Study On The Vegetable Insulating Oil Discharge Characteristics And Its Chemical Components Change

Power as well as distribution transformers use transformer oil for insulation and cooling purposes.Mineral insulating oil because of its low cost,good performance has been widely used for more than and 100 years.But its shortcomings are obviously.The burning and flash point is low,can not meet the requirements of high fire,and natural degradation is very difficult,if the leakage will cause great pollution to the environment.The vegetable insulating oil has the advantages of high ignition point,high dielectric constant,high cost and biodegradability.In recent years,the research of vegetable insulating oil has gradually become a hot topic in the field of electric power.In this paper,the physical and chemical properties of the after refining vegetable insulating oil were studied and illustrate its advantages and disadvantages.The system tested the breakdown voltage and breakdown time of different insulating oil under different gaps.The high-speed camera was used to photograph the discharge process in the liquid,and the above results were compared with the mineral insulating oil.According to the theory of flow injection,the breakdown characteristics of the liquid are briefly explained.In addition,the changes of the composition of the three kinds of vegetable insulating oil before and after the different breakdown times were tested.By comparing the change of fatty acid composition before and after breakdown,the chemical reaction in the process of electrical breakdown of insulating oil can be analyzed from the point of view of chemistry.The investigation shows,after refining the vegetable insulation oil not only met the standard GB2536-90 <Transformer oil> on the insulating oil requirements.But also in the flash point,acid value,dielectric loss and other aspects are better than Cooper's famous FR3 vegetable insulation oil.In addition,through the study of the breakdown characteristics of different insulating oil,it is found that the breakdown voltage of the two kinds of plant insulating oil is lower than mineral insulating oil under the same breakdown gap.The law is more obvious in the long gap and negative polarity when the vegetable insulating oil and mineral insulating oil breakdown voltage peak difference is large,serious only mineral insulation oil breakdown voltage of 70%.The change of fatty acid composition of three kinds of vegetable insulating oil was studied by gas chromatography-mass spectrometry(GCMS).The results showed that the main contents of the three kinds of vegetable insulating oil are oleic acid,palmitic acid,stearic acid,linoleic acid.And in all the oil after the breakdown of the oil,the relative content of oleic acid and palmitic acid have a certain degree of rise,the relative content of linoleic acid and stearic acid decreased.It is suggested that the increase of fatty acid saturation of vegetable insulating oil after electric breakdown.It was found that the oil samples in the different positions of the oil tank after the breakdown,only the oil sample composition near the tip of the needle changed obviously,indicating that the experimental breakdown is only a local breakdown effect.