Abstract
Natural ester has been widely studied as an alternative dielectric liquid to mineral oil in recent years. Unsaturated triacylglycerol molecules are the main components of natural ester; therefore, in this paper, we investigate the molecular structure and electronic properties of the triolein molecule, an oleic-type triacylglycerol molecule, as a representative component of natural ester oils. The effects of external electric fields at the electric field intensity related to streamer initiation and propagation on the bond lengths, dipole moment, total energy, infrared spectra, and orbital energy of the triolein molecule are investigated using density functional theory (DFT). In addition, the excitation energies, transition wavelengths, and oscillator strengths of the first eight excited states of the triolein molecule under external electric fields are calculated by time-dependent DFT. The results show that the bond lengths, dipole moments, total energy, and infrared spectra change obviously under external electric fields. With increasing external electric field intensity, the energy of the highest occupied molecular orbital increases, and the gap between that and the energy of the lowest unoccupied molecular orbital decreases, which make the molecule susceptible to excitation. The calculations contribute to an understanding of the causes behind the degradation of the insulation properties of natural ester oils.
Highlights
In recent years, natural ester has been studied widely as an alternative dielectric liquid to mineral oil in transformers and disconnectors [1,2,3,4,5,6,7,8,9]
In thisunder paper,external we investigate molecular and electronic properties of a natural ester functional theory (DFT)electric and time dependent density functional theory (TD-DFT)
We investigated the influence of external electric fields at the magnitude for streamer initiation and propagation ranging from −25.7 × 108 V/m to 25.7 × 108 V/m along the Z axis on bond lengths, dipole moment, total energy, infrared spectra, and orbital energy of the triolein molecule by DFT with a B3LYP/6-31G* scheme
Summary
Natural ester has been studied widely as an alternative dielectric liquid to mineral oil in transformers and disconnectors [1,2,3,4,5,6,7,8,9]. Natural esters are biodegradable and environmentally friendly. Natural esters are 97% decomposed after 21 days by the CEC-L-33 test [1,2] and, present little threat to soil and watercourses when released into the environment. The environmental benefits of natural esters make the use of this material increasingly attractive. The fire point of natural esters is above 300 ◦ C, which is significantly greater than that of mineral oils (~160 ◦ C) [3]. Natural ester offers better fire resistance than mineral oil
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