Analysis of the influence of environmental factors on the properties of cellulosic electrical insulating materials

  • 1 University of Craiova,Romania
  • 2 National Research, Development and Testing Institute for Electrical Engineering - ICMET Craiova, Romania


From the practical experience regarding maintenance and service life of power transformers, it is important to know the state of degradation (ageing) of the solid insulation and oil transformer. Therefore, it is important to study and analyse how certain factors influence the dielectric properties of insulating materials used in electrical power transformers. This work proposes the experimental study of the behaviour of cellulose type solid materials used to insulate electrical transformers. The aim was to consider the hygroscopicity of cellulose-based products, the influence of temperature, humidity on the insulation resistance, dielectric strength and proof tracking index (PTI) in humid conditions. Experimental determinations were carried out in the framework of the RENAR accredited laboratory within ICMET Craiova. Experimental results have showed that environmental factors (low temperature -40°C and damp heat steady state for 24 hours at 70°C and relative humidity of 95%) strongly negatively influenced some dielectric properties such as insulation resistance and the PTI.



  1. M. Ghiorghiu, C. Ghiorghiu and D. Zlatanovici, Checking the Insulation of Electrical Equipment (Verificarea izolației echipamentelor electrice), Bucharest: Ed. Tehnica, 1984.
  2. G. Tănăsescu, P. Notingher, et al, “Online monitoring and diagnostic system (SMD) for AT 3200 MVA 220/110 kV from Turnu-Măgurele substation” (“Sistem de monitorizare și diagnosticare (SMD) on-line pentru AT 3200 MVA 220/110 kV d in stația Turnu-Măgurele”), National Symposium - Optimizing Energy Services, 5th Ed ition,, Buzău, Romania, 2008, p.1-6.
  3. P. Notingher, Insulation Systems (Sisteme de izolaţie), Bucharest: Printech, 2002.
  4. K.S. Kassi, I. Fofana, F. Meghnefi, A. Betie, J. Perron and Z. Yeo, ”Comparative study between conventional and hybrid solid insulation systems,” IEEE Conference on Electrical Insulation and Dielectric Phenomena CEIDP 2014, p.1-4.
  5. V. Wasserberg, H. Borsi and E. Gockenbach, “Effects of different drying procedures on the composition of a liquid impregnated solid insulation,” IEEE International Symposium on Electrical Insulation, Boston, USA, 2002, p.346-349.
  6. Z. Yan, M. Dong, Y. Shang and M. Muhr, "Ageing diagnosis and life estimation of paper insulation for operating power transformer," IEEE International Conference on Solid Dielectrics, Toulouse, France, 2004, Vol.2, pp. 715-718.
  7. L. Ruijin, T. Chao, Y. Lijun and C. Huanchao, "Thermal aging studies on cellulose insulation paper of power transformer using AFM," IEEE 8th International Conference on Properties & Applications of Dielectric Materials, Bali, Indonesia, 2006, pp. 722-725.
  8. V. Sivaramalakshmi, M. Ravindran, M. W. Iruthayarajan and M. Bakrutheen, "Aging performance of natural ester impregnated Nomex paper insulation," 2019 Fifth International Conference on Electrical Energy Systems (ICEES), Chennai, India, 2019, pp. 1-4.
  9. S. Y. Matharage, Q. Liu, Z. Wang and D. Walker, "Effect of paper type and water content in paper on the partitioning of 2- FAL between liquid and paper insulations," IEEE International Conference on High Voltage Engineering and Application, Beijing, China, 2020, pp. 1-4.
  10. G. Floriganță, Materials in Techniques (Materiale în tehnică), Craiova: Ed. ICMET, 2002.
  11. A. Ifrim and P. Noțingher, Electrotechnical Materials (Materiale electrotehnice), Bucharest: Ed. Didactic and Pedagogical, 1979.
  12. A. Ifrim and P. Noțingher, Electrotechnical Materials (Materiale electrotehnice), Bucharest: Ed. Didactic and Pedagogical, 1992.
  14. SR EN 60068-2-78:2013 - Environmental tests. Part 2-78: Tests. Cab test: Wet, continuous heat.
  15. SR EN 60068-2-1: 2007 - Environmental tests. Part 2-1: Tests. Test A: Cold.
  16. IEC 60112:2003 - Method for the determination of the proof and the comparative tracking indices of solid insulating materials.

Article full text

Download PDF