overhead lines. IEEE Trans. Power Deliv., 33(1), 393–402.

    Article  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to D. Albert.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

D. Albert and P. Schachinger are Cigre NGN Members TU Graz.

Paper submitted for the CIGRE Session 2020, SC-A2, August 31 – September 1, 2020, online.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Albert, D., Schachinger, P., Renner, H. et al. Field experience of small quasi-DC bias on power transformers. Elektrotech. Inftech. 137, 427–436 (2020).

Download citation


  • low-frequency currents
  • quasi-DC
  • transformer neutral point current
  • transformer noise