Energies, Vol. 18, Pages 6311: Research on the Alternating Current Properties of Cellulose–Innovative Bio-Oil Nanocomposite as the Fundamental Component of Power Transformer Insulation—Determination of Nanodroplet Dimensions and the Distances Between Them

Energies, Vol. 18, Pages 6311: Research on the Alternating Current Properties of Cellulose–Innovative Bio-Oil Nanocomposite as the Fundamental Component of Power Transformer Insulation—Determination of Nanodroplet Dimensions and the Distances Between Them

Energies doi: 10.3390/en18236311

Authors:
Konrad Kierczyński
Tomasz N. Kołtunowicz
Vitalii Bondariev
Paweł Okal
Marek Zenker
Marek Szrot
Paweł Molenda
Andrzej Cichoń
Paweł Żukowski

The paper presents measurements of frequency dependence of conductivity and real components of complex permittivity of a nanocomposite consisting of electrical pressboard, bio-insulating oil and water nanodroplets with moisture content ranging from 0.6 wt.% to 5 wt.%. Bio-oil meets high environmental requirements—it is fully biodegradable, and its combustion products are significantly less harmful than those of mineral oil. In addition, the use of bio-oil reduces the carbon footprint of power transformer production. The quantum mechanical phenomenon of electron tunnelling between potential wells created by water nanodroplets was used to analyze the experimental results obtained. The study determined the effect of moisture content on the relative relaxation time values. On this basis, the number of water molecules in nanodroplets, their diameters and the concentration of nanodroplets depending on moisture content were determined. The distances over which electrons tunnel in moist pressboard impregnated with bio-oil were determined. These values are the expected values of the probability distribution of the distance between neighbouring nanodroplets. The values of the number of water molecules in nanodroplets are also the expected values of the probability distribution of the number of molecules in nanodroplets. It has been established that during many years of transformer life, several parallel processes occur as the moisture content in bio-oil-impregnated pressboard increases. One of them involves the accumulation of water molecules collected in the pressboard in nanodroplets. The second is an increase in the concentration of nanodroplets. The third is an increase in the average number of water molecules in nanodroplets.