Preparation And Performance Study Of Glycerol Triacetate Mixed Soybean Insulating Oil

With the continuous deepening of the construction of new socialist countryside and the rapid development of rural industries,the increase in demand for electricity in rural areas poses a more severe challenge to the safe operation of power equipment in the distribution(rural power)network,making it particularly crucial to improve the insulation performance of power equipment in the distribution(rural power)network.Transformers are a crucial part of the power system,and their insulation system is mainly composed of mineral insulating oil and cellulose insulating paper.Mineral insulating oil is a liquid insulating material refined from petroleum.In order to address the challenges posed by environmental issues,our country proposes to accelerate the optimization of energy structure and strictly control fossil energy consumption.Vegetable insulating oil is a new type of liquid insulating medium that is extracted from the seeds or fruits of plants.It has the advantages of renewability,high biodegradability,non-toxicity,and pollution-free,which is in line with the "peak carbon dioxide emissions" and "carbon neutrality" strategy and is an ideal substitute for mineral oil.However,mature foreign manufacturers of vegetable insulating oil possess product intellectual property rights and form technical barriers to our country,resulting in higher prices for imported vegetable insulating oil.Therefore,studying the fabrication and modification methods of vegetable insulating oil to improve its electrical performance,thermal conductivity,and thermal aging characteristics has important academic and engineering application significance.Short-medium chain saturation triglycerides are a low kinematic viscosity,biodegradable liquid insulation material with potential application value in the field of transformer internal insulation.Based on this,this paper first selects soybean insulation oil as the base insulating oil,and adds the glycerol triacetate from short medium chain saturation triglycerides to soybean insulation oil.A mixed insulating oil with different addition ratios in the range of 0-25% was prepared.By testing their kinematic viscosity and electrical performance,the viscosity was reduced as much as possible with minimal electrical performance loss,and a 7.5% addition ratio was determined.Additionally,an accelerated thermal aging test was conducted on the mixed insulating oil to investigate the effect of glyceryl triacetate on the thermal aging characteristics of soybean insulating oil.Finally,molecular simulation methods based on quantum mechanics and Newtonian mechanics were used to investigate the oxidation stability of the main constituent molecules in mixed insulation oil and the microscopic mechanism of the diffusion behavior of aging products(formic acid).The following main conclusions were obtained.(1)This paper fabricated a 7.5% glyceryl triacetate mixed soybean insulating oil,whose breakdown voltage,dielectric loss factor,volume resistivity,viscosity and other parameters meet the standards specified in the "DL/T 1811-2018 Guidelines for the Selection of Natural Ester Insulation Oil for Power Transformers".The kinematic viscosity reached 32.84 mm2/s,with a decrease of 15.97%.Based on the simulation results,the addition of glycerol triacetate can improve the diffusion ability of oil molecules.On the one hand,glyceryl triacetate can increase the free volume of mixed soybean insulating oil,providing necessary diffusion space for oil molecules.On the other hand,the diffusion ability of glycerol triacetate itself is quite strong,which can improve the diffusion ability of overall mixed insulating oil molecules and drive the movement of oil molecules,thereby reducing the kinematic viscosity of the mixed oil.(2)The addition of glyceryl triacetate can inhibit the aging process of soybean insulating oil,slow down the increase in kinematic viscosity and the generation of aging products,and maintain relatively good dielectric properties and insulation performance of insulating paper during the aging process.When soybean insulating oil added with glyceryl triacetate comes into contact with the insulating paper,glyceryl triacetate forms a thin film,making it easier for oil molecules to expand on the surface of the insulating paper and distribute more evenly on the surface of the insulating paper.This helps to improve the coverage and adhesion of insulating oil molecules on the surface of insulating paper,thereby better absorbing the moisture generated in the insulating paper,slowing down the hydrolysis reaction of the insulating paper,extending its service life,and improving the safety and reliability of the equipment.(3)Glycerol triacetate has good oxidation stability and low conductivity,but due to its high polarity,the molecular surface electrostatic potential is large and unevenly distributed,which can lead to a decrease in the breakdown performance of insulating oil.Additionally,the mixed insulating oil with the addition of glycerol triacetate has a stronger binding effect on formic acid.Most of the formic acid is concentrated in the insulating oil instead of the insulating paper,and compared to pure oil,formic acid forms fewer hydrogen bonds with insulating paper in mixed insulating oil,which has a good improvement on the aging stability of the oil-paper insulation system.