Study On The Inhibition Of Sulfur Corrosion In Transformer By Haloalkane

As the core equipment of rural power grid,the stable operation of transformer in distribution(rural)network is very important for the reliable transmission of electric energy,and it is also an important guarantee for promoting rural revitalization and implementing rural construction actions.However,in the long-term operation process,the transformer will be affected by various factors,easy to break down,and even lead to the interruption of power transmission.In recent years,transformer insulation failure occurs from time to time.Among them,corrosive sulfide contained in insulating oil will react with copper windings,leading to sulfur corrosion,which seriously destroys the mechanical and electrical properties of insulating windings and leads to transformer failure.In order to inhibit the occurrence of sulfur corrosion,domestic and foreign scholars have carried out a large number of studies,in accordance with the IEC62535 standard corrosion detection and the addition of metal passivation agent,sulfur corrosion still occurs,affecting the normal operation of equipment.Therefore,how to effectively inhibit the occurrence of sulfur corrosion in transformer oil is very important to ensure the normal operation of equipment.Based on this,in order to study the diffusion law of sulfide in transformer and the inhibition effect of haloalkanes on sulfur corrosion in insulating oil,this paper adopts the method of combining molecular simulation and experiment.First,the mixing model of insulating oil with different sulfides is constructed to screen out the sulfide which has a greater influence on the sulfur corrosion of insulating oil.Then,a mixture model of haloalkanes and insulating oil was constructed to simulate the effect of different structures of monobromopentane on the diffusion of dibenzyl disulfide(DBDS)in insulating oil,and a relatively better structure was selected.By analyzing the inhibition effect of bromoalkanes with different chain lengths on sulfides,the better carbon chain lengths were selected.Then,the suitable substances for inhibiting DBDS were screened from different kinds,structures and chain length of haloalkanes.The selected 1-bromotetradecane was added to the insulating oil with different aging degrees,and the surface topography of the insulating oil,paper and copper windings was detected.The change of acid value in the insulating oil with aging time was studied,and the change of near infrared spectrum of the insulating oil was analyzed.The effects of 1-bromotetradecane on the electrical properties of insulating oil were investigated by testing breakdown voltage,dielectric loss factor and volume resistivity.This paper draws the following conclusions:(1)There is a difference in the binding ability between sulfide and insulating oil,which leads to their different distribution and movement paths in insulating oil.Specifically,DBDS and n-hexadecyl mercaptan are distributed in the insulating oil,while hydrogen sulfide is more likely to escape the insulating oil and distribute at the boundary of the insulating oil system.Therefore,DBDS and n-hexadecyl mercaptan are easy to cause the deterioration of insulating oil.And hydrogen sulfide is easy to enter the insulation paper,the mechanical properties of the insulation paper,electrical properties caused damage.In addition,it is found that the diffusivity of sulfide in insulating oil is negatively correlated with its binding energy.Therefore,when exploring the inhibition methods of sulfur corrosion,the corresponding schemes should be made according to the characteristics of different sulfides to ensure the best inhibition effect.(2)The diffusion of sulfide in insulating oil can be effectively inhibited by the addition of monobromothane.Monobromoides with different structures and chain lengths have different inhibitory effects on sulfides because the molecular weight and structure of the thioether molecules formed by their reaction with sulfides are changed.With the increase of monobromothane chain length,the inhibition effect of monobromothane on DBDS decreased and that of n-hexadecyl mercaptan increased.Although thioether chain length is not necessarily proportional to the free volume size,thioether molecules with shorter chain length may be more prone to form closely packed structures,resulting in a smaller free volume;With the increase of chain length,the spatial arrangement of thioether molecules becomes more complex,and some voids and pores may be formed,resulting in the increase of free volume.The inhibition effect is affected not only by the structure and chain length of halogenated alkanes,but also by the interaction between sulfides.The larger the size of thioether molecules,the stronger the interaction between molecules,the lower the free volume fraction,the lower the kinetic ability,and thus the stronger the ability to inhibit sulfur corrosion.The addition of 1-bromononane,1-bromoundecane and 1-bromotetradecane can effectively inhibit sulfur corrosion in insulating oils.Therefore,the diffusion of DBDS in insulating oil can be effectively inhibited by choosing suitable 1-bromo-alkane,thus inhibiting sulfur corrosion.(3)Adding 1-bromotetradecane to insulating oil can inhibit the sulfur corrosion in transformer oil and improve the electrical performance of insulating oil to a certain extent.It is found that the sulfur corrosion in the transformer will seriously affect the performance and life of the transformer.With the increase of aging time,the insulating paper and winding will gather a lot of black corrosive substances.By near infrared spectroscopy and acid value test,it is found that 1-bromotetradecane inhibits sulfur corrosion to a certain extent.Through the breakdown,dielectric loss and resistivity tests,it is found that the breakdown voltage of insulating oil is increased by 15.3%,which reduces the influence of aging time on the volume resistivity,and reduces the dielectric loss by 5.1%,which improves the electrical performance and operation safety of the transformer to a certain extent.