Precise Measurements of the Temperature Influence on the Complex Permittivity of Power Transformers Moistened Paper-Oil Insulation

Pawel Zukowski, Przemyslaw Rogalski, Konrad Kierczynski and Tomasz N. Koltunowicz
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Pawel Zukowski: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38d, Nadbystrzycka Str., 20-618 Lublin, Poland
Przemyslaw Rogalski: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38d, Nadbystrzycka Str., 20-618 Lublin, Poland
Konrad Kierczynski: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38d, Nadbystrzycka Str., 20-618 Lublin, Poland
Tomasz N. Koltunowicz: Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, 38d, Nadbystrzycka Str., 20-618 Lublin, Poland

Energies, 2021, vol. 14, issue 18, 1-24

Abstract: The reference characteristics of complex permittivity of the transformers insulation solid component were determined for use in the precise diagnostics of the power transformers insulation state. The solid component is a composite of cellulose, insulating oil and water nanoparticles. Measurements were made in the frequency range from 10 −4 Hz to 5000 Hz at temperatures from 293.15 to 333.15 K. Uncertainty of temperature measurements was less than ±0.01 K. Pressboard impregnated with insulating oil with a water content of (5.0 ± 0.2) by weight moistened in a manner maximally similar to the moistening process in power transformers was investigated. It was found that there are two stages of changes in permittivity and imaginary permittivity components, occurring for low and high frequency. As the temperature increases, the frequency dependencies of the permittivity and imaginary permittivity component shifts to the higher frequency region. This phenomenon is related to the change of relaxation time with the increase in temperature. The values of relaxation time activation energies of the permittivity Δ W τε ′ ≈ (0.827 ± 0.0094) eV and the imaginary permittivity component Δ W τε ″ = 0.883 eV were determined. It was found that Cole-Cole charts for the first stage are asymmetric and similar to those described by the Dawidson–Cole relaxation. For stage two, the charts are arc-shaped, corresponding to the Cole-Cole relaxation. It has been established that in the moistened pressboard impregnated with insulating oil, there is an additional polarization mechanism associated with the occurrence of water in the form of nanodrops and the tunneling of electrons between them.

Keywords: power transformer; failure prevention; insulation condition diagnostics; electrotechnical pressboard; mineral oil; moisture; dielectric permittivity; imaginary part of permittivity; environmental pollution (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: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (5)

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