Investigation on micro-mechanism of palm oil as natural ester insulating oil for overheating thermal fault analysis of transformers

In order to explore the pyrolysis mechanism of palm oil as the natural ester insulating liquid from the molecular aspect, the ReaxFF reactive force field was used to simulate the pyrolysis process of palm oil. Firstly, the molecular models of the four main molecules of palm oil-tripalmitin, trilinolein, triolein, and tristearin-are constructed via density functional theory (DFT). Secondly, the vibrational frequencies of the four molecules are calculated, so as to calculate the infrared (IR) spectra. Thirdly, molecular dynamics (MD) simulations employing the ReaxFF method are performed to simulate the pyrolysis reaction of the palm oil system under different temperatures, so as to observe the generation pathways of major products used in the dissolved gas analysis (DGA) in the transformer thermal fault analysis. Finally, hydrogen bonds in the pyrolysis process are counted. It is found that the number of hydrogen bonds gradually increased with the increase of pyrolysis time and pyrolysis temperature. It reveals why the life of the insulating paper immersed with natural esters is prolonged, and why the breakdown voltage is reduced slowly in the actual experiment from another perspective. This study can provide theoretical guidance and effective reference for the thermal fault analysis of an insulating liquid using palm oil as raw material.

Automated summary

This study simulated the pyrolysis process of palm oil and found that the number of hydrogen bonds gradually increased with the increase of pyrolysis time and temperature, which revealed the reasons behind the prolonged lifespan of insulating paper immersed with natural esters and the slow reduction of breakdown voltage in actual experiments.