Research on Changes in the Phase Shift Angle and Admittance of the Cellulose–Bio-Oil Composite under the Influence of Increasing Moisture during the Long-Term Operation of Power Transformers

Pawel Zukowski, Konrad Kierczynski, Paweł Okal, Przemyslaw Rogalski, Marek Zenker, Rafal Pajak, Pawel Molenda, Marek Szrot and Tomasz N. Koltunowicz ()
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Pawel Zukowski: Department of Economics, Vincent Pol University in Lublin, 2, Choiny Street, 20-816 Lublin, Poland
Konrad Kierczynski: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38a, Nadbystrzycka Street, 20-618 Lublin, Poland
Paweł Okal: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38a, Nadbystrzycka Street, 20-618 Lublin, Poland
Przemyslaw Rogalski: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38a, Nadbystrzycka Street, 20-618 Lublin, Poland
Marek Zenker: Department of High Voltage and Power Engineering, West Pomeranian University of Technology, 37, Sikorskiego Street, 70-313 Szczecin, Poland
Rafal Pajak: Nynas AB Raffinaderivagen, 21, 149 82 Nynäshamn, Sweden
Pawel Molenda: Energo-Complex, Sp. z o.o., 9, Lotnikow Street, 41-949 Piekary Slaskie, Poland
Marek Szrot: Energo-Complex, Sp. z o.o., 9, Lotnikow Street, 41-949 Piekary Slaskie, Poland
Tomasz N. Koltunowicz: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38a, Nadbystrzycka Street, 20-618 Lublin, Poland

Energies, 2023, vol. 16, issue 23, 1-17

Abstract: In this study, the temperature–frequency dependencies of the pressboard–bio-oil–water nanoparticle composite’s fundamental parameters—phase shift angle and admittance—were examined using the Frequency Domain Spectroscopy method. Measurements were conducted in a frequency range of 10 −4 Hz to 5 × 10 3 Hz at temperatures ranging from 293.15 K to 343.15 K, with a step of 10 K. The temperature stabilization accuracy was less than ±0.05 K. A total of 15 Arrhenius plots were determined for various phase shift angle values, from which 15 values and the average activation energy of relaxation time were determined. Similarly, the values of the activation energy of admittance relaxation time and the activation energy of admittance were determined. It was established that all three average values are identical within the bounds of uncertainty. Based on 45 values, a generalized activation energy was determined, with a value of Δ W ≈ (1.032 ± 0.0196) eV. Using the generalized activation energy value, the phase shift angle curves determined for all temperatures were recalculated to a temperature of 293.15 K. It was found that after conversion, all curves perfectly overlap. A similar operation was carried out for the frequency dependencies of admittance. In this case, too, the recalculated dependencies perfectly match. This means that the shape of the frequency dependencies of the phase shift angle and admittance depends solely on the moisture content in the pressboard–bio-oil–water nanodrop composite. The position of the curves in doubly logarithmic coordinates depends only on temperature and is determined by the generalized activation energy Using the generalized activation energy determined in this study will allow for the development of accurate methods for estimating moisture content in cellulose insulation of power transformers containing bio-oil. This will contribute to the detection of critical moisture content, which is about 5% by weight, and to the elimination of the risk, associated with such a high moisture content, of catastrophic failure of power transformers.

Keywords: bio-oil; moisture; electrical pressboard; power transformer; AC admittance; phase shift angle (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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